Parapatric pied and red-handed tamarin responses to congeneric and conspecific calls

Abstract

Abstract Aggressive behaviors are widespread among territorial species and asymmetrical aggressiveness may imply differential access to resources. At a larger scale, such asymmetry may also drive shifts in geographic distributions. The pied tamarin (Saguinus bicolor) is an endangered Amazonian primate species with a small natural range. In recent decades further reduction of its range has been observed coincident with the expansion of the range of the red-handed tamarin s (Saguinus midas), which appears to be encroaching into the area otherwise occupied by the pied tamarin. Here we test if, at range boundaries, red-handed tamarin produces more aggressive vocalizations than the pied tamarin. We performed a series of 96 playback trials presenting both congeneric and conspecific long calls to sixteen groups of red-handed tamarins and fourteen of pied tamarins. We recorded their territorial, agonistic, alarm vocalizations, and the duration of their calling displays after broadcasts. In doing so, we assessed whether agonistic displays were more likely to occur in response to congeneric than conspecific calls in areas of sympatry. We found that the red-handed tamarin was more likely to emit more territorial calls when listening to pied tamarins than to its own species in sympatric areas, but found no differences in vocal responses from either species in relation to agonistic calls or duration of display in sympatric and allopatric areas. Furthermore, the red-handed tamarin emitted more alarm calls when listening to pied tamarin, independently of the geographic circumstances. Overall, we found that acoustic displays may be mediating species interaction in areas of sympatry. Together, these observations are suggestive of behavioral interference, including the competitive displacement of pied tamarin by red-handed tamarins.