Sexual phenotype drives variation in endocrine responses to social challenge in a quasi-clonal animal

In many species, males tend to behave more aggressively than females and female aggression often occurs during particular life stages such as maternal defence of offspring. Though many studies have revealed differences in aggression between the sexes, few studies have compared the sexes in terms of their neuroendocrine responses to contest experience. We investigated sex differences in the endocrine response to social challenge using mangrove rivulus fish, Kryptolebias marmoratus. In this species, sex is determined environmentally, allowing us to produce males and hermaphrodites with identical genotypes. We hypothesized that males would show elevated androgen levels (testosterone and 11-ketotestosterone) following social challenge but that hermaphrodite responses might be constrained by having to maintain both testicular and ovarian tissue. To test this hypothesis, we staged fights between males and between hermaphrodites, and then compared contest behaviour and hormone responses between the sexes. Hermaphrodites had significantly higher oestradiol but lower 11-ketotestosterone than males before contests. Males took longer to initiate contests but tended to fight more aggressively and sustain longer fights than hermaphrodites. Males showed a dramatic post-fight increase in 11-ketotestosterone but hermaphrodites did not. Thus, despite being genetically identical, males and hermaphrodites exhibit dramatically different fighting strategies and endocrine responses to contests.

Unstable social structure indicates low diversity of relationships in the spotted forest skink Sphenomorphus maculatus

To the date, we hardly understand what and how affects the social structure in animals. Longevity and social stability must be the key factors influencing the relations among individuals. To test this suggestion, I described the spatial and social structures of the spotted forest skinks (Sphenomorphus maculatus) from southern Vietnam in the breeding seasons of 2008 and 2009. This species is known to have short lifespan and low social stability among seasons. No difference between male and female space use was revealed. Home ranges were 107.7 ± 23.68 m2 in males and 78.9 ± 27.27 m2 in females, and these contained core areas and activity centres within them. Home ranges and their parts overlapped among individuals of all sexes and were used by several residents, although not at the same time. Intrasexual and intersexual relationships were agonistic, more aggressive among males, and characterized by hierarchy with males as dominants and females as subordinates. Dominance status in males was supported by aggression in males and by submission in females. Females avoided sexual encounters, and no affiliation between sexes or mate guarding behaviour were revealed. A poor social behavioural repertoire was limited by aggressive and submissive behaviour, and it was difficult to distinguish sexual courtship from agonistic interactions. Hence, social and spatial structures were relatively simple in comparison with other saurian species and low stability of social composition is the most probable reason of such a social simplicity.

Experimental assessment of social interactions in two species of the genus Teratoscincus (Gekkota)

Social organization of many reptile species that are rare in the wild remains rather unexplored due to difficulties when setting experiments in the field. Behavioral analysis of standard social situations in laboratory conditions is considered an indirect method to reveal social behavior in the field. We studied two rare species of geckos, Teratoscincus scincus and Teratoscincus keyserlingii, inhabiting sand dunes of Uzbekistan and Eastern Iran. A series of experiments was carried out to quantify responses in social interactions among conspecific adults as well as reactions of these towards conspecific/heterospecific subadults and juveniles. We also assessed the effect of species and sex on recorded behavior. Finally, the reaction to threat stimuli simulating predator attack was analyzed. The species effect was recorded only in the response to a simulated predatory attack: T. scincus typically escaped whereas larger T. keyserlingii attacked the stimulus. In accordance with the sexual competition hypothesis, agonistic interactions were nearly exclusively confined to male-male encounters while females were tolerant to each other. Male-female encounters regularly resulted in mating attempts, which suggests that females are not strongly selective in choosing partners. Therefore, male aggression can be linked to mate guarding or territoriality. Adults' lack of interest in immature geckos may indicate generalized tolerance of adults towards young.

Mating behavior and female accompaniment in the whiptail lizard Cnemidophorus ocellifer (Squamata, Teiidae) in the Caatinga region of northeastern Brazil

We report here a set of observations on mating behavior and female accompaniment by the whiptail lizard Cnemidophorus ocellifer in an area of Caatinga (xerophilous open forests) in the state of Rio Grande do Norte, northeastern Brazil. We observed a stationary male lizard performing repeated vibratory movements of the pelvis and tail base upon the sandy soil. Since that male was in front of a burrow in which a female of the same species was sheltered, we hypothesize that this behavior may be part of a courtship display. We continued the observation and later, when the female emerged from the burrow, the male climbed on her and the copulation occurred. The incident of accompaniment observed was characterized by one male continuously accompanying a female during foraging. Plausible functional explanations for a male accompany a female include mating guarding, post-copulatory courtship, and sperm loading. By accompanying females, males would be guaranteeing insemination by multiple copulation and stimulation of the female, and protecting their paternity by chasing away other males, diminishing the chances of extra-pair copulations.