Undesirable Evolutionary Consequences of Trophy Hunting

Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK.
Nature (Impact Factor: 41.46). 01/2004; 426(6967):655-8. DOI: 10.1038/nature02177
Source: PubMed


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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    • "In 1996, the minimum horn curl of a 'legal' ram was increased from 4/5 to full curl (Fig. S1). This change, implemented at a time when horn size had declined (Coltman et al. 2003), drastically decreased the harvest, with only 4 rams shot in the following 15 years. "
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    ABSTRACT: The potential for selective harvests to induce rapid evolutionary change is an important question for conservation and evolutionary biology, with numerous biological, social and economic implications. We analyze 39 years of phenotypic data on horn size in bighorn sheep (Ovis canadensis) subject to intense trophy hunting for 23 years, after which harvests nearly ceased. Our analyses revealed a significant decline in genetic value for horn length of rams, consistent with an evolutionary response to artificial selection on this trait. The probability that the observed change in male horn length was due solely to drift is 9.9%. Female horn length and male horn base, traits genetically correlated to the trait under selection, showed weak declining trends. There was no temporal trend in genetic value for female horn base circumference, a trait not directly targeted by selective hunting and not genetically correlated with male horn length. The decline in genetic value for male horn length stopped, but was not reversed, when hunting pressure was drastically reduced. Our analysis provides support for the contention that selective hunting led to a reduction in horn length through evolutionary change. It also confirms that after artificial selection stops, recovery through natural selection is slow. This article is protected by copyright. All rights reserved.
    Full-text · Article · Jan 2016 · Evolutionary Applications
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    • "In three of the four cases where two traits were paired with the same rate of population change – beak length and depth in finches (Price and Grant 1984), body mass and horn length in bighorn sheep (Coltman et al. 2003), clutch size and egg mass in lizards (Sinervo et al. 2000) – the rates of phenotypic change were nearly identical. "
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    ABSTRACT: It is increasingly recognized that evolution may occur in ecological time. It is not clear, however, how fast evolution – or phenotypic change more generally – may be in comparison with the associated ecology, or whether systems with fast ecological dynamics generally have relatively fast rates of phenotypic change. We developed a new dataset on standardized rates of change in population size and phenotypic traits for a wide range of species and taxonomic groups. We show that rates of change in phenotypes are generally no more than 2/3, and on average about 1/4, the concurrent rates of change in population size. There was no relationship between rates of population change and rates of phenotypic change across systems. We also found that the variance of both phenotypic and ecological rates increased with the mean across studies following a power law with an exponent of two, while temporal variation in phenotypic rates was lower than in ecological rates. Our results are consistent with the view that ecology and evolution may occur at similar time scales, but clarify that only rarely do populations change as fast in traits as they do in abundance.
    Full-text · Article · Nov 2015 · Ecology and Evolution
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    • "A skewed sex ratio may create long-term problems for the maintenance of genetic diversity and population health of species. Selective hunting could also cause species decline and possible local extirpation (e.g., Tuyttens and MacDonald, 2000; Frank and Woodroffe, 2001; Harris et al., 2002; Coltman et al., 2003; Adams, 2004; Lindsey et al., 2007; Caro et al., 2009). "
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    ABSTRACT: ABSTRACT Dhorpatan Hunting Reserve (DHR) of Nepal, the only hunting reserve in the country, is famous for trophy hunting of bharal or ‘blue sheep’ (Pseudois nayaur) and Himalayan tahr (Hemitragus jemlahicus). Although trophy hunting has been occurring in DHR since 1987, its’ ecological consequence is poorly known. We assessed the ecological consequences of bharal and the Himalayan tahr hunting in DHR and measured the economic contribution of hunting to the government and local communities based on the revenue data. The bharal population increased significantly from 1990 to 2011, but the sex ratio was skewed from male-biased (129Male:100Female) in 1990 to female-biased (82Male:100Female) in 2011. Similarly, the recent survey of Himalayan tahr in DHR showed that there was a total of 285 individuals with a sex ratio of 60 Male: 100 Female. Bharal and Himalayan tahr trophy hunting have generated economic benefits through local employment generation and direct income of US$364,072 during the last five years. Government revenue collected from 2007-08 to 2011-12 totalled US$184,372 from hunting of bharal and Himalayan tahr. Male-focused trophy hunting as practiced in DHR may not be an ecologically sustainable practice due to its effect on the sex ratio that may lead negative consequences to the genetic structure of the population in a long term. Therefore, bharal and tahr population dynamics and sex ratios must be considered while setting harvest quotas in DHR. KEYWORDS: bharal, Himalayan tahr, hunting, conservation, local community, revenue, sex ratio, population,
    Full-text · Article · Nov 2015 · Hystrix
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