Effect of energy availability, seasonality, and geographic range on brown bear life history

• Published in: Ecography
• Main Authors: Ferguson, Steven H., McLoughlin, Philip D.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2000
• Subjects: Ecology, Evolution, Behavior and Systematics; Pacific; Ursus arctos
• Online Access: http://dx.doi.org/10.1111/j.1600-0587.2000.tb00275.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1600-0587.2000.tb00275.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1600-0587.2000.tb00275.x

Life‐history theory allows predictions of how changes in environmental selection pressures along a species' geographic distribution result in discrete shifts in life‐history traits. We tested for spatial patterns of 24 populations of brown bears Ursus arctos across North America that grouped according to the following environmental and population parameters: evapotranspiration as a correlate of primary productivity of vegetation, coefficient of variation of monthly evapotranspiration values as a measure of seasonality. population density, and adult female weight. Cluster analysis grouped brown bear populations into two regions: Pacific‐coastal populations characterized by high population density and large females that lived in areas of high primary productivity and low seasonality. and inland and barren‐ground populations characterized by relatively low density and small bears that lived in areas of low productivity and high seasonality. For each region, we tested whether life‐history traits (age at maturity and interbirth interval) related to primary productivity or seasonality. High altitude (interior: > 1000 m) and high latitude (barren‐ground; >65°N) populations respond to extremes in seasonality with risk‐spreading adaptations. For example, age at maturity and interbirth interval increased with greater seasonality. In contrast, Pacific‐coastal populations living on the western edge of brown bear geographic range respond to intraspecific competition at high densities by maximizing offspring competitive ability. For example, age at maturity increased with greater primary productivity and high population density. In each region, the female parent decided on the life‐history trade‐offs required to reduce the risks of offspring mortality depending on the environmental pattern.