Terrestrial Buffer Zones and Wetland Conservation: A Case Study of Freshwater Turtles in a Carolina Bay

Because freshwater wetlands often support diverse and unique species assemblages, wetland loss is a primary concern in biological conservation. U. S. federal statutes protect many wetlands by deterring development within delineated borders that segregate wetland habitats from upland regions. In addition, some state and local jurisdictions mandate buffer zones that afford varying levels of protection to upland habitats adjacent to wetlands. We used geographic information system analysis to test the adequacy of federal and state wetland protection statutes by determining the degree to which protected acreage encompassed the habitats freshwater turtles needed to complete their life cycles. Two critical life-cycle stages, nesting and terrestrial hibernation, occurred exclusively beyond wetland boundaries delineated under federal guidelines. The most stringent state buffer zone insulated 44% of nest and hibernation sites. Our data indicate that the freshwater turtles examined in this study required a 275-m upland buffer zone to protect 100% of the nest and hibernation sites. Insulating 90% of the sites required a 73-m buffer zone. We suggest that the habitat needs of freshwater turtles demonstrate the dependence of wetland biodiversity on the preservation of adequate amounts of upland habitats adjacent to wetlands.     

Changes of movement patterns from early dispersal to settlement

Moving and spatial learning are two intertwined processes: (a) changes in movement behavior determine the learning of the spatial environment, and (b) information plays a crucial role in several animal decision-making processes like movement decisions. A useful way to explore the interactions between movement decisions and learning of the spatial environment is by comparing individual behaviors during the different phases of natal dispersal (when individuals move across more or less unknown habitats) with movements and choices of breeders (who repeatedly move within fixed home ranges), that is, by comparing behaviors between individuals who are still acquiring information vs. individuals with a more complete knowledge of their surroundings. When analyzing movement patterns of eagle owls, Bubo bubo, belonging to three status classes (floaters wandering across unknown environments, floaters already settled in temporary settlement areas, and territory owners with a well-established home range), we found that: (1) wandering individuals move faster than when established in a more stable or fixed settlement area, traveling larger and straighter paths with longer move steps; and (2) when floaters settle in a permanent area, then they show movement behavior similar to territory owners. Thus, movement patterns show a transition from exploratory strategies, when animals have incomplete environmental information, to a more familiar way to exploit their activity areas as they get to know the environment better.     

Demographic Consequences of Terrestrial Habitat Loss for Pool‐Breeding Amphibians: Predicting Extinction Risks Associated with Inadequate Size of Buffer Zones

Abstract: Much of the biodiversity associated with isolated wetlands requires aquatic and terrestrial habitat to maintain viable populations. Current federal wetland regulations in the United States do not protect isolated wetlands or extend protection to surrounding terrestrial habitat. Consequently, some land managers, city planners, and policy makers at the state and local levels are making an effort to protect these wetland and neighboring upland habitats. Balancing human land‐use and habitat conservation is challenging, and well‐informed land‐use policy is hindered by a lack of knowledge of the specific risks of varying amounts of habitat loss. Using projections of wood frog (Rana sylvatica) and spotted salamander (Ambystoma maculatum) populations, we related the amount of high‐quality terrestrial habitat surrounding isolated wetlands to the decline and risk of extinction of local amphibian populations. These simulations showed that current state‐level wetland regulations protecting 30 m or less of surrounding terrestrial habitat are inadequate to support viable populations of pool‐breeding amphibians. We also found that species with different life‐history strategies responded differently to the loss and degradation of terrestrial habitat. The wood frog, with a short life span and high fecundity, was most sensitive to habitat loss and isolation, whereas the longer‐lived spotted salamander with lower fecundity was most sensitive to habitat degradation that lowered adult survival rates. Our model results demonstrate that a high probability of local amphibian population persistence requires sufficient terrestrial habitat, the maintenance of habitat quality, and connectivity among local populations. Our results emphasize the essential role of adequate terrestrial habitat to the maintenance of wetland biodiversity and ecosystem function and offer a means of quantifying the risks associated with terrestrial habitat loss and degradation.     

Terrestrial organic matter as subsidies that aid in the recovery of macroinvertebrates in industrially damaged lakes

The importance of allochthonous carbon to the productivity of stream ecosystems in temperate ecozones is well understood, but this relationship is less established in oligotrophic lakes. The nearshore littoral zones, at the interface of terrestrial and aquatic systems, are areas where the influence of terrestrial subsidies is likely greatest. We investigated the response of nearshore communities to variation in the quantity and composition of allochthonous materials, determined the landscape characteristics that regulate the variation of this subsidy, and explored the potential for terrestrial restoration practices to influence the export of organic matter to lakes. Stepwise multiple regressions revealed that diversity of nearshore macroinvertebrate families increased with the amount of fine particulate organic matter (FPOM) captured in sediment traps. The quantity of FPOM (g) increased with forest cover, and the relative amount of FPOM (percentage of total particulate material) in the traps increased with surface area of wetland in the catchments. These models suggest that terrestrially derived subsidies are important in smelter-impacted watersheds, and that the restoration of forests and wetlands will speed the return of nearshore consumer community diversity in industrially damaged lakes.     

中国西南不同湿地类型水鸟多样性评价

水鸟是反映湿地生态系统健康的指标之一,对不同湿地水鸟多样性进行评价能提出有利于湿地生态系统健康良性发展的湿地管理措施,亦能更好地保护水鸟资源。为缓解近年来中国自然湿地退化和消失的问题,中国政府积极推进实施了大量修复自然湿地和新建人工湿地的工程。然而受限于人力、物力和经费,当前对自然湿地和人工湿地水鸟多样性的系统调查和评价多局限于单一地点或局部区域。因水鸟的分布具有地域性,从地域尺度进行不同湿地类型水鸟多样性评价将更为客观,公众科学数据为区域大尺度数据获取提供了可能。本研究借助中国观鸟记录中心数据,比较了2014年1月至2018年2月中国西南4省(市)自然湿地和人工湿地的水鸟物种多样性和组成相似性;结果共记录到9目19科139种水鸟,其中有94.96%的物种分布于自然湿地,67.63%的物种分布于人工湿地;各类群水鸟在自然湿地中的物种数均高于人工湿地。结果说明自然湿地在水鸟保护中具有重要栖息地功能,人工湿地能为大部分水鸟提供栖息地,但不能完全代替自然湿地。自然湿地中的湖泊湿地、河流湿地和沼泽化草甸以及人工湿地中的水库、城市人工景观水面和娱乐水面是水鸟,特别是受威胁水鸟分布的重要湿地类型;建议政府部门重点对上述湿地亚类进行合理的规划和管理。     

Effects of Landscape Composition and Wetland Fragmentation on Frog and Toad Abundance and Species Richness in Iowa and Wisconsin, U.S.A.

Abstract: Management of amphibian populations to reverse recent declines will require defining high-quality habitat for individual species or groups of species, followed by efforts to retain or restore these habitats on the landscape. We examined landscape-level habitat relationships for frogs and toads by measuring associations between relative abundance and species richness based on survey data derived from anuran calls and features of land-cover maps for Iowa and Wisconsin. The most consistent result across all anuran guilds was a negative association with the presence of urban land. Upland and wetland forests and emergent wetlands tended to be positively associated with anurans. Landscape metrics that represent edges and patch diversity also had generally positive associations, indicating that anurans benefit from a complex of habitats that include wetlands. In Iowa the most significant associations with relative abundance were the length of the edge between wetland and forest ( positive) and the presence of urban land (negative). In Wisconsin the two most significant associations with relative abundance were forest area and agricultural area ( both positive). Anurans had positive associations with agriculture in Wisconsin but not in Iowa. Remnant forest patches in agricultural landscapes may be providing refuges for some anuran species. Differences in anuran associations with deep water and permanent wetlands between the two states suggest opportunities for management action. Large-scale maps can contribute to predictive models of amphibian habitat use, but water quality and vegetation information collected from individual wetlands will likely be needed to strengthen those predictions. Landscape habitat analyses provide a framework for future experimental and intensive research on specific factors affecting the health of anurans.     

Relationships among Isolated Wetland Size, Hydroperiod, and Amphibian Species Richness: Implications for Wetland Regulations

Abstract: Wetland development within the United States is regulated primarily by size. Decisions concerning wetland destruction or conservation are therefore based in part on three inherent assumptions: (1) small wetlands contain water for short portions of the year; (2) small wetlands support few species; and (3) species found in small wetlands are also found in larger wetlands. We tested these assumptions using data on wetland size, relative hydroperiod (drying scores), and relative species richness of amphibians in depression wetlands of the southeastern United States. We found a significant (p = 0.03) but weak (r² = 0.05) relationship between hydroperiod and wetland size and no relationship (p = 0.48) between amphibian species richness and wetland size. Furthermore, synthetic models of lentic communities predict that short-hydroperiod wetlands support a unique group of species. Empirical investigations support this prediction. Our results indicate that hydroperiod length should be included as a primary criterion in wetland regulations. We advocate a landscape approach to wetlands regulation, focused in part on conserving a diversity of wetlands that represent the entire hydroperiod gradient.     

Life history benefits of residency in a partially migrating pond-breeding amphibian

Species with partial migration, where a portion of a population migrates and the other remains residential, provide the opportunity to evaluate conditions for migration and test mechanisms influencing migratory decisions. We conducted a five-year study of two populations of red-spotted newts (Notophthalmus viridescens), composed of individuals that either remain as residents in the breeding pond over the winter or migrate to the terrestrial habitat. We used multistate mark-recapture methods to (1) test for differences in survival probability between migrants and residents, (2) determine if migrants breed every year or skip opportunities for reproduction, and (3) estimate the frequency of individuals switching migratory tactic. We used estimates of life history parameters from the natural populations in combination with previous experimental work to evaluate processes maintaining partial migration at the population level and to assess mechanisms influencing the decision to migrate. Based on capture-recapture information on over 3000 individuals, we found that newts can switch migratory tactics over their lifetime. We conclude that migrants and residents coexist through conditional asymmetries, with residents having higher fitness and inferior individuals adopting the migrant tactic. We found that newts are more likely to switch from residency to migrating than the reverse and males were more likely to remain as residents. Migration differences between the sexes are likely driven by reproduction benefits of residency for males and high energetic costs of breeding resulting in lower breeding frequencies for females. Environmental conditions also influence partial migration within a population; we found support for density-dependent processes in the pond strongly influencing the probability of migrating. Our work illustrates how migration can be influenced by a complex range of individual and environmental factors and enhances our understanding of the conditions necessary for the evolution and maintenance of partial migration within populations.     

Terrestrial Reserve Networks Do Not Adequately Represent Aquatic Ecosystems

Abstract: Protected areas are a cornerstone of conservation and have been designed largely around terrestrial features. Freshwater species and ecosystems are highly imperiled, but the effectiveness of existing protected areas in representing freshwater features is poorly known. Using the inland waters of Michigan as a test case, we quantified the coverage of four key freshwater features (wetlands, riparian zones, groundwater recharge, rare species) within conservation lands and compared these with representation of terrestrial features. Wetlands were included within protected areas more often than expected by chance, but riparian zones were underrepresented across all (GAP 1–3) protected lands, particularly for headwater streams and large rivers. Nevertheless, within strictly protected lands (GAP 1–2), riparian zones were highly represented because of the contribution of the national Wild and Scenic Rivers Program. Representation of areas of groundwater recharge was generally proportional to area of the reserve network within watersheds, although a recharge hotspot associated with some of Michigan's most valued rivers is almost entirely unprotected. Species representation in protected areas differed significantly among obligate aquatic, wetland, and terrestrial species, with representation generally highest for terrestrial species and lowest for aquatic species. Our results illustrate the need to further evaluate and address the representation of freshwater features within protected areas and the value of broadening gap analysis and other protected‐areas assessments to include key ecosystem processes that are requisite to long‐term conservation of species and ecosystems. We conclude that terrestrially oriented protected‐area networks provide a weak safety net for aquatic features, which means complementary planning and management for both freshwater and terrestrial conservation targets is needed.     

Remarkable Amphibian Biomass and Abundance in an Isolated Wetland: Implications for Wetland Conservation

Abstract:  Despite the continuing loss of wetland habitats and associated declines in amphibian populations, attempts to translate wetland losses into measurable losses to ecosystems have been lacking. We estimated the potential productivity from the amphibian community that would be compromised by the loss of a single isolated wetland that has been protected from most industrial, agricultural, and urban impacts for the past 54 years. We used a continuous drift fence at Ellenton Bay, a 10-ha freshwater wetland on the Savannah River Site, near Aiken, South Carolina (U.S.A.), to sample all amphibians for 1 year following a prolonged drought. Despite intensive agricultural use of the land surrounding Ellenton Bay prior to 1951, we documented 24 species and remarkably high numbers and biomass of juvenile amphibians (>360,000 individuals; >1,400 kg) produced during one breeding season. Anurans (17 species) were more abundant than salamanders (7 species), comprising 96.4% of individual captures. Most (95.9%) of the amphibian biomass came from 232095 individuals of a single species of anuran (southern leopard frog [Rana sphenocephala ]). Our results revealed the resilience of an amphibian community to natural stressors and historical habitat alteration and the potential magnitude of biomass and energy transfer from isolated wetlands to surrounding terrestrial habitat. We attributed the postdrought success of amphibians to a combination of adult longevity (often >5 years), a reduction in predator abundance, and an abundance of larval food resources. Likewise, the increase of forest cover around Ellenton Bay from <20% in 1951 to >60% in 2001 probably contributed to the long-term persistence of amphibians at this site. Our findings provide an optimistic counterpoint to the issue of the global decline of biological diversity by demonstrating that conservation efforts can mitigate historical habitat degradation.     

Genetic composition of a green turtle (Chelonia mydas) feeding ground population: evidence for multiple origins

Migratory marine turtles are extremely difficult to track between their feeding and nesting areas, and the link between juvenile and adult habitats is generally unknown. To assess the composition of a feeding ground (FG) population of juvenile green turtles (Cheloniamydas Linnaeus), mitochondrial DNA control region sequences were examined in 80 post-pelagic individuals (straight carapace length = 31 to 67 cm) sampled in September 1992 from Great Inagua, Bahamas, and compared to those of 194 individuals from nine Atlantic and Mediterranean nesting colonies. Evidence from genetic markers, haplotype frequencies, and maximum likelihood (ML) analyses are concordant in indicating that multiple colonies contribute to the Bahamian FG population. ML analyses suggested that most Bahamian FG juveniles originated in the western (79.5%) and eastern (12.9%) Caribbean regions, and these proportions are roughly comparable to the size of candidate rookeries. These data support a life-cycle model in which individuals become pooled in post-hatchling (pelagic) and juvenile (benthic) habitats as a consequence of ocean currents and movement among FGs. A substantial harvest of immature turtles on their feeding pastures will influence the reproductive success of contributing nesting populations over a wide geographic scale. Received: 1 April 1997 / Accepted: 14 October 1997     

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.     

Individual differences in foraging behavior and cortisol levels in recently emerged brook charr (Salvelinus fontinalis)

Recently emerged brook charr (Salvelinus fontinalis) foraging in still-water pools along the sides of streams tend to be either sedentary, feeding from the lower portion of the water column (a sit-and-wait tactic), or very active, feeding from the upper portion of the water column (an active search tactic). We tested whether the individual differences in foraging behavior were associated with baseline concentrations and responses of cortisol, a steroid hormone linked to personality differences in a variety of animals including fishes. We quantified the proportion of time spent on moving by focal charr in the field and then capturing them. Captured individuals were either (i) sacrificed immediately to quantify baseline cortisol concentrations, (ii) held in an unfamiliar field environment for 15 min and then sacrificed to quantify cortisol concentrations in response to handling and holding in a novel field environment, or (iii) held in an unfamiliar field environment with a white Plexiglas base (stressor) for 15 min to quantify cortisol concentrations in response to a novel object. Eleven statistical models relating cortisol concentrations to the proportion of time individuals spent on moving while searching for prey were compared using multi-model inferencing. Cortisol concentrations were higher for charr that spent a lower proportion of time on moving in the field than for charr that spent a higher proportion of time on moving. For a given proportion of time spent on moving, mean cortisol concentrations between baseline and experimental treatments, our measure of cortisol response, did not differ markedly. Our findings suggest that the foraging tactics displayed by wild brook charr in the field could reflect differences in how individuals perceive their environment.     

Safeguarding the Pantanal Wetlands: Threats and Conservation Initiatives

Abstract:  The Pantanal, one of the largest wetlands on the planet, comprises 140,000 km² of lowland floodplain of the upper Rio Paraguai basin that drains the Cerrado of central Brazil. The diverse mosaics of habitats resulting from the varied soil types and inundation regimes are responsible for an extraordinarily rich terrestrial and aquatic biota, exemplified by the bird richest wetland in the world—463 birds have been recorded there—and the largest known populations of several threatened mammals, such as Pampas deer ( Ozotoceros bezoarticus ), marsh deer ( Blastocerus dichotomus ), giant otter ( Pteronura brasiliensis ), and jaguar ( Panthera onca ). Until recently, deforestation of the adjoining Brazilian central plateau was considered the major threat to this area, but now deforestation is a critical problem within the floodplain itself. More than 40% of the forest and savanna habitats have been altered for cattle ranching through the introduction of exotic grasses. And there are other threats that lead to large-scale disruption of ecological processes, severely affecting biodiversity. Although the Pantanal wetland is a Biosphere Reserve and is considered a Wetland of International Importance, only 2.5% of the upper Paraguai River basin is formally protected. To date, protected areas have been created opportunistically and as such, although of undoubted value, protect only a fraction of the Pantanal's wildlife and habitats. Among the conservation initiatives in the area, the private sector is increasingly participating in the establishment of private reserves. The prospects are far from optimistic, however, and the major challenge is to find alternative socioeconomic models that allow for conservation and economic uses of the land in association with the development of specific environmental legislation that reflects the unique characteristics of the region.     

A model of area fidelity,nomadism, and distribution patterns of loggerhead sea turtles (<Emphasis Type="Italic">Caretta caretta</Emphasis>) in the Mediterranean Sea

Sea turtle tagging carried out in Italy in the period 1981–2006 resulted in 125 re-encounters of loggerhead turtles (Caretta caretta) after a mean of 2.5 years, from different marine areas in the Mediterranean. At first finding, turtles ranged 25–83 cm of curved carapace length. Data were analyzed according to size, area, habitat type, season, in order to provide indication of movement patterns. When integrated with other information, results indicate that: (1) a part of turtles in the oceanic stage show a nomad behavior with movements among different oceanic areas; (2) another part show fidelity to an oceanic area; (3) turtles in the neritic stage show fidelity to neritic areas, and once settled to one area, change to other neritic areas is unlikely; (4) nomad oceanic turtles are significantly larger than sedentary ones, and also larger than turtles found in neritic areas; it is hypothesized that these could be Atlantic turtles that eventually leave the Mediterranean; (5) ecological transition from oceanic to neritic habitats occurs at a wide range of sizes, and some turtles may have a very brief oceanic stage; (6) turtles in the oceanic stage are more likely to recruit to neritic areas close to their oceanic areas than to distant ones; (7) part of turtles from some Mediterranean nesting beaches might frequent a relatively limited area range, including both oceanic and neritic areas; (8) in most of the Mediterranean, latitudinal seasonal migrations are unlikely. A general model of movement patterns of loggerhead turtles in the Mediterranean is proposed.     

Sex-specific differences in site fidelity and the cost of dispersal in yellow-headed blackbirds

Male migratory birds tend to be more faithful than females to previous breeding sites, suggesting sex differences in costs or benefits of dispersal. In Illinois, greater site fidelity by male yellow-headed blackbirds (Xanthocephalus xanthocephalus) was associated with reduced reproductive success the following year for dispersers relative to non-dispersers. Dispersing females suffered no reduction in reproductive success the following year. Males that attracted few social mates, and thus had low reproductive success, were more likely to disperse, whereas females dispersed in response to low-patch reproductive success, regardless of their individual performance. Males that dispersed appeared to be successful acquiring territories because none was observed as a floater. The rate of dispersal by males in this low-density population was greater than in more dense populations where dispersing males may be less successful at acquiring territories. Despite success at obtaining territories, males that dispersed acquired territories on the periphery of wetlands where fewer females nested, resulting in lower reproductive success. In the second year after dispersing, however, males moved onto more central territories where they acquired larger harems. Thus, dispersal by males may be a long-term strategy requiring at least 2 years for benefits to be realized. Long-term success was enhanced because dispersing males moved to wetlands on which reproductive success was higher than on the wetlands they left. In addition to demonstrating that both individual and patch reproductive success affect dispersal decisions, these data indicate that when evaluating costs and benefits of dispersal, researchers should use a time frame beyond 1 year.     

Specific targeting of host individuals by a kleptoparasitic bird

Kleptoparasitism is a tactic used to acquire food opportunistically and has been shown to provide several benefits, including greater food intake rate and the acquisition of items not normally available during self-foraging. Host individuals may differ in their ability to defend themselves against kleptoparasitic attacks and therefore identifying those host individuals that are particularly vulnerable to attack could both provide energetic benefits and increase the efficiency of kleptoparasitism as a foraging strategy. Here, we show that the kleptoparasitic fork-tailed drongo (Dicrurus adsimilis) specifically targets juveniles when following groups of cooperatively breeding pied babblers (Turdoides bicolor). Drongos give alarm calls upon sighting a predator, thus providing extra predator vigilance to foraging pied babblers. However, drongos also use alarm calls to steal food items. During kleptoparasitic attacks, drongos give false alarm calls and then swoop down to steal food items dropped by alarmed babblers. Juvenile pied babblers are particularly vulnerable to attack because they (a) spend a longer period handling prey items prior to consumption and (b) respond to alarm calls primarily by immediately moving to cover, in contrast to adults who respond by looking up and visually scanning the surrounding area. Drongos attack juvenile babblers significantly more often than adults, with attacks on juveniles more likely to result in the successful procurement of a food item. This patterns of attack suggests that drongos are able to differentiate between individuals of different age when targeting pied babblers, thus increasing the efficiency of kleptoparasitism as a foraging strategy.     

The influence of disturbance events on survival and dispersal rates of Florida box turtles.

Disturbances have the potential to cause long-term effects to ecosystem structure and function, and they may affect individual species in different ways. Long-lived vertebrates such as turtles may be at risk from such events, inasmuch as their life histories preclude rapid recovery should extensive mortality occur. We applied capture-mark-recapture models to assess disturbance effects on a population of Florida box turtles (Terrapene carolina bauri) on Egmont Key, Florida, USA. Near the midpoint of the study, a series of physical disturbances affected the island, from salt water overwash associated with several tropical storms to extensive removal of nonindigenous vegetation. These disturbances allowed us to examine demographic responses of the turtle population and to determine if they affected dispersal throughout the island. Adult survival rates did not vary significantly either between sexes or among years of the study. Survival rates did not vary significantly between juvenile and adult turtles, or among years of the study. Furthermore, neither adult nor juvenile survival rates differed significantly between pre- and post-disturbance. However, dispersal rates varied significantly among the four major study sites, and dispersal rates were higher during the pre-disturbance sampling periods compared to post-disturbance. Our results suggest few long-term effects on the demography of the turtle population. Florida box turtles responded to tropical storms and vegetation control by moving to favorable habitats minimally affected by the disturbances and remaining there. As long as turtles and perhaps other long-lived vertebrates can disperse to non-disturbed habitat, and high levels of mortality do not occur in a population, a long life span may allow them to wait out the impact of disturbance with potentially little effect on long-term population processes.     

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.