Maybe It Did, Maybe It Didn’t: Distinguishing Alarm Calls for Different Predator Behavior

         Predation, a key biological interaction between various species, has developed as one of the most important contributors to natural selection. As a response, antipredator calls that are specific to different species have evolved over time to help disclose information about the predator, including the type of predator, the distance between predator and prey, the predator’s behavior, etc. One species that demonstrates such antipredator calls are the Siberian jays (Perisoreus infaustus). The major cause of mortality for this group-living bird species is predation, as presented threats are hawks, sparrowhawks, and owls. The purpose of this study was to examine how certain prey signals communicate different information about the behavior of a predator to conspecifics.  In the case of these birds, the conspecifics would more than likely be kin-related individuals, who the callers attempt to protect from the predator. This is the first experiment ever conducted to explore how calls differ upon the predator’s actions (i.e. whether the predator is attacking, perched on a tree, or searching for prey).

          The study described was performed in Arvidsjaur,  located 100 kilometers south of northern Sweden, on Siberian jays. The predator of the experiment was the hawk, and the time period in which data was collected was from fall of 1998 to fall of 2004. The researchers were testing for any differences in signaling to conspecifics based on changes in predator behavior.. For the experiment, data on alarm calls were recorded based on the following hawk-predator behaviors: prey-searching, attacking prey, and perching. According to the findings, the jays would only emit attack calls for hawks that would attack and alert calls for hawks searching for prey. On the other hand, the jays would utter a number of different calls, which were not attack or alert calls, and begin mobbing when a hawk was perched. To further test and confirm these results, the researchers used a playback experiment to test for the behavior of the call receivers  in response to the different calls. For this part, the birds were divided into foraging groups of 2, in which the sample size was n=12 groups. The findings were that, with playback recordings of alert calls, both individuals in all groups stopped foraging and flew to the nearest safe space to passively search for the predator. Following the attack call playbacks, the individuals flew to a safe location and immediately began actively searching for the predator. Lastly, after hearing mobbing calls that were given in response to a perched hawk, jays did not seek cover but did begin both active and passive searches for the predator.

        Based on the findings, the hypothesis was proven that antipredator calls for prey varied depending on the situation of the predator. Each particular behavior that was exhibited by the predator was associated with its own specific call, which helped the receivers to determine the extent of danger and risk as posed by the predator and to respond  accordingly. Furthermore, this experiment was important in developing an understanding of how these birds use calls as a mechanism for their survival. Furthermore, the significance of the study is that it verified a case in which antipredator signals differ with alterations in behavioral contexts. Additionally, the results have notable implications, as it is possible that similarities in call behavior could be observed for species outside of the Siberian jays. The research ultimately conducted further established antipredator signaling as a vital tool for species survival.

Citation:

Griesser, M. (2008). Referential calls signal predator behavior in a group-living bird species. Elsevier, 18(1), 69-73. doi: 10.1016/j.cub.2007.11.069.

URL: https://www.sciencedirect.com/science/article/pii/S0960982207024189