Hyenas (family Hyaenidae), as the sister group to cats (family Felidae), represent a deeply diverging branch within the cat-like carnivores (Feliformia). With an estimated population size of <10,000 individuals worldwide, the brown hyena (Parahyaena brunnea) represents the rarest of the four extant hyena species and has been listed as Near Threatened by the IUCN. Here, we report a high-coverage genome from a captive bred brown hyena and both mitochondrial and low-coverage nuclear genomes of 14 wild-caught brown hyena individuals from across southern Africa. We find that brown hyena harbor extremely low genetic diversity on both the mitochondrial and nuclear level, most likely resulting from a continuous and ongoing decline in effective population size that started ∼1 Ma and dramatically accelerated towards the end of the Pleistocene. Despite the strikingly low genetic diversity, we find no evidence of inbreeding within the captive bred individual and reveal phylogeographic structure, suggesting the existence of several potential subpopulations within the species.

Apex predators can impact smaller predators via lethal effects that occur through direct killing, and non-lethal effects that arise when fear-induced behavioural and physiological changes reduce the fitness of smaller predators. A general outcome of asymmetrical competition between co-existing predator species is that larger predators tend to suppress the abundances of smaller predators. Here, we investigate interference effects that an apex predator, the dingo (Canis dingo), has on the acquisition of food and water by the smaller red fox (Vulpes vulpes), by exposing free-ranging foxes to the odour of dingoes and conspecifics in an arid environment. Using giving-up densities we show that foxes foraged more apprehensively at predator-odour treatments than unscented controls, but their food intake did not differ between dingo- and fox-odour treatments. Using video analysis of fox behaviour at experimental water stations we show that foxes spent more time engaged in exploration behaviour at stations scented with fox odour and spent more time drinking at water stations scented with dingo odour. Our results provide support for the idea that dingo odour exerts a stronger interference effect on foxes than conspecific odour, but suggest that the odours of both larger dingoes and unfamiliar conspecifics curtailed foxes' acquisition of food resources.

1.Introduced predators pose threats to biodiversity and are implicated in the extinction of many native species. In Australia, considerable effort is spent controlling populations of introduced predators, including the dingo Canis dingo and the red fox Vulpes vulpes, to reduce their effects on native species and livestock. Studies describe different outcomes of controlling dingo and fox populations on native species, making biodiversity management decisions difficult for conservation managers. 2. We conduct a meta-analysis to compare the impacts that control programmes targeted towards dingoes and foxes in Australia have on introduced predators and on other mammal species, including native species and prey species. 3. Our results provide evidence that lethal control of dingoes and foxes has different outcomes for different mammalian species. Dingo removal had a negative effect on the abundance of native mammals weighing less than the critical weight range (CWR) of 30-5500 g, and a positive effect on the abundance of mammals above the CWR. Fox abundance increased in response to dingo control, but confidence intervals were large. Fox removal had strong positive effects on ground-dwelling and arboreal mammals. Lethal control of dingoes did not have a significant effect on cats, but where dingoes were removed there was a tendency for foxes to increase, and where foxes were removed there was a tendency for cats to increase. 4. Our results highlight unintended and perverse outcomes of lethal predator control on Australian mammals. Lethal control of dingoes significantly increases abundances of above CWR mammals and significantly decreases abundances of under CWR mammals. Lethal control of foxes significantly increases the abundances of CWR mammals. These findings show how removing dingoes and foxes alters mammal assemblages and provide comprehensive and objective information for conservation managers.

Removal of apex predators can drive ecological regime shifts owing to compensatory positive and negative population level responses by organisms at lower trophic levels. Despite evidence that apex predators can influence ecosystems though multiple ecological pathways, most studies investigating apex predators’ effects on ecosystems have considered just one pathway in isolation. Here, we provide evidence that lethal control of an apex predator, the dingo Canis dingo, drives shifts in the structure of Australia's tropical‐savannah ecosystems. We compared mammal assemblages and understorey structure at seven paired‐sites. Each site comprised an area where people poisoned dingoes and an area without dingo control. The effects of dingo control on mammals scaled with body size. Where dingoes were poisoned, we found greater activity of herbivorous macropods and feral cats, a mesopredator, but sparser understorey vegetation and lower abundances of native rodents. Our study suggests that ecological cascades arising from apex predators’ suppressive effects on herbivores and mesopredators occur simultaneously. Concordant effects of dingo removal across tropical‐savannah, forest and desert biomes suggest that dingoes once exerted ubiquitous top–down effects across Australia and provides support for calls that top–down forcing should be considered a fundamental process governing ecosystem structure.