Scent-post preference of free-ranging Namibian cheetahs

1. What they did

Cheetahs leave scent marks on large, conspicuous landmarks, most often big trees. Namibian farmers call these “playtrees” or “newspaper trees”. Cheetah home ranges in Namibia overlap a lot, and scent marks may let cheetahs share the same area at different times while avoiding unexpected meetings. Some marking trees are used much more often than others, so the authors asked which features of a tree make cheetahs prefer it.

• Measuring the trees. They measured 31 known cheetah scent-marking trees in north central Namibia: tree species, height, canopy area, stem circumference, angle and direction of lean, visibility from the tree, distance to a road or fence line, and the richness of animal species in the area.
• Visit rates. Using camera trap records from 2005 to 2012, they worked out how many times a month cheetahs visited each tree. This was possible for 20 of the trees.
• Analysis. They dropped height and canopy area, which were closely linked to each other and to visibility, and then compared statistical models to find which features best explained how often a tree was visited.

2. What they found

• The camera traps recorded 337 visits by 38 individual cheetahs. Visit rates ranged from 0.08 to 6.50 visits per month per tree.
• Canopy area rose with tree height and with visibility, and taller trees also had better visibility.
• Two models came out almost equally well: stem circumference alone, and stem circumference plus visibility.
• Stem circumference had a clear effect, but in an unexpected direction: trees with thinner stems were visited more often. All the marking trees still had stems at least 1.00 m around, large enough for cheetahs to climb.
• Trees with better visibility tended to be visited more, but this effect was uncertain (its confidence interval included zero).
• The authors report that the angle of lean and the area’s animal species richness did not influence which trees cheetahs preferred.

3. What they concluded

• Cheetahs choose marking trees not on size alone but on how well they can see from the tree and how visually conspicuous the tree is in its surroundings. This matches earlier work showing visibility is key in how cheetahs use habitat, and studies of scent-post choice in other carnivores.
• By marking visible, conspicuous trees, cheetahs may give other cheetahs the best chance of finding their marks, getting the most benefit for the effort of marking.
• These are preliminary findings. Future work with camera traps, scat detection dogs and genetic analysis could show how marking patterns relate to home range size, habitat use and how cheetahs interact with each other.

6. Other technologies, skills or innovations

• Camera traps at known marking trees over eight years, used to count visits by individual cheetahs.
• Model comparison with the small-sample Akaike Information Criterion (AICc) in R.

7. Implications for conservation (from the paper)

• Marking trees are found throughout cheetah ranges and are potentially crucial to how cheetahs organise themselves across Namibian landscapes.
• The study gives new insight into the spatial structure and organisation of Namibian cheetahs, an area the authors describe as largely unexplored.