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The timing and synchrony of sea turtle emergences from the nests are primary factors in determining hatchling vigor and likelihood of survival. A clear benefit of synchronous emergence is a reduction in energy expenditure through social facilitation, but disadvantages also result from reduction in energy stores if hatchlings have to wait any appreciable time in the nest. We investigated hatchling emergence times throughout emergence of the entire clutch for 21 clutches of Flatback Seaturtles, Natator depressus, incubating in a beach hatchery at three clutch sizes and three nest depths. Emergence of the entire clutch spanned an average of 3.1 days, with shallower nests exhibiting greater emergence asynchrony (mean20cm = 4.0 days, mean35cm = 4.5 days) than deeper nests (mean50cm = 1.7 days). Hatchlings emerged through the night, peaking between 2100 and 2200 h, with hatchlings from shallower nests emerging earlier in the night. For natural nests, hatchlings generally emerged within a single night, evident from the low number of hatchlings remaining in the nest the day after emergence. The disparate observations between a beach hatchery, and natural nests provide important conservation implications for hatchery management.
Very few cases of predatory luring by squamate reptiles involve body parts other than the tail. Here, I report the use of the tongue by Mangrove Saltmarsh Snakes (Nerodia clarkii compressicauda) to lure prey, a behavior thus far adequately described for only one other snake species. Fishes are the only verified component of the diet of these snakes and are effectively attracted by the luring behavior. Lingual luring by these snakes is particularly unique in that the tongue is curled upon itself distally such that a conspicuous loop is formed at its terminus. The rapid oscillations typical of chemosensory tongue flicks are absent, though the terminal loop does exhibit some vertical and horizontal movement. The duration of luring tongue flicks is significantly greater than the duration of chemosensory tongue flicks.
Proctoporus consists of six high-elevation lizard species distributed in the cloud forest and puna habitats of Peru and Bolivia. Proctoporus ecology is poorly understood despite a recent increase in phylogenetic research on the clade. To examine differences in diets among species, stomach contents of Proctoporus from 24 sites in central and southern Peru were analyzed, including individuals of all six species. Feeding niches were compared among the species, and differences caused by species, sex, age class, and body size were examined. Proctoporus ate prey items that were large in relation to lizard body size. Collectively, Proctoporus species had broad diets with 10 different arthropod orders represented. Beetles, ants, and spiders made up the largest proportions of diets. Diet overlap was high among species but did not appear to be directly connected to species relatedness. Sex and age class were not important determinants of diet. Despite the small body size and reclusive nature of Proctoporus lizards, they possess the ability to subdue and consume heterogeneous prey species.
The Eastern Red-Spotted Newt (Notophthalmus viridescens) is one of the most widely distributed salamander species in North America. As with many pond-breeding amphibians, little is known about the terrestrial portion of its life cycle. We examined the activities of terrestrial efts and emigrating, postbreeding adults at Mountain Lake Biological Station in Giles County, Virginia, using fluorescent powder tracking. Neither life cycle stage, sex, nor mass affected the distance newts traveled, but emigrating adults traveled in straighter paths than juveniles. Temperature and rainfall affected whether newts emerged from refuge, whereas rainfall and humidity affected the distance traveled of those that emerged. Newts were often found on or close to the surface, using forest debris for cover, and no newts of any stage were observed using subterranean habitat. Our results indicate that newts are wide-ranging and active in the terrestrial habitat postbreeding. We found fluorescent powder tracking to be effective in the field for multiday tracking with some limitations caused by weather and distance. Our results have implications for the conservation of wide-ranging amphibian species, which may travel long distances from wetlands into terrestrial habitat, outside of protective buffer zones.
Surface foraging activity of terrestrial urodeles in northern climates is restricted by unfavorable conditions during extended portions of the year. Thus, salamanders should forage intensively during the short active season in order to reach maturity rapidly and gain sufficient energy to ensure an optimized reproductive frequency. We examined whether the Red-Backed Salamander, Plethodon cinereus, conforms to these predictions at the Mastigouche Reserve (Quebec, Canada) near the northern limits of the species' distribution. During one active season (1997), we monitored surface movements in four subpopulations by a system of drift fences and pitfalls, and we analyzed reproductive traits (testis and follicle sizes) in two of these subpopulations. Age of specimens was determined by skeletochronology. Salamanders captured during the first two weeks of October represented 63.6% of a total of 775 salamanders found in pitfalls in the four study sites for the entire sampling period. None or very few were captured in midsummer although July and August recorded the greatest precipitation; less than 7.8% were from late spring/early summer samplings. Sex ratio of juveniles was skewed toward females. Males reach maturity in 3–5 yr and seem to reproduce annually. Females oviposit for the first time at 4–6 yr but, according to follicular growth rate, necessitate another three years to produce a second clutch. However, longevity in these salamanders is only 8–9 yr. Plethodon cinereus at the study site does not meet our predictions of optimized surface activity and reproductive traits; nevertheless, populations maintained high abundance.
Studies on the effects of group composition (i.e., kin or mixed groups) on metamorphic traits (SVL, body mass, and duration of larval period) can provide insights into the evolution and maintenance of kin selection in anurans. Tadpoles of Bufo scaber from different sibships were reared at varying densities as sibling or mixed groups to determine the influence of kinship on metamorphic traits. Body mass, SVL, and larval period were similar among sibships reared in isolation. When 10 tadpoles were reared in 1- or 5-liter water, growth, larval period, and size at metamorphosis were comparable between sibling and mixed groups. In contrast, when the density of rearing was increased to 20 or 40 tadpoles per five liters, metamorph size was significantly lower in sibling groups than in mixed groups. Crowding negatively affected growth, body mass, and SVL in both kin and mixed groups. In mixed groups, metamorphosis was delayed, and metamorphs were larger than those reared as siblings at corresponding densities. Further, there was a large variation in body mass and larval period indicating, albeit indirectly, asymmetric competition among the mixed group individuals unlike in sibling groups. The present findings demonstrate that, in B. scaber, kinship plays a role in driving the metamorphic traits in a context-dependent manner. They also show that effects of kinship are expressed selectively under adverse ecological situations such as overcrowding.
Nest-site selection and the behavioral mechanisms driving selection have received relatively little attention in nesting ecology studies despite their importance when establishing conservation and management programs for endangered taxa that have obligate habitat-specific nesting requirements. The nesting ecology of Cyclura cychlura cychlura was studied on Andros Island, Bahamas, from 2001 to 2004 to elucidate factors influencing nest site selection and address conservation and management implications. Female iguanas predominantly used active Nasutitermes rippertii (Termitidae: Isoptera) termite mounds as egg incubation chambers. Nesting females selected mounds with >5 cm surrounding soil depth and initiated excavation and oviposition in early May. There was no correlation between female body size and termite mound size. Tunnels were excavated into lateral sides of mounds and terminated in nest chambers. Eggs were deposited outside the mound and pushed into the chamber using thrusts of the forelimbs. Mean egg incubation length for the combined 2003 and 2004 seasons was 75.7 days. Temperatures inside the mound were warmer and less variable than corresponding ambient temperatures. Mean hatching success for clutches in monitored nests ranged from 69.9–100% from 2002 to 2004. The nesting behavior of C. cychlura on Andros most likely reflects the effects of local climatic history and topography on reproductive attributes such as nest success. Elucidating annual female nesting effort, as indicated by active nests, could be an extremely useful indicator to assess both the number of breeding females and, indirectly, the potential for hatchling recruitment.
Demographic studies on long-lived organisms are uncommon, largely because of the long time periods necessary to collect even the most basic data. We report results of the first long-term growth study of a non-Amazonian Neotropical freshwater turtle, the chelid Hydromedusa maximiliani. Differences were detected among males, females, and juveniles. Juveniles had higher growth rates (body size and mass) than adult males and females. A significant negative relationship existed between growth rate and mean body size of males and females, which was best defined by linear equations. Growth constants (k) estimated from the von Bertallanfy model were 0.094 for females and 0.073 for males, and the parameter b was 0.75 for females and 0.77 for males. Based on the von Bertallanfy equation, estimated age at sexual maturity was 14 yr (11.6–16.6 yr) for males and 9 yr (5.7–11.9 yr) for females, whereas longevity was estimated at about 100 yr for both sexes. This represents the greatest expected life span reported for a chelid turtle. Because the geographical distribution of H. maximiliani is restricted to mountainous regions of the Atlantic rain forest, one of the world's biodiversity hotspots, and because the species is long-lived and late maturing and appears to have a set of life-history traits unique among chelid turtles, a conservation program that extends beyond existing conservation units may be necessary to ensure its survival.
Habitat disturbance leading to the breakdown of ecological barriers has resulted in hybridization between numerous sympatric species and the decline or extinction of the parental species. Despite strong postzygotic selection, hybridization occurs between two normally ecologically isolated toad species, the Gulf Coast Toad (Bufo nebulifer) and Fowler's Toad (Bufo fowleri). This hybridization has potentially contributed to a decline of the rarer species, B. fowleri. Putative hybrids may be morphologically cryptic; therefore, molecular methods were used to identify them. We used single nucleotide polymorphisms (SNPs) to identify hybrids, and mitochondrial sequence variation in a segment of the 12S and 16S rRNA region was also used to identify maternal ancestry of hybrids and seek evidence of directional hybridization and introgression of male B. nebulifer with female B. fowleri. Seventy-two individuals of both species from nine breeding populations were directly sequenced. Twelve species-specific SNPs from a 333 base pair fragment in a nuclear intron of the Rhodopsin gene were used to identify each species, and two male hybrids were identified based on heterozygosity at these sites. The possession of a different mtDNA sequence by each hybrid indicated an alternate maternal lineage from each of the parental species and identified the hybrids as progeny from each reciprocal cross. Use of mitochondrial and nuclear molecular markers allowed unambiguous identification of hybrids and their maternal parent that could not have been performed without the use of both datasets. We also investigated phylogenetic relationships among B. fowleri and its close relatives in the B. americanus species complex using mitochondrial sequence variation.
Reproduction can impose “costs” associated with the burden of carrying developing embryos or eggs. Numerous studies using squamate reptiles have documented a reduction in locomotor performance related to reproduction. Recently several experimental studies have attempted to determine whether the reduction in locomotor performance is physical or physiological. However, no consensus has been reached, and there is evidence that effects are species specific. In addition, no previous studies have documented whether the reduction in performance is consistent from year to year. For this study, we measured the endurance performance on a motorized treadmill of Side-Blotched Lizards (Uta stansburiana) during their natural breeding season over two years. Our goals for this study were to determine (1) to what degree reproductive state reduces endurance, (2) whether females recover endurance capacity quickly (evidence of physical burden only), and (3) whether the change in performance associated with reproduction is consistent from year to year. Results from 812 trials over two years revealed a general decrease in endurance capacity associated with reproductive state such that females with shelled eggs were only able to run 80–85% as far as nongravid females. This decrement in performance is not related to relative clutch mass, suggesting a physiological effect. However, post-reproductive females recovered to nongravid levels of endurance within ∼12 h of oviposition, suggesting the decrement in performance was physical. Results were qualitatively similar in both study years indicating that changes in locomotor performance associated with reproduction may be consistently imposed from year to year.
Vertebral remains assignable to the extant snake Boa constrictor, found in the Toropí Formation (Late Pleistocene, Lujanian age) at Arroyo Toropí, northeastern Argentina, are here described. These remains represent the first snake record from the Lujanian age and determine the minimum age for the species as 50–35 ka BP. Boa is presently absent in northeastern Argentina. Interruption of the continuity between the Mesopotamian and Brazilian faunas, including disappearance of Boa from Mesopotamia (northeastern Argentina), occurred subsequent to the Late Pleistocene and might be explained by changes in the Paraná and Uruguay Rivers. In addition, previous taxonomic referral of fossils to ?Boa is revised, with the conclusion that the specimen from the Early Eocene is tentatively referred to this genus, whereas that from the Pliocene is an indeterminate Boinae.
Many of the early indications of climate change detected in the United Kingdom have been changes in phenology and in particular the early occurrence of key biological events. Significant trends toward earlier breeding have been found in recent decades in most amphibian species in the United Kingdom, one notable exception being the Common Frog, Rana temporaria. We examine data for this species from the United Kingdom's Environmental Change Network for trends in breeding timing. Significant trends toward earlier congregation and spawning were found but not earlier hatching. The observed trends are strongly associated with climate, especially temperature.
Southern Leopard Frogs, Rana sphenocephala, are habitat generalists occurring in virtually all freshwater habitats within their geographic range, whereas Gopher Frogs, Rana capito, typically breed in ponds that do not normally contain fish. To evaluate the potential for predation by fish to influence the distribution of these species, we conducted a randomized factorial experiment. We examined the survival rate and behavior of tadpoles when exposed to Warmouth Sunfish, Lepomis gulosus, Banded Sunfish, Enneacanthus obesus, and Eastern Mosquitofish, Gambusia holbrooki. We also conducted a choice experiment to examine the survival rate of the two species of tadpoles when a predator is given a choice of both species simultaneously. Lepomis gulosus consumed the most tadpoles and ate significantly more tadpoles of R. capito than R. sphenocephala. Gambusia holbrooki injured the most tadpoles, especially R. capito. Enneacanthus obesus did not have an effect on behavior or survival of either anuran species. Tadpoles of both anurans increased hiding when in the presence of L. gulosus and G. holbrooki, but a greater proportion of R. capito hid than did R. sphenocephala. Our results suggest that R. capito are more vulnerable to predation by fish than are R. sphenocephala. The introduction of fish may play a role in population declines of certain anurans breeding in normally fish-free wetlands, and even small fish, such as mosquitofish, may have significant negative effects on the tadpoles of R. capito.
The Maya Forest Monitoring Project (Mayamon) was established in 1997 as an outgrowth of the Belize working group of the Declining Amphibian Populations Task Force. For nine years, Mayamon volunteers censused anuran populations using a protocol that estimates numbers of individuals on the basis of male vocalization. To date, the protocol has been evaluated only through a series of post hoc power analyses; I performed the first field test to assess the effect of species-specific mating system characteristics, survey length, survey frequency, and pond selection on census results for anuran communities within a tropical moist forest in Belize. Under the current protocol, it would take, on average, 359 months of sampling to detect the 11 species I detected at this site using vocalization surveys. In addition, I introduce a method using ANCOVA to determine ideal survey length. Arbitrarily setting the ideal detection to 90% yields a required sampling protocol of 21 minutes; the current minimum of 15 min yields only an 80% detection rate. This method could be adapted for use with other monitoring programs, allowing both the assessment of current efficacy and the extrapolation of required sampling length to reach a given efficacy. The results of these approaches indicate that the Mayamon protocol methodology should be extended if it is to allow investigators to adequately understand the community dynamics of amphibians.
The Boreal Toad (Bufo boreas boreas) is widely distributed in the western United States but has declined in portions of its range. Research directed at conserving Boreal Toads has indicated that their movements are largely terrestrial and often limited after the breeding season. We used a combination of stream-based netting, PIT tagging, and radio telemetry to examine patterns in captures, movements, and habitat use of Boreal Toads associated with two stream valleys in western Montana. Netting produced 514 captures of 118 adult and 203 juvenile toads from 8 July to 19 August 2003. Juveniles dominated catches initially but declined throughout the summer, whereas adult catches showed less consistent temporal trends. Of the 122 PIT-tagged toads, nearly two-thirds were recaptured 1–7 times in hoop nets, and the median total distance moved was over 1 km downstream. The median distance moved by radio-tagged toads was 2.1 km (maximum, 12.0 km) or 2.9 km (maximum, 13.0 km) if movements before and after radios were affixed are included. Over 17% of relocations of radio-tagged toads were at upland sites, 56% were in riparian zones, and 26% were in or adjacent to water. We believe that Boreal Toads in this area are engaging in long-distance movements between overwintering, breeding, and summer growth sites. Downward redistribution via streams may be common in montane habitats and warrants examination in other regions.
Apart from certain species of the African clade, the lizard family Lacertidae has generally been described as consisting of active foragers. We made quantitative field observations of 14 species of lacertid lizards, mainly belonging to the more basal Eurasian clade. Our data show that sit-and-wait foraging is much more widespread in Lacertidae than previously alleged. We also investigated the influence of weather and times of day on foraging activity levels and conclude that for comparative purposes observations should be restricted to circumstances that are optimal for activity. We did not find sex differences in foraging behavior.
A new species of the Neotropical frog genus Odontophrynus from coastal regions of Brazil and Uruguay is described. It is included in the americanus species group and has a diploid complement of 22 chromosomes. Odontophrynus sp. nov. is distinguished from the other species of the americanus group by having smaller size, head nearly as wide as long, skin on dorsum bearing small-sized warts, and distinct postorbital and parotoid glands that form a longitudinal ridge. Moreover, the new species has a pair of enlarged postorbital dark blotches around the afore-mentioned glandular ridge and few small-sized dark blotches on the upper lip and forelimbs. Odontophrynus sp. nov. is also characterized by nasals and frontoparietals well separated from one another, frontoparietal fontanelle exposed anteriorly, and the maxillar process of nasals slightly separated from the nasal process of the pterygoids.
The discrimination ability of Texas Horned Lizards (Phrynosoma cornutum) during antipredator responses was tested with snakes of two genera having distinctly different prey foraging and subjugation strategies; Western Diamondback Rattlesnakes (Crotalus atrox) are “sit-and-wait” predators with a venomous strike from ambush, whereas whipsnakes (Masticophis spp.) are nonvenomous, rapid pursuit-and-grasp predators. Neither snake constricts prey; both ingest prey whole. Lizards were watched for reactions during close approaches by moving snakes. All unapproached and some approached lizards remained alert and motionless. Approached lizards that reacted either (1) ran rapidly to a distant point in the large enclosure, or (2) maintained their position but dorsoventrally flattened their body and tilted their stance, orienting a “dorsal shield” posture toward the snake. The distinctly contrasting responses of the lizards to the two snakes were significantly different, relocation running from rattlesnakes and stationary-body reorientation toward whipsnakes. For slow-running, broad-bodied Texas Horned Lizards, running is an appropriate escape response to a nonpursuing venomous predator, whereas the nonrunning body-conformation/orientation change is an appropriate defensive response, advertising size and spiny defenses, to a rapid-pursuit snake that must grasp prey with its jaws to effect capture and subjugation. Apparently horned lizards visually recognized, probably innately, the two snake taxa as different categories of predator threat.
Reproductive patterns are highly variable among Neotropical colubrids. Snakes of the Tribe Xenodontini are widely distributed in South America and show continuous reproductive cycles in many areas. We report interspecific and intraspecific variation in reproductive traits among these snakes and also show that seasonal cycles occur mainly in cooler areas. Clutch size relative to body size is similar among species, but Erythrolamprus spp. seem to lay fewer eggs than other species, and Waglerophis merremii from southeastern and southern Brazil lay more eggs than other species. Newborn Erythrolamprus are larger than all other Xenodontini, which may be related to ophiophagy. As in many other snakes, adult females are larger than males, but both sexes attain maturity with a proportionally similar body size. The sexual size dimorphism index is generally lower in smaller bodied species, and combat may be absent in the tribe. Male reproductive cycles are less well studied but seem to be more conservative, being continuous in all species studied (W. merremii, Xenodon neuwiedii, and Liophis miliaris). Phylogeny has an important role in reproductive patterns but climate and life-history traits can also influence tropical and subptropical species.
Radio telemetry was used to track 16 adult Short-Horned Lizards (Phrynosoma hernandesi) to their individual overwintering sites on the Central Plains Experimental Range (CPER) in Weld County, Colorado. Above-ground habitat characteristics of overwintering sites and randomly selected points within the study area were assessed. All individuals entered overwintering between 29 August and 19 September with a mean estimated entrance date of 7 September. Arrival of the first subzero nighttime air temperatures occurred shortly thereafter on 16 September. No lizard left its normal area of use to overwinter, and there was no tendency to aggregate. Lizards did not necessarily overwinter on warmer south-facing slopes; the proportion of overwintering sites oriented southward (0.62) was not different from random. Most lizards (75%) selected overwintering sites in the banks of washes that had relatively steep slopes and at specific locations where substrate was relatively bare and penetrable. Overwintering sites also tended to have a greater coverage of Yucca glauca (0.02%) than the general study area (0.01%). Analyses of historical soil temperature data from the CPER revealed that lizards would have to overwinter at a subsoil depth of about 1 m to avoid freezing temperatures. Banks that contain suitable hibernation sites that are located within an individual's normal area of use may be the habitat feature most important to successful overwintering.
A new species of Amphisbaena is described from Fazenda Caraibas, municipality of Mucugê, state of Bahia, Brazil, in the northern portion of the Serra do Espinhaço. The new species is a small amphisbaenian without precloacal pores, 210–213 body annuli, 12–13 tail annuli without evident autotomic site, and 14 dorsal and 14–15 ventral segments per annuli at midbody. The striking difference of this form is the presence of small tubercles on the dorsal region of its tail. This feature is unique among its congeners, although Rhineura floridana, a North American amphisbaenian, has tubercles on its tail. We suggest that the presence of tubercles on the tail of Amphisbaena sp. nov. and Rhineura floridana has arisen independently.
The description of patterns of variation in any character system within well-defined species is fundamental for understanding lineage diversification and the identification of geographic units that represent opportunities for sustained evolutionary divergence. In this paper, we analyze intraspecific variation in cranial shape in the Pumpkin Toadlet, Brachycephalus ephippium–a miniaturized species composed of isolated populations on the slopes of the mountain ranges of southeastern Brazil. Shape variables were derived using geometric-statistical methods that describe shape change as localized deformations in a spatial framework defined by anatomical landmarks in the cranium of B. ephippium. By statistically weighting differences between landmarks that are not close together (changes at larger geometric scale), cranial variation among geographic samples of B. ephippium appears continuous with no obvious gaps. This pattern of variation is caused by a confounding effect between within-sample allometry and among-sample shape differences. In contrast, by statistically weighting differences between landmarks that are at close spacing (changes at smaller geometric scale), differences in shape within- and among-sample variation are not confounded, and a marked geographic differentiation among population samples of B. ephippium emerges. The observed pattern of geographic differentiation in cranial shape apparently cannot be explained as isolation-by-distance. This study provides the first evidence that the detection of morphological variation or lack thereof, that is, morphological conservatism, may be conditional on the scale of measurement of variation in shape within the methodological formalism of geometric morphometrics.
We describe a new species of lizard of the genus Liolaemus from northwestern Chubut Province, Argentina. This new species belongs to the fitzingerii group and is easily distinguished from other members of the group by a combination of morphological and genetic characters. The new species is diagnosable in showing the following combination of characters: dorsal pattern with a conspicuous vertebral band, presence of pre- and postscapular spots, prominent neck folds, and analysis of DNA sequence data from 810 base pairs of the cytochrome b gene (∼4% sequence divergence from its sister taxa Liolaemus fitzingerii). The fitzingerii complex now includes three described species, all restricted to Patagonia, and the new species described here is endemic to a small lowland area in central Patagonia.
Reproduction in amphibians is stressful and perhaps more so in females than males because of the higher energetic costs of producing eggs than sperm. The ratio of two white blood cells, neutrophils and lymphocytes, has been shown in birds, turtles, and amphibians to increase with stress. We captured breeding and nonbreeding, paedomorphic Mole Salamanders (Ambystoma talpoideum), to determine whether the stress of reproduction is reflected by neutrophil:lymphocyte ratios in this species. In blood smears of all individuals, we observed approximately 25.5 leukocytes per 1000 erythrocytes, with 13% of the leukocytes being neutrophils, 41% lymphocytes, and 46% eosinophils. Less than 1% of leukocytes were basophils and monocytes. Neutrophil:lymphocyte ratios of gravid females were significantly higher (and also more variable) than those of reproductive males and of nonreproductive individuals, indicating a higher degree of physiological stress in reproductive females. Reproductive males did not have higher ratios than nonreproductive individuals. We found no effect of body size on neutrophil:lymphocyte ratios. Our hematological stress results are consistent with studies of other amphibians where different methods were used and with other taxa.
There are currently few harvest regulations for the Common Snapping Turtle (Chelydra serpentina) in West Virginia. Uncontrolled harvest of long-lived species with delayed sexual maturity may lead to long-term declines in populations. We analyzed a 17-year data set from a mark-recapture study on an unharvested population of the Common Snapping Turtle in Canaan Valley, West Virginia. We captured 91 snapping turtles (47 female, 44 male). Program MARK was used to analyze 10 competing models predicting adult Common Snapping Turtle survival and capture probabilities and compared the models using Akaike Information Criterion values corrected for small sample size (AICc). The estimated annual survival was 0.97 and the annual capture probability was 0.11. We found that the best performing model involved constant survival and capture probability that varied based on the mass at initial capture. This suggests that there is no difference in survival between males and females. Moreover, the size of trap may affect the capture of smaller and larger individuals and researchers should use multiple trap types to assess turtle abundance.
In reptiles, thermoregulation is important because it alters the rate of many physiological processes. Thermoregulation may be especially important to reproductive females that inhabit regions where the growing season is short, because the amount of thermal energy experienced during the season may limit the amount of energy devoted to egg production. We studied basking behavior of Painted Turtles (Chrysemys picta) in Algonquin Park, Ontario, during the period of follicular recrudescence, a time of year when females allocate energy to developing follicles. Based on the notion that females bask (in part) to increase the amount of energy they allocate to developing follicles, we tested whether basking duration was greater in females than in males. Between 14 and 21 August 2003, we found that females basked longer than males on three of seven days, but males never basked significantly longer than females. Within sex, male but not female body size was positively related to basking duration. Our study suggests that the energetic demands of egg production result in an increased basking duration for females in this northern population. Males may bask to reach a certain temperature then return to water because of potential mating opportunities. Future studies should combine body temperature measurements with behavioral observations to elucidate further the reasons for sex-biased basking.