Conséquences de la chasse sur l'écologie et la gestion du chamois (Rupicapra rupicapra)
Harvesting is a human-imposed selective pressure. Harvest-induced mortality is not random and mostly targets heritable traits. Human harvest may impose an artificial selection pressure on life history traits, often opposite to natural selection. Therefore in harvested populations life history strategies will evolve under natural and human imposed selective pressures, favoring individuals with the highest fitness. In ungulate populations hunting is the most common cause of adult mortality. By increasing adult mortality, hunting may have both ecological and evolutionary consequences affecting phenotypic traits and life history strategies. Typically, in sexually dimorphic species large horn and weapon size is the major determinant of success in male-male competition. Large males gain high dominance rank and enjoy high reproductive success. By removing males with large horn and body size, hunters may favor small individuals, opposite to sexual selection. In long lived mammals longevity is the main determinant in female reproductive success. Typically females reproduce once a year, therefore in the energy allocation trade-off they invest more in body maintenance and survival rather than reproduction to increase lifetime reproductive success. By increasing adult female mortality hunting may reduce age and size at maturation, selecting for a strategy of early maturation and great current maternal investment. In this thesis I studied chamois ecology and evolution by comparing hunted and unhunted populations. I tested for possible differences in life history traits and examined the ecological and evolutionary consequence of hunting. In the chamois populations under study phenotypic traits and reproductive strategies were not strongly affected by hunting. There was no evidence of a strong evolutionary effect of sport hunting on horn length or body mass of adult males or yearlings. Although hunters seek long horned males, hunter selectivity is unlikely to lead to an artificial selective pressure on horn size. I found few differences in body and horn size between hunted and protected populations, suggesting the absence of strong effects of hunting on male phenotype. Although yearling body mass declined over time in both hunted populations, environmental factors explained much of the trends. The combination of low variability in adult horn length, weak correlation between horn length and body mass for adult males and strong compensatory horn growth apparently reduced the potential for hunters to selectively remove young adult males with vigorous growth. Although early development in body and horn growth affected reproductive potential in young and senescent females chamois, I found no evidence that female early development affected hunter selectivity. Sport harvest did not appear to have strong impacts on the evolution of phenotypic traits and reproductive strategies of female chamois, likely because of a low harvest rate and weak selection for long-horned females as hunters appeared more concerned with avoiding lactating females. The biology of chamois seems to prevent impact of selective hunting, at least in the case of weak hunting pressure.
- Sciences – Thèses