Such a severe impact of poaching on population recovery may be widespread among large carnivores.

Our simulations suggest that without poaching during the past decade, the population would have been almost four times as large in 2009. Using the Scandinavian wolf ( Canis lupus) population as an illustrative example, we show that poaching accounted for approximately half of total mortality and more than two-thirds of total poaching remained undetected by conventional methods, a source of mortality we term as ‘cryptic poaching’. We show that rigorous estimates of the effects of poaching relative to other sources of mortality can be obtained with a hierarchical state–space model combined with multiple sources of data. Quantifying poaching mortality should be a required knowledge when developing conservation plans for endangered species but is hampered by methodological challenges. Because poaching is illegal, there is strong incentive for poachers to conceal their activities, and consequently, little data on the effects of poaching on population dynamics are available. Poaching is a widespread and well-appreciated problem for the conservation of many threatened species.

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