Sexual-size dimorphism modulates the trade-off between exploiting food and wind resources in a large avian scavenger

Pablo A E Alarcón,Juan M Morales,José A Donázar,Sergio A Lambertucci,Fernando Hiraldo,José A Sánchez-Zapata

doi:10.1038/s41598-017-11855-0

Abstract

Animals are expected to synchronize activity routines with the temporal patterns at which resources appear in nature. Accordingly, species that depend on resources showing temporally mismatched patterns should be expected to schedule routines that balance the chances of exploiting each of them. Large avian scavengers depend on carcasses which are more likely available early in the morning, but they also depend on wind resources (i.e. uplifts) to subside flight which are stronger in afternoon hours. To understand how these birds deal with this potential trade-off, we studied the daily routines of GPS-tagged individuals of the world’s largest terrestrial soaring scavenger, the Andean condor (Vultur gryphus). Andean condors vary largely in weight and show a huge sexual dimorphism that allowed us to evaluate the effect of sex and body size on their daily routines. We found that condors use an intermediate solution strategy between the best times to exploit carcasses and uplifts, with this strategy changing over the year. Bigger males scheduled earlier routines that aligned more closely with uplift availability compared to smaller females, resulting in a partial temporal segregation between sexes. Condors’ routines reflect a sexual-size dependent trade-off that may underpin ecological and sociobiological traits of the studied population.

Highlights

Performance trade-offs are thought to impose strong constraints on the adaptive evolution of animal behavior[1]
Sex and body size explained a large proportion of variability in daily routines (Fig. 3)
Seasonal analysis showed that inbound flights tended to be synchronized with the most profitable uplift conditions in each season (Fig. 4). Andean condors scheduled their daily routines according to an intermediate solution strategy; i.e. they either did not venture out in search of food as early as the first sunlight was available or as late as the best uplift conditions occurred

Summary

Introduction

Performance trade-offs are thought to impose strong constraints on the adaptive evolution of animal behavior[1]. Behavioral routines of animals are shaped by performance trade-offs This is because, in order to make important decisions (e.g. when to feed), individuals need to evaluate costs and benefits in a multidimensional space in whose axes the variables of interest often show mismatched temporal patterns[8]. Large avian scavengers strongly depend on wind resources in the form of uplifts as their body size makes powered flight energetically costly. They are expected to match up activities that require long-distance movements to particular weather conditions[12, 26, 27]. In terrestrial environments the morning hours typically do not present wind speeds and temperatures high enough to create profitable uplift conditions[28] and, there are good reasons to think that these birds face a mismatch between the optimal times to exploit food and wind resources

Methods

Results

Conclusion