Fast food: GPS tracking reveals behavior-specific habitat selection and cattle farm subsidies of three sympatric neotropical vulture species.

Understanding species responses to anthropogenic disturbance is fundamental to ecology and conservation. However, behaviour and inter-individual variation in habitat selection can complicate our understanding of population-level responses to human disturbance, and the initiatives we design to address them. We use a dataset of 601,000 locations from 42 GPS tracked individuals of three sympatric species - king (n = 32), turkey (n = 5) and black vultures (n = 5) - in Costa Rica to explore behaviour-specific habitat selection in a mixed forest-agriculture landscape. We separate the movement data into three key behaviours (flight, feeding and roosting), and then compare their habitat selection preferences using a species-specific generalised mixed modelling framework. We find that the disturbance sensitive king vultures typically prefer mature forest to anthropogenically modified habitats when flying or roosting, however, the difference in relative strength of selection disappears in relation to feeding. These patterns likely reflect king vultures selecting to feed in agricultural landscapes where dead livestock such as cattle are abundant. We find strong evidence for individual heterogeneity in the degree to which they select for livestock pasture as feeding sites, suggesting repeatable individual-variation in foraging tactics. We also found a strong reduction in habitat selection for all behaviours as the distance to contiguous high-quality habitat increases, showing the reliance on tracts of contiguous mature forest for this species. In comparison, the disturbance tolerant species showed idiosyncratic responses to modified habitats, whereby black vultures selected mature forests for flight, but disturbed forest and grassland margins for feeding and roosting, and turkey vultures selected disturbed forest over mature forest and grassland margins for all movement behaviours. These findings represent the first GPS derived habitat selection study of king vultures, the apex obligate scavengers in lowland neotropical habitats and the first multispecies, guild-level, habitat selection analysis of vultures in the lowland neotropics. As expected, we find that king vultures have a stronger affinity to mature forests than their disturbance tolerant counterparts, however cattle farming is likely strongly subsidising some individuals' diets. Despite this, the marked reduction in king vulture habitat use with increasing distances from contiguous mature forests suggests the existence of a disturbance threshold, whereby the carrying capacity of king vulture populations may be reduced in highly anthropogenically modified landscapes.