COSM

Nest Distribution

Loggerhead Nest Distribution

Loggerhead turtles nesting on St. Catherines Island exhibit geographic clustering of their nests along the beach. The reasons for geographic clustering are not yet known. Just what parameters cause a turtle to select one nesting place over another, remain unknown. However, once a site is selected, Loggerheads exhibit a remarkable fidelity to that site, often returning to it to re-nest up to three or four times. Site fidelity is indicated by nests clustering at geographic points, even to the point of being deposited one upon another.

wild_nest_renesting_fidelity_2441

A wild nest [06-113w] was discovered on South Beach next to and almost on top of a known nest [06-020a] marked by a stake and covered by a plastic screen. The wild nest emerged at night and was scavenged by a Raccoon, dragging hatched egg shells onto the surface. Since [06-113w] hatched [98 of 98 eggs (100.0 % success)] first, it was deposited before the unhatched nest [06-020a] marked by the stake. Nest [06-020] subsequently hatched [140 of 145 eggs (96.6 % success)].

Temporal clustering is also evident when one plots the number of nests per day against the day of the year. The reasons for temporal clustering are also not yet known. It appears that once nesting begins, additional females are added in to the nesting population and synchronize somehow with those turtles already nesting. This gives rise to a remarkable graph that illustrates the synchronicity of nesting.

temporal_distribution_1996

Temporal distribution of nests (orange) and emergences (blue) for 1996 St. Catherines sea turtle nests. Hurricane Bertha disrupted nesting in mid-July.

Because we don’t know why geographic and temporal clustering occurs, we have a prime opportunity to develop and test multiple scientific hypotheses to explain the observed phenomena. We invite you to plot the observed data and develop a hypothesis (or better still, hypotheses) to explain the observations and a plan to test each hypothesis in a sea turtle activity in the Activities Section.

Last updated: 12/11/2014

Sea Turtle Program at St. Catherines Island • (912) 478-1744 • jgaskin@georgiasouthern.edu