Hamster

Hamster
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Hamster
Temporal range: Middle Miocene–Recent

Golden Hamster
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Mammalia
Order: Rodentia
Suborder: Myomorpha
Superfamily: Muroidea
Family: Cricetidae
Subfamily: Cricetinae
Fischer de Waldheim, 1817
Genera
Mesocricetus
Phodopus
Cricetus
Cricetulus
Allocricetulus
Cansumys
Tscherskia
Hamsters are rodents belonging to the subfamily Cricetinae. The subfamily contains about 25 species, classified in six or seven genera
Hamsters are crepuscular. Hamsters are also nocturnal, which means they are active at night. In the wild, they burrow underground in the daylight to avoid being caught by predators. Their diet includes a variety of foods, including dried food, berries, nuts, fresh fruits and vegetables. In the wild they feed primarily on seeds, fruits and greens, and will occasionally eat burrowing insectsThey have an elongated pouch on each side of their heads that extend to their shoulders, which they stuff full of food to be stored, brought back to the colony or to be eaten later.
Although the Golden Hamster (Mesocricetus auratus) was first described scientifically in 1839, it was not until 1930 that researchers were able to successfully breed and domesticate hamstersPet Golden Hamsters are descended from hamsters first found and captured in Syria by zoologist Israel Aharoni
Hamster behavior can vary depending on their environment, genetics, and interaction with people. Because they are easy to breed in captivity, hamsters are often used as lab animals in more economically developed countries. Hamsters have also become established as popular small house petsHamsters are sometimes accepted even in areas where other rodents are disliked, and their stereotypically solitary nature can reduce the risk of excessive litters developing in households.
Contents
• 1 Etymology of name
• 2 Characteristics
• 3 Behavior
• 4 Reproduction
o 4.1 Mating and longevity
• 5 Hamsters as pets
• 6 Classification
o 6.1 Relationships among hamster species
• 7 Similar animals
• 8 See also
• 9 References
o 9.1 Notes
o 9.2 Bibliography
• 10 External links
Etymology of name
The name hamster derives from the German Hamster, which itself comes from earlier Old High German hamustro. Possibly related to Old Russian choměstrǔ, which is either a blend of the root of Russian khomiak "hamster" and a Baltic word (cf. Lithuanian staras "hamster")or of Persian origin (cf. Av hamaēstar "oppressor
Characteristics
Hamsters are stout-bodied, with tails shorter than body length, and have small furry ears, short stocky legs, and wide feet. Their thick, silky fur, which can be long or short, can be black, gray, honey, white, brown, yellow, or red depending on the species, or a mix of any of those colors.


Roborovski hamster
Two species of hamsters belonging to the genus Phodopus (Phodopus campbelli, Campbell's Dwarf Hamster, and Phodopus sungorus, the Djungarian Hamster) and also two of the species of the genus Cricetulus, (Cricetulus barabensis, the Chinese Striped Hamster, and Cricetulus griseus, the Chinese Dwarf Hamster) have a dark stripe down the head to tail. The species of genus Phodopus are the smallest, with bodies 5.5 to 10.5 centimetres (2.2 to 4.1 in) long; the largest is the European Hamster (Cricetus cricetus), measuring up to 34 centimetres (13.4 in) long, not including a short tail of up to 6 centimetres (2.4 in). The Angora hamster, also known as the long-haired or Teddy Bear hamster, which is a type of the Golden Hamster is the second-largest hamster breed, measuring up to 18 centimetres (7.1 in) long
Hamsters have poor eyesight; they are nearsighted[citation needed] and colorblind. However, they have an acute sense of smell and can hear extremely well. Hamsters can use their sense of smell to detect gender, locate food, and detect pheremones. They are also particularly sensitive to high-pitched noises and can hear and communicate in the ultrasonic range
The tail is sometimes difficult to see; usually it is not very long (about 1/6 the length of their body) with exception of the Chinese dwarf hamster whose tail is the same length as the body. On a long haired hamster it is barely visible. Hamsters are very flexible, and their bones are somewhat fragile. They are extremely susceptible to rapid temperature changes and drafts, as well as extreme heat or cold. Hamsters are hindgut fermenters and must eat their own feces in order to digest their food a second time. This practice is called coprophagy and is necessary for the hamster to obtain the proper nutrients from its food
Hamsters are omnivorous. They eat most things, and although they should regularly be given a diet of normal hamster food, it is enjoyable for both the owner and the hamster to experiment with other things, such as vegetables, fruits (though these should be removed once they go rotten or bad), seeds, and nuts.
One characteristic of rodents that is highly visible in hamsters is their sharp incisors. They have two pairs in the front of their mouths and these incisors never stop growing and thus must be regularly worn down. Hamsters carry food in their spacious cheek pouches to their underground storage chambers. When full, their cheeks can make their heads double (or even triple) in sizeHamsters in the Middle East have been known to hunt in packs to find insects for food
Behavior


Golden hamster grooming
Golden Hamsters (Mesocricetus auratus) are generally solitary and may fight to the death if put together. Some dwarf hamster species may get along with others of the same species. Siberian hamsters form close, monogamous bonds with their mates. If separated, they may become very depressed. This happens especially in males. Males will become inactive, eat more, and even show some behavioural changes similar to some types of depression in humans. This can even cause obesity in the hamster.
Hamsters are primarily considered crepuscular because they live underground during most of the day, only leaving their burrows about an hour before sundown and then returning when it gets dark. At one point they were considered nocturnal because they are active all night. Some species have been observed to be more nocturnal than othersAll hamsters are excellent diggers, constructing burrows with one or more entrances and with galleries that are connected to chambers for nesting, food storage, and other activitiesThey will also appropriate tunnels made by other mammals; the Djungarian Hamster (Phodopus sungorus), for instance, uses paths and burrows of the pika. Although hamsters do not hibernate per se, they do “close down” a number of systems, such as breathing and heartbeat rate, for short periods of time. These periods of torpor can last up to seven to ten days. Hamsters are known to stockpile large amounts of food where they sleep, making it possible to leave pet hamsters alone for a few days without food
Reproduction


A mother Golden Hamster with pups under one week old.
Hamsters become fertile at different ages depending on their species, but this can be from one month to three months of age. The female’s reproductive life only lasts about 18 months, but male hamsters remain fertile much longer. Females are in heat approximately every four days, indicated by a reddening of genital areas
Hamsters are seasonal breeders. Breeding season is from April to October in the northern hemisphere, with two to five litters of 1 to 13 young being born after a gestation period of 16 to 23 daysGestation lasts 16 to 18 days for Golden Hamsters, 18 to 21 days for the Russian hamsters, 21 to 23 days for Chinese hamsters and 23 to 30 for Roborovski Hamsters. The average litter for Golden Hamsters is about 7, but can be as great as 24, which is the maximum number of pups that can be contained in the uterus. Campbell's Dwarf Hamsters tend to have 4 to 8 in a litter but can have up to 14. Djungarian Hamsters tend to have slightly smaller litters, as do Chinese and Roborovski hamsters.
Chinese hamster females are known for being aggressive toward the male if kept together for too long. In some cases, male Chinese hamsters can die after being attacked by the female. If breeding Chinese hamsters, it is recommended to separate the pair after mating or the hamsters will attack each other.
Golden hamster females are also very aggressive toward male hamsters and must be separated immediately after breeding in order to prevent an attack. Female hamsters are also particularly sensitive to disturbances while giving birth and may even eat her own young if she thinks they are in danger, although sometimes she is just carrying the pups in her cheek pouches
Hamsters are born hairless and blind in a nest that the mother will have prepared in advanceAfter one week they begin to explore outside the nest. They are completely weaned after three weeks, or four for Roborovski Hamsters. Most breeders will sell the hamsters to shops when the hamsters are anywhere from three to nine weeks old.
Mating and longevity
Golden Hamsters typically live no more than two to three years in captivity, less than that in the wild. Russian Hamsters (Campbell's and Djungarian) live approximately 1.5 to 2 years in captivity, and Chinese Hamsters 2.5 to 3 years. The smaller Roborovski Hamster often lives to 2–3 years in captivityBoth Golden and Russian hamsters mature quickly and can begin reproducing at a young age (4–5 weeks), whereas Chinese hamsters will usually begin reproducing at 2–3 months of age, and Roborovskis at 3–4 months of age.
Left to their own devices, hamsters will produce several litters a year with several pups in each litter. When seen from above, a sexually mature female hamster has a trim tail line; a male's tail line bulges on both sides. This might not be very visible in all species. Male hamsters typically have very large testes in relation to their body size. Before sexual maturity occurs at about 4–6 weeks, it is more difficult to determine a young hamster's sex. When examined, female hamsters have their anal and genital openings close together, whereas males have these two holes farther apart (the penis is usually withdrawn into the coat and thus appears as a hole or pink pimple
It should also be noted that if a captive hamster is left for extended periods (3–4 weeks and more) with her litter, there is a high possibility that she will cannibalize the litter. It is therefore imperative that the litter be split up by the time the young can collect their own food and water.
Hamsters as pets


A Sable short-haired Golden Hamster
The best-known species of hamster is the Golden or Syrian Hamster (Mesocricetus auratus), which is the type of hamster most commonly kept as a pet. It is also sometimes called a "fancy" hamster. Pet stores also have taken to calling them "honey bears", "panda bears", "black bears", "European black bears", "polar bears", "teddy bears", and "Dalmatian", depending on their coloration. There are also several variations, including long-haired varieties that grow hair several centimeters long and often require special care. British zoologist Leonard Goodwin claimed that most hamsters kept in the United Kingdom were descended from the colony he introduced for medical research purposes during the Second World War


A Russian dwarf hamster
Other hamsters that are kept as pets are the four species of "dwarf hamster". Campbell's Dwarf Hamster (Phodopus campbelli) is the most common of the four—they are also sometimes called "Russian Dwarfs"; however, many hamsters are from Russia, and so this ambiguous name does not distinguish them from other species appropriately. The coat of the Djungarian or Winter-white Russian Dwarf Hamster (Phodopus sungorus) turns almost white during winter (when the hours of daylight decrease The Roborovski Hamster (Phodopus roborovskii) is extremely small and fast, making it difficult to keep as a petThe Chinese Hamster (Cricetulus griseus), although not technically a true "dwarf hamster", is the only hamster with a prehensile tail (about 4 cm long)—most hamsters have very short, non-prehensile tails.
Many breeders also show their hamsters and so breed towards producing a good healthy show hamster with a view to keeping one or two themselves so quality and temperament are of vital importance when planning the breeding. Although breeders of show hamsters specialise in breeding show hamsters, there are also owners who have bred their pet hamsters. These may be the result of a planned or unplanned pregnancy but the hamsters have usually been cared for well and handled regularly, so make very suitable pets. Buying a hamster directly from a breeder means that there is the opportunity to see the parents and know the dates of birth.[citation needed]

Classification
Taxonomists generally disagree about the most appropriate placement of the subfamily Cricetinae within the superfamily Muroidea. Some place it in a family Cricetidae that also includes voles, lemmings, and New World rats and mice; others group all these into a large family called Muridae. Their evolutionary history is recorded by 15 extinct fossil genera and extends back 11.2 million to 16.4 million years to the Middle Miocene Epoch in Europe and North Africa; in Asia it extends 6 million to 11 million years. Four of the seven living genera include extinct species. One extinct hamster of Cricetus, for example, lived in North Africa during the Middle Miocene, but the only extant member of that genus is the European or Common Hamster of Eurasia.
• Subfamily Cricetinae
o Genus Allocricetulus
 Species A. curtatus—Mongolian Hamster
 Species A. eversmanni—Eversmann's or Kazakh Hamster
o Genus Cansumys
 Species C. canus—Gansu Hamster
o Genus Cricetulus
 Species C. alticola—Tibetan Dwarf or Ladak Hamster
 Species C. barabensis, including "C. pseudogriseus" and "C. obscurus"—Chinese Striped Hamster, also called Chinese Hamster; Striped Dwarf Hamster
 Species C. griseus—Chinese (Dwarf) Hamster, also called Rat Hamster
 Species C. kamensis—Kam Dwarf Hamster or Tibetan Hamster
 Species C. longicaudatus—Long-tailed Dwarf Hamster
 Species C. migratorius—Gray Dwarf Hamster, Armenian Hamster, Migratory Grey Hamster; Grey Hamster; Migratory Hamster
 Species C. sokolovi—Sokolov's Dwarf Hamster
o Genus Cricetus
 Species C. cricetus—European Hamster, also called Common Hamster or Black-Bellied Field Hamster
o Genus Mesocricetus—Golden Hamsters
 Species M. auratus—Golden or Syrian Hamster
 Species M. brandti—Turkish hamster, also called Brandt's Hamster; Azerbaijani Hamster
 Species M. newtoni—Romanian Hamster
 Species M. raddei—Ciscaucasian Hamster
o Genus Phodopus—Dwarf Hamsters
 Species P. campbelli—Campbell's Dwarf Hamster
 Species P. roborovskii—Roborovski Hamster
 Species P. sungorus—Djungarian Hamster or Winter-white Russian Dwarf Hamster
o Genus Tscherskia
 Species T. triton—Greater Long-tailed Hamster, also called Korean Hamster
[edit] Relationships among hamster species
Neumann et al. (2006) conducted a molecular phylogenetic analysis of 12 of the above 17 species of hamster using DNA sequence from three genes: 12S rRNA, cytochrome b, and von Willebrand factor. They uncovered the following relationships:
Phodopus group
The genus Phodopus was found to represent the earliest split among hamsters. Their analysis included both species. The results of another study (Lebedev et al., 2003) may suggest that Cricetulus kamensis (and presumably the related C. alticola) might belong to either this Phodopus group or hold a similar basal position.
Mesocricetus group
The genus Mesocricetus also form a clade. Their analysis included all four species, with M. auratus and M. raddei forming one subclade and M. brandti and M. newtoni another.
Remaining genera
The remaining genera of hamsters formed a third major clade. Two of the three sampled species within Cricetulus represent the earliest split. This clade contains Cricetulus barabensis (and presumably the related C. sokolovi) and Cricetulus longicaudatus.
Miscellaneous
The remaining clade contains members of Allocricetulus, Tscherskia, Cricetus, and Cricetulus migratorius. Allocricetulus and C were sister taxa. Cricetulus migratorius was their next closest relative, and Tscherskia was basal.
[edit] Similar animals
Note that there are some rodents that are sometimes called "hamsters" that are not currently classified in the hamster subfamily Cricetinae. These include the Maned Hamster or Crested Hamster, which is really the Maned Rat (Lophiomys imhausi), although not nearly as marketable under that name. Others are the mouse-like hamsters (Calomyscus spp.), and the white-tailed rat (Mystromys albicaudatus).
See also
• Chinchilla
• Gerbil
• Guinea pig
• Hampster Dance
• Hamster racing
• Hamtaro
• Rat
• Tales of the Riverbank
Bibliography
• Lebedev, V. S., N. V. Ivanova, N. K. Pavlova, and A. B. Poltoraus. 2003. Molecular phylogeny of the Palearctic hamsters. In Proceedings of the International Conference Devoted to the 90th Anniversary of Prof. I. M. Gromov on Systematics, Phylogeny and Paleontology of Small Mammals (A. Averianov and N. Abramson eds.). St. Petersburg.
• Musser, G. G. and M. D. Carleton. 2005. Superfamily Muroidea. In Mammal Species of the World a Taxonomic and Geographic Reference (D. E. Wilson and D. M. Reeder eds.). Johns Hopkins University Press, Baltimore.
• Neumann, K., J. Michaux, V. Lebedev, N. Yigit, E. Colak, N. Ivanova, A. Poltoraus, A. Surov, G. Markov, S. Maak, S. Neumann, R. Gattermann. 2006. Molecular phylogeny of the Cricetinae subfamily based on the mitochondrial cytochrome b and 12S rRNA genes and the nuclear vWF gene. Molecular Phylogenetics and Evolution, in press

Ferret

Ferret
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This article is about the mammal. For other uses, see Ferret (disambiguation).
Ferret

Conservation status
Domesticated
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Mustelidae
Genus: Mustela
Species: M. putorius
Subspecies: M. p. furo
Trinomial name
Mustela putorius furo
Linnaeus, 1758
Synonyms
Mustela furo Linnaeus, 1758
The ferret is a domesticated mammal of the type Mustela putorius furo. Ferrets are sexually dimorphic predators with males being substantially larger than females. They typically have brown, black, white, or mixed fur. They have an average length of 20 inches (51 cm) including a 5 inch (13 cm) tail, weigh about 1.5–4 pounds (0.7–2 kg), and have a natural lifespan of 7 to 10 years.
Several other small, elongated carnivorous mammals belonging to the family Mustelidae (weasels) also have the word ferret in their common names, including an endangered species, the Black-footed Ferret. The ferret is a very close relative of the polecat, but it is as yet unclear whether it is a domesticated form of the European Polecat, the Steppe Polecat, or some hybrid of the two.
The history of the ferret's domestication is uncertain, like that of most other domestic animals, but it is likely that ferrets have been domesticated for at least 2,500 years. They are still used for hunting rabbits in some parts of the world today, but increasingly they are being kept simply as pets.
Being so closely related to polecats, ferrets are quite easily able to hybridize with them, and this has occasionally resulted in feral colonies of polecat-ferret hybrids that have been perceived to have caused damage to native fauna, perhaps most notably in New Zealand. As a result, some parts of the world have imposed restrictions on the keeping of ferrets.
Biology
[Characteristics
As described by the Oakland Zoo,
Ferrets have a long and slender body covered with brown, black, white, or mixed fur ... Average length is 20 inches including a 5-inch tail. They weigh 1.5 to 4 pounds, with males substantially larger than females ... Gestation is 42 days, litters are usually 3 to 7 young, but sometimes more. Females may have two to three litters annually. Young are weaned after 3 to 6 weeks and become independent at 3 months. Sexual maturity may come at 6 months. Average life span is 8 years.
—Conservation and Education: Oakland Zoo
Behavior
Ferrets are crepuscular, which means Unlike their polecat ancestors, which are solitary animals, most ferrets will live happily in social groups. A group of ferrets is commonly referred to as a "business They are territorial, like to burrow, and prefer to sleep in an enclosed area.
Like many other carnivores, ferrets have scent glands near their anus, the secretions from which are used in scent marking. It has been reported that ferrets can recognize individuals from these anal gland secretions, as well as the sex of unfamiliar individuals Ferrets may also use urine marking for sex and individual recognition.
As with skunks, ferrets can release their anal gland secretions when startled or scared, but the smell is much less potent and dissipates rapidly. Most pet ferrets in the US are sold descented (anal glands removed). In many other parts of the world, including the UK and other European countries, de-scenting is considered an unnecessary mutilation.
When excited, they may perform a routine commonly referred to as the weasel war dance, characterized by a frenzied series of sideways hops and bumping into things. Despite its zeal, this is not aggressive but is a joyful invitation to play. It is often accompanied by a soft clucking noise, commonly referred to as dooking. When agitated or upset, on the other hand, ferrets will make a distinct hissing noise.
Diet
Ferrets are obligate carnivoresThe natural diet of their wild ancestors consisted of whole small prey, i.e., meat, organs, bones, skin, feathers, and fur.
Dentition

Ferrets have four types of teeth (the number includes maxillary (upper) and mandibular (lower) teeth)
• Twelve small teeth (only a couple of millimeters) located between the canines in the front of the mouth. These are known as the incisors and are used for grooming.
• Four canines used for killing prey.
• Twelve premolar teeth that the ferret uses to chew food—located at the sides of the mouth, directly behind the canines. The ferret uses these teeth to cut through flesh, using them in a scissors action to cut the meat into digestible chunks.
• Six molars (two on top and four on the bottom) at the far back of the mouth are used to crush food.
Health
Main article: Ferret health
Ferrets are known to suffer from several distinct health problems. Among the most common are cancers affecting the adrenal glands, pancreas, and lymphatic system? Viral diseases include canine distemper and influenza. Health problems can occur in unsprayed females when not being used for breeding. Certain health problems have also been linked to ferrets being neutered before reaching sexual maturity. Certain colors of ferret may also carry a genetic defect known as Warrensburg syndrome. Similar to domestic cats, ferrets can also suffer from hairballs and dental problems.
History of domestication


Women hunting rabbits with a ferret in the Queen Mary Psalter
In common with most domestic animals, the original reason for ferrets' being domesticated by human beings is uncertain, but it may have involved hunting. It was most likely domesticated from the European polecat (Mustela putorius), although it is also possible that ferrets are descendants of the Steppe polecat (Mustela eversmannii), or some hybridization thereof. Analysis of mitochondrial DNA suggests that ferrets were domesticated around 2,500 years ago, although what appear to be ferret remains have been dated to 1500 BC. It has been claimed that the ancient Egyptians were the first to domesticate ferrets, but as no mummified remains of a ferret have yet been found, or any hieroglyph of a ferret, and no polecat now occurs wild in the area, that idea seems unlikely
The Greek word ictis occurs in a play written by Aristophanes, The Acharnians, in 425 BC. Whether this was a reference to ferrets, polecats, or the similar Egyptian Mongoose is uncertain. The name "ferret" is derived from the Latin furittus, meaning "little thief", a likely reference to the common ferret penchant for secreting away small items Ferrets were probably used by the Romans for hunting.
Colonies of feral ferrets have established themselves in areas where there is no competition from similarly sized predators, such as in the Shetland Islands and in remote regions in New Zealand. Where ferrets coexist with polecats, hybridization is common. It has been claimed that New Zealand has the world's largest feral population of ferret-polecat hybrids. In 1877, farmers in New Zealand demanded that ferrets be introduced into the country to control the rabbit population, which was also introduced by humans. Five ferrets were imported in 1879, and in 1882–1883, 32 shipments of ferrets were made from London, totaling 1,217 animals. Only 678 landed, and 198 were sent from Melbourne, Australia. On the voyage, the ferrets were mated with the European polecat, creating a number of hybrids that were capable of surviving in the wild. In 1884 and 1886, close to 4,000 ferrets and ferret hybrids, 3,099 weasels and 137 stoats were turned loose Concern was raised that these animals would eventually prey on indigenous wildlife once rabbit populations dropped, and this is exactly what happened to New Zealand bird species which previously had no mammalian predators.
Ferreting
Main article: Rabbiting


Muzzled ferret flushing a rat, as illustrating in Harding's Ferret Facts and Fancies (1915)
For millennia, the main use of ferrets was for hunting, or ferreting. With their long, lean build, and inquisitive nature, ferrets are very well equipped for getting down holes and chasing rodents, rabbits and moles out of their burrows. Caesar Augustus sent ferrets or mongooses (named "viverrae" by Plinius) to the Balearic Islands to control the rabbit plagues in 6 BC They are still used for hunting in some countries, including the United Kingdom, where rabbits are considered a plague species by farmers. The practice is illegal in several countries where it is feared that ferrets could unbalance the ecology. In 2009 in Finland, where ferreting was previously unknown, the city of Helsinki began to use ferrets to restrict the city's rabbit population to a manageable level. Ferreting was chosen because in populated areas it is considered to be safer and less ecologically damaging than shooting the rabbits.
In England, in 1390, a law was enacted restricting the use of ferrets for hunting to the relatively wealthy:
it is ordained that no manner of layman which hath not lands to the value of forty shillings a year shall from henceforth keep any greyhound or other dog to hunt, nor shall he use ferrets, nets, heys, harepipes nor cords, nor other engines for to take or destroy deer, hares, nor conies, nor other gentlemen's game, under pain of twelve months' imprisonment.
Ferrets were first introduced into the New World in the 17th century, and were used extensively from 1860 until the start of World War II to protect grain stores in the American West from rodents.
Ferrets as pets


A ferret in a war dance jump.
In the United States, ferrets were relatively rare pets until the 1980s. A government study by the California State Bird and Mammal Conservation Program estimated that by 1996 about 800,000 domestic ferrets were being kept as pets in the United States.
Other uses of ferrets
Ferrets are an important experimental animal model for human influenzaand have been used to study the 2009 H1N1 (swine flu) virus. Smith, Andrews, Laidlaw (1933) inoculated ferrets intra-nasally with human naso-pharyngeal washes, which produced a form of influenza that spread to other cage mates. The human influenza virus (Influenza type A) was transmitted from an infected ferret to a junior investigator, from whom it was subsequently re-isolated.
• Ferrets have been used in many broad areas of research, such as the study of pathogenesis and treatment in a variety of human disease, these including studies into cardiovascular disease, nutrition, respiratory diseases such as SARS and human influenza, airway physiologycystic fibrosis and gastrointestinal disease.
• Because they share many anatomical and physiological features with humans, ferrets are extensively used as experimental subjects in biomedical research, in fields such as virology, reproductive physiology, anatomy, endocrinology, and neuroscience
Terminology and coloring


Typical ferret coloration, known as a sable or polecat-colored ferret
Male ferrets are called hobs; female ferrets are jills. A spayed female is a sprite, a neutered male is a gib, and a vasectomised male is known as a hoblet. Ferrets under one year old are known as kits. A group of ferrets is known as a "business"[citation needed], or historically as a "fesnyng".
Most ferrets are either albinos, with white fur and pink eyes, or display the typical dark masked Sable coloration of their wild polecat ancestors. In recent years fancy breeders have produced a wide variety of colors and patterns. Color refers to the color of the ferret's guard hairs, undercoat, eyes, and nose; pattern refers to the concentration and distribution of color on the body, mask, and nose, as well as white markings on the head or feet when present. Some national organizations, such as the American Ferret Association, have attempted to classify these variations in their showing standard
There are four basic colors. The Sable (including chocolate and dark), Albino, Dark Eyed White (DEW), and the silver. All the other colors of a ferret are variations on one of these four categories.
Waardenburg-like coloring
Ferrets with a white stripe on their face or a fully white head, primarily blazes, badgers, and pandas, almost certainly carry a congenital defect which shares some similarities to Waardenburg syndrome. This causes, among other things, a cranial deformation in the womb which broadens the skull, white face markings, and also partial or total deafness. It is estimated as many as 75 percent of ferrets with these Waardenburg-like colorings are deaf.
White ferrets were favored in the Middle Ages for the ease in seeing them in thick undergrowth. Leonardo da Vinci's painting Lady with an Ermine is likely mislabelled; the animal is probably a ferret, not a stoat, (for which "ermine" is an alternative name for the animal in its white winter coat). Similarly, the Ermine portrait of Queen Elizabeth the First shows her with her pet ferret, which has been decorated with painted-on heraldic ermine spots.
"The Ferreter's Tapestry" is a 15th-century tapestry from Burgundy, France, now part of the Burrell Collection housed in the Glasgow Museum and Art Galleries. It shows a group of peasants hunting rabbits with nets and white ferrets. This image was reproduced in Renaissance Dress In Italy 1400–1500, by Jacqueline Herald, Bell & Hyman – ISBN 0-391-02362-4.
Gaston Phoebus' Book Of The Hunt was written in approximately 1389 to explain how to hunt different kinds of animals, including how to use ferrets to hunt rabbits. Illustrations show how multicolored ferrets that were fitted with muzzles were used to chase rabbits out of their warrens and into waiting nets.
Regulation of ferrets as pets
• Australia – It is illegal to keep ferrets as pets in Queensland or the Northern Territory; in the ACT a licence is required.
• Brazil – They are allowed only if they are given a microchip identification tag and sterilized.
• New Zealand – It has been illegal to sell, distribute or breed ferrets in New Zealand since 2002 unless certain conditions are met.
• Portugal – It is illegal to keep ferrets as pets in Portugal.[citation needed] Ferrets can be used for hunting purposes only and can be kept only with a government permit.
• United States – Ferrets were once banned in many US states, but most of these laws were rescinded in the 1980s and '90s as they became popular pets. Ferrets are still illegal in California under Fish and Game Code Section 2118and the California Code of Regulations, although it is not illegal for veterinarians in the state to treat ferrets kept as pets. In November 1995, ferret proponents asked the California Fish and Game Commission to remove the domesticated ferret from the restrictive wildlife list. Additionally, "Ferrets are strictly prohibited as pets under Hawaii law because they are potential carriers of the rabies virus"; the territory of Puerto Rico has a similar law Ferrets are restricted by individual cities, such as Washington, DC, and New York City They are also prohibited on many military basesA permit to own a ferret is needed in other areas, including Rhode Island. Illinois and Georgia do not require a permit to merely possess a ferret, but a permit is required to breed ferretsIt was once illegal to own ferrets in Dallas, Texas, but the current Dallas City Code for Animals includes regulations for the vaccination of ferrets Pet ferrets are legal in Wisconsin, but an import permit from the state department of agriculture is required to bring one into the state.
• Japan – In Hokkaido prefecture, ferrets must be registered with local government In other prefectures, no restrictions apply.
Import restrictions
Australia
Ferrets cannot be imported into Australia. A report drafted in August 2000 seems to be the only effort made to date to change the situation.
Canada
Ferrets brought from anywhere except the US require a Permit to Import from the Canadian Food Inspection Agency Animal Health Office. Ferrets from the US require only a vaccination certificate signed by a veterinarian. Ferrets under three months old are not subject to any import restrictions
European Union
As of July 2004, dogs, cats, and ferrets can travel freely within the European Union under the Pet passport scheme. To cross a border within the EU, ferrets require at minimum an EU PETS passport and an identification microchip (though some countries will accept a tattoo instead). Vaccinations are required; most countries require a rabies vaccine, and some require a distemper vaccine and treatment for ticks and fleas 24 to 48 hours before entry. Ferrets occasionally need to be quarantined before entering the country. PETS travel information is available from any EU veterinarian or on government websites.
United Kingdom
The UK accepts ferrets under the EU's PETS travel scheme. Ferrets must be microchipped, vaccinated against rabies, and documented. They must be treated for ticks and tapeworms 24 to 48 hours before entry. They must also arrive via an authorized route. Ferrets arriving from outside the EU may be subject to a six-month quarantine

9. Iguanas

The history of iguanas as pets


Iguanas can make phenomenal pets. While you won't be required to give them long walks outside and potty training will not be an issue that gets you out of bed at 3 a.m., nevertheless there is a host of other concerns pertaining specifically to caring for iguanas responsibly.

The three major care areas are going to be food, shelter, and taking care of their physical needs. With proper, attentive care, your iguana may even live up to 20 years.

Once you purchase your pet iguana from the pet store, you will need some supplies, which will be listed below in the care directions.

The housing situation. Most iguanas live out their happy lives in a terrarium. When purchasing a terrarium for your pet you should make sure that it will be big enough to give your iguana room to move and comfortably fit any supplies that need to be placed in the cage with him. You would not want to sit in a small confined space for the remainder of your life, so do not assume that your iguana wants this kind of treatment either. Bear in mind that your iguana will grow. You need to place things on the floor of the terrarium to cover the bottom of the glass. Whatever you place down there will have to be washed or replaced on a regular basis. Iguana feces should be removed daily. Make sure that, whatever you choose to place on the floor of the terrarium, it cannot be eaten by your iguana.

Let the sun shine in.Iguanas love the sunlight, so you are going to want to make sure that you do not deprive your new family friend. One of an iguana's favorite activities is to climb on logs and enjoy the shining sun. If your tank is not in an area with lots of sunlight, you may want to move it. If moving it is not an option, you can purchase an artificial light source from the pet store. Talk to your vet about purchasing an artificial UV light anyway, since iguanas benefit from exposure to ultraviolet B. You can also purchase logs and wood for your iguana to climb on.

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For other members of the family Iguanidae, see Iguanidae. For other uses, see Iguana (disambiguation).
Iguana

Green Iguana Iguana iguana
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Sauropsida
Order: Squamata
Suborder: Iguania
Family: Iguanidae
Genus: Iguana
Laurenti, 1768
Species
• Lesser Antillean Iguana, I. delicatissima
• Green Iguana, I. iguana
Iguana is a herbivorous genus of lizard native to tropical areas of Central and South America and the Caribbean. The genus was first described in 1768 by Austrian naturalist Josephus Nicolaus Laurenti in his book Specimen Medicum, Exhibens Synopsin Reptilium Emendatam cum Experimentis circa Venena. Two species are included in the genus Iguana: the Green Iguana, which is widespread throughout its range and a popular pet, and the Lesser Antillean Iguana, which is endemic to the Lesser Antilles and endangered due to habitat destruction.
The word "iguana" is derived from a Spanish form of the original Taino name for the species "Iwana
Contents
[hide]
• 1 Anatomy and physiology
• 2 Gallery
• 3 References
• 4 Bibliography
Anatomy and physiology
The two species of lizard within the genus Iguana possess a dewlap, a row of spines running down their back to their tail, and a third "eye" on their head. This eye is known as the parietal eye, visible as a pale scale on the top of the head. Behind their neck are small scales which resemble spikes, known as tuberculate scales. These scales may be a variety of colors and are not always visible from close distances. They have a large round scale on their cheek known as a subtympanic shield.
Iguanas have excellent vision and can see shapes, shadows, colors and movement at long distances. Iguanas use their eyes to navigate through crowded forests, as well as for finding food. They use visual signals to communicate with other members of the same species.
The tympanum is the iguana's ear drum, and is located above the subtympanic shield and behind the eye. Iguanas are often hard to spot, as they tend to blend into their surroundings. Their scale colors are a mode of hiding from larger predators.
Male iguanas, as well as other male members of the order Squamata, have two hemipenes.
Gallery
•

Green iguana at St. Thomas
•
Another green iguana (Iguana iguana)
•
Green Iguana Iguana iguana from the island of St. Thomas
•
A lesser Antillean iguana in the wild in Dominica.
•
Cayman Iguana
•
Photo taken at La Manzanilla, Jalisco, Mexico at an environmental reserve.

Care and Feeding of Iguanas
March 19, 2011 By Christine Hancock 129 Comments
Iguanas are one of the most popular reptiles purchased from pet shops today. This animal can grow anywhere from 4-6 feet in length, reaching a maximum weight of 10-15 pounds. On average, they live 12-15 years in captivity, however they can live up to 20 years if taken care of properly. Iguanas come from a hot and humid environment, therefore, they are more active during daylight hours. They can become territorial and will not hesitate to use their strong and powerful jaws, nails, or tail.
Indoor Housing
A juvenile iguana can reside in a 30-50 gallon aquarium; however, their rapid growth will cause them to outgrow this enclosure within a few months. Enclosures come in many different sizes, shapes, and styles and are made out of wood, glass, or plexiglass. The substrate should be easy to clean to help you out. Newspaper works well and is most cost efficient, however, artificial grass, indoor-outdoor carpeting, or linoleum are excellent choices as well. Avoid sand, soil, and bark, as these substrates can lead to obstruction or impaction if your pet ingests them. Shallow food and water dishes should be provided, and thoroughly cleaned and disinfected at least twice a week. It is also important to provide your iguana with climbing materials such as branches, pieces of bark, rocks, broad limbs, or drift wood.
Water
Iguanas need water to survive and should have it readily available. Iguanas obtain most of their water intake through the plant matter they consume, however, some iguanas enjoy drinking out of water dishes, or lapping water off leaves or wood in the cage. Misting your iguana and it’s environment daily will help keep it hydrated and provide it water droplets to drink. Some iguanas who are provided water dishes may train themselves to eliminate in their water. Their dishes need to be regularly and thoroughly cleaned and disinfected to prevent internal bacterial infections.
Bathing your iguana is another good way for your friend to obtain water, and is a good habit to get your lizard use to. Bathing should be offered in shallow, lukewarm water, 2-3 times weekly. Always supervise your iguana to prevent any accidents. Remember, not all iguanas enjoy bath time. Some will swim around and enjoy it, others will panic.
Outdoor Sunlight
Iguanas need to be provided with exposure to natural sunlight for at least 5-10 hours per week. When possible, iguanas should spend daylight hours outside in a sunny location. When choosing an outdoor cage for your pet, a couple of things should be kept in mind. No wild animals, or cats or dogs, should be able to break into the cage, and your pet should not be able to escape. A wire mesh cage with a sturdy frame works well. Glass should be avoided at all costs as the glass can develop lethal temperatures even on cool days. Of course, don’t forget to provide food and water to your little friend in it’s outdoor enclosure.
Handling
Iguanas need frequent and regular handling to help tame them. Iguanas can learn to show affection to those who own them and handle them frequently. Juveniles should be held at least 2-3 times daily for approximately fifteen minutes. Stroke the back and neck while holding, and get your iguana accustomed to picking them up and handling them. IGUANAS CAN BE TERRITORIAL AND AGGRESSIVE BY NATURE. ALWAYS USE EXTREME CAUTION WHEN HANDLING ANY IGUANA.
Feeding
Iguanas are herbivores and should only be offered a variety of fruits and vegetables. There is ample information available that states iguanas should be fed protein, however, protein in the diet can lead to kidney failure, metabolic bone disease, and eventually death if fed over the years. The bulk of the diet should be compromised of dark, leafy green vegetables, such as, collard greens, mustard greens, parsley, dandelion greens, escarole, spinach, and kale. Iceberg lettuce should be avoided as it offers no nutritional value and iguanas can become hooked on it, refusing to eat other foods. Other vegetables that are good to offer include green beans, green peppers, frozen mixed vegetables, squash, and fruits, such as, bananas, apples, mangos, papaya. Iguanas should be fed on a daily basis, after their lights have been turned on and the iguana has had a chance to warm up.
Lighting and Heating
Temperature plays an important role to your iguana’s long term and overall health. Iguanas are cold blooded and do not possess the ability to regulate internal temperatures, so they rely on their environment. Iguanas regulate their body temperature by basking in temperatures above 85 degrees, sometimes as high as 100 degrees Fahrenheit. Daytime temperatures should range between 85-95 degrees with a basking point of 110-115 degrees. Nighttime temperatures should not drop below 70-75 degrees. Iguanas should be provided fourteen hours of daylight, and ten hours of night light.
So how do I achieve these heat requirements? There are many products on the market today. The simplest is a basking light. A 60-100 watt incandescent bulb is a radiant source of heat, and is adequate since they are basking animals. An Ultraviolet light, such as Vita-Lite or Duro-Test, available at your local pet store, helps provide heat and aids in the conversion of vitamin D. A UVB fluorescent tube light can also be provided. Heat pads, hot rocks, and heating tape are sold at most pet shops, however, observe extreme caution when using these products. These products have potential to malfunction, causing extreme burns to your iguana, that can potentially prove fatal. Also, these products don’t provide the adequate heat necessary for the required temperature for your iguana.
Common Problems
Metabolic Bone Disease (MBD)
Metabolic bone disease describes most disorders that cause a weakening of the bones or impaired functioning of the body’s organs. It is caused by an imbalance of calcium, phosphorous, and vitamin D3. Proper diet and temperature ranges will help prevent MBD. Symptoms of this disease include swelling of the lower jaw, curvature in the tail or back (‘S’ shaped), the lower jaw may be smaller than the upper jaw, and radiographs will show thin, brittle, curved bone structure. Metabolic bone disease is best avoided with proper diet and correct temperature ranges in the iguanas environment
Kidney Failure
Kidney disease is common in captive iguanas due to poor diet and lack of water or humidity. External signs are anorexia, weight loss, swollen abdomen, dehydration, loss of muscle tone, and eventually lack of elimination. However, your iguana may not show any signs, and act healthy even two weeks before kidney disease turns fatal. Your veterinarian can check blood levels of the phosphorous and calcium in your iguana to try to prevent kidney failure. If caught early enough, treatment would consist of diet and environment improvements. Fed properly on a plant-based diet, access to water and frequent misting helps prevent kidney failure.
Parasites
Iguanas are susceptible to both internal and external parasites. A parasite is an organism that lives in or on another organism. Internal parasites are more difficult to diagnose. They produce microscopic eggs which pass through your iguanas feces. Fecal exams should be performed routinely for newly acquired reptiles. The specimen provided should be fresh, within 24 hours, and needs to be refrigerated to prevent fecal matter from drying out. A negative finding on a fecal exam means, NO PARASITES DETECTED IN THE SAMPLE SUBMITTED. It does not necessarily mean your reptile is free of parasites. It is a good idea to test a few times with negative results in order to ensure your iguana is without parasites.
External Parasites
Mites are blood sucking organisms that may be bright red, black or dried blood in color. Generally they can be found roaming the body, tucked under the edges of scale around the eyes, ears, or tympanic membrane. Mites are microscopically small in most cases and can be difficult to get rid of. Mite treatments sold at pet shops are generally ineffective. There is no easy way to rid mites of your reptile and its environment. The environment and reptile both must be thoroughly treated. Remove all substrate and treat all items in the enclosure. Boil rocks, bake wood, and bleach bowls and the cage. The reptile must be soaked in warm water with mild soap. Any further problems should be reported to your veterinarian.

Dolphin

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For other uses, see Dolphin (disambiguation).


Bottlenose dolphin breaching in the bow wave of a boat
Dolphins are marine mammals that are closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from 1.2 m (4 ft) and 40 kg (90 lb) (Maui's dolphin), up to 9.5 m (30 ft) and 10 tonnes (9.8 long tons; 11 short tons) (the orca or killer whale). They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, mostly eating fish and squid. The family Delphinidae is the largest in the Cetacean order, and evolved relatively recently, about ten million years ago, during the Miocene. Dolphins are among the most intelligent animals, and their often friendly appearance and seemingly playful attitude have made them popular in human culture.
Etymology
The name is originally from Greek δελφίς (delphís), "dolphin", which was related to the Greek δελφύς (delphus), "womb" The animal's name can therefore be interpreted as meaning "a 'fish' with a womb". The name was transmitted via the Latin delphinus (the romanization of the later Greek δελφῖνος - delphinoswhich in Middle Latin became dolfinus and in Old French daulphin, which reintroduced the ph into the word. The term mereswine (that is, sea pork) has also historically been used.
The word is used in a few different ways. It can mean:
• any member of the family Delphinidae (oceanic dolphins),
• any member of the families Delphinidae and Platanistoidea (oceanic and river dolphins),
• any member of the suborder Odontoceti (toothed whales; these include the above families and some others),
• and is used casually as a synonym for bottlenose dolphin, the most common and familiar species of dolphin.
This article uses the second definition and does not describe porpoises (suborder Odontoceti, family Phocoenidae). Orcas and some closely related species belong to the Delphinidae family and therefore qualify as dolphins, even though they are called whales in common language. A group of dolphins is called a "school" or a "pod". Male dolphins are called "bulls", females "cows" and young dolphins are called "calves
Taxonomy


Common dolphin


Bottlenose dolphin


Spotted Dolphin


Commerson's Dolphin


Dusky Dolphin


Killer Whales, also known as Orcas

Hybridization
In 1933, three strange dolphins beached off the Irish coast; they appeared to be hybrids between Risso's and bottlenose dolphins. This mating was later repeated in captivity, producing a hybrid calf. In captivity, a bottlenose and a rough-toothed dolphin produced hybrid offspring. A common-bottlenose hybrid lives at SeaWorld California. Other dolphin hybrids live in captivity around the world or have been reported in the wild, such as a bottlenose-Atlantic spotted hybrid. The best known hybrid is the wolphin, a false killer whale-bottlenose dolphin hybrid. The wolphin is a fertile hybrid. Two wolphins currently live at the Sea Life Park in Hawaii; the first was born in 1985 from a male false killer whale and a female bottlenose. Wolphins have also been observed in the wild.
Evolution and anatomy


The anatomy of a dolphin, showing its skeleton, major organs, tail, and body shape


Pacific white-sided dolphin skeleton (missing pelvic bones), on exhibit at The Museum of Osteology, Oklahoma City, Oklahoma
Evolution
See also: Evolution of cetaceans.
Dolphins, along with whales and porpoises, are descendants of terrestrial mammals, most likely of the Artiodactyl order. The ancestors of the modern day dolphins entered the water roughly 50 million years ago, in the Eocene epoch.


Hind limb buds are apparent on an embryo of a spotted dolphin in the fifth week of development as small bumps (hind limb buds) near the base of the tail. The pin is approximately 2.5 cm (1.0 in) long.
Modern dolphin skeletons have two small, rod-shaped pelvic bones thought to be vestigial hind limbs. In October 2006, an unusual bottlenose dolphin was captured in Japan; it had small fins on each side of its genital slit, which scientists believe to be a more pronounced development of these vestigial hind limbs.
Anatomy
Dolphins have a streamlined fusiform body, adapted for fast swimming. The tail fin, called the fluke, is used for propulsion, while the pectoral fins together with the entire tail section provide directional control. The dorsal fin, in those species that have one, provides stability while swimming. Though it varies by species, basic coloration patterns are shades of grey, usually with a lighter underside, often with lines and patches of different hue and contrast.
The head contains the melon, a round organ used for echolocation. In many species, elongated jaws form a distinct beak; species such as the bottlenose have a curved mouth which looks like a fixed smile. Some species have up to 250 teeth. Dolphins breathe through a blowhole on top of their head. The trachea is anterior to the brain. The dolphin brain is large and highly complex, and is different in structure from that of most land mammals.
Unlike most mammals, dolphins do not have hair, except for a few hairs around the tip of their rostrum which they lose shortly before or after birth. The only exception to this is the Boto river dolphin, which has persistent small hairs on the rostrum.
Dolphins' reproductive organs are located on the underside of the body. Males have two slits, one concealing the penis and one further behind for the anus. The female has one genital slit, housing the vagina and the anus. Two mammary slits are positioned on either side of the female's genital slit.
Though the exact methods used to achieve this are not known, dolphins can tolerate and recover from extreme injuries, such as shark bites. The healing process is rapid and even very deep wounds do not cause dolphins to hemorrhage to death. Furthermore, even gaping wounds restore in such a way that the animal's body contour is restored, and infection of such large wounds seems rare.
A study at the U.S. National Marine Mammal Foundation revealed that dolphins, like humans, develop a natural form of type 2 diabetes, which may lead to a better understanding of the disease and new treatments for both humans and dolphins.
Senses
Most dolphins have acute eyesight, both in and out of the water, and they can hear frequencies ten times or more above the upper limit of adult human hearing though they have a small ear opening on each side of their head, it is believed hearing underwater is also, if not exclusively, done with the lower jaw, which conducts sound to the middle ear via a fat-filled cavity in the lower jaw bone. Hearing is also used for echolocation, which all dolphins have. Dolphin teeth are believed to function as antennae to receive incoming sound and to pinpoint the exact location of an object. The dolphin's sense of touch is also well-developed, with free nerve endings densely packed in the skin, especially around the snout, pectoral fins and genital area. However, dolphins lack an olfactory nerve and lobes, and thus are believed to have no sense of smell. They do have a sense of taste and show preferences for certain kinds of fish. Since dolphins spend most of their time below the surface, tasting the water could function like smelling, in that substances in the water can signal the presence of objects that are not in the dolphin’s mouth.
Though most dolphins do not have hair, they do have hair follicles that may perform some sensory function. The small hairs on the rostrum of the Boto river dolphin are believed to function as a tactile sense possibly to compensate for the Boto's poor eyesight.
Behavior


A pod of Indo-Pacific bottlenose dolphins in the Red Sea.
See also: Whale surfacing behaviour .
Dolphins are often regarded as one of Earth's most intelligent animals, though it is hard to say just how intelligent. Comparing species' relative intelligence is complicated by differences in sensory apparatus, response modes, and nature of cognition. Furthermore, the difficulty and expense of experimental work with large aquatic animals has so far prevented some tests and limited sample size and rigor in others. Compared to many other species, however, dolphin behavior has been studied extensively, both in captivity and in the wild. See cetacean intelligence for more details.
Social behavior


Dolphins surfing at Snapper Rocks, Queensland, Australia
Dolphins are social, living in pods of up to a dozen individuals. In places with a high abundance of food, pods can merge temporarily, forming a superpod; such groupings may exceed 1,000 dolphins. Individuals communicate using a variety of clicks, whistles and other vocalizations. They make ultrasonic sounds for echolocation. Membership in pods is not rigid; interchange is common. However, dolphins can establish strong social bonds; they will stay with injured or ill individuals, even helping them to breathe by bringing them to the surface if neededThis altruism does not appear to be limited to their own species however. The dolphin Moko in New Zealand has been observed guiding a female Pygmy Sperm Whale together with her calf out of shallow water where they had stranded several times. They have also been seen protecting swimmers from sharks by swimming circles around the swimmers[25][26] or charging the sharks to make them go away.
Dolphins also display culture, something long believed to be unique to humans (and possibly other primate species). In May 2005, a discovery in Australia found Indo-Pacific bottlenose dolphins (Tursiops aduncus) teaching their young to use tools. They cover their snouts with sponges to protect them while foraging. This knowledge is mostly transferred by mothers to daughters, unlike simian primates, where knowledge is generally passed on to both sexes. Using sponges as mouth protection is a learned behavior. Another learned behavior was discovered among river dolphins in Brazil, where some male dolphins use weeds and sticks as part of a sexual display
Dolphins engage in acts of aggression towards each other. The older a male dolphin is, the more likely his body is to be covered with bite scars. Male dolphins engage in such acts of aggression apparently for the same reasons as humans: disputes between companions and competition for females. Acts of aggression can become so intense that targeted dolphins sometimes go into exile as a result of losing a fight.
Male bottlenose dolphins have been known to engage in infanticide. Dolphins have also been known to kill porpoises for reasons which are not fully understood, as porpoises generally do not share the same diet as dolphins, and are therefore not competitors for food supplies
Reproduction and sexuality
Dolphin copulation happens belly to belly; though many species engage in lengthy foreplay, the actual act is usually brief, but may be repeated several times within a short timespan. The gestation period varies with species; for the small Tucuxi dolphin, this period is around 11 to 12 months, while for the orca, the gestation period is around 17 months. They usually become sexually active at a young age, even before reaching sexual maturity. The age of sexual maturity varies by species and gender.
Dolphins are known to have sex for reasons other than reproduction[citation needed], sometimes also engaging in homosexual behavior. Various species sometimes engage in sexual behavior including copulation with other dolphin species. Sexual encounters may be violent, with male dolphins sometimes showing aggressive behavior towards both females and other males. Occasionally, dolphins behave sexually towards other animals, including humans.
Feeding
Various methods of feeding exist among and within species, some apparently exclusive to a single population. Fish and squid are the main food, but the false killer whale and the orca also feed on other marine mammals.
One common feeding method is herding, where a pod squeezes a school of fish into a small volume, known as a bait ball. Individual members then take turns plowing through the ball, feeding on the stunned fish. Coralling is a method where dolphins chase fish into shallow water to more easily catch them. In South Carolina, the Atlantic bottlenose dolphin takes this further with "strand feeding", driving prey onto mud banks for easy access. In some places, orcas come to the beach to capture sea lions. Some species also whack fish with their flukes, stunning them and sometimes knocking them out of the water.
Reports of cooperative human-dolphin fishing date back to the ancient Roman author and natural philosopher Pliny the Elder.[34] A modern human-dolphin partnership currently operates in Laguna, Santa Catarina, Brazil. Here, dolphins drive fish towards fishermen waiting along the shore and signal the men to cast their nets. The dolphins’ reward is the fish that escape the nets.
Vocalizations


Spectrogram of dolphin vocalizations. Whistles, whines, and clicks are visible as upside down V's, horizontal striations, and vertical lines, respectively.
Dolphins are capable of making a broad range of sounds using nasal airsacs located just below the blowhole. Roughly three categories of sounds can be identified: frequency modulated whistles, burst-pulsed sounds and clicks. Dolphins communicate with their whistles and burst-pulsed sounds, though the nature and extent of that ability is not known. At least some dolphin species can identify themselves using a signature whistle. The clicks are directional and are for echolocation, often occurring in a short series called a click train. The click rate increases when approaching an object of interest. Dolphin echolocation clicks are amongst the loudest sounds made by marine animals.
Jumping and playing


Pacific white-sided dolphins breaching
Dolphins occasionally leap above the water surface, and sometimes perform acrobatic figures (for example, the spinner dolphin). Scientists are not certain about the purpose(s) of the acrobatics. Possibilities include locating schools of fish by looking at above-water signs like feeding birds, communicating with other dolphins, dislodging parasites or simple amusement.
Play is an important part of dolphin culture. Dolphins play with seaweed and play-fight with other dolphins. At times they harass other local creatures, like seabirds and turtles. Dolphins enjoy riding waves and frequently surf coastal swells and the bow waves of boats, at times “leaping” between the dual bow waves of a moving catamaran. Occasionally, they playfully interact with swimmers. Captive dolphins have been observed in aquariums engaging in complex play behavior which involves the creation and manipulation of bubble rings.[39][40][41][42]
Sleeping


Generally, dolphins sleep with only one brain hemisphere in slow-wave sleep at a time, thus maintaining enough consciousness to breathe and to watch for possible predators and other threats. Earlier sleep stages can occur simultaneously in both hemispheres.[43][44][45] In captivity, dolphins seemingly enter a fully asleep state where both eyes are closed and there is no response to mild external stimuli. In this case respiration is automatic; a tail kick reflex keeps the blowhole above the water if necessary. Anesthetized dolphins initially show a tail kick reflex. Though a similar state has been observed with wild Sperm Whales, it is not known if dolphins in the wild reach this state. The Indus river dolphin has a different sleep method from other dolphin species. Living in water with strong currents and potentially dangerous floating debris, it must swim continuously to avoid injury. As a result, this species sleeps in very short bursts which last between 4 and 60 seconds.
Threats
Natural threats
Except for humans (discussed below), dolphins have few natural enemies. Some species or specific populations have none, making them apex predators. For most of the smaller species of dolphins, only a few of the larger sharks, such as the bull shark, dusky shark, tiger shark and great white shark are a potential risk, especially for calves. Some of the larger dolphinic species, especially orcas (killer whales), may also prey smaller dolphins, but this seems rare. Dolphins also suffer from a wide variety of diseases and parasites.[citation needed]
Human threats
See also: Dolphin drive hunting and Cetacean bycatch.


Dead Atlantic white-sided dolphins in Hvalba on the Faroe Islands, killed in a drive hunt
Some dolphin species face an uncertain future, especially some river dolphin species such as the Amazon river dolphin, and the Ganges and Yangtze river dolphin, which are critically or seriously endangered. A 2006 survey found no individuals of the Yangtze river dolphin, which now appears to be functionally extinct.
Pesticides, heavy metals, plastics, and other industrial and agricultural pollutants that do not disintegrate rapidly in the environment concentrate in predators such as dolphins. Injuries or deaths due to collisions with boats, especially their propellers, are also common.
Various fishing methods, most notably purse seine fishing for tuna and the use of drift and gill nets, unintentionally kill many dolphins. Accidental by-catch in gill nets and incidental captures in antipredator nets that protect marine fish farms are common and pose a risk for mainly local dolphin populations.[52][53] In some parts of the world, such as Taiji in Japan and the Faroe Islands, dolphins are traditionally considered as food, and are killed in harpoon or drive hunts. Dolphin meat is high in mercury, and may thus pose a health danger to humans when consumed.
Dolphin safe labels attempt to reassure consumers fish and other marine products have been caught in a dolphin-friendly way. The original deal with "Dolphin safe" labels was brokered in the 1980s between marine activists and the major tuna companies, and involved decreasing incidental dolphin kills by up to 50% by changing the type of nets being used to catch the tuna. It should be noted that the dolphins are only netted while fishermen are in pursuit of smaller tuna. Albacore are not netted this way, which makes albacore the only truly dolphin-safe tuna.
Loud underwater noises, such as those resulting from naval sonar use, live firing exercises, or certain offshore construction projects, such as wind farms, may be harmful to dolphins, increasing stress, damaging hearing, and causing decompression sickness by forcing them to surface too quickly to escape the noise.
Relationships with humans
Mythology


Fresco of Dolphins, ca. 1600 BC, from Knossos, Crete.


A sketch of the goddess Ganga on her Vahana (mount) Makara.
See also: Dolphins in mythology.
Dolphins have long played a role in human culture. Dolphins are common in Greek mythology and there are many coins from ancient Greece which feature a man or boy or deity riding on the back of a dolphin. The Ancient Greeks welcomed dolphins; spotting dolphins riding in a ship’s wake was considered a good omen. In Hindu mythology, the Ganges River Dolphin is associated with Ganga, the deity of the Ganges river.
Popular culture
In more recent times, the 1963 film Flipper and the subsequent 1964 television series popularized dolphins in Western society. The series, created by Ivan Tors, portrayed a dolphin as a kind of seagoing version of Lassie, the collie made popular in the 1950s TV series. Flipper was a Bottlenose Dolphin who understood commands and always behaved heroically. Flipper was remade as a film in 1996.
The 1973 movie The Day of the Dolphin portrayed kidnapped dolphins performing a naval military assassination using explosives. This was also explored in the similarly named The Simpsons Treehouse of Horror episode, "Night of the Dolphin", where Lisa frees a dolphin at a aquarium exhibit and unwittingly initiates their plan to overthrow the land-dwellers and live in their place. The 1990s science fiction television series seaQuest DSV featured a bottle-nose named Darwin who could communicate using a vocoder, a fictional invention which translated clicks and whistles to English and back.
In The Hitchhiker's Guide to the Galaxy book series, dolphins are the second most intelligent species on Earth (after mice).
Killer whales have also been portrayed in film, though to a lesser extent than bottlenosed dolphins. The 1977 horror movie Orca portrayed killer whales as intelligent and capable of pair-bonding and aggressive behavior. In the movie, a male killer whale takes revenge on fishermen after they kill his mate. The 1993 movie Free Willy made a star of the Orca playing Willy, Keiko.
Dolphinaria
See also: Dolphinarium.
The renewed popularity of dolphins in the 1960s resulted in the appearance of many dolphinaria around the world, making dolphins accessible to the public. Criticism and animal welfare laws forced many to close, although hundreds still exist around the world. In the United States, the best known are the SeaWorld marine mammal parks.
Welfare
Organizations such as the Mote Marine Laboratory rescue and rehabilitate sick, wounded, stranded or orphaned dolphins, while others, such as the Whale and Dolphin Conservation Society and Hong Kong Dolphin Conservation Society, work on dolphin conservation and welfare. India has declared the Dolphin as their national aquatic animal in an attempt to protect the endangered Ganges River Dolphin. The Vikramshila Gangetic Dolphin Sanctuary has been created in the Ganges river for the protection of the animals.
Various scientists to have researched Dolphin behaviour have proposed that their unusually high intelligence compared to other animals means that dolphins should be seen as non-human persons that should have their own specific rights, and that it is morally unacceptable to keep them captive for entertainment purposes, or to kill them; either intentionally for consumption or as by-catch.
Attack on humans


Tilikum at SeaWorld. In 2010 he attacked and killed his trainer Dawn Brancheau, in his third fatal incident.
Although dolphins generally interact well with humans, some attacks have occurred, most of them with small injuries. The attacks can occur both in the wild and captivity.
Orcas, the largest species of dolphin, have been involved in fatal attacks on humans in captivity. The record-holder of documented orca fatal attacks is a male named Tilikum, that belongs to SeaWorld and has played a role in the death of three people in three different incidents (1991, 1999 and 2010). There are documented incidents in the wild too, but none of them fatal.
Fatal attacks from other species are less common, but there is a registered occurrence in the coast of Brazil in 1994, when a man died after injuries suffered during a bottlenose dolphin attack.[65][66] Non-fatal incidents occur more frequently, both in wild and captivity.
While dolphin attacks are much rarer than other sea animal attacks, such as shark ones, some scientists are worried about the careless programs of human-dolphin interaction. Dr. Andrew J. Read, a biologist at the Duke University Marine Laboratory who studies dolphin attacks, points that dolphins are large and wild predators, so people should be more careful when interact with them.
Therapy
Dolphins are an increasingly popular choice of animal-assisted therapy for psychological problems and developmental disabilities. For example, a 2005 study found dolphins an effective treatment for mild to moderate depression However, this study was criticized on several grounds. For example, it is not known whether dolphins are more effective than common pets. Reviews of this and other published dolphin-assisted therapy (DAT) studies have found important methodological flaws and have concluded that there is no compelling scientific evidence that DAT is a legitimate therapy or that it affords more than fleeting mood improvement.
Military


A military dolphin
See also: Military dolphin.
A number of militaries have employed dolphins for various purposes from finding mines to rescuing lost or trapped humans. The military use of dolphins, however, drew scrutiny during the Vietnam War when rumors circulated that the United States Navy was training dolphins to kill Vietnamese divers. The United States Navy denies that at any point dolphins were trained for combat. Dolphins are still being trained by the United States Navy on other tasks as part of the U.S. Navy Marine Mammal Program. The Russian military is believed to have closed its marine mammal program in the early 1990s. In 2000 the press reported that dolphins trained to kill by the Soviet Navy had been sold to
Literature
Dolphins are also common in contemporary literature, especially science fiction novels. Dolphins play a military role in William Gibson's short story Johnny Mnemonic, in which cyborg dolphins find submarines and decode encrypted information. Dolphins play a role as sentient patrollers of the sea enhanced with a deeper empathy toward humans in Anne McCaffrey's The Dragonriders of Pern series. In the Known Space universe of author Larry Niven, dolphins play a significant role as fully recognised "legal entities". More humorous is Douglas Adams’ The Hitchhiker's Guide to the Galaxy series of picaresque novels, in which dolphins are the second most intelligent creatures on Earth (after mice, followed by humans) and try in vain to warn humans of Earth’s impending destruction. Their story is told in So Long, and Thanks for All the Fish. Much more serious is their major role in David Brin's Uplift series. A talking Dolphin named "Howard" helps Hagbard Celine and his submarine crew fight the evil Illuminati in Robert Shea and Robert Anton Wilson's Illuminatus Trilogy.
Dolphins appear frequently in non-science fiction literature. In the book The Music of Dolphins by author Karen Hesse, dolphins raise a girl from the age of four until the coast guard eventually discovers her. Fantasy author Ken Grimwood wrote dolphins into his 1995 novel Into the Deep about a marine biologist struggling to crack the code of dolphin intelligence, including chapters written from a dolphinian viewpoint.
Art
Dolphins are a popular artistic motif, dating back to ancient times. Examples include the Triton Fountain by Bernini and depictions of dolphins in the ruined Minoan palace at Knossos and on Minoan pottery.
Cuisine


Plate of dolphin sashimi.
Dolphin meat is consumed in a small number of countries world-wide, which include Japan[72] and Peru (where it is referred to as chancho marino, or "sea pork").[73] While Japan may be the best-known and most controversial example, only a very small minority of the population has ever sampled it.
Dolphin meat is dense and such a dark shade of red as to appear black. Fat is located in a layer of blubber between the meat and the skin. When dolphin meat is eaten in Japan, it is often cut into thin strips and eaten raw as sashimi, garnished with onion and either horseradish or grated garlic, much as with sashimi of whale or horse meat (basmati). When cooked, dolphin meat is cut into bite-size cubes and then batter-fried or simmered in a miso sauce with vegetables. Cooked dolphin meat has a flavor very similar to