Abstract
Landscape changes are happening at an unprecedented pace, and together with high levels of wildlife harvesting humans have a large effect on wildlife populations. A thorough knowledge of their combined influence on individual fitness is important to understand factors affecting population dynamics. The goal of the study was to assess the individual consistency in the use of risky habitat types, and how habitat use was related to fitness components and life-history strategies. Using data from a closely monitored and harvested population of moose Alces alces, we examined how individual variation in offspring size, reproduction and survival was related to the use of open grasslands; a habitat type that offers high-quality forage during summer, but at the cost of being more exposed to hunters in autumn. The use of this habitat type may therefore involve a trade-off between high mortality risk and forage maximization. There was a high repeatability in habitat use, which suggests consistent behaviour within individuals. Offspring number and weight were positively related to the mothers' use of open grasslands, whereas the probability of surviving the subsequent harvest season was negatively related to the use of the same habitat type. As a consequence, we found a nonsignificant relationship between habitat use and lifetime fitness. The study suggests that harvesting, even if intended to be nonselective with regard to phenotypes, may be selective towards animals with specific behaviour and life-history strategies. As a consequence, harvesting can alter the life-history composition of the population and target life-history strategies that would be beneficial for individual fitness and population growth in the absence of hunting.
Highlights
In many populations, harvesting is the main cause of mortality (Allendorf, England, Luikart, Ritchie, & Ryman, 2008) and may act as a powerful selective force that can influence individual life histories (Darimont et al, 2009; Kvalnes et al, 2016), population dynamics (Biro & Post, 2008) and have evolutionary consequences (Engen, Lande, & Sæther, 2014; Mysterud, 2011)
The goal of the study was to assess the individual consistency in the use of risky habitat types, and how habitat use was related to fitness components and lifehistory strategies
Using data from a closely monitored and harvested population of moose Alces alces, we examined how individual variation in offspring size, reproduction and survival was related to the use of open grasslands; a habitat type that offers highquality forage during summer, but at the cost of being more exposed to hunters in autumn
Summary
In many populations, harvesting is the main cause of mortality (Allendorf, England, Luikart, Ritchie, & Ryman, 2008) and may act as a powerful selective force that can influence individual life histories (Darimont et al, 2009; Kvalnes et al, 2016), population dynamics (Biro & Post, 2008) and have evolutionary consequences (Engen, Lande, & Sæther, 2014; Mysterud, 2011). We predicted that frequent use of open grasslands will increase the exposure and reduce the survival of moose during the hunting season (Ciuti et al, 2012) For such fitness consequences of habitat use to occur, an individual's propensity to use open areas must be consistent over time, that is, that there is high repeatability in the level of use of open areas, and that moose inclined to use open habitats are more often killed by hunters. In a recent study in the same population, Kvalnes et al (2016) found a harvest-induced selection towards smaller calf body masses, presumably because females that were larger as calf lost a higher proportion of calves to hunters as adults This indicates that the costs of using open grassland with respect to survival may be higher than the gains with respect to reproductive performance. We predicted a negative relationship between LRS and the use of open grassland
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