| 1. |
- McNamara, J M, et al.
(författare)
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Bayes' theorem and its applications in animal behaviour
- 2006
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 112:2, s. 243-251
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Tidskriftsartikel (refereegranskat)abstract
- Bayesian decision theory can be used to model animal behaviour. In this paper we give an overview of the theoretical concepts in such models. We also review the biological contexts in which Bayesian models have been applied, and outline some directions where future studies would be useful. Bayesian decision theory, when applied to animal behaviour, is based on the assumption that the individual has some sort of "prior opinion" of the possible states of the world. This may, for example, be a previously experienced distribution of qualities of food patches, or qualities of potential mates. The animal is then assumed to be able use sampling information to arrive at a "posterior opinion", concerning e.g. the quality of a given food patch, or the average qualities of mates in a year. A correctly formulated Bayesian model predicts how animals may combine previous experience with sampling information to make optimal decisions. We argue that the assumption that animals may have "prior opinions" is reasonable. Their priors may come from one or both of two sources: either from their own individual experience, gained while sampling the environment, or from an adaptation to the environment experienced by previous generations. This means that we should often expect to see "Bayesian-like" decision-making in nature.
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| 2. |
- Molokwu, Mary Ngozi, et al.
(författare)
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Seasonal variation in patch use in a tropical African environment
- 2008
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 117:6, s. 892-898
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Tidskriftsartikel (refereegranskat)abstract
- We used giving-up densities (GUD) to study patch use decisions of small granivorous passerines throughout the year. We measured GUDs continuously in four sites for a period of 9-10 months per year during 2004 and 2005 in a savannah area in Jos, central Nigeria. The study thus covered a period from the middle of the dry season, through the wet season to the beginning of the next dry season in each year. We placed experimental food patches in both open areas and in cover to investigate possible effects of predation risk and thermal hazard on the foraging behavior of the birds. We found a difference in GUDs between the microhabitats, with a consistently lower GUD in cover throughout the year and for the two years. During both years GUDs followed a pattern coinciding with the seasonal change in local seed availability. An initial decline in GUDs late in the dry season was followed by a steady increase during and after the rains. A similar trend in GUDs observed for both years supports the conclusion that GUDs measure the feeding birds' assessment of environmental quality, possibly in combination with other factors changing predictably during the year. We conclude that food abundance may act with other environmental and ecological factors to affect foraging decisions throughout the year.
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| 3. |
- Olsson, Ola
(författare)
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Bayesian foraging with only two patch types
- 2006
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 112:2, s. 285-297
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Tidskriftsartikel (refereegranskat)abstract
- model the optimal Bayesian foraging strategy in environments with only two patch qualities. That is, all patches either belong to one rich type, or to one poor type. This has been a situation created in several foraging experiments. In contrast, previous theories of Bayesian foraging have dealt with prey distributions where patches may belong to one out of a large range of qualities (binomial, Poisson and negative binomial distributions). This study shows that two-patch systems have some unique properties. One qualitative difference is that in many cases it will be possible for a Bayesian forager to gain perfect information about patch quality. As soon as it has found more than the number of prey items that should be available in a poor patch, it "knows" that it is in a rich patch. The model generates at least three testable predictions. 1) The distribution of giving-up densities, GUDs, should be bimodal in rich patches, when rich patches are rare in the environment. This is because the optimal strategy is then devoted to using the poor patches correctly, at the expense of missing a large fraction of the few rich patches available. 2) There should be a negative relation between GUD and search time in poor patches, when rich patches are much more valuable than poor. This is because the forager gets good news about potential patch quality from finding some food. It therefore accepts a lower instantaneous intake rate, making it more resistant against runs of bad luck, decreasing the risk of discarding rich patches. 3) When the energy gains required to remain in the patch are high (such as under high predation risk), the overuse of poor patches and the underuse of rich increases. This is because less information about patch quality is gained if leaving at high intake rates (after short times). The predictions given by this model may provide a much needed and effective conceptual framework for testing (both in the lab and the field) whether animals are using Bayesian assessment.
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| 4. |
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| 5. |
- Olsson, Ola, et al.
(författare)
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Smart, smarter, smartest: foraging information states and coexistence
- 2010
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 119:2, s. 292-303
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Tidskriftsartikel (refereegranskat)abstract
- Animals possess different abilities to gain and use information about the foraging patches they exploit. When ignorant of the qualities of encountered patches, a smart forager Should leave all patches after the same amount of fixed search time. A smarter forager can be Bayesian by using information Oil Cumulative harvest and time spent searching a patch to better inform its patch-departure decision. The smartest forager has immediate and continuous knowledge about patch quality, and can make a perfect decision about when to leave each patch. Here we let each of these three strategies harvest resources from a slowly regenerating environment. Eventually a steady-state distribution of prey among patches arises where the environment-wide resource renewal just balances the environment-wide harvest of the foragers. The fixed time forager creates a distribution with the highest mean and highest variance of patch qualities, Followed by the Bayesian and the prescient in chat order. The less informed strategies promote distributions with both more resources and more exploitable information than the more informed strategies. While it is true chat a better-informed strategy will always out-perform a less well-informed, its Increase in performance may not compensate it for any costs associated with being better informed. We imagine that the fixed time strategy may be least expensive and the prescient strategy most expensive in terms of sensory organs and associated assess and respond capabilities. To consider competition between Such strategies with varying costs, we introduced a single individual of each of the strategies into the environments created by populations of the other strategies. There are threshold costs associated with the better-informed strategy such chat it can or cannot outcompete a less-informed strategy. However, over a relatively narrow range of foraging costs, less-informed and better-informed strategies will coexist. Furthermore, for the prescient and the Bayesian strategies, sonic combinations of foraging costs produce alternate stable states - whichever strategy establishes first remains safe from invasion by the other.
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| 6. |
- Olsson, Ola, et al.
(författare)
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The foraging benefits of information and the penalty of ignorance
- 2006
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 112:2, s. 260-273
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Tidskriftsartikel (refereegranskat)abstract
- Patch use theory and the marginal value theorem predict that a foraging patch should be abandoned when the costs and benefits of foraging in the patch are equal. This has generally been interpreted as all patches being abandoned when their instantaneous intake rate equals the foraging costs. Bayesian foraging – patch departure is based on a prior estimate of patch qualities and sampling information from the current patch – predicts that instantaneous quitting harvest rates sometimes are not constant across patches but increase with search time in the patch. That is, correct Bayesian foraging theory has appeared incompatible with the widely accepted cost–benefit theories of foraging. In this paper we reconcile Bayesian foraging with cost–benefit theories. The general solution is that a patch should be left not when instantaneous quitting harvest rate reaches a constant level, but when potential quitting harvest rate does. That is, the forager should base its decision on the value now and in the future until the patch is left. We define the difference between potential and instantaneous quitting harvest rates as the foraging benefit of information, FBI. For clumped prey the FBI is positive, and by including this additional benefit of patch harvest the forager is able to reduce its penalty of ignorance.
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| 7. |
- Bolin, Arvid, et al.
(författare)
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Scale-dependent foraging tradeoff allows competitive coexistence
- 2018
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Ingår i: Oikos. - : Wiley. - 0030-1299. ; 127:11, s. 1575-1585
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Tidskriftsartikel (refereegranskat)abstract
- In spatially heterogeneous environments, coexistence between competing species can be facilitated by spatially mediated tradeoffs. In this paper we develop a mechanistic model to investigate under which circumstances interspecific differences in the tradeoff between foraging efficiency and travel costs can allow two central place foraging species to coexist in spite of considerable overlap in resource use. One species (Flyer) has a high basal metabolic rate, but a low relative cost of travelling such that it can use patches at a greater distance from its central place while the minimum patch quality it can economically use is high. The other species (Forager), by contrast, has a lower basal metabolic rate, but higher relative cost of travelling, and can therefore be a more efficient forager and able to use foraging patches of low quality, as long as they are not too far from the nest. We demonstrate that the coexistence of these two species critically depends on landscape composition and structure, with the Flyer outcompeting the Forager in structurally simple, coarse-grained, landscapes with abundant high-quality forage and the Forager outcompeting the Flyer in fine-grained highly diverse landscapes. Coexistence between the two species is possible when the landscape is structurally and compositionally complex, fine-grained, and has both high and low quality forage. Our results demonstrate that exploitative competition between two contrasting life histories can produce very different community dynamics depending on landscape composition and structure.
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