THE HUH VOCALIZATION OF WHITE-FACED CAPUCHINS - A SPACING CALL DISGUISED AS A FOOD CALL

White-faced capuchins, Cebus capucinus, predictably emit huh vocalizat ions It high rates within dense fruit patches. We sought to determine why white faced capuchins at the La Selva Biological Station, Costa Ri ca produce these food-associated calls. Here we analyze the contests i n which this intra-group vocalization was emitted, including the spati al responses elicited from other troop members. A cumulative 26.6 h of continuous focal samples and 3314 spectrograms (including 1643 huhs) were analyzed from a study troop with 16 focal subjects. The mean indi vidual rate of huhs was greater (1) during foraging versus nonforaging activities; (2) during fruit foraging compared to both visual searchi ng for foraging sites and foraging for arthropod prey; and (3) when th e nearest neighbor was within a 10 m radius of the focal animal compar ed to when the nearest neighbor was at greater distances. A huh also p redicted a significant increase in nearest-neighbour distance; on aver age, mean nearest-neighbor distance increased 3 m within 2 min followi ng a huh vocalization. Null models of change in mean nearest-neighbor distance over time were generated from the original data set by treati ng predetermined time points (140 s intervals) in the focal recordings as if those points marked instances at which huhs were produced by th e focal subject. No significant alterations in nearest-neighbor distan ce were detected within time lags up to 100 s in these null models, su pporting the conclusion that huhs are causally linked with subsequent increases in nearest-neighbor distances. Huhs were most evident when c apuchins were within dense fruit patches, hut these calls were produce d across all foraging contests. Our results suggest that huhs may not be food calls in the usual sense (i.e. informing others of the locatio n of food sources to be shared), but may be more appropriately describ ed as spacing calls. Huhs probably act to increase foraging efficiency by reducing overlap in foraging areas with other troop members.