Vocal Communication in Large Carnivores
From the annual report submitted to the Government of Botswana by The Botswana Predator Conservation Program (Dr. J. W. “Tico” McNutt, Director and Project lead, PhD candidate: Hugh Webster)
Completing work from the 2005 and 2006 field seasons, I completed the sound playback experiments between lions (Panthera leo), spotted hyenas (Crocuta crocuta) and African wild dogs (Lycaon pictus). These playback experiments were designed to investigate in greater depth the relationship between these sympatric large carnivores in northern Botswana through measuring behavioural responses to interspecific vocalizations. I also completed the collection of the wild dog vocal lexicon and made an initial investigation (using playbacks) into the potential for wild dogs’ ultrasonic frequency calls to facilitate individual recognition.
This year was a productive final field season. I have been able to increase the sample sizes for various playback experiments, increasing the strength of significance of the previously noted reactions. Wild dogs flee from lion roars but not spotted hyena whoops; lions approach wild dog vocalizations, but ignore control playbacks of birdcalls; and spotted hyenas either approach or ignore wild dog vocalizations. In addition, I have been able to look more closely at trends suggested by early analyses, such as the affect on response time related to differences in habitat. In comparatively dense vegetation, for example, wild dog visibility is impaired and risk of ambush is predicted to increase. Accordingly, wild dogs were observed to flee more quickly from lion roars in relatively closed habitat, lending reliability to the assumption that behavioural responses reflect perceptions of risk.
I also finished with playback experiments designed to compare the reactions of spotted hyenas versus wild dogs to lion roars. Preliminary results are interesting and suggest that, although spotted hyenas are also inclined to move away from lion roars, they move significantly shorter distances than wild dogs.
During the wild dog denning season (late May to mid September), I recorded both adult and pup vocalizations, providing more examples of types of calls adding to those catalogued to date. This set of recorded calls will allow discriminant function analysis to be used in defining the parameters of the wild dog calls, and will move the wild dog vocal lexicon from previous largely subjective definitions to a statistically based set of definitions. Furthermore, the extent to which wild dogs utilize ultrasonic frequencies in their calls was recorded for the first time.
My initial hypothesis was that wild dogs produce ultrasonic frequency calls to allow communication with the same species, while avoiding the potential costs (kleptoparasitism and predation) incurred by attracting eavesdroppers (lions and spotted hyenas). However, it became clear after several recordings that on the vast majority of occasions, wild dogs produce normally audible and often relatively loud calls concurrently with the ultrasonic frequencies. Therefore I designed a set of playback experiments that would test the wild dogs’ ability to discriminate between familiar (own pack dominant female begging) and unfamiliar (unrelated pack dominant female begging) calls (as an alternative explanation for the function of these ultrasonic calls) with and without the high frequency element included (Fig. 8).
The results suggest that wild dogs are able to discriminate between calls regardless of whether the high frequency element is included (response to unfamiliar calls was stronger for 12 out of 14 pairs), but there is an intriguing trend suggesting that they may be able to do so better with the high frequency element present (response to unfamiliar calls with high frequency element included was stronger for 5 out of 7 sets of calls).
Figure 8. Begging calls of a dominant female wild dog with the high frequency element left in (a) and filtered out (b).