How caracaras defeat wasps

by Matthew Cobb

We’ve previously discussed Apoica wasps, mainly for their nocturnal behaviour and the anatomical adaptations they show. Now Sean McCann and a group of colleagues have looked at them from another point of view: as food for another social organism, the cooperatively-breeding red-throated caracara (Ibycter americanus). This bird is a specialist predator on social wasps, including Apoica. It is also a fine-looking species of falcon from Central and South America, as shown in this picture from Sean’s paper, published in PLoS ONE:

Sean (appropriately aka @Ibycter on Tw*tter) and his colleagues carried out a field study in French Guiana to try and work out how the caracara manages to eat such angry stingy prey. To do so, they set up a cunning arrangement of posts with video cameras and wasp nests:

It had initially been thought that the birds had some kind of chemical defence to protect them from the wasps. Although there are various compounds on the birds’ feet that the wasps can detect (establishing this involved some fairly fancy science), these appeared to have come from ants, and not to have any repellent effect on the wasps.

In fact, it turns out the caracaras exploit a behavioural adaptation shown by the wasps – ‘absconding’. If the nest of these wasps is knocked to the ground or even severely shaken, they simply pootle off and make another nest, rather than trying to save their brood, which can therefore be a tasty meal for the caracara and its babies.

How does the caracara manage this feat without being stung? Well the answer seems to be that caracaras *are* stung when they attack the nests, but they are swift and violent enough in their attack to avoid being hurt too much. Once the nest is on the ground, the wasps seem to chill. Hence the opening title of the paper, “Strike fast, strike hard”.

Sean and his colleagues suggest that wasp absconding behaviour may be an adaptation to vertebrate attack, when the nest is downed and essentially lost as a result, and that, unexpectedly, vertebrates may have shaped the absconding behaviour of the wasp by their predatory attacks.

They have made this excellent brief video summarising their findings, and showing key experimental moments, including a scary shot when Sean imitates a Caracara and brings down an Apoica nest (with a stick). As he told me on Tw*tter: “Those wasps were angry!” You bet – so remember folks, DON’T TRY THIS AT HOME, even if you have your running shoes on.

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S. McCann et al. 2013. Strike Fast, Strike Hard: The Red-Throated Caracara Exploits Absconding Behavior of Social Wasps during Nest Predation. PLOS ONE, Published: December 26, 2013, DOI: 10.1371/journal.pone.0084114