Nest-Site Selection and Offspring Sex Ratio in Painted Turtles, Chrysemys picta

Schwarzkopf, Lin; Brooks, Ronald J.

doi:10.2307/1446037

Cited by 122 publications

(98 citation statements)

References 21 publications

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“…Even if no development occurs within the core areas we defined, subsidized predators originating from urban or suburban areas can penetrate a protected area, although predation patterns are not always easily discerned (Marchand andLitvaitis, 2004, Strickland andJanzen, 2010). In addition, turtles may have a preferred nesting site around a particular wetland (e.g., Lindeman, 1992;Schwarzkopf and Brooks, 1987) or be restricted to a particular nesting area that is within or beyond the core area designations we have identified.…”

Section: Discussionmentioning

confidence: 99%

Terrestrial habitat requirements of nesting freshwater turtles

Steen

Gibbs

Buhlmann

et al. 2012

Biological Conservation

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Because particular life history traits affect species vulnerability to development pressures, cross-species summaries of life history traits are useful for generating management guidelines. Conservation of aquatic turtles, many members of which are regionally or globally imperiled, requires knowing the extent of upland habitat used for nesting. Therefore, we compiled distances that nests and gravid females had been observed from wetlands. Based on records of > 8000 nests and gravid female records compiled for 31 species in the United States and Canada, the distances that encompass 95% of nests vary dramatically among genera and populations, from just 8 m forMalaclemys to nearly 1400 m for Trachemys. Widths of core areas to encompass varying fractions of nesting populations (based on mean maxima across all genera) were estimated as: 50% coverage = 93 m, 75% = 154 m, 90% = 198 m, 95% = 232 m, 100% = 942 m. Approximately 6-98 m is required to encompass each consecutive 10% segment of a nesting population up to 90% coverage; thereafter, ca. 424 m is required to encompass the remaining 10%. Many genera require modest terrestrial areas (zones) for 95% nest coverage (Actinemys, Apalone, Chelydra, Chrysemys, Clemmys,Glyptemys, Graptemys, Macrochelys, Malaclemys, Pseudemys, Sternotherus), whereas other genera require larger zones (Deirochelys, Emydoidea, Kinosternon, Trachemys). Our results represent planning targets for conserving sufficient areas of uplands around wetlands to ensure protection of turtle nesting sites, migrating adult female turtles, and dispersing turtle hatchlings. Our results represent planning targets for conserving sufficient areas of uplands around wetlands to ensure protection of turtle nesting sites, migrating adult female turtles, and dispersing turtle hatchlings.

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Section: Discussionmentioning

confidence: 99%

Terrestrial habitat requirements of nesting freshwater turtles

Steen

Gibbs

Buhlmann

et al. 2012

Biological Conservation

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“…Temperatures in two nests were monitored at intervals over the 1987-1988 winter using a copper-constantan thermocouple placed at the bottom of each nest (4). On April 25th, 1988, the nests were excavated from under a covering, layer of snow.…”

Section: Methodsmentioning

confidence: 99%

“…This strategy combines predator avoidance with delayed emergence until a time when environmental conditions are favorable for juvenile development (2). In the northern regions of their range, the consequence of this behavior must be long exposures to subzero temperatures, since nesting sites (sandy or clay banks without vegetation cover) and nest depths (average, 10 cm) offer limited insulation value (3,4). How do hatchlings survive?…”

mentioning

confidence: 99%

Hatchling turtles survive freezing during winter hibernation.

Storey

Brooks

et al. 1988

Proc. Natl. Acad. Sci. U.S.A.

115

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Hatchlings of the painted turtle (Chrysemys picta marginata) are unique as the only reptile and highest vertebrate life form known to tolerate the natural freezing of extracellular body fluids during winter hibernation. Turtles survived frequent exposures to temperatures as low as -60C to -80C in their shallow terrestrial nests over the [1987][1988] winter. Hatchlings collected in April 1988 had a mean supercooling point of -3.28 ± 0.240C and survived 24 hr of freezing at -40C with 53.4% + 1.98% of total body water as ice. Recovery appeared complete after 20 hr of thawing at 30C. However, freezing at -10.90C, resulting in 67% ice, was lethal. A survey of possible cryoprotectants revealed a 2-to 3-fold increase in glucose content of liver and blood and a 3-fold increase in blood glycerol in response to freezing. Although quantitatively low, these responses by spring turtles strongly indicate that these may be the winter-active cryoprotectants. The total amino acid pool of blood also increased 2.25-fold in freezing-exposed turtles, and taurine accounted for 52% of-the increase. Most organs accumulated high concentrations of lactate during freezing, a response to the ischemic state imposed by extracellular freezing. Changes in glycogen phosphorylase activity and levels of glucose 6-phosphate and fructose 2,6-bisphosphate were also consistent with a dependence on anaerobic glycolysis during freezing. Studies of the molecular mechanisms of natural freeze tolerance in these turtles may identify protective strategies that can be used in mammalian organ cryopreservation technology.Few reptile species occur in northern latitudes. Those that do must have well-developed strategies for winter survival, the most frequent solution being hibernation in thermally buffered sites (underwater or in deep underground dens) (1). However, the survival mechanisms of hatchling painted turtles (Chrysemys picta marginata) have presented an enigma. Hatchlings, born in early autumn from eggs laid in May-June, overwinter in their nests. This strategy combines predator avoidance with delayed emergence until a time when environmental conditions are favorable for juvenile development (2). In the northern regions of their range, the consequence of this behavior must be long exposures to subzero temperatures, since nesting sites (sandy or clay banks without vegetation cover) and nest depths (average, 10 cm) offer limited insulation value (3, 4). How do hatchlings survive? The choices are two: (i) freeze tolerance (a regulated freezing of extracellular water coupled with molecular strategies that render cytoplasmic water unfreezable), and (ii) freeze avoidance (extensive undercooling of body fluids) (5). We report here that hatchling C. picta marginata are freeze tolerant, able to survive for extended times with >50% of total body water frozen as extracellular ice. This is the only known report of natural freezing survival in a reptile. These turtles, along with four species of terrestrially hibernating frogs (5) tTo whom reprint requests ...

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“…However, studies of C. picta have also concluded that gravid females may not have the opportunity to alter clutch sex ratios (Refsnider & Janzen 2012) or may not adjust their nesting behavior sufficiently to alter sex ratios substantially (Schwarzkopf & Brooks 1987, Schwanz & Janzen 2008, Mitchell & Janzen 2010, Renfsnider et al 2013. This supports the conclusion that weather may dominate the sex ratios of hatchling cohorts.…”

Section: Location and Structure Effectsmentioning

confidence: 99%

Weather and sex ratios of head-started Agassiz’s desert tortoise Gopherus agassizii juveniles hatched in natural habitat enclosures

Nagy¹,

Kuchling²,

Hillard³

et al. 2016

Endang. Species. Res.

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Head-starting of Agassiz's desert tortoise, a means to aid recovery of this threatened species, may adversely affect offspring sex ratios via temperature-dependent sex determination combined with possible unnatural thermal conditions in head-start facilities. We determined sex ratios in juvenile tortoises hatched from first clutches of 4 annual cohorts at the head-start facility at the US Marine Corps Base, Twentynine Palms, California, USA, using non-fatal, endoscopic inspection of gonads. Cohort sexes ranged from 97% females (f:m ratio of 6.25:1) in 2008 to 84% males (f:m ratio of 0.19:1) in 2009, apparently primarily in response to local weather conditions during the temperature-sensitive phase of incubation. Warmer weather during development of a second clutch laid in 2009 led to fewer males (55%, f:m ratio of 0.82). Efforts to cool (artificially shade) some nesting burrows were unsuccessful in increasing the proportion of male hatchlings in 2009. Cohort sex ratios were associated with average daily air temperatures during incubation, such that more females were produced during warmer periods, in good agreement with published temperaturecontrolled laboratory experiments. These results suggest that weather played a major role in determining sex ratios, with apparently smaller or negligible influences resulting from initial location, structure and operation of the head-start facility; experimental shading of nests; and individual mothers' variation in the timing of egg laying and placement of nests within the natal burrows. These results, obtained from a remote, mostly natural field site, indicate the potentially great sensitivity of sex determination in nests of wild, free-living desert tortoises to changes in climate.

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Nest-Site Selection and Offspring Sex Ratio in Painted Turtles, Chrysemys picta

Cited by 122 publications

References 21 publications

Terrestrial habitat requirements of nesting freshwater turtles

Terrestrial habitat requirements of nesting freshwater turtles

Hatchling turtles survive freezing during winter hibernation.

Weather and sex ratios of head-started Agassiz’s desert tortoise Gopherus agassizii juveniles hatched in natural habitat enclosures

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