Paper title: Dietary niche overlap of free-roaming dingoes and domestic dogs: the role of human-provided food
Abstract: As both companion animals and opportunistic predators, dogs (Canis lupus spp.) have had a long and complex relationship with humans. In Australia, the dingo (C. l. dingo) was introduced 4,000 years ago and, other than humans, is now the continent’s top mammalian predator. Domestic dogs (C. l. familiaris) were introduced by Europeans more recently and they interbreed with dingoes. This hybridization has caused growing concern about the roles that domestic dogs and dingoes play in shaping ecosystem processes. There is also considerable debate about whether anthropogenic environmental changes can alter the ecological roles of dingoes. We used scat analysis to test whether the dingo, as the longer-established predator, occupies a different dietary niche from that of free-roaming domestic dogs, irrespective of human influence. Our results demonstrate considerable dietary overlap between dingoes and domestic dogs in areas where humans provide supplementary food, providing evidence against our hypothesis. However, the consumption by dingoes of a greater diversity of prey, in association with historical differences in the interactions between dingoes and humans, suggests a partial separation of their dietary niche from that of domestic dogs. We conclude that anthropogenic changes in resource availability could prevent dingoes from fulfilling their trophic regulatory or pre-European roles. Effective management of human-provided food is therefore required urgently to minimize the potential for subsidized populations of dingoes and domestic dogs to negatively affect co-occurring prey.
Just Out – Opinion Piece on Dingoes in The Conversation:
Paper title: Experiments in no-impact control of dingoes: comment on Allen et al. 2013
Abstract: There has been much recent debate in Australia over whether lethal control of dingoes incurs environmental costs, particularly by allowing increase of populations of mesopredators such as red foxes and feral cats. Allen et al. FIZ 10:39, 2013 claim to show in their recent study that suppression of dingo activity by poison baiting does not lead to mesopredator release, because mesopredators are also suppressed by poisoning. We show that this claim is not supported by the data and analysis reported in Allen et al.’s paper.
In December last year I spent two weeks out on the Washington Wolf-Deer project. The biggest eye opener was the diversity of large predators in the system. On top of wolves, there are bears, cougars, coyotes and bobcats.
For an Australian who is used to studying the interactions between three small-medium sized predators (the dingo, red fox and feral cat) the idea of having all these large predators within a study site is a new challenge.
For example, there is debate in Australia about the ecological role of dingoes. Indeed, we struggle to unravel the complex relationships between dingoes, red foxes and feral cats. So attempting to understand how wolves, bears, cougars, coyotes and bobcats interact with each other is a whole new ball game.
Because wolves have recently recolonised Washington State it is possible to study interactions between predators in two different scenarios being with and without wolves.
As mentioned in a previous post (https://thomasnewsome.com/2013/11/26/from-desert-dingoes-to-alpine-wolves/), the research group from the University of Washington are putting camera and GPS collars on two deer species to look at behavioural changes in response to recolonising wolves.
During my first two weeks on the Washington Wolf-Deer project we set out traps to catch the deer each night. Unfortunately the lack of snow made it difficult to lure deer into the traps using alfalfa, old apples and molasses (deer are much easier to catch when there is snow because the grass is covered and inaccessible to eat).
In early January I made the trip back to the field site hoping that with more snow there would be a higher chance of catching deer. Fortunately, success!
The additional impetus for heading back out in the field was the company of a fellow Australian researcher, Prof. Chris Dickman, who had a few days to spare after we attended the Gordon Research Conference on Predator-Prey interactions in California.
Chris has spent his career working in the arid deserts of Australia. Fortunately, I found enough warm clothes to see him through a North American winter field experience.
Working in a complex multi-predator system raises a plethora of ecological questions for consideration.
For example, with wolves in the system, is the “top-dog” canine or feline?
Cougars and wolves will both be competing for resources (deer) so there is the question of whether or not wolves will out-compete cougars. Wolves are also known to suppress coyotes so there is the question of whether or not coyote density will decline in areas where wolves are present.
Some of these questions were addressed after wolves were reintroduced into Yellowstone National Park in 1995-1996. However, in Washington State, wolves have recolonised managed lands where there are hunting seasons, logging and cattle ranching. Therefore, the future persistence of wolves in managed lands depends on minimising negative interactions between people and wildlife.
It also depends on the ecological role of wolves in managed lands i.e. how they interact with other predators and prey.
The results from the Washington Wolf-Deer project therefore have important implications for understanding how people, wolves and other wildlife might be able to coexist in managed lands.
When results from the project become available I will be sure to share them here.
Paper title: Human-resource subsidies alter the dietary preferences of a mammalian top predator
Abstract: Resource subsidies to opportunistic predators may alter natural predator–prey relationships and, in turn, have implications for how these predators affect co-occurring prey. To explore this idea, we compared the prey available to and eaten by a top canid predator, the Australian dingo (Canis lupus dingo), in areas with and without human-provided food. Overall, small mammals formed the majority of dingo prey, followed by reptiles and then invertebrates. Where human-provided food resources were available, dingoes ate them; 17 % of their diet comprised kitchen waste from a refuse facility. There was evidence of dietary preference for small mammals in areas where human-provided food was available. In more distant areas, by contrast, reptiles were the primary prey. The level of seasonal switching between small mammals and reptiles was also more pronounced in areas away from human-provided food. This reaffirmed concepts of prey switching but within a short, seasonal time frame. It also confirmed that the diet of dingoes is altered where human-provided food is available. We suggest that the availability of anthropogenic food to this species and other apex predators therefore has the potential to alter trophic cascades.