SPOTTED HYAENA WHOOPS: FREQUENT INCIDENCE OF VOCAL INSTABILITIES IN A MAMMALIAN LOUD CALL

ABSTRACT Spotted hyaena Crocuta crocuta whoops are loud calls normally produced in a sequence termed a bout. Whoops are produced by hyaenas irrespective of age or sex to display identity and convey information about the location of the caller. The majority (91%, n=460) of whoops produced by spotted hyaenas, from two geographically separate populations in southern Africa and one population in eastern Africa, showed pronounced nonlinear phenomena, predominantly subharmonics. Whoops produced by males and females had a similarly high probability of sub- harmonics, and 91.5% of the 78 bouts examined contained calls with subharmonics. These results provide evidence that nonlinear vocal phenomena are a common feature of hyaena whoops. The presence of subharmonics in whoops may be enhanced by vocal tract resonances when the fundamental frequency and first formant in the calls are close or coincide. Vocal membranes may also play a role. The high incidence of subharmonics in whoops may enhance individual recognitio...