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A Comparative Study of Terrapin Populations in the Hackensack Meadowlands and the Cape May Peninsula of New Jersey
Ceili Bachman, Richard Stockton College
The purpose of my study was to compare several characteristics of two northern diamondback terrapin populations—one in the Cape May peninsula of southern New Jersey and one in the Hackensack Meadowlands of northern New Jersey. These sites were chosen because of the contrasting physical parameters that characterize each ecosystem. Sex ratio, size distribution, shell anomalies, and diet were compared. Fecal samples from trapped terrapins were used to analyze dietary preferences. The results showed that the sex ratio of females to males was higher in the Cape May peninsula population, that there were significant differences in the size distribution of the two turtle populations, and that there were a higher percentage of shell anomalies in the Hackensack Meadowlands population. The results of the fecal sample data are still preliminary, but there are some prey species that are unique to each population as well as a substantial amount of common prey to both populations.
Experiences in the Coastal Conservation and Research Program, Wetlands Institute
Chittaranjan (Chitta) Baruah
I had the opportunity to take part in turtle patrols, terrapin population studies, terrapin barrier fencing, head-started terrapin release, horse shoe crab population surveys. I visited the Richard Stockton College to learn more about the headstar program. I participated in several terrapin release programs.
The Wetlands Institute’s Terrapin Conservation Project is a community-based terrapin conservation initiative, and it is mostly supported by funds collected from the community people. A large section of the community—visitors, students, teachers, parents, lawyers, administrators, and many others—are involved in the release process under the auspices of the Wetlands Institute.
Study of shell growth rings as an indicator of size in northern diamondback terrapins at Hackensack Meadowlands
James Borawski, Rowan University
I was interested in whether there was a correlation between age (determined by counting growth rings) and the size of an individual terrapin. Trapping took place in the Hackensack Meadowlands once per week. For each turtle, I counted growth rings and measured the length of the plastron. Results suggest that, for males, age is not an indicator of size because at the age of three or four their growth rate declines significantly. On the other hand, females continue to grow, as indicated by a positive correlation between number of growth rings and the size of the turtle. This is an interesting finding because it shows that after a certain age, male growth rates slow down significantly and that the age of the turtle does not indicate size. The opposite is shown in females and perhaps a continuous growth is seen in females. More data is needed to validate these findings.
Do larger terrapins have larger eggs?
Britt McGee, Franklin and Marshall College
In my first project I compared the plastron length of road-killed females to the mean weight of the eggs recovered from them. I was curious to find out whether larger females would lay larger eggs. I used the plastron measurements from road-killed females and weighed the intact eggs that were removed from each respective female. I determined that there is not a strong correlation between female plastron length and mean egg weight. There may instead be a trade-off between egg weight and the number of eggs produced by a female.
Preliminary results of a diamondback terrapin headstarting effort in Cape May County, New Jersey
Britt McGee
My second project examined the headstarter and mark-release-recapture data from 1997 to 2010. I wanted to know how many headstarters had been recaptured, whether or not they were nesting, and whether they were nesting at a younger age due to their accelerated growth in the first year in captivity. I entered all of the data into excel and compiled it so that I could determine when headstarters were recaptured. I found that some headstarters have been returning to nest at the Wetlands Institute. There were also some headstarters caught in trapping experiments and a few that were found as roadkill. The data showed that some headstarters are surviving in the wild and exhibiting normal terrapin mating and nesting behaviors.
Food Habits of Nesting Bald Eagles (Haliaeetus leucocephalus) in New Jersey
Sarah Weber, Saint Mary’s College
The bald eagle (Haliaeetus leucocephalus) is an important species in the wetlands ecosystem. This bird of prey is exclusive to North America and has increased its population in recent years, perhaps due to efforts to reduce DDT from their food supply, which includes various fish and other birds (Clark et al., 1998). Bald eagles are carnivores that primarily eat fish but are also extremely opportunistic and will eat almost anything that presents itself as a meal—carrion and trash included (Beans, 2003). While there is a good amount of research on bald eagle diets from all parts of North America, this was the first time that a variety of prey remains were examined from New Jersey bald eagles’ nests. In New Jersey, the greatest number of bald eagles has been recorded in the southern area of the state, adjacent to the Delaware Bay (Beans, 2003). New Jersey has rich diversity in its salt marshes and wetlands, so this study will help better understand why continued enforcement of coastal and forest wetland regulations is important to maintain and support the state’s bald eagle population.
Research on the topic of bald eagle predation has been ongoing for years in a number of states. In Maine food sources for bald eagles were documented to better evaluate potential sources of contamination. The findings supported the piscine portion of the bald eagle diet was the greatest along the coast, whereas avian preferences were seen in the interior of the state (Gramlich et al., 1982). In another study located closer to southern New Jersey, fish of many species made up the bulk of the bald eagle diet in the Chesapeake Bay region, however many species of birds and a few species of mammals occurred regularly as food items (Clark, 1982). Turtles have also been reported as incidental food items of the bald eagle, primarily in the eastern part of its range (Gramlich et al., 1982). The nests of southern New Jersey bald eagles have been evaluated previously by Dr. Roger Wood of The Wetlands Institute in Stone Harbor, New Jersey. Dr Wood focused on the predation of turtles, specifically the northern diamondback terrapin, by bald eagles (Wood, 2009).
The Effects of nest depth on hatchling success rate and sex ratio in diamondback terrapins
Lauren Westley, Franklin and Marshall College
This summer I studied the effects of nest depth on hatchling success rate and sex ratio in diamondback terrapins. I was interested in discovering how temperature variation within a nest would affect the ratio of females to males. I relocated 15 natural nests into a research plot, simulated the natural depths, and placed two ibuttons in the nests to record temperature. I found that shallower nests experienced higher temperatures as well as a greater variation in temperature than deeper nests. Also, nests at extreme depths, whether shallow or deep, contained eggs that were either desiccated or underdeveloped. This data showed that nests of a median depth (11 cm) had a greater hatchling success rate.
Comparison of scute anomalies between headstarters and natural populations of northern Diamondback terrapin (Malaclemys terrapin terrapin)
Jen Savaro, Coastal Carolina University
The northern diamondback terrapin (Malaclemys terrapin terrapin), like all hard-shelled turtles, has a protective shell composed of hard, bone plates covered by keratin scutes. Phenotypic anomalies in regard to the number and shape of scutes on a terrapin's shell are common. This study compared the differences in scute anomalies between diamondback terrapin headstarters and wild populations of terrapins in the Cape May Peninsula of New Jersey. The purposes of the study were to determine whether a particular anomaly might be correlated with headstarter hatchling death and to see if egg incubation has an effect on the amount of anomalies present in hatchlings. Anomalies present on artificially incubated hatchlings were examined and then compared with mark-release-recapture data from the wild population. Anomalies present on deceased hatchlings were then compared with live hatchlings, and the frequency of anomaly occurrence was calculated. It was found that the most common anomalies are split cervical, vertebral, and costal scutes. No clear correlation was found between death of hatchlings and the percentage of scute anomalies. Headstarters tend to have a higher frequency of fourth and fifth vertebral and costal anomalies than the natural population. Incubated hatchlings had a higher percentage of scute anomalies than do the adult natural population, which suggests that the environment of artificial incubation is conducive to development of scute anomalies. This could be due to the constant temperature and drier, warmer conditions than natural nests where temperature and humidity fluctuate daily and throughout the nesting period.
Variation in Scute Anomalies among Three Diamondback Terrapin Populations
Stephanie Wolfe, Stony Brook University
Diamondback terrapin (Malaclemys terrapin terrapin) is a species of special interest in the state of New Jersey. Little is known about terrapin shell anomalies (irregularities of the scales that make up a turtle’s shell). My project analyzed scute anomalies in diamondback terrapin populations located on the Cape May Peninsula, the Hackensack Meadowlands, and the Florida Keys. Previous research indicated that warmer incubation temperatures will produce more anomalies. Since diamondback terrapins have temperature-dependent sex determination, and warmer temperatures are required to produce females, it is predicted that more females will have anomalies than males. The pattern and frequency of each type of anomaly at each of the three populations was also analyzed. It was found that females tend to have more anomalies than males, supporting the hypothesis that warmer incubation temperatures may lead to higher frequencies of anomalies. In all populations, carapace (top shell) anomalies were found to be more common than plastral (bottom shell) anomalies. In the Cape May Peninsula terrapin population, 31% were anomalous. In the Hackensack Meadowlands, 62% of the terrapin population were anomalous. In the Florida Keys mangrove terrapin population, 60% were anomalous. Both New Jersey populations exhibit the same types of anomalies, but the Hackensack Meadowlands has a significantly higher frequency of anomalies than the Cape May Peninsula. Key West has a distinct pattern of anomalies that is different from what was found in the New Jersey populations. These results indicate that one or any combination of biological, environmental, or anthropogenic factors may account for anomaly differences between sexes and between populations.
Factors Influencing Body Temperature and Incubation
Success of Eggs from Road Kill Diamondback Terrapin (Malaclemys terrapin)
Natalie Young, Rowan University
Road patrol efforts have resulted in the collection of thousands of diamondback terrapin eggs. Studying the hatching success and internal body temperatures of roadkills may help conservationists understand critical temperature ranges for terrapin eggs. In this study, internal body temperatures of roadkills were recorded during road patrols. A side study was also conducted to further understand the internal body temperature of roadkills. Twenty four roadkills were placed on asphalt, and their internal body temperatures were measured every five minutes from 8 p.m. to 6 p.m. (22 hours total). The 24 turtles were placed on the asphalt using different start times, beginning with eight turtles at 8 p.m., eight more at 6.a.m., and the last eight at 12 p.m. The data indicate that body temperatures of roadkills vary based on the time of day the turtle was collected. Night time and early morning body temperatures are significantly different from late morning and afternoon body temperatures. Body temperatures at 2 p.m. are significantly higher. Also, body temperature is not significantly influenced by size or degree of damage to the roadkill. Research on hatching success rates is currently ongoing.
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