Displacement experiments can provide useful insights into the orientation and navigational abilities of animals (Gregory et al., 1987). Such experiments have shown that some individuals of some snake species are capable of returning to their home range after displacement (i.e., "homing") from distances of over 1 km (Gregory et al., 1987). Here we report observations of repeated homing by displaced black rat snakes (Elaphe obsoleta), not just to a home range, but to a point within that range where food had been available at the time of displacement.
Observations were made between 24 May–1 Aug. 1988 at the Queen's University Biological Station in eastern Ontario. The simultaneous study of both black rat snakes and American robins (Turdus migratorius) at the Biological Station created a conflict of interest due to the snakes' propensity for eating the eggs and nestlings of the robins. The compromise reached was for snakes caught at or near robins' nests to be held in captivity for several days prior to release 0.1 km from their point of capture. The persistent return of two individuals to their point of capture necessitated more distant (0.5 km) displacements. Snakes were not fed while in captivity and were transported to release sites in cloth bags. All the observations were made at the workshop building (Fig. 1) where one or two robin nests were active most of the summer. Nests on the workshop had been preyed on by black rat snakes in previous years. Frequent use of the workshop and lack of cover adjacent to the building facilitated the detection of snakes.