Undesirable consequences of trophy hunting

Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK.
Nature (Impact Factor: 42.35). 01/2004; 426(6967):655-8. DOI: 10.1038/nature02177
Source: PubMed

ABSTRACT Phenotype-based selective harvests, including trophy hunting, can have important implications for sustainable wildlife management if they target heritable traits. Here we show that in an evolutionary response to sport hunting of bighorn trophy rams (Ovis canadensis) body weight and horn size have declined significantly over time. We used quantitative genetic analyses, based on a partly genetically reconstructed pedigree from a 30-year study of a wild population in which trophy hunting targeted rams with rapidly growing horns, to explore the evolutionary response to hunter selection on ram weight and horn size. Both traits were highly heritable, and trophy-harvested rams were of significantly higher genetic 'breeding value' for weight and horn size than rams that were not harvested. Rams of high breeding value were also shot at an early age, and thus did not achieve high reproductive success. Declines in mean breeding values for weight and horn size therefore occurred in response to unrestricted trophy hunting, resulting in the production of smaller-horned, lighter rams, and fewer trophies.

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Available from: Marco Festa-Bianchet, Jan 12, 2015
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    • "Both populations are the subjects of long-term studies where individuals are followed throughout their lives, and each population has an associated pedigree where relationships among individuals are determined through field observations as well as genetic analyses (Poissant et al. 2010). Ram Mountain is a native population in which individual-based monitoring began in 1972 with genetic sampling starting in 1988 (Jorgenson et al. 1993, 1997; Coltman et al. 2003). Between 1972 and 1989, census size increased from ~100 sheep to ~220. "
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    ABSTRACT: Linkage disequilibrium (LD) is the nonrandom association of alleles at two markers. Patterns of LD have biological implications as well as practical ones when designing association studies or conservation programs aimed at identifying the genetic basis of fitness differences within and among populations. However, the temporal dynamics of LD in wild populations has received little empirical attention. In this study, we examined the overall extent of LD, the effect of sample size on the accuracy and precision of LD estimates, and the temporal dynamics of LD in two populations of bighorn sheep (Ovis canadensis) with different demographic histories. Using over 200 microsatellite loci, we assessed two metrics of multi-allelic LD, D′, and χ′2. We found that both populations exhibited high levels of LD, although the extent was much shorter in a native population than one that was founded via translocation, experienced a prolonged bottleneck post founding, followed by recent admixture. In addition, we observed significant variation in LD in relation to the sample size used, with small sample sizes leading to depressed estimates of the extent of LD but inflated estimates of background levels of LD. In contrast, there was not much variation in LD among yearly cross-sections within either population once sample size was accounted for. Lack of pronounced interannual variability suggests that researchers may not have to worry about interannual variation when estimating LD in a population and can instead focus on obtaining the largest sample size possible.
    Ecology and Evolution 08/2015; 5(16):3401-3412. DOI:10.1002/ece3.1612 · 2.32 Impact Factor
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    • "Anthropogenic activity has the power to dramatically shift the strength and direction of selection on animal phenotypes (Darimont et al. 2009; Barbraud et al. 2013; Brown and Bomberger Brown 2013). Highly trait-selective harvest regimes, such as those exemplified by trophy hunting and commercial fisheries, may have the strongest influence on phenotypic change in exploited populations, acting through both plastic mechanisms driven by altered population densities and demographics and evolutionary change driven by selection for novel, and potentially maladaptive, phenotypes (Coltman et al. 2003; Walsh et al. 2006; Sutter et al. 2012). In particular, fisheries-induced shifts in life history traits represent an important issue facing many exploited fish stocks (Handford et al. 1977; Law 2000). "
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    ABSTRACT: Size-selective harvest of fish stocks can lead to maturation at smaller sizes and younger ages, which may depress stock productivity and recovery. Such changes in maturation may be very slow to reverse, even following complete fisheries closures. We evaluated temporal trends in maturation of five Great Lakes stocks of yellow perch (Perca flavescens Mitchill) using indices that attempt to disentangle plastic and evolutionary changes in maturation: age at 50% maturity and probabilistic maturation reaction norms (PMRNs). Four populations were fished commercially throughout the time series, while the Lake Michigan fishery was closed following a stock collapse. We documented rapid increases in PMRNs of the Lake Michigan stock coincident with the commercial fishery closure. Saginaw Bay and Lake Huron PMRNs also increased following reduced harvest, while Lake Erie populations were continuously fished and showed little change. The rapid response of maturation may have been enhanced by the short generation time of yellow perch and potential gene flow between northern and southern Lake Michigan, in addition to potential reverse adaptation following the fishing moratorium. These results suggest that some fish stocks may retain the ability to recover from fisheries-induced life history shifts following fishing moratoria.This article is protected by copyright. All rights reserved.
    Evolutionary Applications 06/2015; 8(7). DOI:10.1111/eva.12285 · 4.57 Impact Factor
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    • "Crosmary et al. (2015) show that for these 10 species under these circumstances, this level of hunting does not reduce the population of the target species. They did not test for any negative effects on population genetics, such as selective removal of individuals with particular genetic characteristics (Coltman et al., 2003). Nor did they test whether trophy hunting yields any positive conservation effects through social or economic mechanisms. "
    Animal Conservation 04/2015; 18(2). DOI:10.1111/acv.12204 · 2.52 Impact Factor
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