African Cheetahs’ Love Song
When female cheetahs mature in the wild they leave their family group for a life of solitude. Her only real contact with other cheetahs is during breeding and raising young. In stark contrast, sexually mature males remain in groups, or coalitions, of two or three brothers for their entire lives.
At the San Diego Zoo Safari Park our talented team of care staff, curators and researchers study cheetahs in habitats that not only mimic the African savannah but also mirror the social dynamics of these magnificent cats. Our females live alone in areas complete with a climbing tree and sleeping area (in the form of a rugged cat house or “calf-tel”). Coalitions of brothers (unrelated to the females in our collection) share similar areas together.
Although guests can watch at least two of our cheetahs within the Safari Park, the majority of our cheetahs live off-exhibit in an area away from the main Park grounds. It is in this naturalistic setting that we have spent a great deal of time and energy studying these iconic felids.
In 2006, our research team began piecing together an in-depth understanding of cheetah behavior in order to maximize breeding efforts. Our focus for helping to “get cubs on the ground” started with traditional behavioral observations of all our females and males. While the team was busy studying what these cats do on a daily basis via many hours of observations, they also began to realize that the cheetah is a very vocal species: our cats had a lot to say!
This revelation lead to us recording the frequency of their calls, which behaviors they exhibited when certain calls were uttered and ultimately the formulation of a cheetah dictionary. Digital audio recording equipment and sensitive microphones were also used to assemble a bioacoustic library of calls.
Our research revealed that some calls are extremely common and used by both females and males in a variety of contexts from friendly exchanges to more aggressive interactions (an excellent example of this is the “chirp” call, which sounds like the bark of a small dog). Others were rarely heard, such as the male-only stutter-bark, a repetitive staccato call. Contemplation of the evolutionary significance of why some calls were more common than others followed, but without further scientific investigation, we had no idea what that might be.
Since we began recording calls and associated behaviors during breeding attempts, we have expanded our understanding of cheetah conversations by also examining hormone levels. In-depth assessment of calls revealed that the amount of chirping by both males and females doesn’t change even during breeding. By contrast, stutter-barking is only ever heard just prior to breeding opportunities.
Back at our laboratory, examination of stutter-barking frequency and hormone levels revealed that the male-only call was used much more often just before increases in female sex hormones were observed. This was particularly interesting, as female cheetahs don’t cycle like other mammals—their hormone levels flat-line for months on end and they only show interest in males when their hormones are elevated.
It appears that the stutter-bark has evolved to pre-prime the female reproductive system and we are using this to our advantage. Since finding the link between this rare call and increases in female hormone levels we have regularly played back recordings of stutter-barking males over a loudspeaker before breeding introductions to initiate stutter-barking from all of our males.
Our next steps will be to monitor cheetah stress hormone levels, which we believe is the next essential part of the puzzle for ensuring sustainability of this important cat species.
By Matt Anderson, Ph.D., Director of Behavioral Ecology, San Diego Zoo Global.