Are "visitor effects" overestimated? Behaviour in captive lemurs is mainly driven by co-variation with time and weather

The potential influence of visitors on behaviour of captive animals is well known. However, little research on “visitor effects” has also evaluated time of day and weather, which can affect behaviour directly and often also co-vary with visitor numbers. Here, we examine visitor effects on captive ring-tailed lemurs Lemur catta in a walk-through enclosure, where potential for visitor effects is especially high, while specifically considering weather and time of day (between 10:00 hr when lemurs were released into their outdoor enclosure and 16:00 hr when then returned to overnight accommodation). Time, weather and visitor variables interacted in complex ways, but time and weather exerted the strongest effect on behaviour. Weather strongly affected resting, feeding/foraging, and locomotion. Sunbathing was highest in mornings; locomotion increased in afternoons. Visitor numbers were negatively associated with feeding/foraging and sunbathing; visitor activity was positively associated with locomotion and alertness. Crucially, however, “visitor effects” were small both overall and in relation to underlying effects of time/weather. Univariate models suggested visitors accounted for ~20% of behavioural variation; after time/weather had been included this dropped to ~6-8%. We conclude that underlying visitor : time and visitor : weather correlations can lead to overestimation of visitor effects and offer recommendations for future work.