Mites blamed for mange outbreak in state's eagles
Published 5:03 pm, Monday, January 6, 2014
Mysterious microscopic parasites are causing golden eagles in different parts of California to lose their feathers, prompting a statewide alert by wildlife scientists who have never heard of such a condition in the big raptors.
The rare outbreak of mange, caused by tiny burrowing mites, was detected on several eagles found over the last year and a half in Alameda, Monterey and San Benito counties.
"Typically wild birds that are free ranging don't have mange," said Krysta Rogers, environmental scientist for the wildlife investigations laboratory of the California Department of Fish and Wildlife. "There may be some mites or other types of ectoparasites on chicks while the birds are in their nests, but an infestation this severe in a free-ranging adult bird hasn't been documented as far as we know."
Fish and Wildlife officials are urging raptor aficionados, conservationists and birders to be on the lookout for feather loss in golden eagles or other large birds and report cases to the department.
Severe feather loss was first detected on a golden eagle in San Benito in 2012. Suffering young eagles were then found in Alameda and Monterey counties in 2013 and the mites believed to be responsible were collected, Rogers said.
The sample size is small - the tiny burrowing arthropods were collected on only two of the afflicted eagles. The third raptor, which had been hit and killed by a car, was discarded before officials thought to investigate, Rogers said.
Still, it is a potentially serious problem, she said. All three eagles had large bald spots and crusting of the skin on their head, neck, legs and lower abdomen. An eagle that loses its feathers cannot maintain its normal body temperature, which could lead to weakness and trouble obtaining food, Rogers said. That, in turn, could make the bird more susceptible to disease and trauma.
"These eagles experienced significant feather loss and inflammation of the skin, similar to what you'd see on a dog with mange," Rogers said.
It isn't the first time an invasive parasite has cropped up unexpectedly in California. An exotic species of lice was linked earlier this year to baldness in deer. The problem, dubbed hair-loss syndrome, is becoming epidemic across the state and is believed to be a factor in numerous deer deaths, Department of Fish and Wildlife officials said.
Mite infestations have recently afflicted squirrels in the San Bernardino Mountains and bobcats in various locations in California.
Golden eagles are probably the best-known birds of prey in the Northern Hemisphere. The dark-brown raptors, with golden plumage on the underside, are known for their agility and speed. They have powerful feet and large, sharp talons that enable them to snatch and carry a variety of prey, including hares, marmots and ground squirrels. They are not endangered, but they are federally protected under the Bald and Golden Eagle Protection Act.
One of the problems is that nobody knows what kind of mite is attacking the eagles or where it came from. Rogers said the marauders are of the genus knemidocoptes, but scientists have not figured out the exact species. It is a difficult problem because there are tens of thousands of mite species and the invertebrates all go after different hosts. For instance, deer mites do not mingle with dog or squirrel mites and none of them would ever be caught dead or alive on a bird.
Scientists at the U. C. Davis are studying the morphology and genetics of the nearly invisible parasites. State scientists are also working with specialists at the East Bay Regional Park District and the Monterey County SPCA to document cases and identify the mite.
"We need more information basically to make some good assessments of whether this is an isolated case, if these birds were all related and exposed to the same parasite" or if this is an introduced species of mite, Rogers said.
Where to report feather losses in eagles:
Find your local wildlife rehabilitation center at the California Department of Fish and Wildlife website at www.dfg.ca.gov/wildlife/WIL/rehab/facilities.html.