Present address: US Geological Survey, Montana Cooperative Wildlife Research Unit, University of Montana, Natural Sciences Building Room 205, Missoula, MT 59812, USA.
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Linking resources with demography to understand resource limitation for bears
Article first published online: 9 MAY 2007
DOI: 10.1111/j.1365-2664.2007.01317.x
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How to Cite
REYNOLDS-HOGLAND, M. J., PACIFICI, L. B. and MITCHELL, M. S. (2007), Linking resources with demography to understand resource limitation for bears. Journal of Applied Ecology, 44: 1166–1175. doi: 10.1111/j.1365-2664.2007.01317.x
Publication History
- Issue published online: 9 MAY 2007
- Article first published online: 9 MAY 2007
- Received 7 December 2005; final copy received 25 February 2007 Editor: Jenny Gill
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Keywords:
- clearcuts;
- habitat quality;
- lambda;
- recruitment;
- resource limitation;
- survival;
- Ursus americanus
Summary
- 1Identifying the resources that limit growth of animal populations is essential for effective conservation; however, resource limitation is difficult to quantify. Recent advances in geographical information systems (GIS) and resource modelling can be combined with demographic modelling to yield insights into resource limitation.
- 2Using long-term data on a population of black bears Ursus americanus, we evaluated competing hypotheses about whether availability of hard mast (acorns and nuts) or soft mast (fleshy fruits) limited bears in the southern Appalachians, USA, during 1981–2002. The effects of clearcutting on habitat quality were also evaluated. Annual survival, recruitment and population growth rate were estimated using capture–recapture data from 101 females. The availability of hard mast, soft mast and clearcuts was estimated with a GIS, as each changed through time as a result of harvest and succession, and then availabilities were incorporated as covariates for each demographic parameter.
- 3The model with the additive availability of hard mast and soft mast across the landscape predicted survival and population growth rate. Availability of young clearcuts predicted recruitment, but not population growth or survival.
- 4Availability of hard mast stands across the landscape and availability of soft mast across the landscape were more important than hard mast production and availability of soft mast in young clearcuts, respectively.
- 5Synthesis and applications. Our results indicate that older stands, which support high levels of hard mast and moderate levels of soft mast, should be maintained to sustain population growth of bears in the southern Appalachians. Simultaneously, the acreage of intermediate aged stands (10–25 years), which support very low levels of both hard mast and soft mast, should be minimized. The approach used in this study has broad application for wildlife management and conservation. State and federal wildlife agencies often possess long-term data on both resource availability and capture–recapture for wild populations. Combined, these two data types can be used to estimate survival, recruitment, population growth, elasticities of vital rates and the effects of resource availability on demographic parameters. Hence data that are traditionally used to understand population trends can be used to evaluate how and why demography changes over time.