Alaskan Bears Trail Meters-Long Tapeworms From Their Butts Surprisingly Often


Rachael Funnell

Social Editor and Staff Writer

clockAug 18 2021, 12:30 UTC
Alaskan Bears Occasionally Trail Meters-Long Tapeworms From Their Behinds

Dangling worms can be dead or still alive, and are probably pretty uncomfortable. Image credit: Paul Williams via Flickr, CC BY-NC 2.0

With big body size comes an increased internal capacity, and for Alaskan bears it seems their advanced size makes their bodies prime real estate for some astonishingly large tapeworms. "How do we know this?" you may ask. Well, unfortunately, it's not even that uncommon so wildlife photographers and trail cams have picked up an eyeful.

In a recent blog post for Cool Green Science, director of science communications for The Nature Conservancy Matthew Miller shone a light on the impressive body of video evidence that Alaskan bears sometimes wander around with what looks like streamers tailing from their anuses. Far from the remains of some raucous party, the pale tendrils are in fact parasites. Really, heckin’ massive parasites.


One particular video which Miller states to have embedded for your “viewing pleasure” shows a large black bear with one such mystery string dragging along behind it. The stomach-churning scene was captured by conservationist Michael Kampnich on Prince of Wales Island, Alaska, and appears to star a tapeworm that’s at least two-meters (6-feet) long.

Bears can apparently attempt to shake the freeloaders loose by practicing that much-loved bear tree pole dance, but – as was the case for the bear in Kampnich’s video – this isn’t always successful. Harboring mega-worms isn’t all that uncommon for Alaskan bears either, so where do they come from?

Alaskan bears are famous for their love of salmon which they scoop out of freshwater rivers by the pawful. The same rivers are unfortunately home to tapeworm eggs which are nibbled up by crustaceans. Those same crustaceans are chomped up by salmon, with those salmon being the same salmon scooped up by the bears. Capiche?


Having ridden the food chain all the way to the top, the worm sets up camp in the bear’s digestive system where it grows to great lengths before slipping out the exit. During their life, the parasitic worm will release many eggs which slip out with the bear’s fecal matter which they deposit into rivers, and here the lifecycle of the tapeworm begins all over again.

There are many different species of tapeworm hiding out in the guts of various animals across the globe, but that which inhabits Alaskan bears can reach up to nine meters (30 feet). Bears aren’t the only animals vulnerable to a case of the wormies, as demonstrated by this guy who pulled a 9.7-meter (32-foot) tapeworm from his rectum before embarking on quite the photoshoot - you’ve been warned.

Despite the horror of having such a guest gate crash your toilet time, parasites are an important group of animals and play a vital role in the ecosystem. Some are even thought to help us out in slowing the process of aging and are the subject of potentially pivotal research, which is why a scientist volunteered to be parasitized by 50 hookworms.


[H/T: Cool Green Science]

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