Evaluating the efficacy of non-invasive genetic methods and estimating wolf survival during a ten-year period

摘要

Genetic capture–recapture (CR) analysis is a highly promising tool to estimate population parameters and monitor populations through time. However, its level of accuracy has rarely been assessed and comparisons with traditional estimates in controlled settings have rarely been performed. We used CR analysis with long-term fecal genotyping data and applied open-population models to estimate survival rates and assess trend in abundance of wolves in Isle Royale over 10 years, while simultaneously estimating those parameters with traditional aerial-based techniques that are believed to be reasonably accurate. Comparison of the techniques indicated that there is a good correspondence of estimates only when the effort in genetic sampling is high, which guarantees a high recapture probability. Juvenile wolves had higher annual CR survival rates than adult wolves; kill rates most affected wolf survival in this natural ecosystem, and higher annual kill rates were correlated with higher annual adult survival. Adult survival (but not juvenile survival) was an important predictor of population growth rate. Hence, we show that kill rates indirectly affected population growth rate and directly affected adult survival rate. These reliable estimates of survival have unique value because the Isle Royale wolf population is not exposed to any human-caused mortality. Therefore, knowing long-term patterns of annual survival and its relationship to population growth rate for a not hunted wolf population represents a critical baseline for wolf conservation throughout its worldwide distribution.