Dominant–subordinate relationships in hamsters: Sex differences in reactions to familiar opponents

Abstract

In the majority of mammalian species, males are dominant over and more aggressive than females. In contrast, some reports suggest that female golden hamsters are more aggressive than males but systematic comparisons using the same methods for both sexes are rare. We observed same-sexed pairs of hamsters over repeated trials to assess whether sex differences existed in the level of agonistic behavior and in the development and maintenance of dominant-subordinate relationships with familiar partners. There were no sex differences in measures of agonistic behavior or fear responses (fleeing) during the initial series of three trials on the first day of testing. Following a four-day interval, males that had lost in session 1 showed fearful responses to a familiar dominant male and were not likely to engage in a fight with him. In contrast, females that lost the initial fights were not fearful and fought vigorously with the familiar winner in subsequent encounters. Although the amount of agonistic behavior engaged in by females did decrease over the course of the three sessions, females that lost did not demonstrate an increase in fear, as measured by the latency to flee. Males that lost fights did show increased fear during later trials and sessions. These results suggest that female hamsters are less affected by losing fights than males are and thus that females are less likely than males to develop highly polarized dominant-subordinate relationships. Further work is needed to understand the mechanisms underlying these sex differences.

Effect of losing a fight on later agonistic behavior toward unfamiliar conspecifics in male Syrian hamsters

“…These results agree with previous studies (Lai and Johnston 2002;Lai et al 2004;Bath and Johnston 2007). Bath and Johnston (2007) used a slightly different experimental design in which they tested a male that lost a fight with a familiar winner in three tests sepa-rated by 4 days, each test composed of three trials. They reported that latencies to flee during all the trials on tests 2 and 3 were not statistically different from the latency to flee during the third trial on test 1.…”

“…This arena was uncovered and the height (17.8 cm) allowed either male to readily escape the arena. This type of design has been used in previous studies and results in highly consistent results (Lai and Johnston, 2002;Bath and Johnston, 2007). In the first trial, males approach each other, investigate each other for a few seconds, and then start fighting (Siegel, 1985).…”

“…For example, in Syrian hamsters, two unfamiliar males placed together in a neutral arena will fight vigorously during their first interaction and a clear winner/loser relationship will be established (Payne and Swanson, 1970;Bath and Johnston, 2007). In subsequent interactions, the loser of the first fight will flee soon after detecting the winner of the first fight (Petrulis et al, 2004;Lai et al, 2005;Bath and Johnston, 2007). Losers may show avoidance of the familiar winner for at least one week (Lai and Johnston, 2002).…”

“…Using this design, the loser normally does flee the arena after a brief interaction. In subsequent trials, the loser normally escapes the arena very quickly, so that actual fights rarely occur on the second and later trials (Lai and Johnston, 2002;Bath and Johnston, 2007). An important question that has not been investigated using this naturalistic design is whether a loser would escape in response to any conspecific (i.e., as in conditioned defeat studies) or whether a loser would behave as a non-loser in response to an unfamiliar conspecific (i.e., not escaping immediately but instead fighting to determine a new winner/loser relationship with the unfamiliar conspecific).…”

Stress, sex, and motivated behaviors

“…Field observations indicate there may be important sex differences in the context of how Syrian hamster aggressive encounters are staged (cited in Bath & Johnston, 2007). Aggressive interactions observed among male hamsters involved two males competing for a female in estrus.…”