To What Extent Does Group Size Effect Kleptoparasitism?
In 2006, researchers from the Department of Zoology at Cambridge published findings dealing with the ground foraging pied babbler (Turdoides bicolor) and its kleptoparasitic counterpart the drongo (Dicrurus adsimilis). A kleptoparasite is an organism that gets a selection of its food by stealing or scavenging from other animals that it lives within close proximity to. There are many different ways that an individual kleptoparasite can manipulate or mutually exist with its host partner. There are mutually beneficial partnerships, partnerships that are completely one-sided and harmful, and many that run the full spectrum in-between. Though there are numerous different elements that factor in, there is one basic underlying theme. The size of the host group the kleptoparasite is scavenging from greatly affects it’s rate at successfully scavenging. The drongo gives alarm calls warning the ground foraging babblers when there is danger from predators. In smaller groups, where they cannot afford to expend as much energy on sentinel behavior, the babblers are often tricked by false warning calls from the drongos. In the jostle that happens from these false warning calls, the drongo achieves the means to steal the babbler’s hard earned food (Ridley 2006). Larger groups of babblers are able to afford the luxury of posting sentinels to keep watch for predators and kleptoparasites, therefore rendering it not worth the time for the drongo to attempt to steal their food. In fact, in larger groups of babblers, it is more beneficial for the drongo to not be present at all. A part of the sentinel’s responsibility seems to lie in chasing away potential food thieves. Smaller groups are offered protection for a price and larger groups are able to provide their own security and thus avoid the cost of dealing with kleptoparasites (Ridley 2006). This facultative response the babbler displays, shows that there may be a strain in how the food is proportioned to members in larger
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