Dispersal versus site tenacity of adult and juvenile red-backed salamanders (Plethodon cinereus)

Background/Question/Methods

In many species of amphibians that display territoriality, it is unclear at what life stage and to what extent dispersal occurs. We examined whether differences exist between life stages in dispersal and homing behaviors of red-backed salamanders (Plethodon cinereus) in continuous habitat. We quantified the dispersal of juvenile and adult P. cinerus through a 3 year mark-recapture study. We uniquely marked animals captured in a core 12 x 12 m (144 m²) plot, and then searched an extended 36 x 36 m (1296 m²) plot, calculating dispersal distance using the Euclidean distance from captures in previous years. We compared dispersal between years and life stages. To examine site tenacity in adult and juvenile salamanders, we translocated individuals 1.5 - 25 m after dipping them in fluorescent pigment powder. We tracked animals the night of their capture, recording initial orientation and homing success (return to point of capture within 9 days). To assess factors influencing homing success, we performed a logistic regression including life stage, distance translocated, initial orientation and the covariate of snout-vent length (SVL). We used Rayleigh tests for nonrandom movement to determine factors affecting initial orientation, including life stage and distance translocated.

Results/Conclusions

In the mark–recapture study, we found that juvenile and adult movements between years were not significantly different. The median distances moved by both adults (0.85–0.88 m) and juveniles (1.14–1.22 m) of P. cinereus between years were similar to the diameter of adult home ranges in this area (1.15 m). In the homing experiment, we found that, although the probability of recapture of translocated individuals under their original cover object increased with body size, both adults and juveniles successfully orientated toward their original cover objects when displaced over short distances (1.5 m and 6.25 m), but their orientation was random when displaced long distances (12.5 m and 25 m). Despite the current assumption that juveniles of P. cinereus are not territorial, our results suggest that regardless of life stage, site tenacity accounts for lack of movements.