Abstracts of Papers
Hatchling Emergence Patterns from Natural Nests
Northern diamondback terrapin (Malaclemys terrapin terrapin) eggs in natural nests develop throughout the summer and hatch in the fall. However, instead of emerging directly after hatching, some terrapins wait until the following spring to emerge from the nest. Data were collected from 2001-2004 at the Wetlands Institute (Cape May County, New Jersey). This study focuses on comparing the number and size of hatchlings emerging in the fall versus spring. Approximately 75% of hatchlings emerged in the fall whereas 25% emerged in the spring. In over half of the nests (53%) all hatchlings emerged in the fall. About 25% of the nests produced only spring emerging hatchlings and 23% contained a combination of both fall and spring emergers. All hatchlings had similar carapace and plastron lengths. However, hatchlings that emerged in the fall had significantly greater weights than the hatchlings that emerged in the spring. The biological importance of overwintering is uncertain. Possibly, by creating separate sets of emerging hatchlings, severe weather conditions (e.g., hurricanes, unusually harsh winters) are not fatal to all terrapins from a single years nesting cohort.
Factors Bearing on Nest Site Selection in the
Diamondback terrapin (Malaclemys terrapin) nest site selection mechanisms are poorly understood. In this study, the relationships between soil particle size and salinity were compared to the frequency of nesting along the Wetlands Institute nature trail (Cape May County, New Jersey). Particle size determines soil characteristics, including water retention (important to hatchling success rate and size) and thermal properties (important to hatchling sex determination). Soil salinity reflects the frequency of flooding by brackish water. The trail was divided into seven 60-meter sections and 5-10 soil samples were collected from each section. Results showed no significant difference in the percentage of sand along the trail (each section contained over 85%) but percentages of silt and clay did vary with location. The highest salinity was found in a frequently flooded area, a location in which eggs could easily drown. The least nested section of the trail contained the greatest gravel by percent mass (45.8%) and the second least nested section had the highest salinity. Neither soil characteristics nor salinity were optimal in the most frequently nested area (26% of observed nesters), which was towards the middle of the trail.
Nest Site Fidelity of the Northern
Diamondback terrapins (Malaclemys terrapin) are a highly aquatic and very cryptic species of emydid turtle restricted to coastal salt marshes along the Atlantic and Gulf coasts of the United States. Many aspects of terrapin life history and behavioral ecology are poorly understood. Long-term studies at the Wetlands Institute (Cape May County, New Jersey) have proven valuable in determining patterns of nest site fidelity both from year to year and within the same year. Over the past four nesting seasons (20012004), 31 adult female terrapins marked with PIT (passive integrated transponder) tags have been recaptured. Of these, 20 terrapins have been captured at the same location in multiple years, indicating strong nest site fidelity. Fourteen terrapins have been captured multiple times within the same year, providing the first evidence that northern diamondback terrapins lay multiple clutches in a single year. Two of these terrapins laid three clutches within a single nesting season. The average interval between clutches is 18 days.
The northern diamondback terrapin (Malaclemys terrapin terrapin) is one of seven subspecies of diamondback terrapin that are found exclusively in coastal salt marshes along the Atlantic and Gulf coasts of the United States. Terrapins are highly aquatic and very cryptic; therefore, many aspects of their life history, including reproduction, are poorly known. Long-term research studies at the Wetlands Institute have allowed us an opportunity to gather information on various aspects of local terrapin nesting behavior including: length of the nesting season, average clutch size, average size of emerging hatchling terrapins, incubation time and over-wintering of hatchling terrapins in their nest chamber. In addition, we have documented nest site fidelity from year to year, diurnal and nocturnal nesting, double and triple clutching (laying more than one clutch of eggs in a single season), and the interval between successive clutches.