Yellowstone Wolves Face Their Own Natural Enemies
Penn State Scientists are tracking wolf packs reintroduced to Yellowstone in to rebalance the region's ecology. Survival has been a struggle - the wolves face long, frigid winters and are now being ravaged by several devastating diseases.
Yellowstone Wolves Face Their Own Natural Enemies
This is my penultimate column for the Philadelphia Inquirer. It will run in print on Monday. The final one runs the following Monday:
A century ago, Americans so vehemently hated the wolves of their Western states that they attacked them with germ warfare.
Veterinarians deliberately infected coyotes with a disease called mange, hoping it would spread to the wolves, which it did, causing many of them to lose so much fur that they froze to death in the harsh winters.
Now, according to a recent study by Penn State researchers, the mange survived in other animals long after the wolves were gone.
And it has resurfaced in wolf packs reintroduced to Yellowstone National Park in the 1990s. Those wolves are also losing cubs to canine distemper and a disease called parvovirus.
These diseases struck the wolves much faster than scientists expected, said Penn State ecologist Peter Hudson, who is a coauthor on the study, published in the September issue of the Philosophical Transactions of the Royal Society B. But he still expects the wolves to pull through in the long run.
“Healthy ecosystems are full of parasites,” he said. The reintroduced wolves had no natural immunity to these diseases, but eventually he thinks the disease organisms and the wolves will strike a balance.
By tracking the way these outbreaks are spreading among the reintroduced wolves, he and his colleagues hope to learn lessons they can apply to understanding the dynamics of other emerging diseases.
“People used to think parasites and pathogens were of no importance to ecology,” he said. Now, scientists are realizing the pathogens are part of the environment and can cause animal populations to go through big oscillations.
One thriving wolf pack, called the Druids, was hit with mange in 2009 and died out the next year, said Penn State ecologist Emily Almberg, who was lead author on the paper.
But overall, the impact of the wolves continues to be dramatic. Since their reintroduction, she said, exploding populations of elk have declined, allowing some plants to rebound, along with animal species that depended on them.
No one knows exactly how many wolves lived in the region that became Yellowstone National Park before the late 1800s, when humans wiped them out. The wolves were exterminated in a massive, government-led campaign that employed a combination of shooting, germ warfare, and poison.
By the 1940s, wildlife conservation pioneer Aldo Leopold first suggested that wolves played a role in the ecology and should be reintroduced, said Daniel Stahler, a biologist with the Yellowstone Wolf Project and the Yellowstone Center for Resources.
There was tremendous resistance from ranchers, who feared wolves would leave the park and kill their cattle. Meanwhile, elk populations were exploding.
Finally, in 1995 and 1996, 41 wolves were brought down from Canada and released into the park, said Stahler. By 2003, they reached a peak of 170. Now, they are down to 100, and Stahler agrees with the Penn State researchers that the numbers are likely to fluctuate but not collapse.
The elk population has dropped from 20,000 in the mid-1990s to 8,000 today, he said. Scientists don’t know for sure whether the drop is entirely caused by wolf predation or also by other factors such as drought, which affects the plants the elk depend upon for food.
The decline in wolves may also reflect a rebalancing of the ecosystem. Wolves are territorial; their leading cause of death is being killed by another wolf in territorial disputes.
While the wolves have eaten enough elk to reduce their numbers, they have also changed the elks’ behavior, said Penn State’s Almberg. The wolves keep the elk on the move, “so they can’t keep hammering at one willow or aspen stand” and destroying it.
Meanwhile, ecologists have seen a cascade effect on the landscape, with more willow and aspen surviving, which in turn benefits warblers, beavers, and other animals that depend on those trees.
Scavengers such as ravens and grizzly bears also benefit — from the carcasses left by wolf kills.
The researchers saw the first mange cases in 2002, said Almberg, and the first outbreaks of canine distemper in 2005.
Distemper, she said, is a highly contagious viral disease that affects the nervous system and kills some adults and most wolf pups.
Mange is a skin disease caused by mites, and while it’s not fatal by itself, infected wolves can bite and scratch themselves so much that they die from secondary infections. Or they can lose so much fur that they freeze to death. The outbreak, she said, went through most of the park by 2007.
In the future, she and Hudson are calling on locals and tourists to become citizen scientists send them pictures they take of the wolves. “Visitor photographs are really helpful.<TH>… So many people are out there every day taking photos,” she said. “There’s no way our staff could re-create that field effort.”
Contact Faye Flam at 215-854-4977 or fflam@phillynews.com, or follow on Twitter @fayeflam. Read her blog at philly.com/evolution.
Blog post goes here.
Why don't the local vets treat the mange? It is very easily cured by putting the mite-killing drug into food.— racmom- I am disappointed to find this is your next to last column. Where will you write next?— GaryAllan
- That's something I can answer via email. Drop me a line and I'll tell you how to continue to follow my work.— fayeflam
- The Philly will be the poorer for losing you, and I look forward to following you at your next location.
You continue to educate me. I had seen the reintroduction of wolves as an essentially romantic gesture, when in fact it is restoring a healthier balance to the whole system by giving it back its top predator.
There is an enormous amount to be learnt from pathogens, which show such a rich variety of behaviours, including progress from acute to chronic to commensal to symbiotic to, in the extreme case, incorporation and even the assumption of a vital role in their hosts, as in some endogenous retroviral viruses.
All best wishes in your new venture.
— PaulBraterman - Dear Faye,
Thanks for al lthe good stuff
I am outraged at Philly.com for dropping your stuff.
America as a whole needs more of this writing not less.
Our population is quickly becoming one of dunces and badly needs education.
Dr. Jon Berger— jbcanoe - I was really bummed to find out the column is going away - I hope there will be another way we can read Faye's commentary.
I have been noticing new predators changing my suburban ecosystem for years: the rise of foxes and raptors has led to a welcome and noticeable decrease in squirrel, canada goose and rabbit population - I wish we could get in predators to protect us from the deer (and their car accidents, disease and ravaging of ground cover)
- let us know where to find you next, Faye— erickfrieg - What terrible repercussions from that very bad decision of a century ago. Can you imagine the long-term suffering from the consequences of mange? Distemper is also awful, and parvo is nearly a death sentence. I hope Mr. (Dr.?) Hudson is correct, and the colonies will survive. How stupid we humans can often be, setting ourselves back (sometimes irretrievably), before the "lightbulb" goes on. An excellent proposal, though, for tourists - keep your eyes peeled, and record any data you can. Another fine piece from you, Faye. The caliber of your writing remains unequaled. The Inquirer's loss will be another's gain - and we, your readers, will be right along with you for the next adventure!— fineprintJK1
- I enjoyed your columns as well. I hope your next writing job is a better berth.— Dr_GS_Hurd
In pursuit of her stories, writer Faye Flam has weathered storms in Greenland, gotten frost nip at the South Pole, and floated weightless aboard NASA’s zero-g plane. She has a degree in geophysics from the California Institute of Technology and started her writing career with the Economist. She later took on the particle physics and cosmology beat at Science Magazine before coming to the Inquirer in 1995. Her previous science column, “Carnal Knowledge,” ran from 2005 to 2008. Her new column and blog, Planet of the Apes, explores the topic of evolution and runs here and in the Inquirer’s health section each Monday. Email Faye at fflam@phillynews.com.
Reach Planet of the at fflam@phillynews.com.
