Foraging behaviour of the Peaceful Dove (Geopelia striata) in relation to predation risk: group size and predator cues in a natural environment

AbstractWe describe foraging behaviour and time budgets of the gregarious bronze mannikin, Lonchura cucullata. In addition to being the first such study of a southern African granivore, this was the first study of a group-forager to differentiate between vigilance for other flock members (conspecifics) and vigilance for predators. We verified a perception of predation risk by placing five feeders at increasing distances from cover. The mean number of birds at a feeder decreased significantly with increasing distance from cover. We manipulated levels of aggression by restricting access to random numbers of feeding holes at various distances. The treatments succeeded in forcing birds to feed further from cover, and by inference, increased levels of aggression. We measured time budgets with focal samples on marked individuals. There was no influence of group size on time budgets. There was a non-significant (p < 0.06) trend for vigilance to increase with increasing distance from cover (predation risk). There was no pattern in the relative vigilance for predators as opposed to vigilance for other flock members (conspecifics), either with group size, distance from cover, or manipulated levels of aggression. Despite our inability to detect patterns of vigilance for other flock members, we emphasize the importance of studies to elucidate such a process.

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The effect of group size on the foraging behaviour of juvenile coho salmon: reduction of predation risk or increased competition?

Animal Behaviour ◽

10.1006/anbe.1999.1174 ◽

1999 ◽

Vol 58 (2) ◽

pp. 443-451 ◽

Cited By ~ 111

Author(s):

Tamara C. Grand ◽

Lawrence M. Dill

Keyword(s):

Predation Risk ◽

Group Size ◽

Foraging Behaviour ◽

Coho Salmon

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Group size elicits specific physiological response in herbivores

Biology Letters ◽

10.1098/rsbl.2012.0197 ◽

2012 ◽

Vol 8 (4) ◽

pp. 537-539 ◽

Cited By ~ 11

Author(s):

Pablo Michelena ◽

Marie-Hélène Pillot ◽

Carole Henrion ◽

Sylvain Toulet ◽

Alain Boissy ◽

...

Keyword(s):

Predation Risk ◽

Group Size ◽

Small Groups ◽

Physiological Response ◽

Cortisol Concentration ◽

Cortisol Response ◽

Predator Cues

With increasing group size, individuals commonly spend less time standing head-up (scanning) and more time feeding. In small groups, a higher predation risk is likely to increase stress, which will be reflected by behavioural and endocrine responses. However, without any predator cues, we ask how the predation risk is actually processed by animals as group size decreases. We hypothesize that group size on its own acts as a stressor. We studied undisturbed groups of sheep under controlled pasture conditions, and measured in situ the cortisol and vigilance responses of identified individuals in groups ranging from 2 to 100 sheep. Both vigilance and average cortisol concentration decreased as group size increased. However, the cortisol response varied markedly among individuals in small groups, resulting in a lack of correlation between cortisol and vigilance responses. Further experiments are required to explore the mechanisms that underlie both the decay and the convergence of individual stress in larger groups, and whether these mechanisms promote adaptive anti-predator responses.

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Vigilance and foraging behaviour of female caribou in relation to predation risk

Rangifer ◽

10.7557/2.17.2.1302 ◽

1997 ◽

Vol 17 (2) ◽

pp. 55 ◽

Cited By ~ 29

Author(s):

Pernille S. Bøving ◽

Eric Post

Keyword(s):

Predation Risk ◽

Group Size ◽

Rangifer Tarandus ◽

Foraging Behaviour ◽

West Greenland ◽

Vigilance Behaviour ◽

Calving Season ◽

Lying Down ◽

Behavioural Adaptations

Behaviour of female caribou (Rangifer tarandus) was investigated during the calving season on ranges in Alaska and West Greenland with the purpose of determining whether investment in vigilance behaviour differed between areas with and without natural predators of caribou. Female caribou in Alaska foraged in larger groups, displayed a higher rate of vigilance during feeding, spent less time feeding and, when lying, more often adopted a vigilant posture (with head up) than did female caribou in West Greenland. Moreover, a predation-vulnerable posture of lying down flat was observed in West Greenland but not in Alaska. Within Alaska, females with calves spent more time searching the environment than did those without calves. Finally, the amount of time individuals spent searching declined more gradually with group size in Alaska than in West Greenland, suggesting that what caribou perceive as a predator-safe threshold differs in the two areas. These results indicate that caribou, like several other species of ungulates, show behavioural adaptations to the risk of prédation which are relaxed when this risk is reduced.

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Design of experimental food patches to measure foraging intensity for octopus: a case study with the giant Pacific octopus Enteroctopus dofleini

Journal of Molluscan Studies ◽

10.1093/mollus/eyaa039 ◽

2020 ◽

Author(s):

Stephanie Chancellor ◽

David Scheel ◽

Joel S Brown

Keyword(s):

Predation Risk ◽

Foraging Behaviour ◽

Habitat Preferences ◽

High Tide ◽

Intertidal Habitat ◽

Camera System ◽

Subtidal Habitat ◽

Enteroctopus Dofleini ◽

Nontarget Species

ABSTRACT In a study of the foraging behaviour of the giant Pacific octopus Enteroctopus dofleini, we designed two types of experimental food patches to measure habitat preferences and perceptions of predation risk. The first patch successfully measured giving-up densities (GUDs), confirmed by octopus prey presence and higher foraging at sites with historically greater octopus presence. However, nontarget foragers also foraged on these experimental food patches. Our second floating patch design successfully excluded nontarget species from subtidal patches, and from intertidal patches at high tide, but allowed for foraging by E. dofleini. The second design successfully measured GUDs and suggested that octopus preferred foraging in a subtidal habitat compared to an intertidal habitat. We ascribe the higher GUD in the intertidal habitat to its higher predation risk relative to the subtidal habitat. The second patch design seems well suited for E. dofleini and, in conjunction with a camera system, could be used to provide behavioural indicators of the octopus's abundance, perceptions of habitat quality and predation risk.

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