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Models Estimated Broader Wet-Season Space Use and Higher Dry-Season Lion Density in Nairobi National Park

A wild African lion in Nairobi National Park with the Nairobi skyline in the background
Research · Ecology

A 2026 study of African lions (Panthera leo) in Nairobi National Park found strong seasonal differences in how the animals used the small protected area on the edge of Kenya’s capital. Lion density inside the park was higher during two dry-season surveys, while the lions’ estimated space use was much broader during the wet-season survey.

The researchers used spatially explicit capture–recapture models based on repeated searches for individually identifiable lions. Lions were recognised from features including their unique whisker-spot patterns. By combining where the same individuals were encountered again with the amount of search effort in each part of the park, the model could estimate both local density and the spatial scale of each lion’s detections. Three surveys were compared: a wet-season survey in 2018 and dry-season surveys in 2021 and 2022. The field teams and logistics differed between surveys, allowing the researchers to test whether an adaptable monitoring approach could still produce comparable ecological estimates.

Lions used a broader area in the wet-season survey

Estimated density of lions older than one year inside the park was 18.5 animals per 100 km² in the 2018 wet season. In the dry seasons it was 26.9 per 100 km² in 2021 and 27.7 per 100 km² in 2022. At the same time, the model’s movement parameter was much larger in the wet season: 3.4 km compared with 1.4 km in both dry-season surveys. This parameter is not the distance a lion physically travelled. It describes how widely detections were typically spread around the modelled centre of an individual’s area use, so a larger value indicates broader space use during the survey.

Higher dry-season density did not mean the population had increased

The authors stress that these differences should not be interpreted as evidence that the lion population increased between surveys. Instead, the pattern matches the known seasonal ecology of Nairobi National Park. During the dry season, large herbivores concentrate inside the park and lions likewise become more concentrated there. When rains arrive, herbivores disperse southwards beyond the park boundary and lions expand their movements to follow them.

The modelled centres of the lions’ space use were also more clustered towards the open southern boundary during the wet season. The authors connect this seasonal shift with existing evidence that human–lion conflict is more likely to peak when lions move into neighbouring community lands and encounter livestock.

The study had one wet-season survey and two dry-season surveys, so the authors note that more seasonal replication is needed to separate seasonal effects conclusively from differences between years. Even so, they conclude that adaptable spatial capture–recapture monitoring can provide useful information about changes in density and space use when surveys are designed and analysed within a consistent framework.

Sources and image credit

  1. Chege, M., Gopalaswamy, A. M., Bitok, E., Broekhuis, F., Bertola, L. D., Kariuki, L., Kuloba, B., Ndambuki, S., Omondi, P., de Snoo, G. R., de Souza, N., Waiguchu, G., de Iongh, H. H., & Elliot, N. B. (2026). Adaptive data collection strategies for spatial capture–recapture monitoring: Linking monitoring approaches to seasonal variation in density and space use. Ecological Solutions and Evidence, 7(2), e70256. https://doi.org/10.1002/2688-8319.70256Primary peer-reviewed open-access study, first published 26 April 2026.

Image: HarshPohariyal — wild lion in Nairobi National Park with the Nairobi skyline in the background. Source: Wikimedia Commons. Representative image for this story; not presented as an animal or scene from the reported study or event. · CC BY-SA 4.0 · Source

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