Socioecology of a Terrestrial Salamander: Juveniles Enter Adult Territories During Stressful Foraging Periods

Abstract

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 (out of territories) during rainy periods, when prey were more available. Adult ingested significantly larger prey than juveniles but food niche overlap was larger 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 juveniles than of others. We examine 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 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 more 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 adult 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, w...

Direct and Indirect Effects of Climate Change on Amphibian Populations

“…For terrestrial amphibians, higher amounts of precipitation increase humidity on the forest floor and underneath moisture-retaining cover (assuming this is not counteracted by increased temperatures), thus facilitating more opportunities to forage [129][130][131]. Above average rainfall in one year may increase the terrestrial prey base for adult females, which may then translate into greater reproductive success (through more "fit" offspring) in the subsequent year.…”

Seasonal Cell Proliferation in the Chemosensory Epithelium and Brain of Red-Backed Salamanders, <i>Plethodon cinereus</i>

“…Red-backed salamanders can be the most abundant vertebrate in a forest in terms of biomass [Burton and Likens, 1975], forming dense populations at some study sites [e.g. Jaeger et al, 1995]. A life history study of P. cinereus in Maryland suggested that it takes 2 years for eggs to develop, and mature females probably deposit eggs in moist nest sites on land every other year [Sayler, 1966].…”

Cell Birth and Survival following Seasonal Periods of Cell Proliferation in the Chemosensory Epithelia of Red-Backed Salamanders, <i>Plethodon cinereus</i>

“…This information about the scent producer includes gender [Martin et al, 2000], familiarity vs. unfamiliarity [Jaeger, 1981;Gillette et al, 2000b], quality of diet [Walls et al, 1989;Gabor and Jaeger, 1995;Karuzas et al, 2004], kinship [Forester and Anders 2000], and whether or not they had other mating partners [Gillette et al, 2000a]. Adults of both sexes and juveniles can detect the information in pheromones [Horne and Jaeger, 1988;Jaeger et al, 1995], and the vomeronasal system is specifi cally implicated in pheromone detection through a behavior called nose-tapping. Salamanders nose-tap each other [touch the bases of nasolabial grooves which transport odorants preferentially to the vomeronasal organ; 1989] and the substrate, including feces.…”