African wild dogs (Lycaon pictus), photographed at the Bronx Zoo.
African wild dogs (Lycaon pictus) don't have it easy. Their taste for large mammalian prey puts them in competition with lions and spotted hyenas for both prey and living space, meaning that wild dogs regularly have their kills stolen or are even killed by other predators. In fact, the dogs may even be unintentionally attracting the attention of these other hunters.
Like other social carnivores, African wild dogs communicate with each other through body language and olfactory cues, but they also employ a variety of high-pitched vocalizations. Despite their social benefits, however, the chirps and twitterings of these canids also come with costs. Eavesdroppers can use the information gained through what they overhear to their own advantage, and this can be especially dangerous in the case of lions. They kill wild dogs if they can catch them, and by vocalizing wild dogs run the risk of calling attention to their dens, their kills, or even themselves.
That lions do hone in on African wild dog calls is supported by a recent paper by scientists Hugh Webster, John McNutt, and Karen McComb published in the journal Ethology. Over the course of several years the team ran a series of playback experiments in Botswana's Okavango Delta in which African wild dog calls ("twitters") were played in the vicinity of lions and spotted hyenas (as well as bird calls similar to the wild dog vocalizations as a control and spotted hyena whoops to see if there was a difference in reactions). In all the researchers observed the reactions of 51 lions from a minimum of six prides and 11 spotted hyenas from three clans, with one month between each experiment.