A while ago I read the publication ‘An analysis or intrinsic and extrinsic factors affecting the activity of a nocturnal species: The wild boar’ by Brivio, F. et al., 2017.
As I was reading the publication, I was wondering about a certain aspect discussed in it.
Wild boar are a species that supposedly has not evolved nocturnal / crepuscular vision (due to lack of tapetum lucidum and their eyesight is generally not excellent leaving them reliant rather on olfactory and auditory cues).
Still, in some areas the wild boar have become nocturnal or crepuscular, possibly, to avoid contact with humans which, however, places them at greater risk of predation by wolves or other large predators.
The study was analyzing wild boar diel activity in an area with wolf predation and with slight and historic human disturbance (hunting outside of the protected area and former hunting history).
In the publication, it was noted that while the diurnal activity was altogether low, the wild boar used daylight hours opportunistically (when possible, for example, when the temperature was not too high because the wild boar do not have evolved naturally efficient thermoregulation mechanisms).
The wild boar were also more active during bright moonlight despite the predation risk by wolves that could use the illumination to enhance their hunting success and for whom the wild boar is the main prey in the region.
The wild boar did not seem to limit their diurnal or crepuscular activity during the hunting season, either (hunting was organized outside of the protected area).
I was wondering whether the slight selectivity for brightness and daylight (e.g., as long as the thermoregulation needs are met etc.) could be related to foraging or topography specifics in the region.
There might be some influenced, e.g., a rugged terrain or a relatively continuous forest cover (instead of open-closed canopy mosaic) which make the habitat either darker (much movement must occur under dense canopies) or difficult to navigate (rocky ground, steeper slopes etc.).
Such challenges might call for a certain need to use light to a greater extent, especially, for a species with supposedly poorer vision and poorer nocturnal vision.
The wild boar might have adapted to navigate the terrain under nocturnal / crepuscular conditions but they might prefer to use more light when possible in order to ease the travelling or foraging, or even to watch out for predators and ensure a non-obstructed escape.
Thus, while activity in brighter moonlight might appear as a high predation risk choice, in fact, the wild boar might even feel more secure with the greater amount of illumination because they can add the visual cues to their vigilance and they do not have to fear stumbling or falling if making escape on a difficult terrain.
Perhaps wild boar that reside in mountainous areas, denser woodlands or areas that are otherwise hard to navigate, make different decisions regarding predation risk and diel activity patterns.
I have read another publication in Scotland (Sandom, C.J. & Hughes, J., 2013; highlands, forest cover) where the species was diurnal.
Human factors were not discussed at great length but there was an absence of predators in the region.
It might be interesting to analyze wild boar activity patterns in varying regions where wild boar have to make choices weighing the following factors:
- predators;
- human disturbance;
- temperature;
- terrain (navigability, mobility);
- cover (dense canopy vs. open landscape);
- foraging strategy (feeding in concentrated areas or being forced to travel from patch to patch in order to find scattered resources) etc.
Poor vision might play a part in these decisions and what might appear as ‘recklessness’ (activity during bright moonlight despite great predation risk) could, in truth, account for increased vigilance potential and ease of escape on difficult terrain,
Notes by Ieva 