Abstract # 14:

Scheduled for Saturday, August 26, 2017 06:00 PM-08:00 PM: (National Ballroom AB) Poster Presentation


R. G. Steinhardt
University of California, Berkeley, 1640B Allston Way, Berkeley, California 94703, USA
     This study tests the spacing hypothesis as an explanation for long calling in mantled howler monkeys (Alouatta palliata). The spacing hypothesis suggests that howler monkeys use their long calls (howls) to communicate their location to neighboring groups so that the various groups can space themselves out optimally in a feeding area and avoid costly agonistic encounters. Although the spacing hypothesis is well-established, little is known about the underlying cognitive and communicative mechanisms. This study measured activity budgets before and after in-group and out-group howls to test whether howling is associated with an overall increase in activity. I collected 17.5 hours of behavioral data at Maderas Rainforest Conservancy’s field station at La Suerte, Costa Rica. Using modified scan samples, I measured overall activity budgets for the monkeys, then compared these baseline levels to observations taken within 5 and 10 minutes after a neighboring group’s long call. I also compared them to observations taken in the 5 and 10 minutes preceding a call from the focal group. Neighboring long calls had no significant effect on activity budgets in either 5- or 10-minute tests (Mann Whitney U-Test, p>0.2 for all relationships). Based on these findings, howler monkeys do not appear to respond to the calls of their neighbors by changing their activity budgets, nor do changes in the activity budget precede calling.