Three More Hatchlings Scramble Upslope
Posts Tagged ‘pristine’
One surprise we discovered over the last few years is that diamondback terrapin hatchlings employ a variety of strategies to survive their most vulnerable first year. We had all expected that like sea turtles, terrapin hatchlings scramble from their nests in a beeline for the safety of the thick, rich, robust nursery salt marsh habitat ringing Wellfleet’s most productive nesting sites. The first indications that we may have been hasty in this assumption were hatchlings we found in May and June each year heading DOWN HILL from the uplands toward the salt marsh. The first few observations were dismissed as late emerging hatchlings that had overwintered in their natal nests since we had documented a few nests in May and June that had hatched in the fall, but where some hatchlings had remained until the next spring. However, once we spotted yearlings heading down slope from the uplands to the marsh this rationalization collapsed.
Dr. Barbara Brennessel of Wheaton College conducted experiments tracking headstarted hatchlings released in their natal habitat in the Wellfleet Bay system. They were equipped with a transmitter for RDF (radio direction finding) tracking. Although much larger than a normal hatchling due to overwinter feeding, a number of these turtles headed into the salt marsh, behaving precisely as we would have expected a baby terrapin to act. They hid out in the thick Spartina patens, feeding on whatever small critters they could discover in this rich marsh system. However, some number of these headstarts went upland into the vegetated banks abutting sandy nesting areas and the salt marsh. Since these animals were not “pristine” hatchlings, we asterisked their “aberrant behavior.”
But once we began to track baby hatchlings emerging from natural nests on treks upland, we realized that putting all the data together, many hatchlings race into the robust Spartina patens of the Wellfleet salt marsh system, lots of hatchlings dash under the rimming wrack line between sandy nesting banks and the salt marsh, and still others scale the banks and dunes to explore the vegetative uplands above the most productive nesting sites. These terrapins employ a richer, more complex strategy that offers multiple opportunities for survival of hatchlings in a very raw and unpredictable climate at the northernmost edge of their range.
This week we watched the emergence of a nest at Turtle Point. Ten live hatchlings left the nest and we followed them with a long-distance telephoto lens to determine how this group might behave once they had tunneled out of the nest. You may recall earlier reporting of tracking hatchlings into the wrack line and others into the Spartina patens (see Tracking Terrapin Hatchlings, http://www.turtlejournal.com/?p=225)
The first hatchling set out on a solo trek and headed immediately into the vegetation above the nesting bank.
Solo Hatchlings Climbs into Upland Vegetation
Three others seemed to wait for this scout to complete its scramble, and then they too scaled the bank to disappear into upland vegetation.
The last batch of six hatchlings followed suit, with the final two in this pair offering quite a tag team performance.
Final Six Head Upland, Too
Finally, once they had fully dispersed into the uplands, we attempted to find them again. Truth be told, even though we had followed their movements in detail with a long distance telephoto lens, we could only locate four of the ten hatchlings because they were so well camouflaged within the groundcover vegetation.
Hatchlings Camouflaged in Upland Bearberry Vegetation