Parasites have notorious reputations for not only sapping their hosts of valuable resources, but also spreading disease and infection — a serious threat for hosts teetering on the brink of extinction. Unsurprisingly, scientists working to save endangered host species in captivity often kill parasites found on individual hosts. However, these efforts to save some species may drive others to extinction: According to a recent paper published in Conservation Biology, at least two louse species have likely gone extinct as a result of conservation efforts to save their hosts.

In the past, both the California condor and the black-footed ferret suffered such population losses that scientists tried to breed the endangered species in captivity to increase their numbers. As part of both breeding programs, conservationists killed parasites living on or in the individual condors and ferrets. For many species of parasites removal might not have been an issue — others of their kind would live to see another host another day. But for the louse Colpocephalum californianus and the ferret louse Neotrichodectes sp., which are species-specific and rely on those particular hosts to survive, the delousing spelled their doom. Scientists believe both species of parasites are now extinct. “It is unfortunate that these programs did not account for the parasite’s conservation,” wrote Dolly Jørgensen, an environmental historian from Sweden’s Umea University and the paper’s author. In addition, scientists estimate that about 40 species of lice are co-endangered with hosts listed on the International Union for Conservation of Nature (IUCN) red list. And the threat isn’t specific to lice. Elizabeth Nichols, a biologist and parasite researcher from Brazil’s Sao Paulo University, estimated more than 1,000 species of parasitic worms called helminthes are endangered.

“Biodiversity conservation needs to account not only for the large fauna,” wrote Jørgensen, “but also for the small fauna along for the ride,” Unfortunately, parasites don’t have the largest fan following and, as a result, calling for their protection can be a difficult sell. Although they’re often viewed as organisms that inflict harm inside a single host, they tend to play a much more complicated role. Nichols thinks of parasites as ecosystem puppeteers. They pull the strings on the entire population, she explained. In general they separate the sick from the healthy, they determine how many individuals are part of the population, and they can control which individuals can reproduce and which cannot, among other things. Depending on which of these strings they pull, parasites can exert pressure that causes host populations to shift. In this way parasites drive evolution and keep host populations healthy, though at the expense of the infected individual hosts.

Historically, efforts to conserve threatened and endangered species have not often taken parasites into consideration, said Nichols, but a more nuanced approach is emerging. Jesús Péréz from Jaén University in Spain recommends conservationists pick species-specific lice off the endangered Iberian lynx and save them for when the lynx is reintroduced into the wild. Further, in 2013, the IUCN added an amendment to their relocation guidelines recommending wildlife managers consider re-establishing parasites that may also go extinct with their host species when feasible. The subtlety is important because saving parasites isn’t practical for every situation, explained Nichols. “No one is trying to do the wrong thing,” she said. “It’s just really unclear what the right thing is at the right time.”

A polar bear’s signature white pelt does more than camouflage the large hunter on snow-covered terrains. Its thick fur also provides a vital layer of insulation, protecting it from subfreezing temperatures. But some bears in Alaska may have a chink in their thermal armor. A small percentage of polar bears that hunt in Alaska’s southern Beaufort Sea experience hair loss, or alopecia, according to a new U.S. Geological Survey study published in the Journal of Wildlife Diseases.

USGS scientists have been studying polar bears since the mid 1980s, and when they first saw signs of hair loss in the spring of 1998 they took notice. “There weren’t a whole lot of bears that showed signs [of alopecia], but enough where people were noting that it wasn’t what we normally see,” said Todd Atwood, wildlife biologist and leader of the USGS polar bear research group.

Every year, Atwood and a team of scientists weigh, age, measure, and assess the overall health of each bear they encounter during a six- to eight-week survey period in Alaska. From 1998 onward, they added observations regarding alopecia to the repertoire of data they collected. When the researchers found an alopecic polar bear, they plucked hair and scraped skin samples. They also made sure to collect hair and skin from unaffected bears for comparison.

Alopecia can look different from bear to bear, according to Atwood. Some polar bears may have thinning hair around their neck or bald patches anywhere from their shoulder blades to their nose. And the patches can vary in size. Sometimes they are about as big as a sheet of printer paper and other times as small as a silver dollar. Crusty or oozing lesions can dot the leathery, exposed skin.

The cause of polar bear alopecia still eludes Atwood and his team. One theory is that the hair loss may be connected to a bear’s health — the study found that bears with alopecia tended to have poorer body conditions than their unaffected peers. In the winter, a bear’s body heat will escape through bald or thinning patches in their coat. The bear must then exert a tremendous amount of energy to maintain its core body temperature, which would cause the bear to use up vital fat reserves and leave the it vulnerable to other diseases or infections. But it is unclear to the scientists whether the hair loss causes the decline in health or is a symptom of it, leaving scientists with a “chicken-or-the-egg” scenario.

Because alopecia affects such a small number of bears — only 3.4 percent of those sampled experienced hair loss — the scientists do not consider the disease a serious, long-term threat to the polar bear population. However, it may be more serious in some years than others. In 1999, for example, 16 percent of polar bears had alopecia, and in 2012 the number spiked to 28 percent — a “striking” difference from the 14-year average of four percent, according to Atwood. Now, scientists can look at any given year and tell whether they are seeing an unusual number of alopecia cases. “An important aspect of managing at-risk or threatened species is being able to track changes over time,” he said.

Keeva and Rex are the two newest recruits in the efforts to protect Chesapeake Bay wetlands by eradicating invasive nutria from the Delmarva Peninsula. They have been trained to detect the invasive creatures, and will be the key to accomplishing the last phase of The Chesapeake Bay Nutria Eradication Project (CBNEP). Only these two newest workers aren’t people – they’re dogs that have been trained at the National Detector Dog Training Center.

Image Credit: Anson Eaglin, USDA, APHIS

This summer, Keeva and Rex, along with their two handlers, a wildlife biologist and a wildlife specialist from USDA’s Wildlife Services program, completed five weeks of rigorous training to detect nutria scat and build handler skills. They also completed four weeks of application training in Maryland, and have now been certified to search, locate, and respond via a bark to nutria scat (feces).

Nutria are semi-aquatic rodents, similar to muskrats. Devouring up to 25 percent of their body weight in plants and roots per day, they have devastated Chesapeake Bay wetlands, turning them into barren mud flats. The spoiled marshes offer no protection to fish, shellfish, birds or other wildlife. Nutria activity accelerates erosion that smothers oyster beds and degrades Chesapeake Bay water quality. Lost wetlands increase tidal and storm flooding and subsequent damage to upland timber and agricultural areas.

Since the project began in 2002, nutria have been removed from more than 250,000 acres at the refuge and other public and private properties on the Delmarva peninsula. Now comes the beginning of the last phase of the CBNEP – eradication verification. Specifically, the dogs will help determine whether any nutria remain in areas from which they have been previously removed.

These efforts would not be possible without the help and support of many partners, including Federal and State agencies, universities, private organizations and landowners.

Read more about the Chesapeake Bay Nutria Eradication Project in the upcoming Spring 2015 issue of The Wildlife Professional.

Wildlife Services is a Strategic Partner of The Wildlife Society.