Laurel Fortun, University of Utah
Female howler monkeys either rise in the ranks within a group or form their own where they are alpha; rarely do they stay independent or away from a group. This research indicates that female howlers would have more reason to compete to reach these higher positions and therefore display more agonistic behaviors towards their direct competition: other females. It has not documented that female howlers are more agonistic than their male counterparts, therefore, comparing interactions intrasexually to learn which is the more agonistic can help us understand group dynamics. Due to this competition for more of an alpha position, food, and reproductive success, I hypothesized that the female-female interactions would be more agonistic in nature than the interactions between male-male. Data were collected within two weeks in May 2017 at the beginning of the wet season in La Selva Biological Station at Sarapiqui, Costa Rica. Five-minute instantaneous scan sample method was used to record interactions. These interactions were categorized into one of eight (four affiliative and four agonistic) behaviors: biting, fight, threat, supplantation, grooming, playing, hug, and peaceful proximity. A total of 82 interactions were observed between female-female and 58 interactions between male-male. The results of the total female-female interactions were 3.4% hug, 4.6% grooming, 88.5% peaceful proximity, 2.3% threat, and 1.1% fight. In comparison, male-male interactions were 3.5% fight, 1.8% threat, and 94.7% peaceful proximity. This yielded a 1.9% difference between female and male agonistic rates with the males behaving more agonistically, although not by a substantial majority. The hypothesis that female-female interactions being more agonistic than male-male cannot be determined supported nor unsupported as there was not sufficient data.