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Undesirable evolutionary consequences of trophy hunting
David W Coltman1, Paul O'Donoghue, Jon T Jorgenson
1Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK. d.coltman@sheffield.ac.uk
Nature
|December 12, 2003
Summary
Trophy hunting of bighorn sheep (Ovis canadensis) has led to significant declines in body weight and horn size over 30 years. This selective harvest targets heritable traits, impacting the evolution of these wildlife populations.
Area of Science:
- Evolutionary biology
- Wildlife management
- Quantitative genetics
Background:
- Phenotype-based selective harvests, such as trophy hunting, can influence heritable traits in wildlife populations.
- Understanding these evolutionary responses is crucial for sustainable wildlife management.
Purpose of the Study:
- To investigate the evolutionary response of bighorn sheep (Ovis canadensis) to sport hunting.
- To determine if selective harvesting of trophy rams affects body weight and horn size over time.
Main Methods:
- Quantitative genetic analyses were performed on a 30-year study of a wild bighorn sheep population.
- A partly genetically reconstructed pedigree was used to assess heritability and breeding values for weight and horn size.
- Hunter selection data, specifically targeting rams with rapidly growing horns, was analyzed.
Main Results:
- Both body weight and horn size in bighorn sheep were found to be highly heritable traits.
- Trophy-harvested rams possessed significantly higher genetic breeding values for weight and horn size compared to non-harvested rams.
- Selective hunting at an early age for high-value traits reduced the reproductive success of these rams, leading to population-level declines in these traits.
Conclusions:
- Unrestricted trophy hunting of bighorn sheep has driven an evolutionary decline in mean breeding values for body weight and horn size.
- This selective pressure results in the production of smaller-horned, lighter rams, diminishing trophy quality over time.
- The study highlights the significant evolutionary consequences of phenotype-based harvesting on wildlife populations.
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