Costs and benefits of non-predator eavesdropping in mammal-bird  (Page 2/6)

Other animals that recognize and respond to one another’s alarm calls include hornbills and Diana monkeys, dwarf mongooses, and many more. What benefits does an eavesdropper receive, and are there any costs to its behavior? We will explore this question within the context of several sets of organisms ( [link] ).

Overview of alarm calls (conspecific)

Alarm calls within a species can be given for a number of reasons ( [link] , adapted from Wheeler 2008). One of the foremost reasons to alarm one’s community is to warn one’s kin. By helping kin to survive, an animal is ensuring that more of its genes will be passed on to the next generation. Studies have shown that kin warning is the primary reason chipmunks give alarm calls (da Silva et al 2002); studies have also shown that the long-distance calls of Diana monkeys function as kin-warning systems (Zuberbuhler et al 1997). These studies examined what types of stimuli triggered the animals to alarm, as well as studied which animals alarmed. The assumed cost of this behavior is that the predator will be more likely to find and eat the animal that makes a loud alarm noise; the assumed benefit is the probability that more of the alarming animal’s genes will continue on to the next generation, whether through children or close relatives. Parental care and mate protection are also forms of kin selection.

Another key hypothesis for why animals alarm call is the “perception advertisement hypothesis” (Bergstrom&Lachmann 2001; Zuberbuhler et al 1997). This theory states that prey animals will often sound the alarm after they’ve spotted ambush predators – that is, predators that rely on the element of surprise to get their prey. If the predator is spotted, it will likely have less success in hunting and will have to expend more energy to kill the prey that is forewarned. If the prey spots the predator, then, the prey can alarm to tell the predator that it has been spotted and will have to work harder than it had anticipated. This knowledge is sometimes enough to encourage the predator to leave and attempt to sneak up on another meal. The cost here is the same as before: the predator is more likely to spot the caller. But the benefit is that the predator might attack at all: since through alarming the caller is able to save both itself and its kin, the benefits clearly outweigh the cost.