Mesopredator suppression by an apex predator alleviates the risk of predation perceived by small prey

Abstract

Predators can impact their prey via consumptive effects that occur through direct killing, and via non-consumptive effects that arise when the behaviour and phenotypes of prey shift in response to the risk of predation. Although predators' consumptive effects can have cascading population-level effects on species at lower trophic levels there is less evidence that predators' non-consumptive effects propagate through ecosystems. Here we provide evidence that suppression of abundance and activity of a mesopredator (the feral cat) by an apex predator (the dingo) has positive effects on both abundance and foraging efficiency of a desert rodent. Then by manipulating predators' access to food patches we further the idea that apex predators provide small prey with refuge from predation by showing that rodents increased their habitat breadth and use of 'risky 0 food patches where an apex predator was common but mesopredators rare. Our study suggests that apex predators' suppressive effects on mesopredators extend to alleviate both mesopredators' consumptive and non-consumptive effects on prey.

Functional extinction of a desert rodent: implications for seed fate and vegetation dynamics

“…Our specific aims were 1) to compare hopbush cover, hopbush seedling abundance and hopbush seed abundance in areas where N. fuscus were common and rare; 2) compare the rate of hopbush seed removal in areas where rodents were common and rare; 3) to experimentally compare rates of hopbush seed removal by N. fuscus and ants; and 4) compare the rate of hopbush seed accumulation between areas where rodents were excluded and allowed access. Our experiments comparing the effects of rodent decline on hopbush were possible because N. fuscus is abundant on the side of Australia's dingo‐proof Barrier Fence where dingoes are common, but rare on the other side of the fence due to critically high levels of predation by introduced predators whose populations have irrupted where dingoes are rare (Letnic and Dworjanyn , Gordon et al ).…”

Environmental effects are stronger than human effects on mammalian predator-prey relationships in arid Australian ecosystems

“…Letnic et al, 2009;Letnic and Koch, 2010;Gordon et al, 2015). Although the general patterns observed in such studies conform nicely to (and contributed to the development of) the five hypotheses described above, their inferential ability is limited by previously untested plausible alternative hypotheses that may also explain the easily-observed and obvious cross-fence differences in dingo and hopping-mice abundance.…”

“…Previous studies have investigated these hypotheses by undertaking snap-shot or single survey studies, collecting meagre amounts of empirical data, followed by extensive and complex post hoc modelling to try and elucidate causal mechanisms from correlative data (e.g. Moseby et al, 2006;Letnic et al, 2009;Letnic and Koch, 2010;Gordon et al, 2015;Gordon et al, 2017). In contrast to this approach, we focus on obtaining high-quality empirical data capable of addressing the above hypotheses directly.…”

Reintroduction of Tasmanian devils to mainland Australia can restore top-down control in ecosystems where dingoes have been extirpated

“…However, there is evidence also that dingoes are a strongly interactive apex predator and that suppression of dingo populations by humans can drive shifts in the abundances of other species (Letnic et al, 2012). Sustained efforts to eradicate dingoes have resulted in irruptions of herbivores such as kangaroos and wallabies (macropods) (Robertshaw and Harden, 1986;Colman et al, 2014;Allen, 2015) and have, in some but not all cases, been linked to increases in the abundance of invasive mesopredators, the red fox (Vulpes vulpes) and feral cat (Felis catus) (Gordon et al, 2015;Allen et al, 2015;Colman et al, 2014;Johnson and VanDerWal, 2009;Letnic et al, 2011). In turn, predation by foxes and depletion of understorey vegetation by macropods have been identified as drivers of population decline in small and medium sized mammals in forest ecosystems (Robley et al, 2014;Colman et al, 2014;Foster et al, 2014).…”