Food predictability and social status drive individual resource specializations in a territorial vulture

Manuel de la Riva,Laura Gangoso,Niels J. Dingemanse,José A. Donázar,Thijs van Overveld,Marina García-Alfonso,David Serrano,Willem Bouten

doi:10.1038/s41598-018-33564-y

Abstract

Despite increasing work detailing the presence of foraging specializations across a range of taxa, limited attention so far has been given to the role of spatiotemporal variation in food predictability in shaping individual resource selection. Here, we studied the exploitation of human-provided carrion resources differing in predictability by Canarian Egyptian vultures (Neophron percnopterus majorensis). We focussed specifically on the role of individual characteristics and spatial constraints in shaping patterns of resource use. Using high-resolution GPS data obtained from 45 vultures tracked for 1 year, we show that individual vultures were repeatable in both their monthly use of predictable and semi-predicable resources (feeding station vs. farms) and monthly levels of mobility (home range size and flight activity). However, individual foraging activities were simultaneously characterized by a high degree of (temporal) plasticity in the use of the feeding station in specific months. Individual rank within dominance hierarchy revealed sex-dependent effects of social status on resource preference in breeding adults, illustrating the potential complex social mechanisms underpinning status-dependent resource use patterns. Our results show that predictable food at feeding stations may lead to broad-scale patterns of resource partitioning and affect both the foraging and social dynamics within local vulture populations.

Highlights

Foraging tactics are often highly plastic, allowing individuals to adaptively respond to spatial and temporal fluctuations in resource availability and environmental changes
We assessed whether individual vultures were repeatable in their preferences for food resources differing in predictability and levels of mobility
We found strong evidence for level-specific associations between individual resource use and mobility, providing novel insights into the use of human-provided carrion by social avian scavengers

Summary

Introduction

Foraging tactics are often highly plastic, allowing individuals to adaptively respond to spatial and temporal fluctuations in resource availability and environmental changes. For territorial birds, central place foraging constraints during breeding may importantly affect the ability of making use of predictable food[12] Such constraints may in turn differ among individuals depending on social rank if, for instance, the location of predictable food influences local territory quality[13,14]. We assessed whether individual vultures were repeatable in their preferences for food resources differing in predictability (farms vs feeding stations) and levels of mobility (home range size and flight activity). We test whether birds preferring predictable food reduce their overall food searching activities (i.e., showing both smaller home-ranges and reduced flight activity) by analysing both within- and among-individual correlations between resource use and mobility. In territorial birds, we examine the role of spatial constraints in shaping individual resource use and patterns of mobility, by analysing how territory location (i.e. distance to predictable feeding sites) may affect resource use and ranging behaviour, again, in relation to individual traits

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