Female Terrapins Research Articles

HEALTH ASSESSMENT OF WILD NORTHERN DIAMOND-BACKED TERRAPINS (MALACLEMYS TERRAPIN TERRAPIN) IN NEW JERSEY, USA.

A popular species in the pet trade, and therefore in the illegal wildlife trade, the diamond-backed terrapin, Malaclemys terrapin, population has seen significant declines. Associated with the illegal wildlife trade, occasions arise in which terrapins are confiscated, and no standard operating procedures exist for repatriation into the wild. To develop such procedures, an understanding of the pathogens circulating in the wild diamond-backed terrapin population in New Jersey is needed. We sampled 30 wild female diamond-backed terrapins for herpesvirus, Mycoplasmopsis, ranavirus, and intestinal and blood parasites and performed white blood cell counts and differentials and evaluated biochemistry values. Terrapins had an average age of 10 yr (8-15 yr), and 70% were gravid at the time of sampling. Thirty-three percent of the sampled northern diamond-backed terrapins were positive for Mycoplasmopsis sp., and all were negative for ranavirus and herpesviruses. Occasional blood parasites were found, and few intestinal parasites were noted. There was no significant difference between gravid status and any of the blood parameters (P<0.05). Blood chemistry values appeared to vary according to feeding activity; no differences were noted in the values in relation to gravid status. Four terrapins had heterophil to lymphocyte (H:L) ratios above 4.5, significantly higher than the other terrapins sampled, which may indicate inflammation. Two of the four had Mycoplasmopsis, one sample was contaminated by other bacteria and was discarded, and one was negative. No significant difference was found between Mycoplasmopsis infection status and H:L ratio (P=0.926). Our findings, though conducted on a small number of female terrapins at a specific time point, provide data on the pathogens that may be circulating in this population, adding to the current body of knowledge and helping to guide decision making for the reintroduction of confiscated diamond-backed terrapins into New Jersey's wild population.

Plasma Vitellogenin and Testosterone in Diamond-backed Terrapins (Malaclemys terrapin) during the Nesting Season in Coastal New Jersey

Vitellogenesis is the process in which female oviparous vertebrates synthesize the protein vitellogenin to develop egg yolk. In some species, vitellogenin has been used to investigate reproductive status, as a biomarker of clutch size and nesting frequency, and as a biomarker of exposure to endocrine-disruptive chemicals. The Diamond-backed Terrapin (Malaclemys terrapin) is an obligate coastal species that in the northern extent of its range nests in the spring and summer months. Diamond-backed Terrapins serve as a key indicator species of coastal ecosystem health; thus, furthering our understanding of the endocrine control of reproduction may inform biologists of the health and status of coastal ecosystems. The objective of this study was to quantify baseline values of vitellogenin and testosterone in Diamond-backed Terrapins during the nesting season, in the northern part of their range. Blood samples were taken from adult female terrapins from two populations in coastal New Jersey from June–August. Enzyme-linked immunosorbent assays (ELISAs) were used to quantify vitellogenin (VTG) and testosterone (T) across the nesting season. VTG concentrations showed peak values in the earliest part of the nesting season, significantly declining through the summer before reaching basal values in August, with T showing a similar trend. This suggests that terrapins in New Jersey follow a similar reproductive cycle to other turtle species from temperate latitudes. Additionally, we found that larger females exhibited higher concentration of T and VTG than smaller females. This suggests that VTG and T are useful biomarkers of reproductive output in these animals. Lastly, we also noted that larger females tended to nest earlier in the nesting season than smaller females. We hypothesize that larger females may compete for resources more effectively and efficiently than smaller females, which may confer larger individuals a fitness advantage.

Survival rates of two nesting aggregations of diamondback terrapins at neighboring sites in New York City

AbstractThe diamondback terrapin (Malaclemys terrapin) is a charismatic and long‐lived species of the United States eastern coast, and the only North American turtle that exclusively inhabits coastal brackish waters. Many terrapin populations are declining, and these declines have been largely linked to human activities; however, few studies have documented human and natural factors affecting terrapin population demography. Jamaica Bay, an urban estuary located in southern New York City, USA, is home to 2 nesting aggregations of terrapins, located at Ruler's Bar Hassock (RBH) and John F. Kennedy Airport (JFK). We analyzed mark‐recapture data for RBH from 2003–2018 and JFK from 2011–2018 to estimate annual survivorship of female diamondback terrapins and test the effects of 3 factors (a hurricane, water quality represented by nitrogen concentration, and injuries) on survival. The initial estimated annual survival was high (0.93) at RBH but declined to 0.89, while survival remained constant at JFK (0.92). Models examining the effect of Hurricane Sandy (2012) indicated a significant decline in survival in the 2 years following the hurricane in the RBH nesting aggregation but no change at JFK. Water quality did not influence trends in either aggregation, but the presence of major injuries (caused by boat collisions, predators, and the hurricane) significantly reduced annual survival at RBH. We propose increasing terrapin survivorship through mitigation of boat traffic, reducing populations of northern raccoons (Procyon lotor) to reduce injury to female terrapins and decrease egg and hatchling mortality, and increased law enforcement to reduce on‐going poaching and capture as illegal by‐catch.

Home ranges and Movements of Two Diamondback Terrapins (Malaclemys terrapin macrospilota) in Northwest Florida

The diamondback terrapin (Malaclemys terrapin) is a small estuarine turtle distributed along the Atlantic and Gulf Coasts of the USA that is threatened by drowning in crab pots, road mortality, exploitation in the pet trade, and habitat loss. Little is known about the movement patterns and home ranges of these turtles, particularly along the U.S. Gulf of Mexico coast. Satellite tags were deployed on two adult female terrapins captured at two distinct sites in Northwest Florida. A first-difference correlated random walk approach was used to determine distances traveled and estimate home range for each individual. The two terrapins were tracked for 146 and 147 days, and the total distance traveled for each terrapin was 70.1 km and 723.0 km, respectively. The maximum distance moved from capture location was 11.3 km and 49.6 km. Home ranges here were much larger than those previously reported in other studies. The movements we documented were greater than expected and indicate habitat protection for this species may need to be expanded to incorporate more distant foraging sites.

Evaluating a portable cylindrical bait trap to capture diamondback terrapins in salt marsh

ABSTRACTDiamondback terrapins (Malaclemys terrapin) are currently in decline across much of their historical range, and demographic data on a regional scale are needed to identify where their populations are at greatest risk. Because terrapins residing in salt marshes are difficult to capture, we designed a cylindrical bait trap (CBT) that could be deployed in shallow tidal waters. From 2003 to 2006, trials were conducted with CBTs in the Chesapeake Bay, Maryland (USA) to determine terrapin sex, size, and age distribution within 3 salt marsh interior habitats—open bays, tidal guts, and broken marshes—using 15 traps/habitat. Analyses based on 791 total captures with CBTs indicate that smaller terrapins, (i.e., adult male and subadult) were more prevalent within the transecting tidal guts and broken marshes, whereas the adult females were more evenly distributed among habitats, including open bays. Subadult females made up the largest percent of catch in the CBTs deployed within the 3 marsh interior habitats. During a 12‐day trial in which we compared capture performance of CBTs and modified fyke nets along open shorelines during the nesting season, fyke nets outperformed CBTs by accounting for 95.2% of the 604 terrapin captures. Although the long drift leads of the fyke nets proved more effective for intercepting along‐shore travel of adult female terrapins during the nesting season, CBTs provided a more effective means of live‐trapping terrapins within the shallow interior marshes. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

Between the bay and a hard place: Altered diamondback terrapin nesting movements demonstrate the effects of coastal barriers upon estuarine wildlife

ABSTRACTHuman development can impede wildlife moving between complementary habitats, particularly in highly disturbed coastal ecosystems. Coastal barriers may affect the behavior of diamondback terrapins (Malaclemys terrapin), a salt‐tolerant estuarine turtle that requires access to complementary upland habitat for annual nesting. We used telemetry to quantify terrestrial and aquatic movements of 78 nesting female terrapins in response to coastal barriers at 2 sites in Barnegat Bay, New Jersey, a heavily developed estuary. Nesting female terrapins traveled significantly greater distances with more tortuous paths or spent significantly more time in the water when their movements were obstructed than females nesting at beaches with no obstructions. We hypothesize that the additional effort and displacement associated with reproduction where obstructions exist will reduce terrapin fitness and potentially contribute to population declines. Our study demonstrates a unique approach to quantifying effects of barriers on organisms requiring complementary habitats, and improves our understanding of the impacts of shoreline hardening on estuarine wildlife threatened by encroaching coastal development. © 2015 The Wildlife Society.

The blood biochemistry of overwintering diamondback terrapins (Malaclemys terrapin)

Estuarine ectothermic vertebrates, such as diamondback terrapins (Malaclemys terrapin, Schwartz 1955), inhabit a dynamic environment, and many aspects of their biology reflect their ability to withstand and respond to these environmental challenges. The physiological adjustments necessary to maintain water and salt balance and the metabolic adjustments that accompany seasonal changes in activity and behavior have not been well-characterized for overwintering terrapins under field conditions. To investigate terrapin osmotic and metabolic physiology during winter when activity levels are depressed, we obtained repeat blood samples from 10 radio-tagged female terrapins maintained in a semi-natural, open-air salt marsh enclosure in southeastern North Carolina, USA. From November 2011 to April 2012, we measured monthly plasma osmolality, plasma concentrations of inorganic osmolytes (Na+, K+, Cl−), and protein catabolic indices (urea and uric acid), as well as monthly plasma concentrations of total Ca2+, lactate, and glucose as metabolic indices. We used linear mixed models to determine the best predictors of blood chemistry, where time (i.e., day) and environmental variables were fixed factors and individual terrapins were random factors. Day was a poor predictor of blood chemistry concentrations, indicating that the progression of winter did not elicit corresponding changes in biochemical indices as documented in other semi-aquatic turtles exposed to more severe winter and/or laboratory conditions. Carapace temperature was the most common predictor of blood chemistry concentrations in all models, underscoring its relative influence on physiology. In contrast to previous laboratory-based studies on the overwinter physiology of terrapins, our study demonstrates that terrapins in their natural environment are able to maintain biochemical homeostasis throughout winter. The use of evasive behavioral strategies may be an important factor for terrapins to reduce the passive exchange of water and salts with the estuarine environment.

Size-Based Mortality of Adult Female Diamond-Backed Terrapins (Malaclemys terrapin) in Blue Crab Traps in a Gulf of Mexico Population

Mortality incidental to trapping for blue crabs is a primary threat to diamond-backed terrapin (Malaclemys terrapin) populations. Due to sexual size dimorphism in this species, crab-trap mortality is believed to be biased toward smaller adult males and juvenile females. However, a comparison of commercial trap funnel openings and adult female size from a Gulf Coast population suggested that crab-trap mortality is a larger threat than previously thought to adult female terrapins in this population and possibly others.

Nesting Habitat Creation Enhances Recruitment in a Predator‐Free Environment: Malaclemys Nesting at the Paul S. Sarbanes Ecosystem Restoration Project

AbstractAquatic turtles worldwide are plagued with habitat loss due to development and shoreline alteration that destroys the terrestrial–aquatic linkage which they must cross to reproduce successfully. Furthermore, nesting habitat loss can concentrate nesting, increasing nest predator efficiency. We describe how the Paul S. Sarbanes Ecosystem Restoration Project at Poplar Island created nesting habitat for Malaclemys terrapin (Diamondback Terrapin), and document nesting success in response to construction progress and the absence of raccoons and foxes, the primary nest predators. We monitored terrapin nests throughout the nesting seasons from 2002 to 2011 to determine overall and within‐nest survivorship. Female terrapins began nesting on the restoration project within 1 year but planned construction during the study eliminated some nesting areas and opened previously inaccessible areas. Overall, nest survivorship was considerably higher than mainland nesting areas due to the absence of raccoons and foxes on the island and within‐nest survivorship was similar. Egg size, hatchling size, and the frequency of shell scute anomalies were similar to other terrapin populations, suggesting normal developmental conditions on the island. We documented annual variation in hatchling size that correlated negatively with mean air temperature during the incubation season. Our results indicate that restored or created isolated island habitat can be located rapidly by terrapins and can become an important source of recruitment in regions where nesting habitat is limited and predation is high. Poplar Island illustrates how habitat loss and restoration can affect turtle populations by revealing the changes in nesting patterns and success in newly created, predator‐free habitat.

Total body water and water turnover rates in the estuarine diamondback terrapin (Malaclemys terrapin) during the transition from dormancy to activity.

Water and salt concentrations in an animal's body fluids can fluctuate with changing environmental conditions, posing osmoregulatory challenges that require behavioral and physiological adjustments. The purpose of this study was to investigate body water dynamics in the estuarine diamondback terrapin (Malaclemys terrapin), a species that undergoes seasonal dormancy in salt marsh habitats. We conducted a field study to determine the total body water (%TBW), water turnover rate (WTR) and daily water flux (DWF) of female terrapins in south eastern North Carolina pre- and post-emergence from winter dormancy. Terrapins were injected with [(2)H]deuterium on two occasions and washout of the isotope was monitored by taking successive blood samples during the period of transition from dormancy to activity. The WTR and DWF of dormant terrapins were significantly lower than those of active terrapins (WTR(dormant)=49.70±15.94 ml day(-1), WTR(active)=100.20±20.36 ml day(-1), DWF(dormant)=10.52±2.92%TBW day(-1), DWF(active)=21.84±7.30%TBW day(-1)). There was no significant difference in %TBW between dormant and active terrapins (75.05±6.19% and 74.54±4.36%, respectively). The results from this field study provide insight into the terrapin's ability to maintain osmotic homeostasis while experiencing shifts in behavioral and environmental conditions.

Sexual Dimorphism and Feeding Ecology of Diamond-backed Terrapins (Malaclemys terrapin)

Natural and sexual selection are frequently invoked as causes of sexual size dimorphism in animals. Many species of turtles, including the Diamond-backed Terrapin (Malaclemys terrapin), exhibit sexual dimorphism in body size, possibly enabling the sexes to exploit different resources and reduce intraspecific competition. Female terrapins not only have larger body sizes but also disproportionately larger skulls and jaws relative to males. To better understand the relationship between skull morphology and terrapin feeding ecology, we measured the in-lever to out-lever ratios of 27 male and 33 female terrapin jaws to evaluate biomechanics of the trophic apparatus. In addition, we measured prey handling times by feeding Fiddler Crabs (Uca pugnax), a natural prey item, to 24 terrapins in the laboratory. Our results indicate that although females have disproportionately larger heads, they have similar in:out lever ratios to males, suggesting that differences in adductor muscle mass are more important in determining bite force than jaw in:out lever ratios. Females also had considerably reduced prey handling times. Understanding the factors affecting terrapin feeding ecology can illuminate the potential roles male and female terrapins play as top-down predators that regulate grazing of Periwinkle Snails (Littorina irrorata) on Cord Grass (Spartina alterniflora).

Geographic Variation in Egg Size and Lipid Provisioning in the Diamondback TerrapinMalaclemys terrapin

Understanding phenotypic differentiation among populations of wide-ranging species remains at the core of life-history research, because adaptation to local environmental conditions is expected. For example, when energy resources influence offspring fitness (as in oviparous ectotherms), the egg and hatchling environments are expected to influence selection by acting on the amount of energy allocated to offspring. Here we identify population variation in egg mass, length, width, and volume from diamondback terrapin Malaclemys terrapin eggs collected in Rhode Island (RI), Maryland (MD), and South Carolina (SC). Egg size (mean volume: 7.6, 8.1, and 9.1 cc in RI, MD, and SC, respectively) and clutch size (mean no. eggs: 16.1, 12.2, and 6.0 in RI, MD, and SC, respectively) differed among populations, which indicated that females produce larger clutches with smaller eggs at high latitudes and smaller clutches of larger eggs at lower latitudes. Lipid analyses indicated that eggs from SC contained yolks with a higher proportion of nonpolar lipids than did eggs from MD or RI (mean percentage of nonpolar lipids: 22.3%, 22.5%, and 31.8% in RI, MD, and SC, respectively). Thus, female terrapins in SC are laying larger eggs with increased lipid content to provide more energy for the developing embryo. Interestingly, total triacylglycerol (energetic lipid) was greater in southern populations but occurred in higher proportions in northern populations (total triacylglycerol: 88.0%, 85.4%, and 81.9% in RI, MD, and SC, respectively). This variation in triacylglycerol levels demonstrates the necessity for quantifying each lipid component. These data indicate a difference in reproductive strategy by which females in northern populations invest in higher fecundity with less energetic resources per offspring, whereas females in southern populations invest in larger eggs with considerably greater energy reserves.

Crab trapping causes population decline and demographic changes in diamondback terrapins over two decades

Diamondback terrapins ( Malaclemys terrapin) are thought to be declining throughout their range. Although many factors have been proposed to contribute to terrapin declines, including increased predation of nests and adults, habitat loss and degradation, road mortality, commercial harvest for food, and mortality as bycatch in crab traps, few studies have provided evidence linking these agents to population declines. Because male and small female terrapins are most susceptible to mortality in crab traps, population declines should coincide with shifts in the age and size distributions of the population and a shift to a more female-biased sex ratio. We used twenty-one years of mark-recapture data (>2800 captures of 1399 individuals) from a declining diamondback terrapin population in South Carolina to test the prediction that the decline is the result of mortality in crab traps. Since the 1980s, the modal size of both male and female terrapins has increased substantially and the proportion that are females is higher than in earlier samples. Additionally, the population now contains more old and fewer young individuals than before. The changes in demography and sex ratio we observed suggest that this terrapin population has declined as a result of selective mortality of smaller individuals in crab traps. The use of bycatch-reduction devices on crab traps may help prevent terrapins from entering the traps, but current models are too large to prevent mortality of males and many females in this population. Future research should focus on design and testing of effective bycatch-reduction devices for specific regions and other methods to prevent terrapin mortality in crab traps.

Nesting Ecology and Predation of Diamondback Terrapins, Malaclemys terrapin, at Gateway National Recreation Area, New York

We studied Diamondback Terrapins, Malaclemys terrapin, at Gateway National Recreation Area, New York. We found evidence of nesting terrapins at three locations within the Recreation Area and focused our research on the islands of Jamaica Bay Wildlife Refuge. Female terrapins nested from early June through early August and oviposited at least two clutches per year. Mean clutch size was 10.9 eggs. Nesting activity increased with daily high temperature and high tide. The greatest number of terrapin nests was found in shrubland, dune, and mixed-grassland habitats, but nest densities were higher on a human-made sandy trail and on sandy beaches. We estimate that approximately 2053 nests were oviposited on the largest island in the refuge in 1999. In 1998 and 1999, we counted 1319 and 1840 depredated nests, respectively, throughout the refuge. Raccoons were introduced into Jamaica Bay Wildlife Refuge approximately 20 yr prior to this study. Raccoons depredated 92.2% of nests monitored on the largest island during the 1999 nesting season. We also found the carcasses of adult female terrapins that apparently were killed by raccoons as they came on land to nest. This terrapin population may be undergoing demographic changes as a result of the introduction of raccoons.

Estimates of adult survival and migration for diamondback terrapins: conservation insight from local extirpation within a metapopulation

As a case study we analyze a recent extirpation within a metapopulation of diamondback terrapins (Malaclemys terrapin) in a South Carolina salt marsh. Survival and migration probabilities were estimated by means of a multistratum approach in Cormack–Jolly–Seber mark–recapture models to obtain transition probabilities among four tidal creeks adjoining a river. Terrapins showed high fidelity to each subpopulation and the low migration rates were insufficient for recolonizing a creek that had suffered extirpation. Annual survival rates for adult female terrapins averaged 0.84 across all creeks, ranging from 0.748 to 0.971. Survival rates were converted to instantaneous mortality rates (M) for the purpose of calculating the mean life-span as 1/M. When re-expressed in terms of mean life-span, the results confirmed that the average female terrapin did not survive to its estimated age at maturity, as might be predicted if additional mortality of females in crab pots was implicated. The results emphasize that incidental mortality of terrapins in crab pots is a conservation concern. Simple modifications of crab-pot design, such as an entrance reducer, can successfully mitigate this threat to the survival of terrapin populations.

Estimates of adult survival and migration for diamondback terrapins: conservation insight from local extirpation within a metapopulation

As a case study we analyze a recent extirpation within a metapopulation of diamondback terrapins (Malaclemys terrapin) in a South Carolina salt marsh. Survival and migration probabilities were estimated by means of a multistratum approach in Cormack–Jolly–Seber mark–recapture models to obtain transition probabilities among four tidal creeks adjoining a river. Terrapins showed high fidelity to each subpopulation and the low migration rates were insufficient for recolonizing a creek that had suffered extirpation. Annual survival rates for adult female terrapins averaged 0.84 across all creeks, ranging from 0.748 to 0.971. Survival rates were converted to instantaneous mortality rates (M) for the purpose of calculating the mean life-span as 1/M. When re-expressed in terms of mean life-span, the results confirmed that the average female terrapin did not survive to its estimated age at maturity, as might be predicted if additional mortality of females in crab pots was implicated. The results emphasize that incidental mortality of terrapins in crab pots is a conservation concern. Simple modifications of crab-pot design, such as an entrance reducer, can successfully mitigate this threat to the survival of terrapin populations.

Diamondback Terrapin (Malaclemys terrapin) Mortality in Crab Pots

The entrapment of diamondback terrapins ( Malaclemys terrapin) in crab pots frequently results in drowning and death of the trapped turtles. We determined the rate of capture, size, sex, and age of terrapins captured, and the potential impact crab pot mortality has on local terrapin populations. We estimated terrapin capture rates of 0.17 terrapins/pot/day in shallow water areas of Chesapeake Bay (Maryland, USA). The sex ratio of terrapins caught in crab pots was 3:2 male biased because female terrapins become too large to enter crab pots by the time they reach 8 years of age. Males, however, remain vulnerable to entrapment throughout their life. Our estimates of capture rates and local population size suggest that 15–78% of a local population may be captured in a single year. As a consequence, crab pots may be the major reason terrapins are extirpated in coastal, shallow water areas with heavy crab pot fisheries. Additionally, the selective removal of males may also contribute to female‐biased sex ratios observed in this diamondback terrapin population. We developed and tested a modified crab pot that increases terrapin survival and does not reduce the number of crabs caught. Our modified crab pot maintained permanent access to air and prevented the drowning of terrapins. Additionally, our modified crab pot caught more crabs than standard commercial crab pots, suggesting that the modified crab pot could be a viable alternative to standard traps that result in terrapin mortality.

Incidental Capture of Diamondback Terrapin by Crab Pots

Two-hundred eighty-one diamondback terrapins (195♂, 86♀) were captured in baited and unbaited crab pots during premolt crab capture studies in South Carolina. Sampling was conducted four consecutive days each week from mid April to mid November, 1979, in the Ashley River estuary, and daily from April to July, 1980 and 1981, in the Wando River estuary. Fifty-five percent of the total were captured in April, and 32% in May. Males outnumbered females 2.3∶1, but this ratio may reflect crab pot entrance bias which restricted entry of large females. Median plastron length of females was 121 mm (range 76–175) and that for males 100 mm. (range 79–128); only two male terrapins equalled or exceeded the minimum legal size limit of 127 mm. Few captured terrapins were drowned when crab pots were checked daily, and it is estimated that capture mortality amounted to 10%. Terrapin catch per baited crab pot averaged 0.16 daily in April and May. Incidental terrapin capture by 743 commercial crabbers (fiscal year 1982 numbers) in South Carolina during April and May was estimated at 2,853 daily, and mortality was estimated at 285. These estimates are exclusive of mortalities resulting from lost pots. The impact of crabbing activities is believed to pose no threat to the terrapin population at current levels of commercial terrapin harvest. Because female terrapins mature at the minimum legal size, no segment of the egg laying population is protected except seasonally. If direct harvest of terrapins ever approaches that of the early twentieth century, then it is recommended that legal size limits be changed to protect a segment of the mature female population.