Conflict and postconflict behaviour in two lemur species with different social organizations (Eulemur fulvus and Eulemur macaco): A study on captive groups

Although the brown lemur (Eulemur fulvus) and the black lemur (Eulemur macaco) share many life parameters and are genetically closed, they show considerable difference in social organization. Dominance relationships with no systematic effect of gender characterize the former, whereas the latter is based on female dominance. The present study was done on two captive groups of brown lemurs and one semi–free‐ranging group of black lemurs. To reveal links between the specific pattern of social organization and agonistic behaviors, agonistic interactions were analyzed for each species as for their context of occurrence, symmetry, initiation, and outcome. The effect of gender in the initiation of conflicts appeared as the only notable interspecific difference, aggression being mostly initiated by females in E. macaco and by males in E. fulvus. Conflict outcome was generally in favor of the initiator, regardless of gender in both species. The analysis of postconflict behaviors revealed conciliatory processes in the brown lemur, whereas reconciliation seemed to be absent in the black lemur, a characteristic shared with the ring‐tailed lemur (Lemur catta), another lemur species with female dominance. Aggr. Behav. 28:62–74, 2002. © 2002 Wiley‐Liss, Inc.     

Endocrine Mediators of Masculinization in Female Mammals

ABSTRACT— Most mammal species show traditional patterns of sexual dimorphism (e.g., greater male size and aggression), the proximal mechanism of which involves the male's greater pre- and postnatal exposure to circulating androgens. But in several species, females diverge from the traditional pattern, converging on the male form or even reversing sexual dimorphisms. Such "masculinized" females might show elongation of the clitoris, enhanced body size, and aggressively mediated social dominance over males, and they are interesting case studies for examining the role of androgens in females. This review addresses our understanding of the mediating mechanisms of morphological and behavioral development in both traditional and exceptional mammal species. Although certain lines of evidence implicate testosterone in female masculinization, the role for sex steroids in female development remains unclear. The results call for continued study of both hormonal and nonhormonal mechanisms of sexual differentiation, particularly focused on active processes of feminine development.     

Targets,tactics, and the open mouth face during play fighting in three species of primates

The play fighting of many mammals involves the nonserious use of behavior patterns derived from serious fighting. A major question of theoretical importance has been that of how, given this overlap in patterns of behavior, the animals can distinguish between playful and nonplayful intent. One proposed solution is that animals use play signals to inform each other about the playful intent of their actions. The most widely reported play signal amongst primates is the open mouth play face. The manner in which this so-called signal functions is based on correlational evidence, with most reports simply noting its presence or absence in a given species. This study involved a detailed video-based analysis of the occurrence of open mouths during the play fighting of three species of primates. One captive troop each of ring-tailed lemurs, black-handed spider monkeys, and patas monkeys was used. By examining all open mouths in the context of the species-typical style of play fighting, several conclusions were empirically verified. 1) Most open mouths occur as a functionally necessary precursor for biting. 2) Some open mouths occur as a defensive threat which deters further contact. 3) The residual open mouths which may function as contact promoting play signals, constituted about 20–25% of all open mouths by the lemurs and patas monkeys, but less than 5% for spider monkeys. These species differences appeared to arise from two causes. Firstly, the spider monkeys used another signal, the head shake, in situations where lemurs and patas monkeys used open mouths. Secondly, the style of play fighting greatly influenced the frequency and duration of open mouths. This was most marked in the face-to-face combat style of patas monkeys. These findings show that comparative studies of the occurrence and function of play signals need to take into account species-typical styles of playful combat. Aggr. Behav. 23:41–57, 1997. © 1997 Wiley-Liss, Inc.