International Journal of Comparative Psychology

Molecular genetics studies on the chymomyzids have produced divergent results on their relation to the genus Drosophila . Behavior has been used to assess the appropriateness of their inclusion in the genus (Maclntyre and Collier, 1986) or off the drosophilid main stem (Beverley and Wilson, 1984). Laboratory and natural population studies on Chymuniyza amoena in Michigan and Virginia and observations on multiple species aggregations at natural sites in 1986 and 1987 in Virginia's Allegheny Mountains have been carried out. Wing-waving and foreleg splaying are characteristics of both sexes. In nature, females do not approach males until sexually mature. All population sizes seem small. Studies on C. amoena indicate that behavioral phenotypic plasticity exists for all stages: lanal feeding substrates, pupation site choice, mating system, egg deposition and oviposition site selection. Behavioral traits shared with the lek Drosophila (Hawaiian and Australian), genus Scaptomyza , subgenus Scaptodrosophila , subgenus Sophophora and genua Lissocepha Ia among the drosophilids, and the tephritids, otitids and hyinenopterans outside the family Drosophilidae suggest that chymomyzids retain characteristics of primitive drosophilids that have undergone selective modification in the evolution of different drosophilid lineages. Significant differences in aggression between Michigan and Virginia C. amoena populations support this conclusion. Throckmorton (1962, 1966) anticipated the chymomyzid relation to the drosophilid stem from external and internal anatomical studies. A wood breeding habitat of most forest chymomyzids is also in agreement with recent molecular genetics evidence that fermented fruit breeding evolved later in drosophilid evolution.

Social experience has been shown to mask or eliminate heritable effects on aggressive behavior in male mice. This work assesses the impact of social experience in females from lines of mice selectively bred for differential male aggressiveness. These results confirm the earlier report of cross-sex similarity in aggressive behavior after selection directed only at male behaviors ( Hood & Cairns, 1 988 ). Repeated test experience increased aggressive behavior of S ₆ females. In addition, a genetic-developmental interaction was found, with enhanced aggressiveness in mature vs. young high-aggressive line females. Repeated test experience in 4 daily trials with mature S ₁₅ females obscured the clear line differences in attack frequency obtained on the first trial. In particular, a few highly aggressive individuals emerged among the group-reared low-aggressive line females. Isolation housing did not alter female aggressiveness. These findings are discussed in regard to conceptions of genetic-experiential-developmental interactions, and the role of female social behavior in microevolutionary processes.

Two investigations examine the hypothesis that one function of exploration is to create situations in which there is an opportunityto acquire useful information. In the first, male rats { Rattus nonvgicus , Sprague Dawley strain) with enriched (EC) or impoverished ( IC) experience ( leading to differences in exploratory behavior documented previously) were given an opportunity to explore an arena with a hidden escape route on two consecutive days. On the following day, subjects were chased by a mechanical device and the time required to escape the arena was recorded. No group differences were seen in pre-chase behaviors other than those related to the hidden escape route, or in stress-related behaviors while being chased. EC rats escaped significantly more quickly than IC rats, and a composite .score derived from pre-challenge behavior in the arena was correlated significantly with escape time under challenge. In the second experiment, EC and IC subjects were chased without previous experience in the area; EC rats escaped significantly more quickly than IC rats. In an analysis of the combined results from the two experiments, both environmental history and pre-challenge arena experience were found to exert significant influence on escape time. These findings demonstrate that different behaviors during exploration can lead to functionally significant differences in the information acquired as a result of exploration.

Three chimpanzee infants were separated from their mothers. The behavior of the mothers was monitored before and after separation. Data were equally divided between pre- and post-separation observation periods. The mothers exhibited significantly reduced levels of play and significantly more time spent in proximity to an older offspring after they were permanently separated from their infants. No other recorded behaviors were significantly altered. The mothers exhibited individual differences immediately following the separation. The findings are consistent with other studies that noted the relatively mild maternal reactions to infant separation and the attenuating effect of familiar conspecifics in the post-separation environment.