Lawrence LeBlond for redOrbit.com – Your Universe Online
Scientists and land managers who have used vocalization surveys since the 1980s to track down northern spotted owls have found that detection dogs have a much better track record at finding the species.
Vocalization surveys rely on using simulated northern spotted owl calls to elicit owl responses. The surveys have been carried out to find how the species is handling increasing encroachment from barred owls, which displace and even often kill spotted owls. Experts are concerned that spotted owls may be timid about responding to vocalizations for instinctual fear that they are opening themselves up to attack if they do.
“Wildlife managers spent years trying to get good forest practices in place that are contingent on spotted owl presence and now the invading barred owl is hindering our ability to show it’s there,” said Samuel Wasser, University of Washington research professor and director of the UW Center for Conservation Biology.
Detection dogs were brought in to aid researchers in finding the vulnerable species. The dogs were specially trained to sniff out northern spotted owl pellets — pieces of undigested foods regurgitated by owls. The experts said the detection dogs improved the probability of finding the owls by 30 percent over the traditional vocalization methods.
“Vocalization surveys have a lot of value and by no means are we suggesting that the dogs should replace the vocalization surveys. But dogs can add value,” noted Wasser. “The dogs have higher detection probabilities than vocalization surveys under some circumstances, can simultaneously detect spotted and barred owls and don’t need owls to vocalize to be detected. The vocalization surveys have the advantage of being able to cover a much, much bigger area. The two together would be very complementary.”
Researchers published a comparison of both approaches in the journal PLoS ONE. The spotted owl searches took place in the Shasta-Trinity national Forest in northern California.
Two dogs — Shrek, a Labrador retriever mix, and Max, an Australian cattle dog mix — were trained to sniff out the pellets and feces of both species of owl at tree bases where owls generally roost. UW researchers used maps showing habitat types to hone in on the best places to carry out searches. DNA analysis of the samples confirmed the species of owl.
The detection rate for northern spotted owls was 87 percent after three searches by dogs, compared to 59 percent after six vocalizations following US Fish and Wildlife Service protocols, Wasser explained. With barred owls, the detection rate was lower for both methods. Wasser noted this may have been due to barred owls being relatively uncommon in the search area. However, the dogs performed 13 percent better for barred owls as well.
“This was a carefully planned study to try to make everything as equivalent as we could,” said Wasser. “More work is needed to determine when the two methods work best together or if one is preferable over the other.”
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