Original Paper

Behavioral Ecology and Sociobiology

, Volume 64, Issue 3, pp 443-454

First online:

How unpredictable is the individual scanning process in socially foraging mammals?

  • Olivier PaysAffiliated withLEESA–Groupe Ecologie et Conservation, Université d’Angers Email author 
  • , Simon P. BlombergAffiliated withFaculty of Biological and Chemical Sciences, The University of Queensland
  • , Pierre-Cyril RenaudAffiliated withLEESA–Groupe Ecologie et Conservation, Université d’AngersProgramme ECOFAC/PDZCV
  • , François-René FavreauAffiliated withLEESA–Groupe Ecologie et Conservation, Université d’Angers
  • , Peter J. JarmanAffiliated withEcosystem Management, University of New England

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Abstract

In group-forming prey species, theory assumes that individuals within groups should scan independently of one another, with vigilance sequences being relatively unpredictable, making interscan durations highly variable. We attempted to detect any divergence from randomness in the scanning process in three mammalian prey species phylogenetically and geographically separated and exposed to different levels of predation: waterbuck, Kobus ellipsiprymnus defassa, under a high observed predation risk, eastern grey kangaroo, Macropus giganteus, still experiencing occasional predation and European roe deer, Capreolus capreolus, under a very low natural predation risk. Our results revealed that the focal interscan duration increased when the duration of the preceding interscan increased, whatever the studied species and the predation risk that its individuals experienced, and decreased with the preceding scan duration in two species under, respectively, occasional and low predation risks. The exponential distribution was the tested model that fitted the observed distributions of interscan durations least well. We discuss what can trigger non-randomness in scanning, through a non-homogenous Poisson process, at both intra-individual and inter-individual levels, particularly with regard to previous studies that have demonstrated synchronisation of vigilance in such mammals. Our results suggest the need to reconsider any assumption of randomness in scanning in the basic model predicting form and frequency of scanning behaviour by prey species.

Keywords

Vigilance Anti-predator behaviour Poisson process Exponential distribution Gamma distribution Group living Large mammalian herbivores