Biodiversity friend or foe: land use by a top predator, the dingo in contested landscapes of the Australian Wet Tropics

Laying low: Rugged lowland rainforest preferred by feral cats in the Australian Wet Tropics

Invasive mesopredators are responsible for the decline of many species of native mammals worldwide. Feral cats have been causally linked to multiple extinctions of Australian mammals since European colonization. While feral cats are found throughout Australia, most research has been undertaken in arid habitats, thus there is a limited understanding of feral cat distribution, abundance, and ecology in Australian tropical rainforests. We carried out camera-trapping surveys at 108 locations across seven study sites, spanning 200 km in the Australian Wet Tropics. Single-species occupancy analysis was implemented to investigate how environmental factors influence feral cat distribution. Feral cats were detected at a rate of 5.09 photographs/100 days, 11 times higher than previously recorded in the Australian Wet Tropics. The main environmental factors influencing feral cat occupancy were a positive association with terrain ruggedness, a negative association with elevation, and a higher affinity for rainforest than eucalypt forest. These findings were consistent with other studies on feral cat ecology but differed from similar surveys in Australia. Increasingly harsh and consistently wet weather conditions at higher elevations, and improved shelter in topographically complex habitats may drive cat preference for lowland rainforest. Feral cats were positively associated with roads, supporting the theory that roads facilitate access and colonization of feral cats within more remote parts of the rainforest. Higher elevation rainforests with no roads could act as refugia for native prey species within the critical weight range. Regular monitoring of existing roads should be implemented to monitor feral cats, and new linear infrastructure should be limited to prevent encroachment into these areas. This is pertinent as climate change modeling suggests that habitats at higher elevations will become similar to lower elevations, potentially making the environment more suitable for feral cat populations.

The myth of wild dogs in Australia: are there any out there?

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 with domestic dogs, and that feral dogs have established populations in rural Australia. We collate the results of microsatellite DNA testing from 5039 wild canids to explore patterns of domestic dog ancestry in dingoes and observations of feral domestic dogs across the continent. Only 31 feral dogs were detected, challenging the perception that feral dogs are widespread in Australia. First generation dingo × dog hybrids were similarly rare, with only 27 individuals identified. Spatial patterns of genetic ancestry across Australia identified that dingo populations in northern, western and central Australia were largely free from domestic dog introgression. Our findings challenge the perception that dingoes are virtually extinct in the wild and that feral dogs are common. A shift in terminology from wild dog to dingo would better reflect the identity of these wild canids and allow more nuanced debate about the balance between conservation and management of dingoes in Australia.

Distribution and diet of feral cats (Felis catus) in the Wet Tropics of north-eastern Australia, with a focus on the upland rainforest

Abstract ContextFeral cats have been identified as a key threat to Australia’s biodiversity, particularly in arid areas and tropical woodlands. Their presence, abundance and potential impacts in rainforest have received less attention. AimsTo investigate the distribution and diet of feral cats (Felis catus) in upland rainforest of the Wet Tropics. MethodsWe collated available occurrence records from the Wet Tropics, and data from upland camera-trapping surveys over an 8-year period, to assess geographic and elevational distribution of feral cats in the bioregion. We also assessed the diet of feral cats from scats collected at upland sites. Key resultsFeral cats are widespread through the Wet Tropics bioregion, from the lowlands to the peaks of the highest mountains (>1600m), and in all vegetation types. Abundance appears to vary greatly across the region. Cats were readily detected during camera-trap surveys in some upland rainforest areas (particularly in the southern Atherton Tablelands and Bellenden Ker Range), but were never recorded in some areas (Thornton Peak, the upland rainforest of Windsor Tableland and Danbulla National Park) despite numerous repeated camera-trap surveys over the past 8 years at some of these sites. Scat analysis suggested that small mammals comprise ~70% of the diet of feral cats at an upland rainforest site. Multivariate analysis could not detect a difference in mammal community at sites where cats were detected or not. ConclusionsFeral cats are widespread in the Wet Tropics and appear to be common in some upland areas. However, their presence and abundance are variable across the region, and the drivers of this variability are not resolved. Small mammals appear to be the primary prey in the rainforest, although the impacts of cats on the endemic and threatened fauna of the Wet Tropics is unknown. ImplicationsGiven their documented impact in some ecosystems, research is required to examine the potential impact of cats on Wet Tropics fauna, particularly the many upland endemic vertebrates. Studies are needed on (1) habitat and prey selection, (2) population dynamics, and (3) landscape source–sink dynamics of feral cats in the Wet Tropics.

Zoonotic Helminth Diseases in Dogs and Dingoes Utilising Shared Resources in an Australian Aboriginal Community

The impacts of free-roaming canids (domestic and wild) on public health have long been a concern in Australian Indigenous communities. We investigated the prevalence of zoonotic helminth diseases in dogs and sympatric dingoes, and used radio telemetry to measure their spatial overlap, in an Aboriginal community in the Wet Tropics of Australia. Samples collected from dingoes and dogs showed high levels of infection with the zoonotic hookworm, Ancylostoma caninum. Dingoes were also positive for A. ceylanicum infection (11.4%), but dogs were infection free. Whipworm, Trichuris vulpis, infection was far more prevalent in necropsies of domestic dogs (78.6%) than dingoes (3.7%). Dogs were free from Dirofilaria immitis infection, while dingoes recorded 46.2% infection. Eleven dingoes and seven free-roaming domestic dogs were fitted with Global Positioning System collars and tracked over an extended period. Dingo home-ranges almost completely overlapped those of the domestic dogs. However, dingoes and dogs did not utilise the same area at the same time, and dogs may have avoided dingoes. This spatial overlap in resource use presents an opportunity for the indirect spill-over and spill-back of parasites between dogs and dingoes. Tracking and camera traps showed that the community rubbish tip and animal carcasses were areas of concentrated activity for dogs and dingoes.

Anthropogenic Food Subsidy to a Commensal Carnivore: The Value and Supply of Human Faeces in the Diet of Free-Ranging Dogs

Simple Summary

Free-ranging dog populations are growing worldwide, posing threats to human health and wildlife conservation. Dog population management requires a better understanding of the supply and quality of human-derived food. We studied the diet of free-ranging dogs in a remote area of Zimbabwe to explore the relationships between human waste, dog condition, and fertility, with a focus on the value of human faeces. We found that mammal remains, ‘sadza’ (maize porridge, the human staple) and human faeces were the most important food items, and unlike other items, faeces and sadza were consistently available. Nutritional analysis showed that human faeces was comparatively high in protein and energy content, exceeding that of sadza, and equivalent to mammal remains. Adult female dog condition was good throughout the year, indicating a diet sufficient to maintain fertility, and dogs largely fed alone, suggesting that food was abundant. We conclude that the lack of sanitation allows an important food subsidy to free-ranging dogs, but improved sanitation is unlikely to limit population growth as long as alternative human waste is available. Reproductive control by owners is more likely to reduce fertility rates.

Abstract

As the global population of free-ranging domestic dogs grows, there is increasing concern about impacts on human health and wildlife conservation. Effective management of dog populations requires reliable information on their diet, feeding behavior, and social ecology. Free-ranging dogs are reliant on humans, but anthropogenic food subsidies, particularly human faeces (i.e., coprophagy) have not previously been fully quantified. In this study we assess the contributions of different food types to the diet, and their influences on the social behaviour of free-ranging dogs in communal lands of rural Zimbabwe, with a focus on coprophagy. Free-ranging dog diets, body condition, and sociology were studied amongst 72 dogs over 18 months using scat analysis and direct observations. Human faeces constituted the fourth most common item in scats (56% occurrence) and contributed 21% by mass to the observed diet. Human faeces represented a valuable resource because relative to other food items it was consistently available, and of higher nutritional value than ‘sadza’ (maize porridge, the human staple and primary human-derived food), yielding 18.7% crude protein and 18.7 KJ/kg gross energy, compared to 8.3% and 18.5 KJ/kg for sadza, respectively. Human faeces had protein and energy values equivalent to mammal remains, another important food item. Dog condition was generally good, with 64% of adult females and 74% of adult males in the highest two body condition scores (on a five point scale), suggesting a plentiful and high quality food supply. Dogs largely fed alone, perhaps as a consequence of the small, inert, and spatially dispersed items that comprise their diet, and its abundance. We discuss the relationships between sanitation, human development, the supply of human faeces, female dog fertility, and population control.

Prey use by dingoes in a contested landscape: Ecosystem service provider or biodiversity threat?

In Australia, dingoes (Canis lupus dingo) have been implicated in the decline and extinction of a number of vertebrate species. The lowland Wet Tropics of Queensland, Australia is a biologically rich area with many species of rainforest-restricted vertebrates that could be threatened by dingoes; however, the ecological impacts of dingoes in this region are poorly understood. We determined the potential threat posed by dingoes to native vertebrates in the lowland Wet Tropics using dingo scat/stomach content and stable isotope analyses of hair from dingoes and potential prey species. Common mammals dominated dingo diets. We found no evidence of predation on threatened taxa or rainforest specialists within our study areas. The most significant prey species were northern brown bandicoots (Isoodon macrourus), canefield rats (Rattus sordidus), and agile wallabies (Macropus agilis). All are common species associated with relatively open grass/woodland habitats. Stable isotope analysis suggested that prey species sourced their nutrients primarily from open habitats and that prey choice, as identified by scat/stomach analysis alone, was a poor indicator of primary foraging habitats. In general, we find that prey use by dingoes in the lowland Wet Tropics does not pose a major threat to native and/or threatened fauna, including rainforest specialists. In fact, our results suggest that dingo predation on "pest" species may represent an important ecological service that outweighs potential biodiversity threats. A more targeted approach to managing wild canids is needed if the ecosystem services they provide in these contested landscapes are to be maintained, while simultaneously avoiding negative conservation or economic impacts.