Ken R. Marion

Thermal Ecology of the Lizard, Anolis Limifrons with Comparative Notes on Three Additional Panamanian Anoles

Data on the thermoregulation of Anolis limifrons in Panama suggest that at least some tropical species are less warm adapted than previously thought. Anolis limifrons has a lower minimum voluntary temperature, eccritic temperature, and critical thermal maximum than a majority of the temperate zone lizards thus far studied. Thermoregulatory adjustment is by behavioral mechanisms as indicated by observations on basking and orientation. A seasonality in the preferred temperature is indicated by field data from the wet and dry seasons. It is suggested that the lower preferred temperature in the dry season is an adaptation to conserve water or minimize water loss. Anoles (A. limifrons and A. frenatus) in colsed canopy forests are less warm adapted than the grassland A. auratus, whereas an ecotone species (A. tropidogaster) is intermediate in its thermoregulatory characteristics. Differences in dermal morphology in three species of Panamanian anoles are suggested to be an adaptation to varied capacities of heat gain.

Duration of Incubation of Sceloporus undulatus Eggs at Constant Temperature

Examination of the extensive literature on incubation of eggs of oviparous reptiles reveals little precise information about the duration of the incubation periods. Most laboratory studies have been carried out under conditions of room temperature in all continents save Antarctica and with eggs in all stages of development. Precise information about the relation of length of incubation to such abiotic factors as temperature can be useful in several ways. First, physiological limits during

Natural Growth Rates of Ambystoma maculatum in Alabama

Abstract The Spotted Salamander (Ambystoma maculatum) is widespread throughout the eastern United States and southern Canada. In 1997, we initiated a long-term study of A. maculatum at a breeding pond in Calhoun County, Alabama. Each winter, we captured salamanders as they returned to breed and inserted passive integrated transponders to permit positive identification of recaptures. We fit the von Bertalanffy growth-interval equation to data on snout–vent length taken from individuals captured and recaptured in different years and estimated intrinsic growth rates for both males and females. Males displayed rapid juvenile growth, which slowed as they neared estimated maximum size. Females, however, displayed relatively constant growth until nearing their estimated maximum size. The intrinsic growth rate of females was lower than that estimated for males. We hypothesize that sex-specific growth patterns maximize reproductive efforts of A. maculatum.

A Model for Growth in the Musk Turtle, Sternotherus minor, in a North Florida Spring

Mark-release-recapture measurements were obtained for 120 growth intervals (56 females, 64 males) in a spring-dwelling population of Sternotherus minor in northwestern Florida. Calculation of relative instantaneous growth rates revealed considerable variation in individual growth, especially in smaller animals. Growth curves for straight midline carapace length (CL) and whole body mass (M) were derived separately for each sex by nonlinear least-squares fitting of these data to Gompertz and von Bertalanffy models. Data from concurrent studies on reproductive cycles were combined with growth results to yield the following estimates: the mean age and size at maturity in females is 8.0 yr and 80 mm CL (ranges = 5.6-10.1 yr; 70-85 mm CL), with 90% attaining maturity between 7.1 and 9.0 yr; males mature at a mean age of 5.6 yr and 55 mm CL (ranges = 4.49.25 yr; 50-70 mm CL), with 90% maturing in 4.6-6.6 yr. We suggest independent selection for age and size at maturity between sexes in S. minor, as has been proposed for other species of freshwater turtles.

ANNUAL VARIATION IN POPULATION ESTIMATORS FOR A SOUTHERN POPULATION OF AMBYSTOMA MACULATUM

For six breeding seasons (1997–2002), we conducted an intensive mark-recapture study on a breeding population of the spotted salamander, Ambystoma maculatum, near the southern edge of their range in east-central Alabama. A drift fence completely encircling an ephemeral pond was used to capture all adult salamanders migrating into or out of the pond, and passive integrated transponders were used to provide individual identification. The Jolly-Seber method of population estimation was used to estimate three population parameters (size, gains, and survivorship); population growth rate was also estimated. Gains varied annually, ranging from 24 ± 16 to 101 ± 24, and population growth rate was low (r = 0.18 ± 0.188), suggesting inconsistent recruitment. Consistent with life history parameters of long-lived, late-maturing species, survivorship (range 0.629 ± 0.064 to 0.699 ± 0.08) and breeding population sizes (range 189 ± 24 to 260 ± 16) remained essentially constant. The demographics for A. maculatum provided by this study are useful for planning conservation initiatives.

Growth of the Flattened Musk Turtle, Sternotherus depressus Tinkle and Webb

Abstract Sternotherus depressus (Flattened Musk Turtle) is a threatened endemic of the Black Warrior River basin in northern Alabama. Carapace lengths taken from recaptures of turtles individually marked over an 18-year period were used to generate von Bertalanffy growth curves for both sexes. Females grew faster than males early in life and reached estimated asymptotic size at a younger age. Size-at-sexual-maturity data from previous studies indicate that males reach maturity in 10–12 years, while females mature at 12–15 years. Compared to a spring-dwelling Florida population of S. minor (Loggerhead Musk Turtle), the Flattened Musk Turtle has a slower growth rate, a greater age at maturity, and a smaller asymptotic size. These differing life-history characteristics likely reflect cooler water temperatures and reduced food availability in Flattened Musk Turtle habitats.

Demographic Comparisons between Reservoir-Dwelling and Stream-Dwelling Populations of a Threatened Turtle (Sternotherus depressus Tinkle and Webb)

Abstract n Sternotherus depressus (Flattened Musk Turtle) is a federally threatened species endemic to the Black Warrior River drainage in north-central Alabama. Individuals of both stream-dwelling and impoundment-dwelling populations were trapped for comparative demographic analyses. Carapace length was significantly longer for reservoir turtles than for stream turtles. Size-class distributions between the two populations were also significantly different, with reservoir turtle collections biased toward the larger size classes, and presumably older age classes. These results suggest a reduced recruitment in the reservoir population, and raise concerns about long-term population sustainability in impoundment habitats.

Dispersal Behavior of Diamond-Backed Terrapin Post-Hatchlings

Abstract n Post-emergence dispersal behavior of hatchling turtles has been investigated in several species, and a variety of species-specific orientation patterns have been reported. In the current study, we examined the orientation and dispersal behavior of hatchling, post-hatchling, and yearling Malaclemys terrapin pileata (Mississippi Diamond-backed Terrapin) by utilizing an orientation arena on two natural nesting beaches. Each age group displayed strong orientation and dispersal towards high-marsh vegetation instead of open water. The results suggest an innate behavior in young Diamond-backed Terrapins in which they orient from open beach areas toward vegetated marsh areas. The results also stress the importance of having healthy marsh habitat adjacent to nesting areas to provide critical habitat for these vulnerable life-history stages of Diamond-backed Terrapins.