SOCIOECOLOGY OF A TERRESTRIAL SALAMANDER - JUVENILES ENTER ADULT TERRITORIES DURING STRESSFUL FORAGING PERIODS

When adults of a species defend feeding territories, juveniles may benefit from access to those territories during periods when prey decline between territorial spaces. Adults may either deny or allow such access, thus impacting the foraging success of the juveniles. We examined a dense population of the terrestrial red-backed salamander (Plethodon cinereus) in which male and female adults hold territories (cover objects on the forest floor that act as patches of moisture and prey during rainless periods) that should be attractive to juveniles as the surrounding leaf litter dries. The purpose of our research was to determine whether adults of P. cinereus exclude juveniles from their territories, as they do consexual adults, and to explore how juveniles respond to adult territoriality. We found that adults were uniformly distributed intrasexually under cover objects but positively associated intersexually, during the summer when courtship does not occur. Juveniles entered territories of some adults during dry weather, when foraging in the leaf litter was difficult due to desiccation, but moved back into the leaf litter (out of territories) during rainy periods, when prey were more available. Adults ingested significantly larger prey than juveniles but food niche overlap was large between juveniles and adults, suggesting that competition for limited prey occurs when they share territories during rainless periods. In laboratory experiments, juveniles were attracted to territorial pheromones of adult males and females, and males were less aggressive toward such juveniles than toward intruding adult males, Adults were more tolerant of juveniles with which they had cohabited previously in the forest than of juveniles that were ''strangers''; in turn, juveniles spent more time near and less time escaping from previously cohabiting adults than from adult ''strangers.'' Thus, adults appeared to tolerate territorial intrusions by juveniles but were more tolerant of some juveniles than of others. We examined several hypotheses that may explain why adults might allow certain juveniles into their feeding territories during stressful periods. Our data best fit a ''kin recognition'' hypothesis. Kin recognition is known to occur in other species of salamanders and, in our study, adults and juveniles that had previously cohabited on the forest floor were more benign toward each other than were those that had not cohabited, Our data do not favor the ''no competition'' hypothesis because juveniles entered adult territories just when both adults and juveniles were able to ingest fewer prey (dry weather). Our results do not favor the hypothesis that juveniles sneak into adult territories undetected because juveniles move into adults' territories when adults are present, and histological evidence suggests that juveniles possess glands used in social communication. We do not favor the hypothesis that adults habituate to cohabiting juveniles because habituation is not likely to occur between food competitors when the adults can easily defeat the juveniles. The hypothesis of ''dear enemy'' (neighbor) recognition, which occurs between territorial adults of this species, is unlikely to be correct because juveniles do not act as territorial neighbors. Adults appear to act as time minimizers during territorial defense. Juveniles, whether or not related to those adults, appear to act as energy maximizers, moving from leaf litter to cover objects as prey availability shifts.