Painted turtle

Taxonomy

Description

The painted turtle is 10 to 26 centimeters (4 to 10 in) long ^[2] and has a smooth, flat, oval, and keelless carapace. ^{[3] [4]} The carapace is olive to black with darkness being related to substrate darkness (the lighter the substrate, the lighter the painted turtle's carapace is likely to be and vice versa). ^[5] The plastron is yellowish and has a black or red-to-brown spot. The skin of the turtle is black to olive but the neck, legs, tail, and face have red and yellow stripes (however, the face has exclusively yellow stripes). ^{[2] [4]} Behind each eye is a large, yellow spot and streak. The chin has two wide yellow stripes that meet at the tip of the jaw. ^[5]

Compared to males, the female painted turtle is larger in overall size but has a shorter, thinner tail, and has shorter foreclaws. ^{[2] [3] [4]} Females weigh 500 grams (18 oz) while males weigh 300 grams (11 oz). ^[6] The painted turtle's karyotype is composed of 50 chromosomes. ^{[4] [5]}

Male eastern painted turtles (Chrysemys picta picta) are 13.1–16.5 cm (5.2–6.5 in) and females are 14.3–17.1 cm (5.6–6.7 in) in length. The carapace is green and has a yellow stripe down the middle. The shell plates are edged with yellow lines and the edge of the entire carapace is red. ^[7] It also has a small, faint mid-dorsal stripe and its plastron is plain yellow or lightly spotted. The western painted turtle (Chrysemys picta bellii) is the largest subspecie of painted turtle. The reticulated (net-like) pattern of light lines on its carapace is its defining characteristic. Also, most of the plastron is covered in a dark coloration that begins in the seems and spreads outward. The mid-dorsal stripe is either missing or faint as in the eastern painted turtle. ^[8] The southern painted turtle (Chrysemys picta dorsalis), the smallest subspecie, has a red or yellow mid-dorsal stripe and either a spotless, or near spotless, tan plastron. ^[9] The midland painted turtle's (Chrysemys picta marginata) carapace is bordered by a dark coloration and the plastron contains a dark figure which varies in darkness and, unlike the one found in the western painted turtle, does not extend out along the seams. Its mid-dorsal stripe may be poorly developed or missing. ^[10]

Distribution and habitat

The painted turtle is unique in that it is the only turtle found across the entire North American continent. It reaches southern Quebec, New Brunswick, Nova Scotia, and British Columbia in the north and the coast of Louisiana in the south. It also lives on the eastern coast of the United States, from Maine to Georgia, west to the state of Washington. ^[8]

The eastern painted turtle (Chrysemys picta picta) is found in southeastern Canada south to Georgia and, from there, west to Alabama. The western painted turtle (Chrysemys picta bellii), ranges from western Ontario south to British Columbia, Missouri, Oklahoma, Colorado, Wyoming, Idaho, and Oregon. It is also found scattered throughout the southwestern United States and in Chihuahua. ^[8] The southern painted turtle (Chrysemys picta dorsalis) lives in southern Illinois south to the Gulf Coast of Louisiana and northeast through central Mississippi. The midland painted turtle (Chrysemys picta marginata) ranges from the southern reaches of Ontario and Quebec south the central United States to Tennessee and Alabama. It also exists eastward through Pennsylvania, Virginia, West Virginia, North and South Carolina, Maryland, and into New England. ^[9]

The painted turtle lives in bodies of water with slow moving currents. This includes: ponds, marshes, lakes, and creeks (also called streams). These locations require soft bottoms, adequate basking sites, and the presence of aquatic vegetation. In areas along the Atlantic coast, these turtles have been seen in brackish waters. ^[11]

Evolutionary history

The four subspecies of painted turtle have evolved due to of partial geographic isolation (each has independently adapted to their different surroundings). ^[8] It has been suggested that, after the receding of ice from the last ice age, painted turtles were divided into three different populations: C. picta, which inhabited the southeastern Atlantic coast, C. dorsalis, which occupied the southern Mississippi River Valley area, and C. bellii, which found a home in the southwestern United States. Despite this, the populations were not completely isolated, thus completely different species did not result. The retreat of the glaciers resulted in an overall northern movement by all three of the painted turtle populations. As a result, C. dorsalis and C. bellii' to meet in Missouri where hybridization produced the fourth contemporary subspecie: C. marginata (which likely originated near the Tennessee River Valley). ^[10]

Painted turtle fossils, of many different ages, have been found all over its current range. ^[5]

Ecology and behavior

The painted turtle is most active from March to October, yet, even in the north, individuals can be seen basking in February during periods of warmth. ^[13] It is diurnal, becoming active at sunrise when it basks for several hours before feeding. ^[14] After that, another period of basking follows, than another period of foraging continues into the early evening. ^[15] Nighttime is spent sleeping at the bottom of the turtle's pond or small creek, or perched on a part-way submerged object. ^[14] All ages of painted turtle have been observed basking for warmth: sometimes 50 or more individuals can be seen on one log at a time. Also, other species of turtle have been seen basking with painted turtles. Three major periods of basking exist: one in the early morning, one during midday, and another in the early afternoon with each one lasting about 2 hours. The months of most frequent basking is April through September. Air and water temperatures are used throughout the day to maintain a high body temperature. The optimum body temperature range for the painted turtle is between 17 and 23 °C (63 and 73 °F). Interestingly, laboratory tests have revealed that when a painted turtle has a bodily infection (caused by a bacteria for example), it is capable of adjusting its behavior so that its body temperature will be about 4 to 5°C higher than normal. Apparently the painted turtle has the capability of developing a fever to fight off the infection. ^[16]

Dormancy through winter lasts five or six months in the north, but in other locations the period is not as long. There is evidence that, in the far south of its range, the painted turtle may not even hibernate at all, ^[17] however, the overwhelming majority of populations do. Throughout hibernation, during periods of warmth, the painted turtle can become active, until the cold temperatures return. It can hibernate in various locations: on the bottom of a body of water, within the burrow of a muskrat, underneath banks of dirt, or on land in woods or pastures. When hibernating underwater, a painted turtle can be as deep as 2 metres (6.6 ft), but usually shallower, and may bury itself as deep as 95 centimetres (37 in) in the soft mud. During hibernation, the body temperature of the painted turtle averages 6.2 °C (43.2 °F). The turtles generally emerge from early March to mid-April (depending on how long cold temperatures persist), when the ice cover of the water-body (if indeed it hibernated in water) has completely disappeared. ^[18]

The painted turtle are preyed on by various animals throughout its life, however, raccoons are its biggest natural enemy. Nests are destroyed or raided by thirteen-lined ground squirrels, chipmunks, woodchucks, gray squirrels, skunks, badgers, two types of fox ( Urocyon and Vulpes), fish crows, garter snakes, humans, and worst of all, raccoons. Young turtles fall prey to rice rats, muskrats, mink, Procyon raccoons, snapping turtles, three types of snake ( Agkistrodon, Coluber, and Nerodia), bullfrogs, to types of large fish ( Micropterus and ictalurus), herons, and water bugs. Adults are taken by alligators, raccoons, bald eagles, osprey, and red-shouldered hawks. The painted turtle's only defenses when attacked or handled are to kick, scratch, bite, or void bladder water. ^[19]

The probability of a painted turtle surviving from egg to one year of age is 19%. From one year to the next, the survival rate among juvenile females is 45% and among adult females the rate is about 95%. Males however, have a greater mortality rate, thus the males of a given population are on average younger than the females. Factors that can effect the age distribution of a painted turtle population include natural disasters. Hurricanes can destroy most or all of the nests of a given season, resulting in proportionally more adults and juveniles than hatchlings in the subsequent year. ^[20]

The painted turtle eats a large array of food items with feeding habits depend largely on water temperature. In the spring, when the water reaches 15 to 18 °C (59 to 64 °F), they begin feeding for the season. However, when the water temperature surpasses 30 °C (86 °F) (usually in July or August), it will not forage. Finally, in September, eating ceases at the same range it began in the spring. It hunts along the bottom of small rivers, streams, and ponds and among clumps of algae and aquatic vegetation. The turtle quickly juts its heads in and out of aquatic plants to stir potential prey items out into the open water, where they are pursued. The painted turtle also skims the surface of the water with its mouth open to catch fine particulate matter. Large prey is held in the mouth and torn up with the forefeet. ^[21] The painted turtle eats a broad range of food including plants and animals either alive or dead ^[21] and each subspecies has its own unique diet. ^[22] The eastern painted turtle's diet is the least studied of the four subspecies. It is known to be omnivorous and take in a number of different plants and animals with most of the fish consumed being either already dead or injured. The eastern painted turtle prefers to eat in the water, but it has been observed eating on land. ^[22] The western painted turtle is omnivorous and its proportionate consumption of plants and animals changes seasonally. During early summer (specifically the month of June), 60% of this turtle's diet is insects. Yet in late summer (September), 55% of its diet is plants. Also of note, white water-lily seeds are consumed by this turtle in high numbers. The hard-coated seeds remain viable as they pass through its digestive system, which suggests that the western painted turtle is a significant disperser of water lily seeds. ^[23] The southern painted turtle is omnivorous and its diet changes with age. Adults of this subspecies obtain 88% of their food from plants while immature specimens consume 13% of their food from plants. The most common plants eaten by the adults are duckweed and algae and dragonfly larvae and crayfish constitute most of the animal prey. The reversal of feeding habits due to age has also been observed in the False map turtle. ^[24] The midland painted turtle is also omnivorous, eating mostly aquatic invertebrates and plants. It mostly eats insects, Non-vascular plants, and vascular plants. ^[25]

Movement

The painted turtle often travels vast distances (sometimes several kilometers in one trip) either between neighboring wetlands or linearly along the same creek. Due to heat and overgrowth of vegetation, some individuals will move from shallow marshes to more permanent ponds or lakes during the summer months. Field research and the repeated capturing of painted turtle individuals have revealed that, overall, males move the most (up to 26.0 kilometres (16.2 mi) between captures), females the second most (around 7 to 8 kilometres (4.3 to 5.0 mi) between captures), and juveniles of either gender the least (less than 2 kilometres (1.2 mi)). ^[26]

The painted turtle, apparently through the use of visual recognition of landmarks, has homing capability. Many individuals are able to return to their collection point after being captured and released somewhere else, a trip that may require them to traverse over land. One experiment was done in which 98 specimens were placed varying distances away from their home wetland. Of the original number, 41 returned. When living in a single, large body of water, the painted turtle can home from a maximum of 5.8 kilometres (3.6 mi) away. it has also been hypothesized that pregnant females may use some simple for of homing to locate a proper nest sight. ^[26]

Life cycle

Depending on their size, males reach sexual maturity at about 2 to 4 years old, and females from about 6 to 10. ^[27] Increased food access (and thus growth) is a factor in the earlier maturation of males. The size and age at maturity of the painted turtle increases with the latitude at which it is found. ^[28] The painted turtle mates after emerging from hibernation, throughout spring and summer ^[6] and into early fall. ^[29] Spermatogenesis (which begins earlier and ends later in southern populations) ^[30] begins in March; the minimum temperature required for initiation is 17 °C (63 °F). ^[27] The female's ovarian cycle begins in July or August, and ovulation takes place the following spring. ^[29]

The courtship ritual occurs in water and begins when the male follows a female until he meets her face to face. He then strokes her face and neck with his front claws, a gesture that a receptive female will return. This process is repeated several times, with the male retreating from and then returning to the female until she swims to the bottom, where copulation occurs. ^{[6] [29]} The female has the ability to store sperm, which can be used for up to three clutches in a season, in her oviducts. ^[31] As males are smaller than females, they are not dominant during the mating ritual. ^[6]

Nesting of the eggs starts in late May and lasts until mid-July. The majority of nests are constructed in the late afternoon and early evening (after the hottest part of the day), but for a female to construct one earlier is not unusual. ^[32] When preparing to dig a nest, the female sometimes presses her throat against the ground of potential sites, perhaps feeling for their moisture, warmth, texture, or smell, although the behavior is as yet unexplained. ^[33] She may begin by preparing several false nests, ^[33] a behavior also exhibited by wood turtles. ^[34] The female accumulates so much sand and mud on her hind feet while digging that her mobility can be reduced, making her vulnerable to predation. Vulnerability of the eggs is a concern when several females make their nests in close proximity. The process of digging and preparing the nest may take up to four hours to complete. ^[33] The nests are vase-shaped and are dug in sandy soil by the female, using only her back claws. ^{[29] [33]} The optimum female body temperature during nest construction is 29 to 30 °C (84 to 86 °F).

Nests are exposed to the south and often occur within 200 metres (660 ft) of water, but may be as far away as 600 metres (2,000 ft) depending on the age of the mother; younger females often nest closer to water. The female may return to the same nesting site several year in a row. The size of the nest varies widely depending on the size of the female and the geographical location. ^[33]

While laying the eggs, the female will moisten the area with bladder water. ^[33] If conditions are unsuitable for nesting, i.e., if it is excessively hot or dry, the female can delay her egg laying. The elliptical eggshells are flexible, white, and porous. ^[35] The gender of painted turtle fetuses is temperature dependent and is determined during the middle third of incubation. Temperatures between 23 and 27 °C (73 and 81 °F) produce males, and anything above or below that females. ^[29] It does not appear that the female chooses nesting sites based on what the subsequent sex of the hatchlings will be. ^[36] In the wild, eggs incubate for between 72 and 80 days before hatching. ^{[29] [37]} The female can lay up to five clutches each year, but the average number is two. It has been found that northern painted turtles produce larger but fewer clutches. A positive correlation exists between female size, clutch size, and egg mass and width. ^[38] Studies suggest that larger eggs have a better chance of producing viable offspring than smaller ones. ^[30] As many as 30–50 percent of a population's females will not produce any eggs in a given mating season. ^[33]

Hatching occurs in August and September, but not all of the offspring will emerge from the nest immediately; hatchlings may overwinter in the nest and emerge the following spring, ^[29] this is especially common in the northern part of the turtle's range where, despite seeking shelter within the nest, subzero temperatures result in high hatchling mortality rates. Compared to adults, the baby painted turtle has a proportionally larger head, eyes, and tail and is more brightly colored. ^[36]

Growth starts when the turtles first start feeding: usually 7–10 days after hatching. The young painted turtle grows rapidly, sometimes doubling in size in the first year with smaller ones growing more rapidly than larger ones. Young C. picta bellii, the largest subspecies, are the fastest growers. ^[39] Likely due to differing environmental conditions and diet, growth rates may change from population to population in the same area. Overall, females grow more rapidly and reach a larger size than males. For both genders, growth slows down sharply once maturity is reached (growth may even stop completely). ^[40] In the wild, painted turtles aged 40 years have been found. ^[21]

The differences seen here are thought to be related more to environmental adaptation rather than taxonomic differences. ^[38]

References

Footnotes

Bibliography