We used two field experiments to examine the nature and effects of size-dependent interactions between two terrestrial salamanders, Plethodon cinereus and Plethodon glutinosus. We reared juveniles of P. cinereus in an enclosure alone, with a similarly-sized conspecific, with a similarly-sized P. glutinosus, and with a larger P. glutinosus. We also reared juveniles of Plethodon glutinosus alone. We found that both intraspecific and interspecific competition reduced growth in juveniles of P. cinereus, but the effect of intraspecific competition did not differ from that of interspecific competition. Interspecific competition reduced growth in juveniles of P. glutinosus. Size asymmetry did not appear to affect competition between juveniles. Size, not species identity, determined the use of the space beneath wooden cover objects placed in the enclosures.

In the second experiment, we housed adults of P. cinereus and juveniles of P. glutinosus with similarly-sized conspecific individuals to simulate intraspecific competition. Adults of P. cinereus were also paired with similarly-sized, smaller, and larger individuals of P. glutinosus. Interspecific competition did not affect growth differently than intraspecific competition for P. cinereus, and the size of the competitor did not affect the growth of this species. Interspecific competition reduced the growth of P. glutinosus significantly more than intraspecific competition and had the greatest effect when competing individuals were similarly-sized.

This study examines the mutual competitive effects among larvae of two syntopic salamanders, Ambystoma macrodactylum and Ambystoma gracile. Evidence for competitive equivalence and constant per capita effects among these syntopic species could justify the use of simple models for describing competition. The species were raised alone and together at two densities in replicated artificial ponds. Hatchlings of Ambystoma macrodactylum were smaller than A. gracile, yet larger at the end of the experiment when A. macrodactylum began to metamorphose. Competition was detected as a decrease in growth rate with increasing density, but competition was not so strong as to influence the survival of either species. Ambystoma macrodactylum grew slowly relative to heterospecifics, and growth declined more with increasing conspecific density than with heterospecific density. In contrast, growth of A. gracile was depressed more by increasing density of the slower growing heterospecifics. These differences in effects of competition likely arise from differing breeding phenology—A. macrodactylum breeds earlier than A. gracile, and A. macrodactylum was larger than A. gracile when the latter were added to the experimental ponds. The results provide no evidence for competitive differences or interaction at the low density used here. Assuming a coexistence mechanism exists to offset the competitive asymmetry at high density, I present a testable hypothesis on the mechanism of differential susceptibility of the species to predation.

Intraspecific communication is an important component of social behavior in many species. In urodeles, chemical signals found in scent marks or other glandular secretions are often the mechanism by which such communication occurs. I tested the hypothesis that individuals of Batrachoseps attenuatus, the California slender salamander, can discriminate between self-marked substrates and substrates marked by conspecifics. After housing salamanders (n = 30) for five days with moistened sphagnum moss, I presented each individual in 15-min behavioral trials with two pieces of moss, one from the individual's own housing chamber and the other from a conspecific's chamber. Individuals nose-tapped (chemodetection) significantly more often and spent significantly more time in the threat posture when in the vicinity of conspecific-marked substrates relative to self-marked substrates. This suggests that individuals of B. attenuatus discriminate between self-marked substrate and conspecific-marked substrate, implying self-recognition, and that this discrimination may be effected by scent marks.

We studied sea kraits (Laticauda colubrina) on a small Fijian island during the mating season (September–December) in two successive years. These snakes forage at sea but return to islands to mate (and to lay their eggs, slough their skins, and digest their prey). On land, many females are accompanied by one or more courting males. The males align their bodies with that of the female and occasionally twitch spasmodically. These groups may remain together for days, with overt courtship by males much less frequent and intense than in most previously-studied snake species. Experimental trials in outdoor arenas showed that larger females attracted more intense courtship than did smaller animals. Females containing recently-ingested prey items were no more or less attractive to males than were unfed females. The intensity of courtship did not vary significantly among different times of day, nor was it consistently correlated with ambient temperature or with group size (operational sex ratio). Male sea kraits did not interact with each other in any overt way during courtship, and larger body size did not enhance male reproductive success. In several respects, the courtship of L. colubrina differs from that reported for other snake species.

We evaluated age structure in three species of desmognathine salamanders at Coweeta Hydrologic Laboratory, North Carolina, for comparison with the results of an earlier study of age structure in these species at a nearby locality (Wolf Creek, North Carolina). At Coweeta, both Desmognathus quadramaculatus and D. monticola attain larger adult body sizes and greater ages than their Wolf Creek counterparts. The differences appear to stem in part from greater ages at sexual maturation in both species at Coweeta versus Wolf Creek. This disparity is most pronounced in D. quadramaculatus, where the estimated ages at first reproduction are 7–8 yr in males and 9–10 yr in females. The Coweeta populations of D. quadramaculatus and D. monticola may also have higher survivorship and higher rates of post-maturational growth than those at Wolf Creek. In contrast, in the third and smallest species, D. ocoee, the Coweeta population did not differ in size and age attributes from that at Wolf Creek. We hypothesize that the more mesic climate of Coweeta versus Wolf Creek is a safer environment for the two larger, aquatic to semi-aquatic desmognathines, eliciting selection for later maturation and thus larger body sizes. In contrast, selection on the life history of the smaller and more terrestrial D. ocoee at both localities may derive mainly from factors other than the climatic differential.

A reanalysis of our allozyme data (Dowling et al., 1996) for four slowly-evolving loci in 215 species of snakes by Buckley et al. (2000) concluded that because of ties in genetic distances our published UPGMA tree had “little resolution, indicating that these data are highly ambiguous regarding higher-level snake phylogeny.” They also concluded that “the high degree of resolution in the published phenogram is an analytical artifact.” Our study was intended to obtain information on lower-level relationships for the snake species that we had available, and it provided support for some current hypotheses of snake relationships at that level. Buckley et al. (2000) reached their conclusions because in their analysis they used only strict consensus trees and did not randomize the order of their input data. By randomizing data input order and using a majority-rule consensus tree, we show that there is considerable phylogenetic signal in our data.