Neotropical understory birds and mammals show divergent behaviour responses to human pressure

Human pressures such as hunting and habitat destruction can generate a deep fear in animals and this fear can influence their diel activity patterns and use of space. However, whether these behavioural responses to human pressure are consistent among key functional groups has been poorly studied. For example, while mammal species tend to become more nocturnal in areas with high human pressure, it is unclear if co-occurring birds display similar or opposite patterns. Here we used information from camera trapping (367 camera stations and 16,939 camera/days) along a gradient of human pressure in the Colombian Llanos to assess diel activity changes in understory birds and mammals. We found that diel activity significantly changed with higher human pressure for 45% of the birds (five species) and 36% of the mammals (five species) assessed, with four of five birds becoming more diurnal and all five mammals becoming more nocturnal. The average increase in nocturnality for the mammals was 11.3% while the average increase in diurnality for the birds was 7%. There was high variation in body size and dietary guild within impacted species, and only some were directly persecuted or hunted, suggesting that there are different pathways through which human pressure can affect vertebrates’ activity patterns. The contrasting behavioural responses to humans among vertebrate functional groups has significant repercussions for the fields of community ecology, including intraguild predation and competition, and should be a significant ecosystem-level conservation consideration.