Locomotor performance and dominance in male Tree Lizards, Urosaurus ornatus

Fighting behaviour in adult male copperheads, Agkistrodon contortrix (Serpentes, Viperidae), was investigated in the laboratory to assess the relative importance of body size and type of agonistic experience as determinants of dominance and mating success. Seven experiments were conducted. In each experiment, trials were run using two adult males and one female in a large arena. The first experiment tested the influence of body size. All males tested had no recent fighting experience for 6-12 months, and one male of each pair was 8-10% longer in snout-vent length and had greater mass. In all cases, larger males won fights and were first to locate, court and guard females; thus, larger snout-vent length was an important determinant of fighting success and priority of access to potential mates. Males with either winning or losing experience from the first experiment were used in six subsequent experiments on the relative importance of snout-vent length and agonistic experience in attaining dominance and mating success. Losing experience had a greater effect than snout-vent length on subsequent fighting success and gaining priority of access to females. Winning experience, in contrast, did not increase the probability of winning subsequent fights; however, winners appeared more excitable and none deferred from challenges of other males. The asymmetry in effects of single experiences of victory and defeat is consistent with studies on other vertebrates and supports the hypothesis that losing fights in males negatively affects behaviour directly related to their fitness.

The relationship between urinary concentrations (free + sulfates + glucuronides) of the steroids testosterone (T), 11-ketotestosterone (11KT), 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one (17, 20 beta-P) and 17 alpha, 20 alpha-dihydroxy-4-pregnen-3-one (17, 20 alpha-P), and the social behavior of males of the cichlid fish Oreochromis mossambicus was investigated. After 8 days of isolation none of the steroids were good predictors of social dominance developed after subsequent formation of all-male groups. One day after group formation dominance indexes were good predictors of the urine concentrations of all sex steroids. Dominance indexes and androgen concentrations measured after all-male group formation were positively correlated with territoriality, courtship rate, and nest size. Similar relationships were found for progestins with the exception that they were not correlated with courtship rate. All-male group formation was also accompanied by an increase in urinary sex steroid concentrations in fish that became territorial and a decrease in non-territorial fish with the exception of T, which increased in both groups. Addition of ovulating females caused steroid concentrations to return to levels near isolation, except for 17, 20 alpha-P in territorials, which underwent a large increase. Thus, social interactions may have an important modulatory effect on sex steroid concentrations in O. mossambicus.