Diverse behavioural responses of vampire bats to human disturbance revealed by state-space modelling of sparse GPS data

Human activities can alter animal movement, having unexpected consequences for disease transmission. In Latin America, culls of common vampire bats ( Desmodus rotundus ) for rabies control have been indicated to raise viral spatial spread by increasing long-range movement and inter-colony mixing among surviving bats, but behavioural responses to disturbance have not been quantified.

We used Global Positioning System (GPS) tags to track the movements of 93 vampire bats from 5 roosts in the Peruvian Andes over 9 nights after human disturbance (capture, handling and tag attachment). Responses to disturbance were modelled under a Bayesian state-space framework that estimated bat departure time, activity duration, and travel distances while accounting for the sparse GPS data obtainable in a topographically complex landscape where vampire bats occur.

A large fraction of bats (43%, 39/90) abandoned the study area on the night of disturbance, with more abandonment observed in groups expected to have greater dispersal capacity (males and bats with longer forearms). Among the remaining bats, we observed high individual heterogeneity on the night of disturbance, with some bats staying atypically close to the roost and others travelling unusually long distances. With increasing time post-disturbance, bats tended to remain closer to the roost.

Analysis of inferred flight histories showed that bats travelled >5 km on most nights, with high variability both within individuals across nights and between individuals in the same roost.

By inferring movement from irregular and error-prone data, our model extends the utility of animal-borne GPS tracking to landscapes with poor satellite visibility, revealing greater complexity in vampire bat movement than previously recognised. Vampire bat disturbance was associated with three distinct behavioural responses: roost abandonment, increased flight distances and extreme individual heterogeneity on the night of disturbance. In the context of vampire bat management, such perturbations would be expected to exacerbate the spatial spread of rabies and potentially undermine the efficacy of culling activities which are currently practiced by most Latin American governments.