Reduced horn size in two wild trophy‐hunted species of Caprinae

Jesús M Pérez,José E Granados,Ramón C Soriguer,Emmanuel Serrano,Miguel A De Simón,Luis León‐Vizcaino,Gonzalo G Barberá,Paulino Fandos,Mónica González‐Candela,Marco Festa‐Bianchet

doi:10.2981/09-102

Abstract

AbstractFactors affecting horn size in wild Caprinae are of biological and socio‐economic interest because several species are selectively harvested on the basis of this heritable character. We analysed temporal trends in horn size in two mountain ungulates from south‐eastern Spain, the Iberian wild goat Capra pyrenaica and the aoudad Ammotragus lervia. Trophy harvest is the main way in which these two species are exploited, although ‘poor‐quality’ aoudads are also selectively removed. In recent years, both populations have suffered drastic decreases in number due to outbreaks of sarcoptic mange that led to the suspension of hunting for several years. Horn length in harvested male wild goats and aoudads declined during our study period. Over an 18‐year period, the mean age of male goats shot as trophies rose by four years, while the age of trophy‐harvested aoudads decreased by around six months over a 9‐year period. Age and environmental conditions during the first few years of life explained 20% of variance in horn size in Iberian wild goat and 53% in aoudad. Population density early in life explained much of the reduction in goat horn size over time. Nevertheless, the major fall in population densities after the sarcoptic mange outbreaks did not lead to a recovery in horn size in either species. We suggest that the selective removal of large‐horned animals may contribute to a decline in horn size. Other factors that may also explain the observed pattern include changes in interspecific competition, long‐lasting maternal effects and reduced carrying capacity due to overgrazing during high density periods. Unfortunately, our data sets did not allow us to account for the possible effects of these factors.

Highlights

Horn size in mountain ungulates has important and diverse implications for conservation biology and evolution (Coltman et al 2002, Singer & Zeigenfuss 2002)
Horn size signals individual quality and reflects the environmental conditions experienced both during early development (Coteet al. 1998, Toıgo et al 1999) and throughout an animal’s entire life, especially in species where substantial horn growth continues throughout life
If horn growth rates decrease over time, the age of males harvested during our study period should increase, as slow-growing males will require more time to develop into desirable trophies (Garel et al 2007)

Summary

Introduction

Horn size in mountain ungulates has important and diverse implications for conservation biology and evolution (Coltman et al 2002, Singer & Zeigenfuss 2002). Males with greater horn growth obtain high-quality resources, are more resistant to parasites (Luzon et al 2008) and have better sperm quality (SantiagoMoreno et al 2007) Artificial selective pressures such as trophy hunting may lead to a reduction in horn size in wild ungulates (Coltman et al 2003, Garel et al 2007, Bonenfant et al 2009b) by removing individuals with large horns. For both species we expected a decrease in horn size with increasing population density (Jorgenson et al 1998) and with the selective harvesting of large-horned males (Coltman et al 2003). Since food availability depends on temperature and rainfall, we expected a decrease in horn length of both species for individuals that grew during drought years

Methods

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Discussion

Conclusion