Hughes, Melanie K.2025-02-052025-02-051995-05http://hdl.handle.net/11603/37617Adult male mice defend small territories and compete for mates by engaging in agonistic interactions. A dominance hierarchy is established based on the outcome of these agonistic encounters and the urinary marking behavior of adult male mice is usually strongly dependent on their social dominance ranks. Animals do not behave selfishly all the time but in some circumstances may behave cooperatively, particularly with kin. Hamilton (1964) proposed the theory of kin selection which predicts that the evolution of social behavior is influenced by the degree of kinship between two individuals. I tested Hamilton's theory, that kinship influences agonistic behavior in a preliminary experiment in which I observed agonistic encounters between brothers and nonbrothers. If kin selection on male mice influences interactions between brothers, agonistic interactions between them should be infrequent relative to nonbrothers. The preliminary experiment showed that the mean latency to fight was longer for brothers than for nonbrothers. The mechanism(s) controlling this nepotistic behavior among brothers may be emotional attachment due to association of littermates during early development and/or degree of relatedness per se. I used a cross-fostering procedure to establish four categories of male mice: brothers in same litter, nonbrothers in different litters, brothers in different litters, and nonbrothers in same litter. My results indicate that both attachment and relatedness influence agonistic interactions. To investigate the relevance of open arena tests and whether male mice will continue to display nepotistic behavior in the presense of a limited resource, the pairs of mice were fought a second time with an estrous female present. The male mice had significantly lower latencies which may have resulted from their prior fighting experience, although the pattern of latencies in relation to attachment and relatedness remained the same. Finally, I tested whether kinship influences the nature of urinary marking patterns of male mice and found no significant difference in the urine pattern.52 pagesen-USText