An analysis of intrinsic and extrinsic factors affecting the activity of a nocturnal species: The wild boar

Abstract

Over the last century, the wild boar (Sus scrofa) has become an important wildlife species in both economic and ecological terms. Considered a pest by some and a resource by others, its rapid increase in population and distribution has raised management concerns. Studies on activity rhythms may provide useful insights into its overall ecology and help develop effective management strategies. By examining highly detailed activity data collected by means of accelerometers fitted on GPS-collars, we studied wild boar daily activity rhythms and the effect of environmental conditions on their diurnal and nocturnal activity. We thus provided evidence of the predominantly nocturnal and monophasic activity of wild boars. All year round, we reported low activity levels during the day, which opportunistically increased under the most favourable environmental conditions. Activity was found to be significantly affected by such weather conditions as temperature, precipitation and air relative humidity. Moreover, we found that nocturnal activity slightly increased as moonlight increased. Part of our analysis was focused on the hunting period in order to investigate whether wild boars modify their activity levels in response to hunting disturbance. Our results suggested that wild boar nocturnal habits are not directly influenced by the current hunting disturbance, though we hypothesised that they may have evolved over several decades of hunting harassment. Alternatively, but not exclusively, nocturnal habits may have evolved as a low-cost strategy to achieve an optimum thermal balance (i.e., behavioural thermoregulation)

Variability of daily space use in wild boar Sus scrofa

“…We chose these methods, because they do not rely on parameter choices which may warp comparisons between our samples or hamper comparisons with other studies (Laver and Kelly 2008). For daily ranges, density based methods would lead to an underestimation of areas used during active behaviour because wild boar rest about half of the day (Brivio et al 2017) and locations while resting are aggregated.…”

“…Hence, we presumed 2) larger daily ranges during winter and 3) time dependent effects of the land-use type. At the same time, we expected 4) lower temperatures and 5) higher snow cover to be accompanied by smaller ranges because wild boars are less active (Brivio et al 2017) and move less at low temperatures and with higher snow cover (Thurfjell et al 2014). 6) For lower elevations we presumed smaller ranges, because a longer vegetation period at lower elevation may offer better food supply.…”

“…In our study we analysed daily used areas. The activity pattern of wild boar with mostly nocturnal activity and resting during daylight (Brivio et al 2017) suggests that the cycle of 24 h is a biologically important period of wild boar behaviour. One day is also a relevant period in terms of wild boar management.…”

“…Furthermore, we hypothesised 7) a negative correlation of precipitation and daily range size as precipitation promotes greater likelihood of mud wallows at shorter distances and sodden soil facilitates rooting. It has been shown that wild boars are more active during brighter nights (Brivio et al 2017); therefore, we assumed 8) that increased moonlight is accompanied by larger daily ranges. We also expected 9) a social class effect, with smaller ranges of females during the reproduction period (Janeau and Spitz 1984) and 10) significant differences between daily ranges of individuals.…”

Wild boar under fire: the effect of spatial behaviour, habitat use and social class on hunting mortality

“…If compared to other European ungulates, this species is characterized by uncommon life history traits and behavioral responses to environmental stress and hunting pressure, which may result in the modification of reproduction phenology and social class contribution to reproduction (Servanty et al, 2009(Servanty et al, , 2011Gamelon et al, 2011;Frauendorf et al, 2016), and the alteration of habitat selection (Theuerkauf & Rouys, 2008;Sa€ ıd et al, 2012), spatial behavior (Calenge et al, 2002;Sodeikat & Pohlmeyer, 2002;Keuling, Stier & Roth, 2008a;Scillitani, Monaco & Toso, 2010) and activity budget (Brivio et al, 2017). Several studies have dealt with the spatial behavior of this species in relation to hunting, though their results are controversial in that they vary according to refuge position and intensity and type of hunting (see, for instance, Maillard & Fournier, 1995;Calenge et al, 2002;Keuling et al, 2008a;Scillitani et al, 2010;Morelle et al, 2015).…”