Chelonian Conservation and Biology: Celebrating 25 Years as the World's Turtle and Tortoise Journal Volume 19: Issue 1

Peter C.H. Pritchard and an adult male Western Santa Cruz Giant Tortoise, *Chelonoidis porteri,* in La Reserva, Santa Cruz, Galápagos Islands, Ecuador, 1982. Photo by Anders G.J. Rhodin
Citation: Chelonian Conservation and Biology: Celebrating 25 Years as the World's Turtle and Tortoise Journal 19, 1; 10.2744/1071-8443.19.1.1

“Many express surprise that a career based on seeking to discover, observe and understand the shelled reptiles could have any breadth or depth; but I can assure such doubters that my life and travels have been joyous and far-reaching. For it is only travel with a theme that takes one to the remote corners of the world where the voyager, simply because he is a rare species, is embraced

Abstract

The Coahuila box turtle (Terrapene coahuila) is an endangered species of chelonian endemic to the Cuatro Ciénegas valley in northern Mexico. It is the only aquatic member of the genus Terrapene and is dependent on permanent and seasonal wetlands. Over the past several decades, T. coahuila populations have declined from habitat loss as the wetlands have dried due to human modification of the valley. We conducted a survey of the status of the species from 2011 to 2018, updating previous estimates of population density and overall population size. We also collected data on sex ratio in each of the 8 wetland study areas in the valley and report a strongly male-biased sex ratio. Our results indicate a total population size of approximately 1791 individuals, based on recorded densities from 0.24 to 3.3 individuals/ha among 539.76 ha of suitable habitat in the 8 wetland areas. This estimate is lower than previous studies indicated, implying direct effects of habitat loss on T. coahuila. If habitat loss due to lowering of the water table continues, this species will become extinct. We recommend conservation measures including upgrading the species' International Union for Conservation of Nature Red List status to Critically Endangered, protecting and restoring key wetlands in the valley, and establishing captive assurance colonies in Mexico.

Abstract

Understanding the interface between spatial and thermal ecology is integral to understanding energy acquisition and the life histories of ectotherms. Snapping turtles (Chelydra serpentina) occupy a wide range of habitats that vary greatly in their thermal properties. We studied activity, movements, and thermoregulation of C. serpentina in a small, land-locked lake in central Michigan, USA, using radiotelemetry. Consistent with our a priori predictions, turtles were active within core areas along the lake's edge, showed both diurnal and nocturnal activity, and did not make extensive interwetland movements. Turtles left the lake only for nesting or to hibernate in Sphagnum peat or in the banks of a nearby stream. Home range and core area size estimates of C. serpentina were small compared with other previously studied populations, perhaps in part because of the small dimensions of our lake. Contrary to our prediction of a broad T_set (thermoregulatory set-point) range for a large-bodied, habitat generalist turtle, we found a comparatively low and narrow laboratory-determined T_set range (22°C–26°C). Turtle body temperatures (T_b) cycled between May and August and attained maximal values during the evening hours, a pattern that likely results from thermal inertia, the selection of aquatic thermal patches, or both, as T_e (operative temperatures) declined. Turtles most effectively maintained T_b within T_set during July and August when thermal conditions were most favorable. Throughout most of the active season the highly aquatic habits of C. serpentina apparently negated the effects of variations in daily weather conditions and their effects on incoming levels of solar radiation on variation in T_b. However, turtles maintained higher average T_b on sunny days compared with overcast days in April and May, the coolest months of the study. Diel T_b cycling ceased during September and October and average T_b declined despite favorable thermal conditions, at least during September, a pattern that could reflect a downward shift in the T_set range. Comparatively, C. serpentina is less effective at thermoregulating than is a small-bodied species at a similar latitude (Chrysemys picta marginata). Apparently, thermal inertia and lack of atmospheric basking proclivities influenced the thermoregulatory precision in our turtles.

Abstract

The loggerhead musk turtle (Sternotherus minor) and eastern musk turtle (Sternotherus odoratus) are widespread species considered common throughout much of their respective ranges. Florida populations of S. minor and S. odoratus inhabit a variety of habitats, including freshwater springs and spring runs. We sampled populations of S. minor and S. odoratus from May 2000 through July 2015 as part of a long-term freshwater turtle assemblage study in a state-protected spring-run complex in central Florida. For each species, we 1) generated population estimates, 2) quantified survivorship and recruitment, and 3) calculated sex ratios, biomass, and density. Population estimates were 3417 for S. minor and 1977 for S. odoratus. Sex ratios were approximately 1:1 for both species, and density and biomass estimates were higher than most previous studies. Annual apparent survivorship was higher in male S. minor than in females, but the opposite was true for S. odoratus. Lambda values (k) suggest stable to slowly increasing populations for both species. Population growth rates for S. odoratus were equally influenced by both adult female mortality and mortality of first-year turtles, while those for S. minor were influenced by only adult female mortality. The lower fecundity values for S. odoratus may increase the importance of younger age classes in maintaining populations. Healthy populations of common species are important in maintaining overall community functions, as they often provide the base for many ecosystems. Therefore, it is prudent to promote conservation of common species to protect ecosystem structures and services.

“Distribution, Size, and Demographics of Eastern Hermann's Tortoise, Testudo hermanni boettgeri, in Turkey” by O. Turkozan, C. Yilmaz, Ş. Karakaya, S. Karaman, and C. Ulger, Chelonian Conservation and Biology 18(2):210– 216 (2019).

Unfortunately, Figure 5A of the original article was accidentally published twice. The correct figure is presented below.

Figure 5Relationship of mass to straight carapace length in male (A, n = 131) and female (B, n = 94) *Testudo hermanni boettgeri* in European Turkey, 2014, 2015, and 2016.
Citation: Chelonian Conservation and Biology: Celebrating 25 Years as the World's Turtle and Tortoise Journal 19, 1; 10.2744/1071-8443.19.1.i