Randomness, chaos and confusion in the study of antipredator vigilance

Visual perception and social foraging in birds

“…One reason why oversimplified assumptions of social foraging models persist without challenge is that empirical studies tend to devote little attention to critical tests of the assumptions and, instead, focus on the predictions of the models (but see [4,10]). Because predictions are often qualitative and almost never unique to the specific model being discussed, prediction testing is only meaningful when the assumptions are corroborated.…”

Re–examining safety in numbers: interactions between risk dilution and collective detection depend upon predator targeting behaviour

“…Following other models of vigilance (Pulliam 1973;Pulliam et al 1982;Lima 1987), we assume that scans are initiated at a constant rate per unit of time spent feeding (see also Bedneko¡ & Lima 1998). In each model, the focal animal initiates scans at a rate !…”

“…This scanning behaviour, labelled vigilance, changes reliably with changes in predation risk, and is directed in large part towards detecting potential predators (Elgar 1989;Lima & Dill 1990;Roberts 1996). The study of anti-predator vigilance developed after`safety in numbers' was identi¢ed as one of the potentially large advantages for group living (Bedneko¡ & Lima 1998). Subsequently, the novel theoretical prediction that vigilance should decrease with group size was developed and borne out by many empirical studies.…”

“…Other studies have shown that animals are more vigilant not only in smaller groups, but also more generally in situations where predation risk is likely to be higher (see Elgar 1989;Lima & Dill 1990;Bedneko¡ & Ritter 1994). The study of vigilance has enjoyed a productive interaction between theoretical and empirical work, which continues to this day (Lima 1990;McNamara & Houston 1992;Bedneko¡ & Lima 1998). In the spirit of this interaction, we re-examine existing theory in light of recent empirical ¢ndings.…”

The loss of anti-predator behaviour following isolation on islands

“…Two models of predation hazard assessment (detection and dilution; Krause & Ruxton 2002) predict that animals should forage more and allocate less time to anti-predator vigilance as group size increases, because predation risk declines with the addition of alternative prey, and collective vigilance. Animals living with predators commonly trade off foraging with anti-predator vigilance (Bednekoff & Lima 1998;Beauchamp 2003) so we should expect differences when predators are present or not. And, the distance at which animals flee an approaching human-flight initiation distance-is a standardized metric by which to quantify perceived predation risk (Bonefant & Kramer 1996;Blumstein et al 2003a).…”