Why did terrapins cross the runway?

Background/Question/Methods

Each summer 2009-2011 domestic and international news agencies carried stories about diamondback terrapins (Malaclemys terrapin) causing delays on runways at John F. Kennedy International Airport, one of the busiest airports in the world. JFK Airport is located within New York City on the eastern edge of Jamaica Bay, and has a number of associated wildlife issues.  Airport construction was started in 1942, eventually covering 2000 ha of smooth cord grass salt marsh with solid fill and destroying considerable amounts of terrapin marsh habitat. Nevertheless, incidental evidence indicates that a large terrapin population persists, likely in excess of 10,000 individuals.  Most Jamaica Bay salt marshes are eroding for a variety of reasons, but the marsh near the airport appears to disintegrating most slowly, perhaps because it is the youngest and the highest.

Results/Conclusions

Terrapins have been reported on JFK runways annually since 2001, and a small number were killed each year until the recent surge in terrapin numbers. This increase is due to a surge in recruitment, movement of individuals from other parts of the bay, a change in nesting behavior, and/or increased detection by airport personnel.  Elsewhere in Jamaica Bay, terrapins have undergone dramatic changes in reproductive patterns over the last decade, including reduced clutch frequency, increased egg size, and increased clutch size.  These changes are unexplained but may be due to the deteriorating marshes.