Directness of resource use metrics affects predictions of bear body fat gain

Ayers, Christopher R.; Belant, Jerrold L.; Millspaugh, Joshua J.

doi:10.1007/s00300-012-1247-7

Cited by 13 publications

(13 citation statements)

References 38 publications

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“…Beaver forage availability may need to be addressed at within-territory spatial scales as available forage at the territory scale was not a good predictor of body condition and fitness. Along a gradient of resource metrics that could be measured, forage availability is the least directly linked to fitness and other biological outcomes (Ayers et al, 2012). Availability is difficult to quantify and may not be a good predictor of use and therefore condition and fitness.…”

Section: Discussionmentioning

confidence: 99%

The role of forage availability on diet choice and body condition in American beavers (Castor canadensis)

et al. 2013

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Section: Discussionmentioning

confidence: 99%

The role of forage availability on diet choice and body condition in American beavers (Castor canadensis)

et al. 2013

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“…Previous studies also have demonstrated a direct relationship between salmon consumption, body condition and reproductive output in both species (Hilderbrand et al , Belant et al ). Because fat deposition in ursids is critical for meeting the costs of hibernation and reproduction, percentage body fat can be used to index physiological condition and has been used to infer individual fitness (Hilderbrand et al , Belant et al , Ayers et al ).…”

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confidence: 99%

Testing the niche variation hypothesis with a measure of body condition

Lafferty

Belant

Phillips

2014

Oikos

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Individual variation and fitness are cornerstones of evolution by natural selection. The niche variation hypothesis (NVH) posits that when interspecific competition is relaxed, intraspecific competition should drive niche expansion by selection favoring use of novel resources and that among‐individual variation should confer a selective advantage. Population‐level niche expansion could be achieved by all individuals using all available resources, or by each individual using a unique combination of resources, thereby increasing among‐individual dietary niche variation. Although individual variation can lead to species‐level evolutionary and ecological change, observed variation does not ensure a beneficial outcome. We used carbon and nitrogen stable isotope analysis of claw keratin and a Bayesian stable isotope mixing model to estimate the summer (July–September) assimilated diet of individual female black Ursus americanus and brown U. arctos bears. We quantified variation in dietary niche in both populations, and assessed diet relative to percentage body fat. We hypothesized that if the NVH held, percentage body fat would be similar for individuals of the same species across much of the dietary range of observed proportional salmon contributions to individual bear diets. Although we found greater differences in dietary niches between than within species, we observed greater among‐individual dietary variation in the brown bear population. Moreover, we found that within each species individual female bears achieved similar ranges of percentage body fat at various levels of salmon in the diet. Our results provide support for the NVH. Linking individual dietary niches to measures of physiological condition related to fitness can offer new insights into eco‐evolutionary processes related to food resource use.

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“…K is the number of parameters used to estimate dependent variable including intercept and error term. w is the model weight, representing strength of a model compared with other models in the set (Burnham & Anderson 2002) ing energetics) may be a better approach than using landcover because energy has a more direct effect on an animal's ability to survive and reproduce than many habitat selection metrics (Homyack 2010, Ayers et al 2013. For example, energetic expenditure has been demonstrated to have a significant effect on body condition of many species through lipid storage (Speakman 2001).…”

Section: Discussionmentioning

confidence: 99%

“…They described using metrics closely tied to energetics because of the effects of energy use on body condition, survival, and reproduction in many species. Movement metrics have been successfully used as predictors of body condition, likely because of their close associations with energy use (Mautz & Fair 1980, Ayers et al 2013.…”

Section: Introductionmentioning

confidence: 99%

“…For example, Blouin-Demers & Weatherhead (2001) observed extensive predation of bird nests by black rat snakes Elaphe obsoleta obsoleta in forest edge habitat; however, thermoregulation was found to be the ultimate driver behind selection for the habitat type, and exploitation of nests was secondary or coincidental. Ayers et al (2013) hypothesized a gradient of the direct effect of resource use metrics on biological outcomes (i.e. measures of animal condition or performance) of animals.…”

Section: Introductionmentioning

confidence: 99%

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Relating resource use to body condition and survival of Ozark hellbenders Cryptobranchus alleganiensis bishopi

Ayers

Belant²,

Bodinof³

et al. 2013

Endang. Species. Res.

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Endangered species conservation requires the understanding of factors affecting animal condition and performance. However, commonly investigated resource-use metrics such as habitat selection may not accurately predict biological outcomes because some components of habitats are more important to animals than others. We examined individual level resource− outcome relationships and the relationship between 2 biological outcome metrics -body condition and fate -in Ozark hellbenders Cryptobranchus alleganiensis bishopi, which were recently included on the US Endangered Species List by the United States Fish and Wildlife Service. Our regression models included proportional use of a stream substrate, average distance to cover, distance moved, and water temperature as predictors of daily change in body condition or fate of captive-reared, radio-marked released hellbender populations in 2 sections of the North Fork of the White River in Missouri in 2008−2009. Distance moved between observations helped predict change in body condition, but no variable predicted fate well. We infer that resource use of selected substrate features did not predict biological outcomes in the short term. Our results indicate that energetic metrics such as distance moved can predict biological outcomes better than use of substrate features. Body condition did not correlate with fate and may be a poor indicator of an animal's ability to survive and reproduce. These investigations improve our understanding of influences on biological outcomes in hellbenders, which may improve efficacy of management and conservation of this species through efforts to increase abundance of important resources to improve hellbender condition and performance.

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Directness of resource use metrics affects predictions of bear body fat gain

Cited by 13 publications

References 38 publications

The role of forage availability on diet choice and body condition in American beavers (Castor canadensis)

The role of forage availability on diet choice and body condition in American beavers (Castor canadensis)

Testing the niche variation hypothesis with a measure of body condition

Relating resource use to body condition and survival of Ozark hellbenders Cryptobranchus alleganiensis bishopi

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