Document Detail

Detecting predators and locating competitors while foraging: an experimental study of a medium-sized herbivore in an African savanna.
MedLine Citation:
PMID:  22200851     Owner:  NLM     Status:  Publisher    
Vigilance allows individuals to escape from predators, but it also reduces time for other activities which determine fitness, in particular resource acquisition. The principles determining how prey trade time between the detection of predators and food acquisition are not fully understood, particularly in herbivores because of many potential confounding factors (such as group size), and the ability of these animals to be vigilant while handling food. We designed a fertilization experiment to manipulate the quality of resources, and compared awareness (distinguishing apprehensive foraging and vigilance) of wild impalas (Aepyceros melampus) foraging on patches of different grass height and quality in a wilderness area with a full community of predators. While handling food, these animals can allocate time to other functions. The impalas were aware of their environment less often when on good food patches and when the grass was short. The animals spent more time in apprehensive foraging when grass was tall, and no other variable affected apprehensive behavior. The probability of exhibiting a vigilance posture decreased with group size. The interaction between grass height and patch enrichment also affected the time spent in vigilance, suggesting that resource quality was the main driver when visibility is good, and the risk of predation the main driver when the risk is high. We discuss various possible mechanisms underlying the perception of predation risk: foraging strategy, opportunities for scrounging, and inter-individual interference. Overall, this experiment shows that improving patch quality modifies the trade-off between vigilance and foraging in favor of feeding, but vigilance remains ultimately driven by the visibility of predators by foragers within their feeding patches.
Olivier Pays; Pierrick Blanchard; Marion Valeix; Simon Chamaillé-Jammes; Patrick Duncan; Stéphanie Périquet; Marion Lombard; Gugulethu Ncube; Tawanda Tarakini; Edwin Makuwe; Hervé Fritz
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-12-27
Journal Detail:
Title:  Oecologia     Volume:  -     ISSN:  1432-1939     ISO Abbreviation:  -     Publication Date:  2011 Dec 
Date Detail:
Created Date:  2011-12-27     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0150372     Medline TA:  Oecologia     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
LEESA, Groupe Ecologie et Conservation, Université d'Angers, Campus Belle Beille, 2 Bd Lavoisier, 49045, Angers, France,
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