Physiological and Behavioral Variation in Estivation among Mud Turtles (Kinosternonspp.)

Abstract

Kinosternid mud turtles, a primarily aquatic group, exhibit variable degrees of terrestrial activity in the Sonoran and Chihuahuan Deserts. We compared behavioral and physiological responses to dry conditions in four populations representing three species, Kinosternon sonoriense, Kinosternon flavescens, and Kinosternon hirtipes. All four groups were subjected to simulated dry season conditions in the laboratory, during which activity was monitored and physiological responses (blood chemistry and rates of resting metabolism and evaporative water loss) were measured. Kinosternon flavescens and K. hirtipes represented extremes in apparent ability to estivate, based on activity and rate of increase of plasma osmolality. Two populations of K. sonoriense exhibited intraspecific differences in behavioral and physiological measures that were related to extant environmental conditions. Large numbers of K. sonoriense from Arizona and K. hirtipes, the poorest estivators, had to be rehydrated after only 30 d out of water. Kinosteron flavescens had the lowest metabolic rates, but no evidence of metabolic depression during dehydration was found for any of the four populations. We conclude that the differences in capacity for estivation among populations are primarily linked to variable behavioral responses to dry conditions, though high rates of evaporative water loss in K. hirtipes represent a probable physiological constraint.

Generally specialized or especially general? Habitat selection by Snapping Turtles (Chelydra serpentina) in central Ontario

“…Although specialization of different phenotypes on different habitat types has been demonstrated in some birds (Ebenman and Nilsson 1982), and evidence for individual diet specialization has been found in lizards (Lister 1976) and in some snails (West 1986), there are still large knowledge gaps regarding individual specialization and its effects on resource selection. Variation in behaviour between populations (Ligon and Peterson 2002;Rees et al 2009) and within populations (Roe and Georges 2008) has been shown to be important in some turtle species and may represent physiological constraints, heritable traits, and (or) behavioural plasticity in response to environmental factors. Resource selection may also undergo ontogenetic shifts (Stamps 1983;Lind and Welsh 1994) or differ between the sexes (Ardia and Bildstein 1997;Bull 2006).…”

Reproductive Characteristics of Colostethus marchesianus from Its Type Locality in Amazonas, Brazil

“…Thus, they are confirmed to make behavioral use of the physiological capacity for estivation that has been demonstrated in the laboratory (Peterson and Stone, 2000;Ligon and Peterson, 2002). All animals equipped with radiotransmitters engaged in terrestrial estivation during the study, all were estivating at the onset of the rainy season, and all returned to the aquatic environment within a few days of the onset of the rainy season.…”

“…Because water is periodically unavailable during periods of drought, Stone (2001) also hypothesized that K. sonoriense engaged in terrestrial estivation to survive drought. Simulated estivation trials in the laboratory revealed that K. sonoriense is capable of surviving many weeks without food and water (Peterson and Stone, 2000;Ligon and Peterson, 2002). The response of K. sonoriense to such conditions was similar to K. flavescens, a welldocumented terrestrial estivator (Seidel 1978;Iverson, 1990), treated identically (Peterson and Stone, 2000;Ligon and Peterson, 2002).…”

“…Populations of K. sonoriense in Arizona and New Mexico appear to differ in proclivity for terrestrial activity (Ligon and Peterson, 2002). In Arizona, K. sonoriense are reported to be highly aquatic, inhabiting permanent creeks, streams, and ponds.…”

“…In several years of collecting I observed only one specimen, a basking male, out of the water.'' Evidence suggests that behavioral differences affect the capacity for estivation among populations (Ligon and Peterson, 2002). However, it remains unclear if the lack of published data on estivation in Arizona K. sonoriense accurately reflects the degree to which estivation is used by this species.…”