Distress calls may honestly signal bird quality to predators.
In predator-prey interactions, both interactors may benefit from sharing information about prey vulnerability. We examined the relationship between calls used to discourage close predators (distress calls) and the health condition of the caller to test whether these signals are reliable indicators of prey quality. The structure of calls from captured lesser short-toed larks Calandrella rufescens was related to their body condition and T-cell-mediated immunocompetence. Birds in better nutritional and immunological condition utter harsher calls (i.e. they spread the call energy over a wider range of frequency) than birds in poorer conditions. Hence, the harshness of distress calls seems honestly to signal the health status of prey and thus their ability to escape, on which the predator might base its optimal foraging choice. Previous studies have investigated the honesty of songs that have evolved via sexual selection, but this is the first study, to our knowledge, the demonstrates a relationship between individual quality and a vocalization primarily shaped by natural selection.
Laiolo
Paola
P
Department of Applied Biology, Estación Biológica de Doñana (CSIC), 41013 Sevilla, Spain.
Tella
José L
JL
Carrete
Martina
M
Serrano
David
D
López
Guillermo
G
D000704:Analysis of Variance; D000818:Animals; D001266:Atlantic Islands; D001824:Body Constitution / Q000502:physiology*; D001835:Body Weight; D001837:Body Weights and Measures; D007121:Immunocompetence / Q000502:physiology*; D046109:Passeriformes / Q000276:immunology / Q000502:physiology*; D010835:Phytohemagglutinins; D011235:Predatory Behavior; D025341:Principal Component Analysis; D012641:Selection, Genetic; D013018:Sound Spectrography; D013637:Tape Recording; D014828:Vocalization, Animal / Q000502:physiology*
D010835:Phytohemagglutinins