2/13/2024 0 Comments Predator vs prey and humans( c) As wildlife diel activity changes, so does predator access to individual prey. ( b) The diel activity patterns of both predators and prey are expected to shift in response to human presence, generally increasing nocturnal activity to avoid humans during the day. Dotted lines within each circle depict the species’ temporal activity distribution. ( a) Circles represent the temporal niche occupied by each species (three prey and one predator), and shaded regions indicate temporal overlap between the predator and a prey species (i.e. Such perturbations to predator-prey dynamics can have cascading impacts that alter population regulation, habitat structure, and various ecosystem processes, such as carbon storage, herbivory, and seed dispersal ( Pringle et al., 2007 Terborgh et al., 2008 Asner et al., 2009 Schmitz et al., 2018 Atkins et al., 2019). As predator and prey species alter their diel activity to adaptively respond to human presence, predator-prey temporal overlap and resulting encounter rates are likely to be changed ( Patten et al., 2019), thus altering predator access to a suite of prey resources ( Figure 1). Human activities concentrated in the day and predator activity at night reduce the availability of temporal refugia for prey from risky encounters, and can constrain species’ abilities to optimize activity along the temporal niche axis ( Kohl et al., 2019 Vinne et al., 2019). Specifically, human presence engenders shifts in diel activity patterns across guilds, altering their temporal niche to incorporate avoidance of human encounters ( Gaynor et al., 2018 Frey et al., 2020). The fear of humans can suppress spatiotemporal activity in both carnivores and herbivores with cascading impacts to lower trophic levels ( Dorresteijn et al., 2015 Gaynor et al., 2018 Suraci et al., 2019a). How human-induced responses of many species cascade to alter the dynamics of predation and other ecological interactions at the community level remains understudied ( Guiden et al., 2019). However, pervasive human pressures disrupt individual behaviors that facilitate coexistence of predator and prey populations alike ( Wolf and Ripple, 2016 Shamoon et al., 2018 Xiao et al., 2018 Sévêque et al., 2020). As a result, large carnivores are predominantly nocturnal while ungulates often exhibit more diurnal behavior, although neither exclusively so. Prey commonly employ predator avoidance strategies along the temporal niche axis ( Kohl et al., 2019), which is contrasted by predators selecting for temporal activity patterns that maximize hunting success and minimize competitive encounters ( Cozzi et al., 2012 Dröge et al., 2017). Wildlife can adaptively respond to their environment by modifying their diel activity and partitioning time to maximize survival and limit exposure to risks, producing a species’ temporal niche ( Bennie et al., 2014 Vinne et al., 2019). Human presence considerably influenced the composition of available prey, with implications for prey selection, demonstrating how humans perturb ecological processes via behavioral modifications. Although leopard prey access was not affected by humans, lion and spotted hyena access to three prey species significantly increased when prey increased their nocturnal activity to avoid humans. Rather than traditional pairwise predator-prey diel comparisons, we considered spatiotemporally explicit predator access to several prey resources to evaluate community-level trophic responses to human presence. Over two-thirds of species exhibited diel responses to mainly diurnal human presence, with ungulate nocturnal activity increasing by 7.1%. We assessed wildlife diel activity responses to human presence and consequential changes in predator-prey overlap using 11,111 detections of 3 large carnivores and 11 ungulates across 21,430 camera trap-nights in West Africa. Wildlife respond to human presence by adjusting their temporal niche, possibly modifying encounter rates among species and trophic dynamics that structure communities.
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