Several species of large neotropical hawks and eagle, including the Harpy Eagle, Crested Eagle, and the Ornate Hawk-eagle

Forest eagles are found in many tropical habitats and are thought to strongly affect ecosystem structuring through both direct and indirect effects of predation. Mixed-species groupings of primates and bird are a common feature of many intact rainforest communities, yet may be the result of comparatively rare interactions with predators like raptors. The exact mechanisms and details of hunting forest raptors are not completely known. Hawk-eagles are by nature species with low population densities and large territories, making direct behavioral observation difficult. Given that rainforests are dense with vegetation and offer limited visibility, soundscapes are an important means of prey communication within and between species.  Using sequential acoustic recordings, we documented the hunt of a Black-capped Squirrel monkey (Saimiri boliviensis) by an Ornate Hawk-eagle (Spizeatus ornatus) in an Amazonian forest. By comparing the vocal behavior of three different mixed-species communities present during the hunt, we illustrate community-wide effects of large raptors at the smallest scale possible. 

We show that the hawk-eagle stopped calling 600 meters from the targeted mixed-species group of primates. During the time of attack, 3 species of primate and 3 species of bird either alarm or vocalize. By comparing the recorded vocalizations with those recorded during previous research into alarm signals, we are able to describe the alternation of information about predators among birds and primates of several species.

​Figure 1. Trail markers, Timeline of Vocalizations, and Important Events. Notable alarms are represented by spectrograms. Vocalization events are shown as colored dots on the timeline. Vertical position of colored dots indicates the forest strata used by the alarming species. Notable behavioral events are represented by the green letters e (events) 1-4. Trail locations are represented by letters t (trail) A-D. The trail markers are labeled as points 2200m-3000m, representing trail marker names. Distances between points are 200 meters.

 In addition to the recorded audio, inspection of the primates body immediately following the attack gives insight into the relationship between predator attack strategies and taphonomic study. The hallux is the likely source of a single visible puncture through the ribs of the monkey. Blood in the primate’s mouth, and a lack of facial tissue trauma suggest internal bleeding was the proximate cause of death.

Figure 2 Photographs of prey, predator, and habitat. (a) Sight of kill as seen upon approach with both predator and prey in frame, shown within squares. (b) Ornate Hawk-eagle Spizeatus ornatus. (c) Black-capped Squirrel monkey Saimiri boliviensis. (d) Close-up photo of the face of the squirrel monkey showing blood in the mouth and no damage to facial tissue. (e) Site of single observed puncture wound on squirrel monkey.