Mike Letnic

UNSW Sydney | UNSW · School of Biological, Earth and Environmental Sciences (BEES)

It is widely assumed that organisms at low trophic levels, particularly microbes and plants, are essential to basic services in ecosystems, such as nutrient cycling. In theory, apex predators’ effects on ecosystems could extend to nutrient cycling and the soil nutrient pool by influencing the intensity and spatial organization of herbivory. Here, w...

Vegetation cover is fundamental in the formation and maintenance of geomorphological features in dune systems. In arid Australia, increased woody shrub cover has been linked to removal of the apex predator (Dingoes, Canis dingo) via subsequent trophic cascades. We ask whether this increase in shrubs can be linked to altered physical characteristics...

The abundance of shrubs has increased throughout Earth's arid lands. This ‘shrub encroachment’ has been linked to livestock grazing, fire‐suppression and elevated atmospheric CO 2 concentrations facilitating shrub recruitment. Apex predators initiate trophic cascades which can influence the abundance of many species across multiple trophic levels w...

Invasive species are frequently blamed for faunal declines, but there is little direct evidence about the pathways, magnitude and size-selectivity of mortality induced by invaders. Top predators are of particular interest in this context, because their removal can generate substantial cascades of secondary effects on community composition. Cane toa...

Top-order predators often have positive effects on biological diversity owing to their key functional roles in regulating trophic cascades and other ecological processes. Their loss has been identified as a major factor contributing to the decline of biodiversity in both aquatic and terrestrial systems. Consequently, restoring and maintaining the e...

Camera traps are widely used in wildlife research and monitoring, so it is imperative to understand their strengths, limitations, and potential for increasing impact. We investigated a decade of use of wildlife cameras (2012–2022) with a case study on Australian terrestrial vertebrates using a multifaceted approach. We (i) synthesised information...

The increased severity and frequency of bushfires accompanying human-induced global warming have dire implications for biodiversity conservation. Here we investigate the response of a cryptic, cool-climate elapid, the mustard-bellied snake Drysdalia rhodogaster , to the extensive Black Summer fires of 2019/2020 in south-eastern Australia. The speci...

With large wildfires becoming more frequent1,2, we must rapidly learn how megafires impact biodiversity to prioritize mitigation and improve policy. A key challenge is to discover how interactions among fire-regime components, drought and land tenure shape wildfire impacts. The globally unprecedented3,4 2019–2020 Australian megafires burnt more tha...

Protected areas form the backbone of global conservation efforts. Vegetation is the primary foundation for achieving conservation goals, and soil seed banks is a cryptic biodiversity reservoir for recruiting species that may not be represented in above‐ground vegetation. Unfortunately, unmanaged grazing by wild herbivores has led to vegetation degr...

Understanding the factors that limit the abundance of threatened species is critical for the development of effective conservation strategies. However, gaining such knowledge from monitoring programs and using it to inform decision‐making for rare species can be difficult due to methodological issues posed by the problems of distinguishing true abs...

Many terrestrial vertebrates require microhabitat shelter structures for survival. Where anthropogenic or environmental disturbances have degraded or depleted shelter, artificial shelters are increasingly used to provide supplementary habitat for various taxa. However, their application to medium‐sized ground‐dwelling mammals (MGMs) remains largely...

The Australian megafires of 2019–2020 were considered catastrophic for flora and fauna, yet little is known about their impacts on reptiles. We investigated the impacts of the 2019–2020 megafires on reptiles in Morton National Park, New South Wales, in eastern Australia. To understand how fire severity affects reptile species richness and occupancy...

Prey naiveté has been implicated in the global decline and reintroduction failure of many threatened species. A number of tools have been developed to combat prey naiveté including in situ predator exposure using live predators. However, determining the effectiveness and persistence of these interventions can be difficult, and requires comparisons...

Drylands are characterized by high spatial variability in resource availability due to sporadic rainfall, topography of the landscape and important effects of animals. Resource availability gradients may trigger patterns in decomposer population abundances and activity, which could affect ecosystem functions such as decomposition. Here, we examined...

Novel interactions between invaders and native species that have evolved in their absence may impose strong selective pressures that drive species to extinction or prompt rapid co-evolution and learning. Here, we report on the effects that invasive cane toads, a toxic prey species, have had on freshwater crocodile populations in 7 waterholes of the...

In the spring and summer of 2019–2020, the ‘Black Summer’ bushfires burned more than 97 000 km ² of predominantly Eucalyptus dominated forest habitat in eastern Australia. The Black Summer bushfires prompted great concern that many species had been imperilled by the fires. Here, we investigate the effects that fire severity had on the habitat and a...

Carnivores fulfil important ecological roles in natural systems yet can also jeopardise the persistence of threatened species. Understanding their diet is, therefore, essential for managing populations of carnivores, as well as those of their prey. This study was designed to better understand the diet of an Australian apex predator, the dingo, and...

Admixture between species is a cause for concern in wildlife management. Canids are particularly vulnerable to interspecific hybridisation, and genetic admixture has shaped their evolutionary history. Microsatellite DNA testing, relying on a small number of genetic markers and geographically restricted reference populations, has identified extensiv...

Irruption of herbivore populations due to the extirpation of predators has led to dramatic changes in ecosystem functioning worldwide. Herbivores compete with other species for their primary source of nutrition, plant biomass. Such competition is typically considered to occur between species in closely related clades and functional groups but could...

Unprecedented anthropogenic changes to biodiversity and biogeography demand a greater understanding of the consequences of altered faunal composition for ecosystem functioning. Selective predation has important, yet poorly understood effects on ecosystem stability, and can be strongly influenced by the relative frequencies of different prey types i...

Expert elicitation can be valuable for informing decision-makers on conservation and wildlife management issues. To date, studies eliciting expert opinions have primarily focused on identifying and building consensus on key issues. Nonetheless , there are drawbacks of a strict focus on consensus, and it is important to understand and emphasize diss...

Harnessing natural selection to improve conservation outcomes is a recent concept in ecology and evolutionary biology and a potentially powerful tool in species conservation. One possible application is the use of natural selection to improve antipredator responses of mammal species that are threatened by predation from novel predators. We investig...

Food webs can be conceptualized as being powered by energy derived from living and dead vegetation, respectively. Most food web research has focused on “green food webs” which begin with the consumption of living vegetation by herbivores. However, “brown food webs” which stem from the consumption of senescent vegetation by detritivores are also an...

Predator naivety negatively affects reintroduction success, and this threat is exacerbated when prey encounters predators with which they have had no evolutionary experience. While methods have been developed to inculcate fear into such predator-naïve individuals, none have been uniformly successful. Exposing ontogenetically- and evolutionary-naïve...

Unprecedented anthropogenic changes to biodiversity and biogeography demand a greater understanding of the consequences of altered faunal composition for ecosystem functioning. Selective predation has important, yet poorly understood effects on ecosystem stability, and can be strongly influenced by the relative frequencies of different prey types i...

Removal of apex predators can have far-reaching effects on the organization and structure of ecosystems. This occurs because apex predators can exert strong suppressive effects on their prey and competitors and perturbation of these interactions can shift the balance of interactions between dyads of species at lower trophic levels and trigger troph...

The mesopredator release hypothesis predicts that abundance of smaller predators should increase in the absence of larger predators due to release from direct killing and competition. However, top predators’ effects on mesopredators are unlikely to operate in isolation but interact with other factors such as primary productivity of the landscape an...

Invasive predators, land clearing and altered fire regimes have been implicated in species decline and extinction worldwide. Enhanced knowledge of how these factors interact and influence medium-sized mammals is warranted. We tested three hypotheses using occupancy data for a diverse mammal assemblage including three threatened species, five common...

Hybridisation between wild and domestic canids is a global conservation and management issue. In Australia, dingoes are a distinct lineage of wild-living canid with a controversial domestication status. They are mainland Australia’s apex terrestrial predator. There is ongoing concern that the identity of dingoes has been threatened from breeding wi...

In desert ecosystems, some argue that primary productivity controls vertebrate populations while others contend that predators' top-down effects are under-appreciated. While seldom used to explain population dynamics in desert environments, the exploitation ecosystems hypothesis (EEH) unites bottom-up and top-down processes by conceptualizing how t...

Nomadism is an advantageous life history strategy for specialised predators because it enables the predator to respond rapidly to changes in prey populations. The letter-winged kite (Elanus scriptus) is a nomadic nocturnal bird of prey endemic to arid and semi-arid zones of Australia. Letter-winged kites prey almost exclusively on nocturnal rodents...

The impact of hybridisation between dingoes and domestic dogs, and the subsequent introgression of domestic dog genes into dingo populations, remains a topic of significant impact. It has been claimed, but with little evidence or logical argumentation, that dingoes with significant dog introgression have different effects on agriculture and ecosyst...

The 2019–2020 Australian megafires were unprecedented in their intensity and extent. These wildfires may have caused high mortality of adult broad-headed snakes Hoplocephalus bungaroides which shelter inside tree hollows during summer. We evaluated the impacts of two high-intensity wildfires (2002 Touga Fire and 2020 Morton Fire) on a broad-headed...

Complete separation of endangered prey from introduced predators improves prey survival at the cost of reduced predator recognition and antipredator behaviours, termed ‘prey naiveté’. Headstarting is a conservation strategy that has been used to improve the survival of juveniles for numerous species, whereby prey is separated from predators only in...

In arid environments, shade provided by vegetation forms the crux of many facilitation pathways by providing other organisms with relief from high levels of solar radiation and extreme temperatures. Shade is an important determinant that structures arid ecosystem processes and functioning. While shade is considered an essential refuge for many orga...

Overgrazing by introduced herbivores is widely recognized as a threatening process in Australia's semi-arid rangelands. Comparatively, grazing by native herbivores is generally considered to have benign effects. Populations of introduced herbivores are controlled in conservation reserves, but populations of native kangaroos and wallabies are seldom...

How to manage hybridization and introgression in wild animals is controversial. Wildlife managers and researchers may often rely upon phenotypic variables such as coat colour to inform on ground management decisions. In Australia, dingoes are typically believed to be ginger in colour, and unusual coat colours such as brin-dle or sable are widely po...

Introduced predators threaten prey species worldwide, but strategies to protect vulnerable wildlife from introduced predators can be expensive, time-consuming, and logistically difficult¹,². Novel conservation strategies that reduce predation affordably and efficiently must be explored. ‘Headstarting’ is one such strategy, whereby prey are isolated...

Predation is a key factor contributing to the failure of reintroductions of vertebrates but there is variation in predation risk between individuals. Understanding the traits that render some animals less susceptible to predation, and selecting for these traits, may help improve reintroduction success. Here, we test whether prior exposure to predat...

The diets of many animals are influenced by resource availability, competition, and evolutionary selected traits enabling the utilization of palatable foods. Omnivores are species that maintain their macronutrient balance by supplementing highly abundant but poor nutritional quality food items, with sporadically available but high nutritional quali...

There is currently a paucity of publications reporting different ways of minimising stress in collared mammals. We describe the construction of a DIY (do-it-yourself; i.e. self-made) radio-collar attachment that can improve the animal welfare outcomes of radio-tracking surveys for small macropods. The flexible collar is light, designed for long-ter...

The 5500 km long dingo barrier fence (DBF) is a boundary at which the goal of dingo control programs shifts from management to elimination. Since 1980 ecologists have used the discrepancies in dingo densities across the DBF to study the ecological role of Australia’s largest terrestrial predator. We used drone imagery, ground based shrub and tree c...

ContextTrophic cascade theory predicts that predators indirectly benefit plants by limiting herbivore consumption. As humans have removed large predators from most terrestrial ecosystems the effect of their absence is unrecognized.ObjectivesA manipulation of dingo populations across Australia’s dingo-proof fence, within the Strzelecki Desert, was u...

Inability to recognise and/or express effective anti-predator behaviour against novel predators as a result of ontogenetic and/or evolutionary isolation is known as ‘prey naiveté’. Natural selection favours prey species that are able to successfully detect, identify and appropriately respond to predators prior to their attack, increasing their prob...

Arid rangelands are degraded worldwide, suffering vegetation transformation, soil erosion, introductions, and extinctions. Wild deserts is restoring a desert ecosystem in Sturt National Park, New South Wales, Australia (35,000 ha), eradicating or controlling introduced animals, managing native herbivores, and reintroducing regionally extinct mammal...

Pollution and pesticide use have been linked to evolution of chemical resistance and phenotypic shifts in invertebrates, but less so in vertebrates. Here we provide evidence that poisoning directed towards a mammalian carnivore, the dingo (Canis dingo), is linked to an increase in dingo body mass. We compared the skull length of dingoes, a proxy fo...

Pollution and pesticide use have been linked to evolution of chemical resistance and phenotypic shifts in invertebrates, but less so in vertebrates. Here we provide evidence that poisoning directed towards a mammalian carnivore, the dingo (Canis dingo), is linked to an increase in dingo body mass. We compared the skull length of dingoes, a proxy fo...

The “life-dinner principle” posits that there is greater selection pressure on the species that have more to lose in an interaction. Thus, based on the asymmetry within predator-prey interactions, there is an advantage for prey to learn quickly, especially in response to novel, introduced predators. Here, we test the “learned recognition” hypothesi...

Fire is an important ecological process that shapes vegetation structure and habitat for faunal assemblages globally. Prescribed burns are increasingly being used in conservation and management to restore fire regimes in fire‐suppressed vegetation communities. Small threatened macropods require structurally complex habitat that allows them to evade...

Apex predators can have substantial and complex ecological roles in ecosystems. However, differences in species‐specific traits, population densities, and interspecific interactions are likely to determine the strength of apex predators’ roles. Here we report complementary studies examining how interactions between predator per capita metabolic rat...

Hybridisation resulting from human-driven shifts in species ranges is a global conservation concern. In Australia, hybridisa-tion between dingoes (Canis dingo) and domestic dogs (Canis familiaris) has been identified as an extinction threat to the dingo, and is thought to be particularly widespread in southeastern Australia. Here, we investigated t...

Invasive vertebrates are frequently reported to have catastrophic effects on the populations of species which they directly impact. It follows then, that if invaders exert strong suppressive effects on some species then other species will indirectly benefit due to ecological release from interactions with directly impacted species. However, evidenc...

The mesopredator release hypothesis (MRH) predicts that the removal of apex predators should lead to increased abundance of smaller predators through relaxation of suppressive, top-down effects. However, apex predators' effects on meso-predators are also likely to be modulated by interactions with human activities and ecosystem productivity. The ex...

In ecosystems, some organisms facilitate others indirectly, by interacting with one or more common mediator organisms. Thus, the indirect effects of introducing or removing species can be resonant, sometimes leading to successional extinctions. The dingo (Canis dingo) is the apex predator in Australian deserts and was introduced to the continent be...