From personal experience, I know that a trained fox scat detecting dog is better at finding fox scats than me. Which is good, because I didn't want to take it up as a career anyway. In the small demonstration I described in an earlier post, one dog was actually better than more than a dozen people working together to find fox scats. The dogs, magnificent black labradors, have been employed in the effort to rid Tasmania of a small number of foxes.
Some people in Tasmania have asked why use scat-detecting dogs? It seems a complex way to find a fox - why not just trap the foxes or use traditional methods like sand pads (a layer of sand is raked and smoothed, usually where you'd expect animals to be, like a trail or near something attractive like food or scent markings, then you look for the tracks)?
The reason is that trained scat detecting dogs are better at detecting the presence of animals in low-density than other detection methods. Remote cameras are nowadays often employed in wildlife management. In recent years, the price of cameras has dropped dramatically and their efficiency has improved so they now form part of the toolbox of many wildlife people. A group of researchers in Vermont compared detection of black bears, fishers (the North American marten, which actually rarely eats fish) and bobcats using scat detecting dogs, cameras and a third method, hair snares.
The researchers found that all three methods detected the bears but they didn't detect either the fishers or the bobcats using hair snares. But dogs performed the best. In other words, if one of these species were around, a dog looking for a scat was more likely to detect it than a remote camera.
Bears, fishers and bobcats are all much more common in Vermont than foxes are in Tasmania. But scat detecting dogs still won't find them every time. The dogs would detect the presence of bobcats in only one out of four visits to a site, for example. But that "detection probability" is still better than using remote cameras. So these researchers recommend the use of scat detector dogs when the target species is in relatively low abundance, despite the fact that dogs are usually more expensive than alternate methods. In the case of Tasmania, "relative" low abundance probably means "super" low abundance.
What about for foxes? Californian researchers have assessed scat detecting dogs to determine kit fox distribution and found them useful for searching the historic range of the kit fox, where populations are in very low densities. They used the method for determining presence or absence of a population, rather than estimating the number of kit foxes. This example is more like Tasmania: once densities are below the normal levels of detection, everything is happening "below the radar" so to speak. Making a population estimate is not valid at such low levels. That's actually a brilliant thing in terms of an eradication program: it shows the density of foxes is exceptionally low. The Tassie situation is different to virtually every study because they are trying to eradicate the fox, so if the program is working, they want to see less evidence over time not more.
There's always complications though and here's one - "scat removers" (read "scat eaters" errh). American researchers looked at whether scat removal was an issue and found up to half the coyote and bobcat scat left on trails was eaten, mainly by opossums. This was seasonally influenced, with opossums much hungrier for carnivore scat in the summer.
Another complexity is the cryptic nature of foxes. We don't know how they behave at really low densities. On the mainland, foxes are generally showing themselves under three circumstances: defending territory, finding a mate or dispersing from the den. From around March to May, the young adults are dispersing from their mother's den and that's when most Australians are likely to see a fox - dead on the road when they are naive of traffic; stressed by trying to establish their own place in the landscape. No one knows how they'll behave in a landscape that doesn't have an established fox population.
Foxes also make a variety of calls that could potentially be used for detection but an acoustic signature is not left behind like a scat or hair. So it isn't currently possible to design a survey using sound, along the lines of the scat survey underway in Tasmania. Nevertheless, calls are reported and could potentially deliver more information. Sound detection technology is developing rapidly and has been successfuly tried with cane toads in Australia's north - and of course there are ears. Any detection method is worth trialling but there is a lot of research pointing to scat detecting dogs as the current leading edge.
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