Population size, density, and ranging behaviour in a key leopard population in the Western Cape, South Africa
Lana Müller, Willem Daniel Briers-Louw, Barbara Catharine Seele, Christiaan Stefanus Lochner, Rajan Amin
Summarized by Habiba Rabiu, a student of environmental geosciences at Fort Hays State University. Habiba is interested in all aspects of environmental science and conservation & sustainability. She would like to work in educating others about those topics. In her free time, she likes to read, write, and bake.
What data were used? The researchers chose an area in the Cederburg Mountains in Western Cape, South Africa, about 200 km north of Cape Town. In the Western Cape Province, there is about 50,000 km² of potential leopard habitat, but only 30% of it is in conservation areas or mountain catchment zones. The density of the leopard population in the province is among the lowest in the country with only 0.25–2.3 individuals per 100 km2, however their home ranges are relatively large (35–910 km²). The aim was to determine the number of individual leopards in the region and the amount of land they occupy.
Methods: The area of study chosen was 2,823 km² in size and 73 camera traps were set up with a mean distance of 2.78 km between each trap. The cameras were placed along any trails or natural features that the leopards were likely to come across or had shown evidence of having already been there. The cameras operated 24 hours a day and took three images each time they were motion-triggered. From the pictures taken, the leopards were manually identified and digitally differentiated using a software that could distinguish each leopard’s unique spotted pattern.
In addition to the pictures, the researchers also used various software and databases to track the population size and density, site use, and ranging habits of the leopard population, as well as any livestock depredation (or attacks) that occurred. This information contributed to creating a more complete picture of the leopards in the area and their movements. One topic that required special attention was the difference between the leopard movements in winter versus the summer, as the changing seasons had a significant effect on how far the leopards had to move for food and other resources.
Results: From the photographs taken, 63 adult leopards were identified (31 females, 26 males, and 6 of unknown sex.) In the summer, the leopard density was estimated to be 1.62 leopards per 100 km² and more concentrated towards the center of the study area, while in the winter the leopards were more spread out, causing the density to decrease to 1.53 leopards per 100 km². In both seasons, leopard density was higher in females with a female to male ratio of 2.42:1 in the summer and 2.45:1 in the winter.
The leopards were found to be present in nearly the entire area studied, with a total of 2,638 pictures being taken of them at 95% of the camera traps. The habitat type and altitude of the different parts of the study area did not seem to make a difference in the leopards’ movement. As could be inferred from the density measurements, the female leopards tended to keep their activity within a smaller radius around the center of the study area, occupying an average space of 117 km² in the summer and 182 km² in the winter, while the male leopards had an average range of 456 km² in the summer and 856 km² in the winter. The average number of instances of livestock attacks did not appear to differ in number from previous research. The mean number of livestock killed was 7.7 during the summer and 14.9 during the winter.
Why is this study important? This research is a thorough study of the leopard population in the Cederburg Mountain region that employed several methodologies and programs. It supports previous research regarding the average low density (less than 2 leopards per 100 km2) of the leopard population in the Eastern and Western Cape Provinces of South Africa.
The big picture: Since 2016, leopards have been listed as Vulnerable on the International Union for Conservation of Nature’s Red List. This status is due to a variety of factors, many of which are anthropogenic, or human caused, including habitat loss, loss of food sources, poaching for sale or body parts, and killing by farmers attempting to protect their livestock. Tackling issues of conserving threatened animals requires precise data about the animals’ population and activity.
Citation: Müller L, Briers-Louw WD, Seele BC, Stefanus Lochner C, Amin R (2022) Population size, density, and ranging behaviour in a key leopard population in the Western Cape, South Africa. PLOS ONE 17(5): e0254507. https://doi.org/10.1371/journal.pone.0254507