Linking habitat selection to fitness-related traits in herbivores: the role of the energy landscape
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Animals may partially overcome environmental constraints on fitness by behaviorally adjusting their exposure to costs and supplies of energy. Few studies, however, have linked spatiotemporal variation in the energy landscape to behaviorally mediated measures of performance that ostensibly influence individual fitness. We hypothesized that strength of selection by North American elk (Cervus elaphus) for areas that reduced costs of thermoregulation and activity, and increased access to high-quality forage, would influence four energetically mediated traits related to fitness: birth mass of young, nutritional condition of adult females at the onset of winter, change in nutritional condition of females between spring and winter, and neonatal survival. We used a biophysical model to map spatiotemporally explicit costs of thermoregulation and activity experienced by elk in a heterogeneous landscape. We then combined model predictions with data on forage characteristics, animal locations, nutritional condition, and mass and survival of young to evaluate behaviorally mediated effects of the energy landscape on fitness-related traits. During spring, when high-quality forage was abundant, female elk that consistently selected low-cost areas before parturition gave birth to larger young than less-selective individuals, and birth mass had a strong, positive influence on probability of survival. As forage quality declined during autumn, however, lactating females that consistently selected the highest quality forage available accrued more fat and entered winter in better condition than less-selective individuals. Results of our study highlight the importance of understanding the dynamic nature of energy landscapes experienced by free-ranging animals.
KeywordsBehavior Biophysics Energetics Thermoregulation Ingesta-free body fat
This research was funded by the US Forest Service, the Shikar Safari Club, and Idaho State University. R. Long was supported by a STAR Fellowship from the Environmental Protection Agency, a GK-12 Fellowship from the National Science Foundation, and the American Society of Mammalogists Fellowship in Mammalogy. We are indebted to R. Kennedy, D. Rea, and M. Vavra of the US Forest Service, B. Johnson of the Oregon Department of Fish and Wildlife, and K. Stewart, C. McKee, D. Walsh, and J. Zweifel of the University of Nevada Reno for providing substantial logistical support during the study. We thank K. Aho for assistance with statistical analyses. W. Porter is an author of Niche Mapper, patented software that may be purchased for independent research or commercial use. The authors declare that they have no conflict of interest.
Author contribution statement
R. A. L. conceived of the study; J. G. K., R. A. L., and R. T. B. designed the study; B. L. D., K. L. M., R. A. L., and S. L. F. conducted fieldwork; P. M., R. A. L., and W. P. P. carried out the biophysical modeling; K. L. M. and R. A. L. analyzed the data; and R. A. L. wrote the manuscript; other authors provided editorial advice.
- Bubenik AB (1982) Physiology. In: Thomas JW, Toweill DE (eds) Elk of North America: ecology and management. Stackpole, Harrisburg, pp 125–179Google Scholar
- Burnham KP, Anderson DR (2002) Model selection and multimodel inference: a practical information theoretic approach, 2nd edn. Springer-Verlag, New York, USAGoogle Scholar
- Cook JG (2002) Nutrition and food. In: Toweill DE, Thomas JW (eds) North American elk: ecology and management. Smithsonian, Washington, DC, pp 259–349Google Scholar
- Cook JG, Johnson BK, Cook RC, Riggs RA, DelCurto T, Bryant LD, Irwin LL (2004) Effects of summer–autumn nutrition and parturition date on reproduction and survival of elk. Wildl Monogr 155(1):1–61Google Scholar
- Leckenby DA (1984) Elk use and availability of cover and forage in the Blue Mountains, northeast Oregon, 1976–1982. Research report number 14. Oregon Department of Fish and Wildlife, Portland, ORGoogle Scholar
- Loudon ASI, Racey PA (eds) (1987) Reproductive energetics in mammals. Symposium of the Zoological Society of London 57. Oxford University Press, OxfordGoogle Scholar
- Neter J, Kutner MH, Nachtsheim CJ, Wasserman W (1996) Applied linear statistical models, 4th edn. McGraw-Hill, BostonGoogle Scholar
- Noyes JH, Sasser RG, Johnson BK, Bryant LD, Alexander B (1997) Accuracy of pregnancy detection by serum protein (PSPB) in elk. Wildl Soc B 25:695–698Google Scholar
- Porter WP, Mitchell JW (2006) Method and system for calculating the spatial-temporal effects of climate and other environmental conditions on animals. US patent 7,155,377, December 2006. http://www.warf.org/technologies.jsp?ipnumber=P01251US
- R Development Core Team (2011) R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna. ISBN 3-900051-07-0. http://www.R-project.org/
- Rowland MM, Bryant LD, Johnson BK, Noyes JH, Wisdom MJ, Thomas JW (1997) The Starkey Project: history, facilities, and data collection methods for ungulate research. General technical report PNW-GTR-296. US Forest Service, Portland, ORGoogle Scholar