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Large Lodges Were Linked to Higher Faecal Glucocorticoid Metabolites in Serengeti Impalas

Male impala standing in Serengeti National Park, Tanzania
Research · Physiology

A 2026 study of free-ranging impalas (Aepyceros melampus) in Serengeti, Tanzania National Park found higher levels of faecal glucocorticoid metabolites near large permanent lodges than near permanent tented camps or seasonal campsites. The modelled difference remained at zero tourist occupancy, showing that the association with large lodges was not explained by visitor numbers alone. The study did not identify which features of the infrastructure were responsible for the higher faecal glucocorticoid-metabolite levels.

Researchers collected 213 fresh faecal samples from individually observed impalas in January and February 2025, during the Serengeti wet season. The samples came from 39 males and 174 females. Faecal glucocorticoid metabolites provide a non-invasive measure of adrenal activity and were analysed using a validated enzyme immunoassay.

The researchers compared impalas around three types of accommodation: permanent lodges, permanent tented camps and seasonal campsites. They also accounted for tourist occupancy, vegetation quality, land-surface temperature, time of day, group size, behaviour and age group. Impalas around the large lodges had significantly higher glucocorticoid-metabolite concentrations than animals near the smaller forms of accommodation.

Large lodges were linked to higher glucocorticoid-metabolite levels even at zero tourist occupancy

The model showed that lodges had a high baseline association with stress-marker levels even at zero tourist occupancy. The authors therefore argue that infrastructure itself — not only the immediate presence of visitors — deserves attention when tourism facilities are planned in protected areas. They call for further research to identify which features of large facilities produce the strongest physiological responses.

Graph of predicted impala stress-marker levels by tourist occupancy and accommodation type
Predicted faecal glucocorticoid-metabolite levels across tourist occupancy and accommodation types. Lodges show the highest baseline at zero occupancy. Figure 2 from Kessy et al. (2026), CC BY 4.0.

Greener vegetation was linked to lower glucocorticoid-metabolite levels

Environmental conditions mattered as well. Glucocorticoid-metabolite levels decreased as NDVI, a satellite-based measure associated with greener and more productive vegetation, increased. The authors interpret this negative relationship as evidence that better forage quality can buffer physiological stress.

Because samples were collected during a single wet-season period, when vegetation was generally productive, the authors recommend longer-term work to examine how these relationships vary through the year. They conclude that tourism planning should consider both visitor numbers and the scale and design of permanent infrastructure when balancing conservation with tourism revenue.

Sources and image credit

  1. Kessy, B. M., Arukwe, A., Mbise, F. P., Hariohay, K. M., Palme, R., Røskaft, E., & Ranke, P. S. (2026). Tourism infrastructure and physiological stress in free-ranging impalas (Aepyceros melampus) of Serengeti National Park. Global Ecology and Conservation, 67, e04130. https://doi.org/10.1016/j.gecco.2026.e04130

Image: Charles J. Sharp — male impala in Serengeti National Park, Tanzania. 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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