The stomach contents of post-hatchling green and loggerhead sea turtles in the southwest Pacific: an insight into habitat association

Dietary information obtained from stomach contents can provide a wealth of information on an animal’s ecology. Where animals are cryptic, such as the post-hatchling life history stage of a sea turtle, the ecological insight that dietary analyses can provide, may be otherwise unobtainable. Investigations into post-hatchling turtle stomach contents have found planktonic organisms, dominated by pelagic molluscs and crustaceans, hydrozoans, Sargassum and fish eggs. The nature of these dietary organisms provides evidence for the widely accepted hypothesis that, with the exception of the flatback turtle (Natator depressus), the post-hatchling stage of a sea turtle’s life history is pelagic and oceanic. As the majority of studies that have investigated the stomach contents of post-hatchling sea turtles have been conducted on loggerhead turtles (Caretta caretta) in the northern Atlantic and Pacific Oceans, insight derived from dietary investigations into post-hatchling ecology is biased. This study investigates the diet of post-hatchling green turtles (Chelonia mydas) and loggerhead turtles in the southwest Pacific Ocean. Stomach contents were obtained from 55 green and loggerhead post-hatchling turtles that had stranded or been consumed by Coryphaena hippurus. Our findings demonstrate that loggerhead and green post-hatchlings in the southwest Pacific share similar feeding ecology and feed on a variety of neustonic items that are indicative of an oceanic and pelagic existence. The dietary items consumed by both species investigated belong to similar taxonomic groups as those found in previous studies with species level distinctions occurring owing to the different geographical location.     

Habitat use of a multispecific seagrass meadow by green turtles Chelonia mydas at Mayotte Island

We investigated the habitat use in green turtles exploiting a 13-ha multispecific seagrass meadow at Mayotte Island, south-western Indian Ocean. A phyto-ecological survey shows the occurrence of eight seagrass species, dominated by Halodule uninervis and Syringodium isoetifolium, distributed according to four distinct seagrass communities along the depth gradient. Direct underwater censuses show that green turtles occurred all over the meadow. Yet when community relative surface area was taken into account green turtles preferentially frequented the most seaward, biomass-richer S. isoetifolium-dominated community, suggesting that green turtles compensate for their intrinsically nutrient-poor herbivorous diet. Additionally, smaller (<80 cm standard curved carapace length, SCCL) individuals also preferentially occurred in the most shoreward H. univervis-dominated community where no larger (>80 cm SCCL) individuals were sighted, suggesting habitat use is indicative of diet selection and may reflect size-specific food requirements and physiology.     

Delayed ontogenic dietary shift and high levels of omnivory in green turtles (<Emphasis Type="Italic">Chelonia mydas</Emphasis>) from the NW coast of Africa

Young green turtles (Chelonia mydas) spend their early lives as oceanic omnivores with a prevalence of animal prey. Once they settle into neritic habitats (recruitment), they are thought to shift rapidly to an herbivorous diet, as revealed by studies in the Greater Caribbean. However, the precise timing of the ontogenic dietary shift and the actual relevance of animal prey in the diet of neritic green turtles are poorly known elsewhere. Stable isotopes of carbon, sulfur and nitrogen in the carapace scutes of 19 green turtles from Mauritania (NW Africa), ranging from 26 to 102 cm in curved carapace length (CCLmin), were analyzed to test the hypothesis of a rapid dietary shift after recruitment. Although the length of residence time in neritic habitats increased with turtle length, as revealed by a significant correlation between turtle length and the δ¹³C and the δ³⁴S of the scutes, comparison of the δ¹⁵N of the innermost and outermost layers of carapace scutes demonstrated that consumption of macrophytes did not always start immediately after recruitment, and turtles often resumed an animal-based diet after starting to graze on seagrasses. As a consequence, seagrass consumption did not increase gradually with turtle size and animal prey largely contributed to the diet of turtles within the range 29–59 cm CCLmin (76–99% of assimilated nutrients). Seagrass consumption by turtles larger than 59 cm CCLmin was higher, but they still relied largely on animal prey (53–76% of assimilated nutrients). Thus, throughout most of their neritic juvenile life, green turtles from NW Africa would be better classified as omnivores rather than herbivores. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

A jellyfish diet for the herbivorous green turtle Chelonia mydas in the temperate SW Atlantic

Feeding ecology of juvenile green turtles (Chelonia mydas) was studied from 2008 to 2011 at Samborombón Bay (35°30′–36°30′S, Argentina), combining data on digestive tract examination and stable isotope analysis through a Bayesian mixing model. We found that animal matter, in particular gelatinous plankton, was consumed in large proportions compared to herbivorous food items such as terrestrial plants and macroalgae. This diet is facilitated by the high abundance of gelatinous plankton in the region, thus confirming the adaptive foraging behaviour of the juveniles according to prey abundance in the SW Atlantic. To our knowledge, this is the first study to employ this combination of techniques and to conclusively demonstrate that animal matter, in particular gelatinous plankton, is important in the diet of the neritic green sea turtles.     

Population ecology of the green/black turtle (<Emphasis Type="Italic">Chelonia mydas</Emphasis>) in Bahía Magdalena,Mexico

The mangrove channels of Bahía Magdalena, Mexico, are important developmental areas for juvenile green, or black turtles (Chelonia mydas), but incidental bycatch and illegal hunting threaten population persistence. We studied size distribution, condition index (CI), growth rates, and mortality of black turtles in Estero Banderitas, the largest mangrove channel in Bahía Magdalena, to supply information for the development of effective conservation strategies. A total of 213 black turtles (including 88 recaptures) were caught in entanglement nets between July 2000 and July 2003. Average yearly catch per unit of effort (CPUE, 1 unit: 100 m of net fishing for 12 h) dropped during the study from 2.19 to 0.76. About 97% of all turtles were considered juveniles, average size was 54.6 ± 9.5 cm. Turtles were significantly smaller at the head of Estero Banderitas than in the central part of the Estero and in the open bay, indicating size-based habitat segregation. Average growth rate was 1.62 cm/year and declined with increasing size. Growth was seasonal and three times higher in summer (0.28 cm/month) than in winter (0.09 cm/month), body CI was also significantly higher during the summer months. A seasonalized von Bertalanffy growth function (VBGF) was used to model growth for the size range studied (43–73 cm SCL), with the parameters: L _∞ = 101 cm SCL; K = 0.04 year⁻¹; t ₀ = 0; C = 0.4 and t _s = 0.75. Growth data indicate that black turtles may spend up to 20 years in Bahía Magdalena before they reach maturity at about 77 cm SCL. The total mortality estimate (Z) from the length converted catch curve was 0.16, corresponding to a yearly survival probability of 0.85.     

Dietary selectivity in the field and food preferences in the laboratory for two herbivorous fishes (Cebidichthys violaceus and Xiphister mucosus) from a temperate intertidal zone

Diets and food selectivity of two stichaeid fishes (Cebidichthys violaceus and Xiphister mucosus) from the rocky intertidal zone of the central California coast (USA) were studied at each season of the year by gut content analysis and abundance measurements of potential macrophyte food items. Both fishes, after reaching a standard length of about 44 mm, were almost exclusively herbivorous. The bulk of the diet consisted of 8 to 10 species of chlorophytes and rhodophytes. These main dietary components were chiefly annual seaweeds with high surfaceto-weight ratios (sheetlike forms or small, highly branched forms). Perennial seaweeds were eaten in relatively large amounts only during the winter. Macrophytes eaten in only trace amounts included about 20 species of chlorophytes, chrysophytes, phaeophytes, rhodophytes and a spermatophyte. The small amount of animal material in the diet (never more than 2% by weight) could well have been ingested incidentally while the fishes were feeding on seaweeds. Food preference tests with up to 19 macrophyte species in the laboratory revealed that both fishes chose to eat three annual rhodophytes (Smithora naiadum, Porphyra perforata and Microcladia coulteri) in preference to Ulva lobata, an annual chlorophyte that was more abundant in the diets of field-caught specimens.     

Home range and habitat use of juvenile Atlantic green turtles (Chelonia mydas L.) on shallow reef habitats in Palm Beach, Florida, USA

Many animals, including sea turtles, alter their movements and home range in relation to the particular type and quality of the habitat occupied. When sufficient resources are available, individuals may develop affinities to specific areas for activities, such as foraging and (or) resting. In the case of green sea turtles (Chelonia mydas L.), after a number of years in the open ocean, juveniles recruit to shallow-water developmental habitats where they occupy distinct home ranges as they feed and grow to maturity. Our goal was to study the habitat use and home range movements of juvenile green turtles along a shallow, worm-rock reef tract in Palm Beach, Florida. Six turtles, measuring from 27.9 to 48.1 cm in straight carapace length and from 7.2 to 12.6 kg in mass, were tracked via ultrasonic telemetry from August to November 2003. Upon capture, each turtle’s esophagus was flushed via lavage to determine recently ingested foods. In addition, four turtles were recaptured and fitted with a time-depth recorder to study dive patterns. Home range areas measured with 100% minimum convex polygon and 95% fixed kernel estimators varied from 0.69 to 5.05 km² (mean=2.38±1.78 km²) and 0.73 to 4.89 km² (mean=2.09±1.80 km²), respectively. Home ranges and core areas of turtles were largely restricted to the reef tract itself, and showed considerable overlap between food and shelter sites. The mean number of dives during daylight hours (0600–1800 hours) was 84±5.0 dives, while the mean during night hours (1800–0600 hours) was 39±3.0 dives. Dives during the day were shallower (mean=3.20±1.26 m) than dives at night (mean=5.59±0.09 m). All six turtles were found to have a mixed diet of similar macroalgae and sponge fragments. Our results reveal that juvenile green turtles occupy stable home ranges along the nearshore worm-rock reefs of Southeast Florida, during the summer and fall. Determining which habitats are used by green turtles will assist conservation managers in their global effort to protect this endangered species.     

Shark-inflicted injury frequencies, escape ability, and habitat use of green and loggerhead turtles

Interactions between large marine predators and their prey are difficult to observe and little is known about the risk of predation faced by sea turtles. The frequency of predator-inflicted injuries, however, has afforded insights into the predation risk faced by many taxa. We measured the frequency of shark-inflicted injuries on green (Chelonia mydas) and loggerhead (Caretta caretta) sea turtles in Shark Bay, Western Australia with a view to determining differences between species and sex-classes in the risk of predation from tiger sharks (Galeocerdo cuvier). Furthermore, we investigated how escape ability and habitat use might influence the probability of turtles being injured by sharks. Shark-inflicted injuries were more frequent on loggerhead than on green turtles, and most frequent on adult male loggerhead turtles. Species effects could not be attributed to differences in habitat use, since green turtles were found in habitats favored by tiger sharks more often than were loggerhead turtles. Green turtles, however, were faster and maneuvered better than loggerhead turtles, suggesting that escape ability is a factor in interspecific differences in injury frequency. The sex-class difference in injury frequency of loggerhead turtles suggests that males face greater predation risk than females and may take more risks. For green turtles, the lack of a sex difference in injury frequency might be due to greater escape ability lowering overall predation risk or to no differences between sexes in the benefits of risk-taking.     

Migration of green turtles <Emphasis Type="Italic">Chelonia mydas</Emphasis> from Tortuguero,Costa Rica

During 1955–2003, flipper tags were attached to 46,983 green turtles and ten turtles were fitted with satellite transmitters at Tortuguero, Costa Rica. Eight satellite-tracked turtles stayed within 135 km of the beach and probably returned to nest after release. The internesting area is more extensive than previously documented. Post-nesting migration routes of satellite-tracked turtles varied. Seven turtles swam close to the coast and three turtles swam through oceanic waters before moving toward nearshore areas. Sea surface height anomaly maps indicate that oceanic movements were consistent with the southwestern Caribbean gyre. Circling and semi-circling turtles could have been disoriented but submergence and surface times suggest they may have been feeding in Sargassum sp. concentrations. Rapid post-nesting migrations (mean 2.2 km hr⁻¹) ended on benthic feeding grounds in shallow waters (<20 m) off Belize (n=1), Honduras (n=1) and Nicaragua (n=8). The spatial distribution of migration end points (n=10) and tag returns (n=4,669) are similar. Fishermen in Nicaragua target green turtles along migratory corridors and on foraging grounds. Management efforts are urgently needed in Nicaragua, particularly in the high-density feeding areas south and east of the Witties (N14°09 W82°45). The proximity of foraging grounds to the nesting beach (mean 512 km) may permit female turtles to invest more energy in reproduction and hence the Tortuguero population may have greater potential for recovery than other green turtle nesting populations. Recovery of the Tortuguero green turtle population will benefit countries and marine ecosystems throughout the Caribbean, especially Nicaragua.     

Feeding ecology of the mangrove crab <Emphasis Type="Italic">Ucides cordatus</Emphasis> (Ocypodidae): food choice,food quality and assimilation efficiency

Food preferences, consumption rates and dietary assimilation related to food quality were investigated for the large semi-terrestrial and litter-consuming mangrove crab Ucides cordatus cordatus (Ocypodidae, L. 1763) in northern Brazil. Stomach contents were composed of mangrove leaves (61.2%), unidentified plant material and detritus (28.0%), roots (4.9%), sediment (3.3%), bark (2.5%), and animal material (0.1%). U. cordatus prefers Rhizophora mangle over Avicennia germinans leaves despite a higher nitrogen content, lower carbon to nitrogen (C/N) ratio and lower tannin content of the latter. Also, assimilation rates for senescent R. mangle leaves (C: 79.3%, N: 45.4%) were higher than for A. germinans leaves (C: 40.6%, N: 9.1%). Faeces composition indicates that A. germinans leaves were more difficult to masticate and digest mechanically. The leaf-ageing hypothesis, according to which crabs let leaves age in burrows to gain a more palatable and nutritive food, was rejected for U. cordatus since N content, C/N ratio and the abundance of microorganisms did not differ significantly between senescent leaves and leaves taken from burrows. The low microbial biomass on leaf surfaces and in the sediment indicates its minor importance for the nutrition of U. cordatus. It is concluded that high ingestion and assimilation rates of a R. mangle diet together with the consumption of algae allow for a high intake of C, N, and energy. The data suggest that the digestibility of mangrove leaves by U. cordatus is not hampered by tannins. This may have provided a competitive advantage over other leaf-consuming invertebrates unable to digest mangrove litter with high tannin concentrations. Due to the large stock biomass of U. cordatus in the study area, a great amount of finely fragmented faeces is produced (about 7.1 ton dry matter ha⁻¹ year⁻¹ in a R. mangle forest) which is enriched in C, N and bacterial biomass compared to the sediment. The decomposition of mangrove litter, and thus nutrient and energy transfer into the sediment, is greatly enhanced due to litter processing by U. cordatus.     

Role of grapsid crabs, Parasesarma erythrodactyla, in entry of mangrove leaves into an estuarine food web: a mesocosm study

The influence of the crab Parasesarma erythrodactyla on the entry of the organic matter derived from Avicennia marina mangrove leaves in a sub-tropical mangrove ecosystem of southeast Queensland, Australia, was simulated using tidal mesocosms. Degradation of mangrove leaf organic matter was followed by analysing the fatty acid composition, carbon, and nitrogen isotopic signatures of the surface sediment and suspended particulate organic matter (SPOM) with and without the presence of crabs. Assimilation of mangrove organic matter by P. erythrodactyla was also assessed by stable isotope and fatty acid analyses in tissues and faeces. Results of the chemical tracer analyses question the adaptability of P. erythrodactyla to a diet comprised exclusively of mangrove leaves, and suggest that these organisms were dependent on additional food sources in their natural environment. Crab processing of senescent leaves significantly accelerated the transfer of mangrove organic matter to the surface sediments, as shown by a higher C/N ratio, a higher contribution of long-chain fatty acids and a more depleted C isotopic signature of sediment samples in the mesocosms with crabs compared to those without crabs.     

Simulated green turtle grazing affects nutrient composition of the seagrass <Emphasis Type="Italic">Thalassia testudinum</Emphasis>

Before populations of green turtles (Chelonia mydas) were severely reduced by human overexploitation, the seagrass Thalassia testudinum was intensively grazed by green turtles in the Caribbean. To explore how nutrient composition of T. testudinum pastures responds to intense grazing pressure, we simulated green turtle grazing in 15 plots (each 3 m × 3 m) for 16 months in the central Bahamas. Comparisons of clipped plots with 15 adjacent control (unclipped) plots revealed that simulated grazing resulted in significantly higher energy, nitrogen, phosphorus, lignin, cutin, and condensed tannin content in blades in clipped plots, but sediment organic content was not affected. By continually re-cropping blades in grazing plots, turtles ingest young, actively growing blade tissue with higher energy, nitrogen, and phosphorus concentrations. Our 16-month clipping trial did not generate the expected decline in nutrient content in T. testudinum blades under intensive grazing. However, significant decreases in nitrogen and organic matter reserves in rhizomes, with declines apparent after 16 and 11 months, respectively, indicate that nutrient content of blades and/or blade productivity may decline under continued clipping.     

<Emphasis Type="Italic">Terebralia palustris</Emphasis> (Gastropoda; Potamididae) in a Kenyan mangal: size structure,distribution and impact on the consumption of leaf litter

Although the role of macroinvertebrates in the nutrient cycling of the Indo-Pacific mangrove ecosystems is now a paradigm of ecological research, most of the research and scientific assumptions deal with decapod crustaceans alone. However, decapods are not the only representatives of mangrove macrobenthos and in certain mangals they are surely outnumbered by gastropods, especially by potamidids of the genus Terebralia. This paper aims at bridging the gap in the knowledge of the ecological role of the largest and most abundant potamidid species of the Indo-Pacific mangals, the semiterrestrial T. palustris. In particular we studied size structure and distribution in relation to micro-environmental factors and feeding ecology, both in terms of diet composition and grazing rate, of two populations of this gastropod colonising a Kenyan mangrove creek. In contrast to what has been described by various authors concerning other mangals, in our study site juveniles and adults of T. palustris were present throughout the whole forest, from the landward belt to the seaward fringe, locally reaching very high densities at various levels. Both life stages showed a preference for patches characterised by soil with high organic content; thus the habitat of juveniles largely overlapped with that of the adults, although they are known to occupy different ecological niches. Indeed, gut-content analysis confirmed that juveniles are detritivorous and adults are mainly leaf-litter consumers. In situ experiments on the grazing activity of the adult snails showed that, in contrast to the litter-consuming crabs, they feed in every light and tidal condition, for an hourly consumption rate of ~0.65 g per snail. Considering an average density of about 10.5 adults m^–2, it is estimated that a total of 10.5 leaves m^–2 are removed by adult snails in each tidal cycle (i.e. about every 6 h). T. palustris is the only leaf consumer capable of searching for food under water during high tide and is responsible for the removal of a great quantity of mangrove litter. The results of the present study strongly suggest that T. palustris plays a major role in the food web, mangrove litter degradation and nutrient cycling of the Kenyan mangal.Communicated by R. Cattaneo-Vietti, Genova     

An energy–distance trade-off in a central-place forager,the Antarctic fur seal (<Emphasis Type="Italic">Arctocephalus gazella</Emphasis>)

We tested the prediction that lactating fur seals (Arctocephalus gazella) at South Georgia will take prey of greater energy density with increasing distance of foraging from the colony. The study investigated the differences in diet of fur seals foraging within two regions, one near the breeding colony and the other at greater distance. Diet varied significantly in relation to foraging location. Dietary items of low quality were eaten in both regions but more food items with a high-energy content appeared in the diet of seals travelling to distant oceanic waters. We conclude that there is likely to be a trade-off between energy gain and distance travelled which enables female fur seals to maintain a relatively constant rate of energy delivery to their offspring irrespective of the distance travelled to find food.     

Feeding ecology of the green turtle (Chelonia mydas) at rocky reefs in western South Atlantic

Feeding ecology of green turtles was investigated between January 2005 and April 2008 at Arvoredo Reserve, Brazil (27°17′S, 48°18′W). Data were obtained through the performance of observational sessions, geo-referenced counts, benthic surveys, capture and recapture of individuals, and oesophageal lavages. This protected area was identified as an important green turtle feeding ground, used year-round by juveniles (curved carapace length = 32–83 cm). Turtles fed close to the rocky shores of the area and selected grazing sites commonly at hard-to-reach, near-vertical portions of the rocks. They were less active in cold months, and more abundant at shallow areas of the reef (0–5 m), where their preferred food items occurred. Their diet was dominated by macroalgae species but invertebrates were also present. Their main food item was the red algae Pterocladiella capillacea, which seems to be eaten through periodical cropping of its tips. Observational methods such as the ones applied here could be incorporated to other research programs aiming to understand the relationships between Chelonia mydas feeding populations and their environment.     

Competition and interaction between Neosarmatium smithi (Crustacea: Grapsidae) and Terebralia palustris (Mollusca: Gastropoda) in a Kenyan mangrove

 In a Kenyan mangrove, we studied the interactions between the gastropod Terebralia palustris and the crab Neosarmatium smithi when foraging on decaying mangrove leaves. Interactions are considerable on account of their wide overlap in zonation (Rhizophora mucronata belt), food items (mangrove leaves) and activity window (diurnal low water). The snails find a leaf by a systematic transecting of the platform and eat the leaf after crawling on to it, usually en masse. The crabs rarely venture beyond 80 cm from their burrows, and once they find a leaf they quickly drag it back into their burrow, probably to reduce the strong intra-specific competition. A crab is able to drag a leaf away even if a number of snails are already feeding on it, by strongly pulling the leaf away or by pushing the snails off the leaf. The success of the “thief ” depends on both the crab's size and the number of snails on the leaf. Received: 25 July 1999 / Accepted: 27 April 2000     

Thalassia testudinum productivity and grazing by green turtles in a highly disturbed seagrass bed

There has been an historical decline in the seagrass beds in Maho and Francis Bays, St. John, U.S. Virgin Islands: presently (1986) there are only five small seagrass beds in shallows water. These seagrass beds are highly disturbed by heavy boat usage and are intensively grazed by the green turtle Chelonia mydas L. Fifteen to 50 boats anchor each night in the bays: anchor scars cause a loss of up to 6.5 m² d^-1 or 1.8% yr^-1 of the seagrass beds. Seagrasses regrew into such scars only minimally within a period of 7 mo. The size of the green turtle population was estimated at 50 subadults and their feeding behavior was determined by direct observation and radiotelemetry. The behavior of the green turtles differed from other observations published on the species. Here, the turtles grazed all available Thalassia testudinum, their preferred seagrass food, rather than creating discrete grazing scars, and spent all their waking hours (9 h per day) feeding. Areal productivity of T. testudinum leaves (33 to 97 mg dry wt m^-2d^-1) in the bays was at least an order of magnitude lower than published values or than the productivity of another, lessdisturbed seagrass bed on St. John, despite having comparable leaf-shoot density. Leaf shoots were stunted, fragile, achlorotic, and had only two leaves as opposed to the five leaves per shoot more typically seen. The green turtle population was near the estimated carrying capacity of T. testudinum, based on the standing crop and productivity of T. testudinum and the grazing rate of the turtles. The effect of disturbance of T. testudinum from boats and turtles was assessed by excluding these with emergent fences. Within 3 mo of protection, the areal and shoot-specific productivity of T. testudinum leaves as well as leaf size increased significantly compared to unprotected areas. Conservation efforts are recommended in Maho Bays and Francis because seagrass productivity is low, disturbance rates are higher than recovery rates, the turtles cannot increase further their feeding rate in order to compensate for such factors, and there are few alternate sources of T. testudinum on the north shore of St. John.Contribution No. 175 from West Indies Laboratory, Teague Bay, Christiansted, St. Croix, U.S. Virgin Islands 00820, USA     

A Contemporary,Sex‐Limited Change in Body Size of an Estuarine Turtle in Response to Commercial Fishing

Abstract: Juvenile growth rate and adult body size are important components of life‐history strategies because of their direct impact on fitness. The diamondback terrapin (Malaclemys terrapin) is a sexually dimorphic, long‐lived turtle inhabiting brackish waters throughout the Atlantic and Gulf coasts of the United States. In parts of its range, terrapins face anthropogenically imposed mortality: juveniles of both sexes inadvertently enter commercial crab traps and drown. For adult females, the carapace eventually grows large enough that they cannot enter traps, whereas males almost never reach that critical size. We compared age structure, carapace dimensions, growth curves, and indices of sexual dimorphism for a Chesapeake Bay population of terrapins (where mortality of turtles is high due to crab traps) with contemporary terrapins from Long Island Sound and museum specimens from Chesapeake Bay (neither group subject to commercial crab traps). We also calculated the allochronic and synchronic rates of evolutionary change (haldanes) for males and females to measure the rate of trait change in a population or between populations, respectively. We found a dramatic shift to a younger male age structure, a decrease in the length of time to terminal female carapace size, a 15% increase in female carapace width, and an increase in sexual dimorphism in Chesapeake Bay. In a new twist, our results implicate a fishery in the selective increase in size of a reptilian bycatch species. These sex‐specific changes in life history and demography have implications for population viability that need to be considered when addressing conservation of this threatened turtle.     

Discrimination of predatory versus nonpredatory mammals by box turtles, <Emphasis Type="Italic">Terrapene carolina</Emphasis>

Summary. Although terrestrial turtles have served as a model for studies of olfactory neurophysiology, little is known about how they use chemical information in an ecological sense. We tested whether box turtles (Terrapene carolina) use chemical information to distinguish between predatory and nonpredatory mammals. Box turtles in our study exhibited more escape behavior when exposed to urine from a predator (coyote, Canis latrans) than when exposed to urine from a nonpredator (white-tailed deer, Odocoileus virginianus) or a blank control. Escape behavior is consistent with an antipredator response. In addition, the turtles decreased their handling time for food when in the presence of urine from either species of mammal in comparison to the blank, indicating that chemical cues from mammals in general may result in increased vigilance by terrestrial turtles. Examination of a variety of response variables may be important for adequate assessment of the ecological role of chemosensory behavior.