Fear of the dark? A mesopredator mitigates large carnivore risk through nocturnality, but humans moderate the interaction

Abstract

While constrained by endogenous rhythms, morphology and ecology, animals may still exhibit flexible activity patterns in response to risk. Temporal avoidance of interspecific aggression can enable access to resources without spatial exclusion. Apex predators, including humans, can affect mesopredator activity patterns. Human context might also modify temporal interactions between predators. We explored activity patterns, nocturnality and the effects of human activity upon a guild of carnivores (grey wolf, Canis lupus; Eurasian lynx, Lynx lynx; red fox, Vulpes vulpes) using travel routes in Plitvice Lakes National Park, Croatia. Humans were diurnal, foxes nocturnal and large carnivores active during the night, immediately after sunrise and before sunset. Carnivore activity patterns overlapped greatly and to a similar extent for all pairings. Activity curves followed expectations based on interspecific killing, with activity peaks coinciding where body size differences were small (wolf and lynx) but not when they were intermediate (foxes to large carnivores). Carnivore activity, particularly fox, overlapped much less with that of diurnal humans. Foxes responded to higher large carnivore activity by being more nocturnal. Low light levels likely provide safer conditions by reducing the visual detectability of mesopredators. The nocturnal effect of large carnivores was however moderated and reduced by human activity. This could perhaps be due to temporal shielding or interference with risk cues. Subtle temporal avoidance and nocturnality may enable mesopredators to cope with interspecific aggression at shared spatial resources. Higher human activity moderated the effects of top-down temporal suppression which could consequently affect the trophic interactions of mesopredators. Significance statement Temporal partitioning can provide an important mechanism for spatial resource access and species coexistence. Our findings show that carnivores partition the use of shared travel routes in time, using the cover of darkness to travel safely where their suppressors (large carnivores) are more active. We however observed fox nocturnality to be flexible, with responses depending on the activity levels but also the composition of apex predators. High human activity modified the top-down temporal suppression of mesopredators by large carnivores. The use of time by predators can have demographic and trophic consequences. Prey accessibility and susceptibility can be temporally variable. As such, the ecosystem services and the ecological roles of predators may be affected by human time use as well as that of intraguild competitors. Temporal interactions should not be overlooked when evaluating human use and conservation priorities in protected areas.

Threading the needle: How humans influence predator–prey spatiotemporal interactions in a multiple‐predator system

“…We show that in a human-dominated landscapes, spatial, temporal and spatiotemporal co-occurrence of bears, coyotes, bobcats, adult male deer and fawns across multiple scales changed in nature, with anthropogenically disturbed habitat often related to increased spatiotemporal overlap among species. Our results add to the growing body of work that suggest that as human presence increases, we reduce available niche space for wildlife, causing what can be seen as 'neutral' or 'positive' spatiotemporal associations among species (Bonnot et al, 2020;Haswell et al, 2020;Parsons et al, 2019;Smith et al, 2018;Wang et al, 2015). This reduction in available niche space and increase in spatiotemporal overlap among predators, and predators and prey, has important implications for interspecific interactions like predation and competition.…”

Spatiotemporal patterns of wolf, mesocarnivores and prey in a Mediterranean area

“…Ripple et al 2014;Martin et al 2020;but see Mech 2012;Barber-Meyer 2015). While it has been suggested that the potential for wolves to influence behaviour and ecology of other organisms should be limited in ecosystems largely modified by human activities (Kuijper et al 2016;Ciucci et al 2020;Haswell et al 2020), the ecological role of wolves should be more evident in complete ecological communities. In our study area, wild ungulates dominated the diet of wolves (Ferretti et al 2019).…”

Camera‐trap data do not indicate scaling of diel activity and cathemerality with body mass in an East African mammal assemblage

“…Several diurnal species (especially those with lower activity levels) may not have such adaptive potential along the time axis, yet face the dual challenge to adjust their activity patterns to human activities and those of competitors and predators (Frey et al., 2020 ; Haswell et al., 2020 ; Shamoon et al., 2018 ). In LMNP, where human disturbance is limited to photographic tourism (which mostly occurs during daytime) and occasional illegal hunting (which mostly occurs during night time), the majority of herbivores was primarily diurnal whereas the majority of faunivores was primarily nocturnal (Table 1 ).…”