Starving or Stuffing? Plasticity in Wild Boar Body Mass Variations During Summer in a Mediterranean Area.

Abstract

Identifying determinants of key phenotypic indicators driving animal population dynamics is fundamental to address measures aimed at mitigating human-wildlife interactions. In Mediterranean areas, summer drought reduces the availability of water and food resources for wild ungulates, potentially affecting body conditions. Since summer is a crucial period for the nursing/weaning of offspring, a seasonal bottleneck for ungulates would be expected to occur, especially in females. However, data on fluctuations of ungulate body mass during summer are scarce. We investigated the effects of summer progression, aridity, population density, and land use on body mass variation of adult/yearling wild boar (Sus scrofa) in a mixed forested-rural Mediterranean protected area, over a 16-year period (2007-2022). Data were gathered from individuals harvested during population control management actions, in summer. In contrast with our predictions, no consistent mass loss was observed throughout the summer. According to expectations, body mass was favored by decreasing aridity in the previous 3 months. In males, the positive effect of rainfall was mitigated by population density. Females experienced mass gain in non-arid years, mass loss in arid years, and no change in "average" years. The importance of edge habitats located at the interface between wooded and cultivated areas was confirmed by a positive relationship between female body mass and ecotone availability. The results indicate that, in a mixed forested-rural area, wild boar could maintain, or even increase, their body mass during summer. Moreover, findings emphasize the crucial role of rainfall in modulating a key driver of population dynamics for this ungulate in Mediterranean areas.