Science Snippet:
How to count lions in Africa
By Lizanne Roxburgh and Erin Adams
Knowing how many individuals of a species exist in the wild is important for managing that species. It is also important to know the trend in the number of individuals in a population. Whether the number is increasing, stable or declining will have implications for what management interventions should be used to conserve that population. There are currently many methods that can be used to estimate population size, however, each have their own strengths and weaknesses.
In a recent study*, scientists from the EWT, in collaboration with researchers from other institutions, reviewed all of the methods that are used to survey lion populations across Africa. They looked at 93 different studies from 1991 to 2022. Seven broad survey methods were identified. These included spoor counts, call-ups, genetic surveys, direct observations, camera trap studies, spatially-explicit capture-recapture (SECR) for both direct observations as well as camera traps, and distance-based sampling.
Pic: Eleanor Momberg
The scientists found that the most reliable methods for estimating lion population in Africa were those that included spatially-explicit capture-recapture (SECR) analysis. SECR is a method used to model animal capture-recapture data collected with a network of “detectors.” SECR takes into account both where the individual lions were captured by the detectors (such as camera traps or through direct observations) and where they were not captured. It’s like solving a puzzle where you piece together information about where animals were detected to estimate their overall population density. Sampling techniques such as spoor counts and call-ups were found to be less reliable, as they tended to over-estimate population size.
The scientists strongly recommended that standardized methods be developed that can produce comparable estimates of the number of lions, both within and between sites and years. These methods can then be used to survey lion populations in areas where gaps in our knowledge of lion populations exist.
*Samantha K. Nicholson, David R. Mills, Erin C. Adams, David G. Marneweck, Hans Bauer, Lizanne Roxburgh, Rob Slotow. 2024. Towards effective and harmonized lion survey methodologies: A systematic review of practice across Africa. Global Ecology and Conservation. https://doi.org/10.1016/j.gecco.2024.e02908