Observations on Mammalian Prediation of Snapping Turtle Nests (Reptilia, Testudines, Chelydridae)

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An investigation of the ecology of the common snapping turtle within the Great Swamp National Wildlife Refuge, Basking Ridge, New Jersey, was initiated in 1975. Observations made during three turtle nesting seasons indicated that a large number of nests fell victim to mammalian predation pressure. The study reported here was undertaken in an attempt to determine how predators locate turtle nests and to ascertain which factors may either promote or inhibit predation efficiency. Location of turtle nests may be facilitated by the predator's sighting of the female turtle during nesting or by olfactory clues associated with: (1) secretions of the nesting female; (2) the egg; or (3) disturbance of soil layers during nest digging. We were also concerned with: (1) whether predation will occur during periods other than the regular turtle nesting season; (2) whether established turtle nesting areas along watercourses experience greater predation pressure than locations not normally used for nesting; and (3) precipitation levels have any effect on predation efficiency. An informal study was conducted 8-19 April 1977 using decoy nests stocked with chicken and/or dove eggs buried to an approximate depth of 10 cm, an average derived from measurements of opened turtle nests. Results suggested that: (1) predators would readily open these nests in the absence of visual or olfactory clues associated with nesting turtles; (2) established nesting areas adjacent to watercourses were no more vulnerable to predation than areas where nests were not normally found; (3) predation pressure appeared to be as intense in mid-April as during May-June, the regular turtle nesting period; and (4) live trapping at the location of the decoy nests resulted in the capture of raccoons exclusively. As a result of this work, further studies were undertaken to confirm these findings and to elucidate the other possible parameters of predation already mentioned.