Press release, 8/23/18
In the animal kingdom, access to critical resources is the most important priority for any species. Many species – including most big cats – will use as much space as they need to secure access to an adequate supply of the main resources.
Home ranges of female individuals tend to reflect the area the animal needs to secure food and shelter for itself and its offspring, and are therefore generally smaller in areas with higher resource availability. This behavior is often referred to as ‘area minimization’. Based on GPS location data from 17 pumas and 14 snow leopards that were compared in a new study published in the journal Ecosphere1, females of both of these species appear to follow that strategy. “It’s particularly evident in pumas. Their prey tends to cluster in lower elevations during winter, and the cats’ home range sizes shrink accordingly”, says Dr. Örjan Johansson who is the lead author of the paper.
However, while females minimize the area they use, male big cats usually have larger territories than their food requirements predict – and indeed , that was the case both for pumas and snow leopards, “Snow leopard males used up to 1.75 times more space than females throughout the year, while for pumas it was about 1.5 times”, says Örjan Johansson.
Animals are Hard-Wired for Efficiency
Animals are generally hard-coded for efficient energy use and would rarely use more space than they need, so the larger home range by the males must serve a purpose. Most likely, female animals are the most important resource for males, who try to maximize their access to that resource by using as large of an area as possible.
Snow leopards and pumas are territorial, which means they use exclusive home ranges that they defend against neighbors of the same sex. For such territorial species, the common hypothesis for why males have such large home ranges is that they try to ensure exclusive sexual access to females by encompassing a set of female territories, thereby keeping other males away from the females and monopolizing their breeding.
“Snow leopards have a distinct and exclusive mating season from January to March. If male snow leopards indeed try to monopolize females for breeding, they would be expected to maximize their territory size during the mating season and minimize it during the rest of the year, so as not to waste energy”, says Dr. Charu Mishra, the Snow Leopard Trust’s Director of Science and a co-author of the study. “Pumas, on the other hand, don’t have an exclusive mating season, so male pumas would be expected to show less seasonal adjustments in their territory size compared to snow leopards.”
Apart from the seasonal changes in home range size, the researchers were also looking for another telltale sign of males trying to monopolize females during mating season: “If a male wants to ensure exclusive access to a female, he’d make sure that his home range completely encompasses that of the female during mating season to keep other males away”. Charu Mishra explains.
Are Female Cats Choosing Their Mates?
Surprisingly, Mishra, Johansson and their colleagues found neither of the two expected results. In both pumas and snow leopards, there was very little overlap in home ranges between females and the male most strongly associated with them, suggesting that there was no monopolizing of females. Male pumas and snow leopards also seemed to use relatively less space during mating season (or, for pumas, the peak mating period) than during of the rest of the year.
“Our ideas of male choice; that the males monopolize females and that females have no role in mate selection, are not supported by the results at all”, Örjan Johansson says.
In fact, it appears more likely from the data that an opposite mechanism may be at play. “Ecology has so far largely ignored the idea of female choice governing cats’ mating behavior- but that’s exactly what our data suggests is happening”, Johansson says.
“In our study, both pumas and snow leopards had the highest level of female home range overlap with male most strongly associated with them during the mating period, when the male’s home ranges were the smallest. Paradoxically and contrary to our expectation, as males expanded their home range utilization outside of the mating season, female monthly home range overlap with the focal male decreased. This suggests that the females’ home ranges were located such that single males did not encompass them, but rather that the females were generally centered on the border between two or more males, providing them with a choice as to which of the overlapping males they would mate with.”
The results of this study make it clear that access to food and mates are indeed key factors that govern the seasonal space use in snow leopards and pumas – but some of the assumptions around the drivers of the spatial behaviors of these cats have clearly turned out to be wrong.
The research paper can be downloaded for free at http://onlinelibrary.wiley.com/doi/10.1002/ecs2.2371/full
We are thankful to our collaborators: Snow Leopard Conservation Foundation (SLCF), Swedish University of Agricultural Sciences (SLU), Mongolia Ministry of Nature Environment & Green Development, and Mongolia Academy of Science. Special thanks to James Cook University and University of Aberdeen for supporting graduate student projects through our long-term study. Special thanks to Nordens Ark, Kolmarden Zoo, Woodland Park Zoo, and all our Natural Partnership partners for technical guidance and support. The following organizations are currently major sponsors ($10K+) of our long-term snow leopard study: Acacia Conservation Fun, Disney Conservation Fund, David Shepherd Wildlife Foundation, Columbus Zoo and Aquarium, Snow Leopard Trust UK and Edrington group, National Geographic Society, Regina Bauer Frankenberg Foundation, King Carl XVI Gustaf Foundation, Zoo Basel, and Cheyenne Mountain Zoo.
Funding and support for the puma research were provided by National Science Foundation (Grant No. 0423906), U.S. DOE Bonneville Power Administration Fish and Wildlife Program, U.S. Forest Service, Washington Department of Fish and Wildlife, Washington State University, Washington State Department of Transportation, Laura Foreman, Bombardier Inc., The Cougar Fund, Boeing Corporation and Cle Elum/Roslyn School District.