Shared predators between primate groups and mixed species bird flocks: The potential for forest-wide eavesdropping networks

A basic tenet of animal behavior is that animal groupings (e.g., schools
of fishes or flocks of birds) are widely influenced by predators. Many
studies have focused on communication between individuals within the same
species or different species within a defined social group; but predators
typically select from a number of different co-occurring species. To
evaluate whether two distantly-related species with similar predators
share vocal information regarding predator threats, we conducted a field
experiment in the Amazonian rainforest involving an avian prey-species, a
primate prey-species, and a shared predator. In our reciprocal field
experiment, we elicited alarm calls from birds (Bluish-slate antshrikes,
Thamnomanes schistogynus) and primates (Saddle-backed
tamarins, Saguinus fuscicollis) by exposing them to a trained
raptor (Bicolored Hawk, Accipiter bicolor). We then played all
types of recorded alarm calls back to birds and tamarins, and measured 1)
the time to respond (for both birds and tamarins), and 2) the distance
moved across the substrate (for tamarins). Our results show that both
birds and tamarins were significantly more likely to flee when hearing
vocal alarms compared to a control (a common bird call, the Screaming
Piha, Lipaugus vociferans), regardless of the species who produced the
alarm. In addition, tamarins moved significantly more upon hearing bird
alarm calls when compared to the control. We suggest that signals
regarding shared predators may be highly valued across prey from distinct
social groups. These data support the hypothesis that overlapping
potential predators can drive communication between distinct prey groups,
resulting in taxonomically diverse eavesdropping networks within tropical
rainforests.