Shoot, shovel and shut up: cryptic poaching slows restoration of a large carnivore in Europe

Olof Liberg Guillaume Chapron Petter Wabakken Hans Christian Pedersen N. Thompson Hobbs Hkan Sand 0 Norwegian Institute for Nature Research , Tungasletta 2, 7485 Trondheim , Norway 1 Department of Applied Ecology and Agricultural Sciences, Hedmark University College , Evenstad 2480, Koppang , Norway 2 Grimso Wildlife Research Station, Department of Ecology, Swedish University of Agricultural Sciences , 73091 Riddarhyttan , Sweden 3 Natural Resource Ecology Laboratory and Graduate Degree Program in Ecology, Colorado State University , Fort Collins, CO 80523 , USA Articles on similar topics can be found in the following collections Receive free email alerts when new articles cite this article - sign up in the box at the top right-hand corner of the article or click here - Subject collections Email alerting service Shoot, shovel and shut up: cryptic poaching slows restoration of a large carnivore in Europe Poaching is a widespread and well-appreciated problem for the conservation of many threatened species. 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. Quantifying poaching mortality should be a required knowledge when developing conservation plans for endangered species but is hampered by methodological challenges. 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. 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. Our simulations suggest that without poaching during the past decade, the population would have been almost four times as large in 2009. Such a severe impact of poaching on population recovery may be widespread among large carnivores. We believe that conservation strategies for large carnivores considering only observed data may not be adequate and should be revised by including and quantifying cryptic poaching. 1. INTRODUCTION The illegal killing of animals, hereafter poaching, threatens the viability of many species worldwide [1 5]. Because of their characteristic low densities combined with their slow rates of population growth, top predators are particularly vulnerable to effects of poaching. Almost all large carnivore species have endured a long history of human persecution and have been eradicated from substantial parts of their historical ranges [6]. Although most species of large carnivores are now legally protected, poaching remains a widespread problem for their conservation [6]. Some species are commercially poached for pelts or body parts used in traditional medicine [7], but many are killed because of conflicts with human interests, such as competition for game, depredation of livestock and threats to human safety [8]. It follows that dealing with poaching mortality often emerges as a required condition for the restoration, conservation and sustainable management of large carnivore populations. * Author for correspondence (). The first two authors contributed equally to this work. Electronic supplementary material is available at http://dx.doi.org/10. 1098/rspb.2011.1275 or via http://rspb.royalsocietypublishing.org. A near universal problem with understanding poaching is the absence of rigorous estimates of its effects relative to other sources of mortality [1]. There are several recent attempts to assess the extent, mechanisms and effects of poaching [2,9 12] but remarkably little quantitative data exist, although new methods to measure its extent have recently been developed [13]. One obvious reason for the absence of data is methodological. The most reliable method of quantifying causes of mortality in populations of large wild mammals is to observe their fates over time using radio-tracking [14]. However, when a radio-collared animal is poached, there is a high probability that the poacher promptly destroys the transmitter and hides (or consumes) the carcass, leaving the researcher with a lost radio contact without known cause [15]. Treating cases of lost radio contact in a survival analysis based on radio-tracking is not a trivial problem, especially not for such poaching-prone animals as large carnivores. One can never exclude the possibility that a certain proportion of animals with lost radio contact in fact died from poaching that cannot be verified. We define this unobserved source of mortality as cryptic poaching. Estimating a quantity in ecological processes that is not amenable to direct observation is feasible with hierarchical models because these models allow multiple sources of data to inform estimates of model parameters, including un (...truncated)