Ecological Archives A022-023-A1

Richard Bischof and Jon E. Swenson. 2012. Linking noninvasive genetic sampling and traditional monitoring to aid management of a transborder carnivore population. Ecological Applications 22:361–373.

Appendix A. Age distribution augmentation.

During simulations, we used the assumed age distribution of brown bears in Sweden for parameterization. This age distribution was derived from hunted bears, which is incomplete, because cubs are excluded from legal hunting. To augment the age distribution with cubs, we estimated their number by using the age distribution of breeding-age females (≥ 4 years), their age- and region-specific probability of producing cubs (see main document), and an estimate of litter size. The latter we obtained through a linear regression analysis, which indicated that litter size was greater for females ≥ 7 than females < 7 years old (β = 0.632, SE = 0.112, P < 0.001) and, as a trend, lower in the southern study area than in the north (β = -0.17, SE = 0.096, P = 0.073). With this information, we could calculate the number of female cubs-of-the-year (assuming a 1:1 sex ratio at birth) as:

where Na,r is the number of individuals of a given age and in a given region, pa,r is the age and region-specific probability of producing cubs, and la,r is the age and region specific litter size.

FIG. A1. Age distribution of female bears killed by hunters in Sweden between 1998 and 2008 (dark bars). The age distribution was augmented with cubs (light gray bar, see text above for information about the augmentation procedure), because cubs accompany their mother during the hunting season and are consequently protected from legal hunting.


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