Optimal Foraging, Predation Risk and Territory Defence

Krebs, John R.

doi:10.5253/arde.v68.p83

Cited by 83 publications

(65 citation statements)

References 18 publications

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“…Optimality models predict that when compromising between predation risk and starvation risk, hungry animals should take greater risks in terms of predator avoidance than animals near satiation (Krebs 1980;Sih 1992). In accordance with this prediction, our experiment suggested that the nutritional state of bugs affected their resurfacing times.…”

Section: Discussionsupporting

confidence: 80%

Balancing predation risk, social interference, and foraging opportunities in backswimmers, Notonecta maculata

Martı́n

López

2004

Acta ethologica

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Loss of foraging opportunities and intraspecific competition for prey may be important costs of using refuges, because a hiding animal is unable to use or defend its foraging area from conspecific intrusions. Thus, animals should balance antipredator demands with other requirements in deciding when to come out from a refuge after a predator's unsuccessful attack. Observations on foraging and social interactions of backswimmers Notonecta maculata suggest that foraging may be costly in terms of intraspecific agonistic interactions. When prey density is low, increasing the probability of finding a prey may require active exploration of a larger area, but this also increases the probability of encountering a competitor. After simulated exposure to predators, unfed bugs resumed feeding positions after a significantly shorter hiding period than recently fed bugs. We hypothesized that hiding time may also be reduced by recent interactions with conspecific competitors, due to an increased perceived need to defend feeding opportunities. Thus, when a predator attack occurred immediately after an agonistic conspecific interaction, backswimmers resumed feeding positions more quickly, and closer to the original position from which they were disturbed, suggesting shortterm defense of particular positions. We conclude that when foraging, backswimmers balance the benefits of finding prey with the costs of predation risk and social interference in deciding their foraging strategy.

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Section: Discussionsupporting

confidence: 80%

Balancing predation risk, social interference, and foraging opportunities in backswimmers, Notonecta maculata

Martı́n

López

2004

Acta ethologica

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“…Fig. 6 Scatter plots of the proximity to forest and nutrient variables against the amount of haystack remaining at the start (left column) and end (right column) of winter Foraging resource selection is driven by optimality theory (Charnov 1976;Pyke et al 1977;Krebs 1980;Belovsky 1984), however for the bison this meant travelling further to access higher quality hay (reflecting the nutritional state-dependency in this test of the marginal value theorem). This also drove the amount of haystack consumed.…”

Section: Discussionmentioning

confidence: 99%

Risk perception by endangered European bison Bison bonasus is context (condition) dependent

2015

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Context Patch use can illustrate the contributions that forage quality and foraging risk make in shaping foraging decisions made under the risk of being killed. Objectives We aimed to determine whether forage selection by European bison Bison bonasus was state-dependent in being shaped by risk (wolf predation or human poaching/culling avoidance) or nutrient quality at two time periods-early winter (when resources are abundant) and at the end of winter (when resources are scarce)-in Białowie_ za Primeval Forest (Poland). Methods We used a giving-up density framework using the proportional consumption of hay provided by humans to measure the perceptions of risk in European bison. Results European bison resource selection was primarily driven by minimising the distance they travel over open ground in early winter (i.e. avoiding humans), however by the end of winter, when resources are scarce, bison selected haystacks for their nutrient quality (low fibre, high Mg and energy). Conclusions This study illustrates how resource selection varies according to the condition of animals (i.e. state-dependency affects the marginal value theorem). It also indicates conservation managers using hay quality may actively manage human-bison conflicts in trouble spots and that bison are currently free from top-down limitation in Białowie _ za as they do not perceive wolves as threatening enough to alter their foraging behaviour.

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“…Individuals may alter their use of space, increase vigilance, and change foraging patterns according to perceived risk of predation (Krebs 1980;Lima and Dill 1990). Nutritionally stressed individuals are expected to take increased risks to access food sources and may thus be disproportionately exposed to predation [referred to as predation-sensitive foraging (PSF) hypothesis] (Sinclair and Arcese 1995).…”

Section: Introductionmentioning

confidence: 99%

Implications of body condition on the unsustainable predation rates of endangered mountain caribou

et al. 2011

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Both top-down and bottom-up processes influence herbivore populations, and identifying dominant limiting factors is essential for applying effective conservation actions. Mountain caribou are an endangered ecotype of woodland caribou (Rangifer tarandus caribou) that have been declining, and unsustainable predation has been identified as the proximate cause. To investigate the role of poor nutrition, we examined the influence of sex, season, age class, and available suitable habitat (i.e., old-growth forest>140 years) per caribou on bone marrow fat content of caribou that died (n = 79). Sex was the only strong predictor of marrow fat. Males that died during and post rut had lower marrow fat than females or males at other times of year. Old-growth abundance per caribou, season, and age class did not predict marrow fat. Caribou killed by predators did not have less marrow fat than those that died in accidents, suggesting that nutritionally stressed caribou were not foraging in less secure habitats or that predators selected nutritionally stressed individuals. Marrow fat in endangered and declining populations of mountain caribou was similar to caribou in other, more viable populations. Our results support previous research suggesting that observed population declines of mountain caribou are due to excessive predation that is not linked to body condition.

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Optimal Foraging, Predation Risk and Territory Defence

Cited by 83 publications

References 18 publications

Balancing predation risk, social interference, and foraging opportunities in backswimmers, Notonecta maculata

Balancing predation risk, social interference, and foraging opportunities in backswimmers, Notonecta maculata

Risk perception by endangered European bison Bison bonasus is context (condition) dependent

Implications of body condition on the unsustainable predation rates of endangered mountain caribou

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