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.

侵略行为在各个领土物种中普遍存在，不对称的侵略性可能意味着对资源的获取存在差异。在更大范围内，这种不对称也可能会推动地理分布的变化。斑叶绢毛猴（Saguinus bicolor）是一种濒临灭绝的亚马逊灵长类动物，其自然分布范围很小。近几十年来，观察到其范围的进一步缩小与红猴（Saguinus midas），似乎已经侵入了绢毛绢毛猴所占据的区域。在这里，我们测试了在距离边界处，红手绢毛猴是否比花斑绢毛猴产生更具侵略性的发声。我们进行了96次回放试验，向16组赤手绢毛猴和14个斑绢毛猴提出了同种和同种长叫。我们记录了他们的地域性，激动性，警报声以及广播后他们的通话显示持续时间。在此过程中，我们评估了在共形区域中，对同质响应的反应是否比对同质响应的反应更可能发生激动显示。我们发现，红sym猴在聆听染色猴时，更有可能发出更多的领土号召，而不是在同居地区听到自己的物种，但发现这两种物种在同声和异影区域的激动声或显示持续时间方面的声音反应均无差异。此外，红猴在聆听染色猴时发出更多警报声，不受地理环境的影响。总体而言，我们发现，声学显示可能会介导共生区域中的物种相互作用。总之，这些观察结果表明存在行为干扰，包括红手绢毛猴竞争性地取代了绢毛绢毛猴。