Red-eared slider

The red-eared slider (Trachemys scripta elegans), also known as red-eared terrapin, is a semiaquatic turtle belonging to the family Emydidae. It is a subspecies of the pond slider. It is the most popular pet turtle in the United States and is also popular as a pet in the rest of the world,^[3] as, among other factors, it is easy to maintain. It has, therefore, become the most commonly traded turtle in the world.^[4] It is native to the southern United States and northern Mexico, but has become established in other places because of pet releases and has become an invasive species in many areas, where it outcompetes native species. The red-eared slider is included in the List of the world’s 100 most invasive species^[5] published by the International Union for the Conservation of Nature.

Name

Red-eared sliders get their name from the small red dash around their ears. The "slider" part of their name comes from their ability to slide off rocks and logs and into the water quickly. This species was previously known as Troost's turtle in honor of an American herpetologist; Trachemys scripta troostii is now the scientific name for another subspecies, the Cumberland slider.

Taxonomy

The red-eared slider belongs to the order Testudines, which contains about 250 turtle species. It is a subspecies of Trachemys scripta. They were previously classified under the name Chrysemys scripta elegans.

The species Trachemys scripta contains three subspecies: T. s. elegans (red-eared slider), T. s. scripta (yellow-bellied slider) and T. s. troostii (Cumberland slider).^[6]

Description

The carapace of this species can reach up to 30 cm in length, although some individuals have been known to reach more than 40 cm, but the average length ranges from 12 to 20 cm.^[7] The females of the species are usually a little larger than the males. They can live between 20 and 30 years, although some individuals have lived for more than 40 years.^[8] Their life expectancy is shorter when they are kept in captivity.^[9] The quality of the habitat where they live can also influence their lifespans and quality of life.

These turtles are poikilotherms, so are unable to regulate their body temperatures independently; they are completely dependent on the temperature of their environments.^[3] For this reason, they continually need to sunbathe to warm themselves and maintain their body temperatures. If their body temperature falls below a threshold of 21°C, they are unable to carry out normal functions of digestion and defecation.

The shell is divided into two sections: the upper or dorsal carapace and the lower, ventral carapace or plastron.^[3] The upper carapace consists of the vertebral scutes, which form the central, elevated portion, pleural scutes that are located around the vertebral scutes and then the marginal scutes around the edge of the carapace, the rear marginal scutes are notched. The scutes are bony keratinous elements. The carapace is oval and flattened (especially in the male) and has a weak keel that is more pronounced in the young.^[10] The color of the carapace changes depending on the age of the turtle. The carapace usually has a dark green background with light and dark, highly variable markings. In young or recently born turtles, it is leaf green and gets slightly darker as a turtle gets older until it is a very dark green and then turns a shade between brown and olive green. The plastron is always a light yellow with dark, paired, irregular markings in the centre of most scutes. The plastron is highly variable in pattern. The head, legs, and tail are green with fine, yellow, irregular lines. The whole shell is covered in stripes and marks that aid in camouflaging an individual.

Turtles also have a complete skeletal system, with partially webbed feet that help them to swim and that can be withdrawn inside the carapace along with the tail. The head can also be completely withdrawn inside the carapace. The red stripe on each side of the head distinguishes the red-eared slider from all other North American species and gives this species its name, as the stripe is located behind the eyes where their ears would be. These stripes lose their color over time.^[9] Some individuals can also have a small mark of the same color on the top of their heads. The red-eared slider does not have a visible outer ear or an external auditory canal; instead, they rely on a middle ear entirely covered by a cartilaginous tympanic disc.^[11]

The main internal organs of these reptiles are the lungs, heart, stomach, liver, intestines and the urinary bladder, in addition to the cloaca and the tail, which are important external organs. The tail is important as it helps an individual to steer as it is swimming.

Sexual dimorphism

Some dimorphism exists between males and females.^[12]

Red-eared slider young look practically identical regardless of their sex, making it difficult to determine their sex. It is much easier to distinguish the sex of adults, as the shells of mature males are smaller than those of females when they reach maturity.^[13] Male red-eared sliders reach sexual maturity when their carapaces measure 10 cm and females reach maturity when their carapaces measure 15 cm. The male is normally smaller than the female, although this parameter is sometimes difficult to apply as individuals being compared could be of different ages. Males have longer claws on their front feet than the females; this helps them to hold on to a female during mating and is used during courtship displays.^[14] The male’s tail is thicker and longer. Typically, the cloacal opening of the female is at or under the rear edge of the carapace, while the male's opening occurs beyond the edge of the carapace. The male’s plastron is slightly concave, while that of the female is totally flat. The male’s concave plastron also helps to stabilize the male on the female’s carapace during mating.^[15] The red marking on the males is also thought to be larger and brighter. Older males can sometimes have a dark greyish-olive green melanistic coloration, with very subdued markings. The red stripe on the sides of the head may be difficult to see or be absent. The female’s appearance is practically the same during all its life.

Both the male and female reach maturity at five to six years of age, but when kept in captivity, they do not hibernate and they feed more so they grow more rapidly and reach maturity slightly sooner than in nature.

Distribution and habitat

The red-eared slider originated from the area around the Mississippi River and the Gulf of Mexico, in warm climates in the southeastern corner of the United States. Their native areas include the southeast of Colorado, Virginia, and Florida. In nature, they inhabit areas with source of still, warm water, such as ponds, lakes, swamps, creeks, streams, or slow-flowing rivers. They live in areas of calm water where they are able to leave the water easily by climbing onto rocks or tree trunks so they can warm up in the sun. Many individuals are often found sunbathing together in a group or even on top of each other. They also require abundant aquatic plants, as this is the adults' main food, although they are omnivores.^[16] Turtles in the wild always remain close to water unless they are searching for a new habitat or when females leave the water to lay their eggs.

Owing to their popularity as pets, red-eared sliders have been released or escaped into the wild in many parts of the world.^[17] Feral populations of red-eared sliders are now found in Australia, Europe, South Africa, the Caribbean, Israel, Bahrain, Mariana Islands, Guam, and southeast and far east Asia.^[18] In Australia, it is illegal for members of the public to import, keep, trade, or release red-eared sliders, as they are regarded as an invasive species.^[19] Their import has been banned by the European Union^[20] and specific member countries.^[21] Invasive red-eared sliders cause negative impacts in the ecosystems they occupy because they have certain advantages over the native populations, such as a lower age at maturity, higher fecundity rates, and larger body size, which gives them a competitive advantage at basking and nesting sites, as well as when exploiting food resources.^[22] They also transmit diseases and displace the other turtle species with which they compete for food and breeding space.^[23]

Behavior

Red-eared sliders are almost entirely aquatic, but, as they are cold-blooded, they leave the water to sunbathe to regulate their temperature.

They are excellent swimmers. When they are out of the water, they remain alert and flee from any predators or from humans. On sensing a threat, they rapidly launch themselves back into the water. During the day, they usually alternate between warming themselves in the sun and spending time in the water.

They can become aggressive if they become overcrowded or if the ratio of the sexes is not balanced. In captivity, a ratio of two or three females per male is usually recommended.

Hibernation

Reptiles do not hibernate, but actually brumate, as they become less active, but occasionally rise to the surface for food or air. Brumation can occur to varying degrees. Red-eared sliders brumate over the winter at the bottom of ponds or shallow lakes; they become inactive, generally, in October, when temperatures fall below 10 °C (50 °F).^[10] During this time, the turtles enter a state of sopor, during which they do not eat or defecate, they practically do not move, and the frequency of their breathing falls. Individuals usually brumate under water, but they have also been found under banks and hollow stumps and rocks. In warmer winter climates, they can become active and come to the surface for basking. When the temperature begins to drop again, however, they will quickly return to a brumation state. Sliders will generally come up for food in early March to as late as the end of April.

During brumation, T. s. elegans can survive anaerobically for weeks, producing ATP from glycolysis. The turtle's metabolic rate drops dramatically, with heart rate and cardiac output dropping by 80% to minimise energy requirements.^[24][25] The lactic acid produced is buffered by minerals in the shell, preventing acidosis.^[26] Red-eared sliders kept captive indoors should not brumate.

Reproduction

Courtship and mating activities for red-eared sliders usually occur between March and July, and take place under water. During courtship, the male swims around the female and flutters or vibrates the back side of his long claws on and around her face and head, possibly to direct pheromones towards her.^[27] The female swims toward the male and, if she is receptive, sinks to the bottom for mating. If the female is not receptive, she may become aggressive towards the male. Courtship can last 45 minutes, but mating takes only 10 minutes.^[23]

On occasion, a male may appear to be courting another male. In reality, this is a sign of dominance and the males may start to fight. Young turtles may carry out the courtship dance before they reach sexual maturity at five years of age, but they are unable to mate.^[28]

After mating, the female spends extra time basking to keep her eggs warm.^[28] She may also have a change of diet, eating only certain foods or not eating as much as she normally would. A female can lay between two and 30 eggs depending on body size and other factors.^[18] One female can lay up to five clutches in the same year, and clutches are usually spaced 12 to 36 days apart.^[29] The time between mating and egg-laying can be days or weeks. The actual egg fertilization takes place during the egg-laying. This process also permits the laying of fertile eggs the following season as the sperm can remain viable and available in the females body in the absence of mating. During the last weeks of gestation, the female spends less time in the water and smells and scratches at the ground, indicating she is searching for a suitable place to lay her eggs. The female excavates a hole using her hind legs and lays her eggs in it.^[30]

Incubation takes 59 to 112 days.^[18] Late-season hatchlings may spend the winter in the nest and emerge when the weather warms in the spring. Just prior to hatching, the egg contains 50% turtle and 50% egg sac. A new hatchling breaks open its egg with its egg tooth, which falls out about an hour after hatching. This egg tooth never grows back. Hatchlings may stay inside their eggshells after hatching for the first day or two. If they are forced to leave the eggshell before they are ready, they will return where possible. When a hatchling decides to leave the shell, it has a small sac protruding from its plastron. The yolk sac is vital and provides nourishment while visible, and several days later it will have been absorbed into the turtle's belly. The sac must be absorbed, and does not fall off. A split may be noticeable in the hatchling's plastron for turtles found in the field, indicating the age of the turtle to be about three weeks old. The split must heal on its own before the turtle is able to swim. It takes 21 days between the egg opening until water entry.

Damage or motion of the egg yolk protruding, enough to allow air into the turtle's body results in death. This is the main reason for marking the top of turtle eggs if their relocation for any reason is required. An egg turned upside down will eventually terminate the embryo growth by the sac smothering the embryo. If it manages to reach term, the turtle will try to flip over with the yolk sac, which allows air into the body cavity and death follows. The other fatal danger is water getting into the body cavity before the sac is absorbed completely and the opening has not completely healed yet.

The sex of red-eared sliders is determined by the incubation temperature during critical phases of the embryos' development. Only males are produced when eggs are incubated at temperatures of 22–27 °C (72–81 °F), whereas females develop at warmer temperatures.^[31]

Red-eared sliders as pets

The red-eared slider is the most common type of water turtle kept as pets.^[32] As with other turtles, tortoises, and box turtles, individuals that survive their first year or two can be expected to live generally around 30 years. Red-eared sliders can be quite aggressive—especially when food is involved. Behavior is usually noted to become this way when fed live food. If being kept as a pet, care must be taken to prevent injury or even death of smaller tank mates. Additional care is needed if shrimp are used as food. Smaller red-eared sliders less than a year old have been known to choke on the shells of the shrimp and suffer from lung puncture.

Infection risks and United States federal regulations on commercial distribution

Reptiles are asymptomatic carrier of bacteria of the genus Salmonella.^[33] This has caused justifiable concerns given the many references to infection of humans caused by the handling of turtles ^[34] that has led to restrictions in the sale of red-eared sliders in the US. A 1975 U.S. Food and Drug Administration (FDA) regulation bans the sale (for general commercial and public use) of turtle eggs and turtles with a carapace length of less than 4 in (100 mm). This regulation comes under the Public Health Service Act, and is enforced by the FDA in cooperation with state and local health jurisdictions. The ban was enacted because of the public health impact of turtle-associated Salmonella. Turtles and turtle eggs found to be offered for sale in violation of this provision are subject to destruction in accordance with FDA procedures. A fine of up to $1,001 and/or imprisonment for up to one year is the penalty for those who refuse to comply with a valid final demand for destruction of such turtles or their eggs.^[35] Many stores and flea markets still sell small turtles due to an exception in the FDA regulation which allows turtles under 4 in (100 mm) to be sold "for bona fide scientific, educational, or exhibition purposes, other than use as pets."^[36] As with many other animals and inanimate objects, the risk of Salmonella exposure can be reduced by following basic rules of cleanliness. Small children must be taught to wash their hands immediately after they finish "playing" with the turtle, feeding it, or changing the water.

US state law

Some states have other laws and regulations regarding possession of red-eared sliders because they can be an invasive species where they are not native and have been introduced through the pet trade. Now, it is illegal in Florida to sell any wild-type red-eared slider, as they interbreed with the local yellow-bellied slider population – Trachemys scripta scripta is another subspecies of pond sliders, and intergrades typically combine the markings of the two subspecies. However, unusual color varieties such as albino and pastel red-eared sliders, which are derived from captive breeding, are still allowed for sale.^[37]

In popular culture

Within the second volume of the Tales of the Teenage Mutant Ninja Turtles, the popular comic book heroes are revealed as specimens of the red-eared slider. The popularity of the Turtles led to a craze for keeping them as pets in Great Britain.^[38]

See also

• Yellow-eared slider

References

Further reading

• Carl H. Ernst, Jeffrey E. Lovich: Turtles of the United States and Canada. Johns Hopkins University Press 2009, ISBN 978-0-8018-9121-2, pp. 444–470 (online copy, p. 444, at Google Books)
• John B. Jensen, Carlos D. Camp, Whit Gibbons: Amphibians and Reptiles of Georgia. University of Georgia Press 2008, ISBN 978-0-8203-3111-9, pp. 500–502 (online copy, p. 500, at Google Books)
• James H. Harding: Amphibians and Reptiles of the Great Lakes Region. University of Michigan Press 1997, ISBN 0-472-06628-5, pp. 216–220 (online copy, p. 216, at Google Books)
• Rachel M. Bowden,"A Modified Yolk Biopsy Technique improves survivor ship of turtle eggs". Cal State East Bay Press Sep./Oct. 2009, ISSN:15222152 p. 611–615 (online copy, p. 216, at Google Books)

External links

Wikimedia Commons has media related to Trachemys_scripta_elegans.

• Red-ear slider
• Discovery Channel's Animal Planet: Red-eared slider
• Information on aquatic turtles & tortoises including a few articles specific to Red-eared Terrapin
• Gulf Coast Turtle & Tortoise Society: Natural History: Red-eared slider

Family Emydidae (pond turtles) Kingdom: Animalia Phylum: Chordata Class: Reptilia Order: Testudines Suborder: Cryptodira Superfamily: Testudinoidea Family: Emydidae Genus Species of the subfamily Deirochelyinae Chrysemys Painted turtle Deirochelys Chicken turtle Graptemys Alabama map turtle Barbour's map turtle Black-knobbed map turtle Cagle's map turtle Escambia map turtle False map turtle Northern map turtle Ouachita map turtle Pascagoula map turtle Pearl River map turtle Ringed map turtle Texas map turtle Yellow-blotched map turtle Malaclemys Diamondback terrapin Pseudemys Alabama red-bellied cooter Northern red-bellied cooter Florida red-bellied cooter Peninsula cooter Rio Grande cooter River cooter Texas river cooter Trachemys Big bend slider Baja California slider Central Antillean slider Colombian slider Cuatro Cienegas slider Cuban slider D'Orbigny's slider Hispaniolan slider Jamaican slider Maranhão slider Meso-American slider Nicaraguan slider Ornate slider Pond slider Yaqui slider   Species of the subfamily Emydinae Clemmys Spotted turtle Emys Blanding's turtle European pond turtle Sicilian pond turtle Western pond turtle Glyptemys Bog turtle Wood turtle Terrapene Coahuilan box turtle Common box turtle Ornate box turtle Spotted box turtle Phylogenetic arrangement based on turtles of the world 2011 update: annotated checklist. Subspecies and the extinct (Gyremys sectabilis) are not included.

Extant turtle taxonomy Kingdom: Animalia Phylum: Chordata Class: Reptilia Subclass: Anapsida Order: Chelonii or Testudines Suborder Superfamily Family Subfamily Genus Cryptodira   Chelydridae   Chelydra Macrochelys Chelonioidea Cheloniidae Carettinae Caretta Lepidochelys Cheloniinae Chelonia Eretmochelys Natator Dermochelyidae   Dermochelys Kinosternoidea Dermatemydidae   Dermatemys Kinosternidae Kinosterninae Kinosternon Sternotherus Staurotypinae Claudius Staurotypus Testudinoidea Emydidae Deirochelyinae Chrysemys Deirochelys Graptemys Malaclemys Pseudemys Trachemys Emydinae Clemmys Emys Glyptemys Terrapene Geoemydidae Geoemydinae Batagur Cuora Cyclemys Geoclemys Geoemyda Hardella Heosemys Leucocephalon Malayemys Mauremys Melanochelys Morenia Notochelys Orlitia Pangshura Sacalia Siebenrockiella Vijayachelys Rhinoclemmydinae Rhinoclemmys  Platysternidae   Platysternon Testudinidae   Aldabrachelys Astrochelys Chelonoidis Chersina Cylindraspis Geochelone Gopherus Homopus Indotestudo Kinixys Malacochersus Manouria Psammobates Pyxis Stigmochelys Testudo Trionychia Carettochelyidae   Carettochelys Trionychidae Cyclanorbinae Cyclanorbis Cycloderma Lissemys Trionychinae Amyda Apalone Chitra Dogania Nilssonia Palea Pelochelys Pelodiscus Rafetus Trionyx Pleurodira   Chelidae Chelinae Acanthochelys Chelus Mesoclemmys Phrynops Platemys Rhinemys Chelodininae Chelodina Elseya Elusor Emydura Flaviemys Myuchelys Pseudemydura Rheodytes Hydromedusinae Hydromedusa Pelomedusidae   Pelomedusa Pelusios Podocnemididae   Erymnochelys Peltocephalus Podocnemis Phylogenetic arrangement based on turtles of the world 2012 update: annotated checklist. Extinct turtles not included. Portal Book See also List of Testudines families