Barred owls are notorious for taking habitat away from the now-endangered Northern spotted owl, but one creature that doesn't seem to mind this newly established species is the parasite.
Ian Oliphant, a Vancouver Island University biology student, conducted the first survey in B.C. on the population of helminth parasites in barred owls. He examined the corpses of 23 barred owls donated by the B.C. SPCA Wild Animal Rehabilitation Centre, birds that weren't able to be saved.
The deceased owls had an average of about 113 neodiplostomum delicatum, a helminth flatworm parasite, and one bird, an outlier, had more than 600.
The parasites aren't necessarily deadly, instead relying on the owl to be in good health for their own survival. Having a high population of helminth parasites in the owl's system simply means the owl likely needed to consume more calories to stay healthy, and the parasites could play a role in reproductive success and immune function.
"Every animal has different parasites associated with it and the majority of individuals will have [them]," Oliphant said. "If you've got a population of owls, the majority of them will have next to no parasites, and then some of them 鈥� very few of them 鈥� will have the vast majority of the parasites in the population."
The barred owl frequents the same habitats as the endangered spotted owl, and is a major reason for the spotted owl's endangered status. Barred owls arrived in B.C. in the 1940s as part of an westward expansion of the species, competing with spotted owls for habitat and food sources. By the late 1960s, they had made their way onto Vancouver Island.
While Oliphant's study is the first documentation of helminths in barred owls from British Columbia, the subject of parasitic infection in barred owls is a popular one among researchers due to the potential to learn more about the health impacts for the similar spotted owl.
Other research, such as a, found that out of 69 barred owls tested, 49 per cent were infected with periorbital nematodes, a type of roundworm parasites that can infect the area around the eyes.
Oliphant's research focused exclusively on helminth parasites, which can be found in the owls' intestinal tract. Six different subspecies of these parasites, including the neodiplostomum delicatum, were found inhabiting the 23 owls tested.
"Helminth parasites are just like your worm-type parasites. They are classic-looking worm-like creatures and they just live inside the intestinal tract of these barred owls and they use their nutrients to reproduce."
While it may not have been lethal for the barred owl to have over 600 parasites, Oliphant said it likely wasn't pleasant.
"You have to remember parasites are feeding off of whatever you're eating, so the owl with 602 individuals probably needed a larger caloric intake than someone who didn't have as many. It was probably already at a disadvantage because it was having to eat much more to try to cope with the amount of parasites."
Intensity of helminth species in barred owls from southern Vancouver Island. Red points on the graph represent each host, while black points indicate the host with the highest intensity. (Image courtesy Ian Oliphant)
His study found that every single owl had at least one species of parasite, with the neodiplostomum delicatum being the most popular. Others living inside the owls, like the capillaria intestianial parasite, had an average of 8.3 per owl.
"I think it warrants further study鈥�" Oliphant said. "We only used 23 owls, but in a much larger study you would get a way better picture of what's going on."
One big takeaway, he said, was that people shouldn't be scared of parasites.
"There are definitely human parasites that are worrying, etc., but parasites like this are purely just interesting. They can't affect us, they just affect the ecology of the animals they interact with."
