Tapeworms in Alaskan Bears

Tapeworms in Alaskan Bears


Many people are surprised to learn that Alaskan bears frequently have issues with tapeworms. Videos often circulate showing bears trailing long tapeworms behind them as they walk. This may seem unusual, but it’s actually a relatively common issue, especially for Alaskan black and brown bears.

How Bears Get Tapeworms

How Bears Get Tapeworms

  • Salmon Consumption
  • Alaskan bears get tapeworms from eating infected salmon in rivers during salmon runs.
  • Salmon pick up tapeworm eggs that are present in river water.
  • When bears eat infected salmon, tapeworm larvae lodge in the bear’s digestive system.

Life Cycle

Bears Tapeworms Lifecycle

  • Tapeworm eggs in the river water are eaten by small crustaceans.
  • The crustaceans are eaten by salmon, infecting them.
  • Bears eat the infected salmon, becoming infected themselves.
  • Adult tapeworms live inside the bears, shedding eggs.
  • The bear deposits the eggs back into the water through feces, restarting the cycle.

Effects on Bears

  • Discomfort
  • Passing long tapeworms causes visible discomfort for bears.
  • Bears may rub their behinds against trees.
  • Bears shake themselves in an effort to dislodge tapeworms.

Health Impacts

  • Tapeworms feed off the food bears consume, diverting nutrients.
  • Some bears become lethargic, anemic or lose weight.
  • However, most bears tolerate tapeworms well. The parasites need the host to survive.

Extreme Cases

  • In extreme cases, tapeworms inside bears may reach over 30 feet long.
  • Sometimes dead or living tapeworms are defecated fully intact.

Prevalence of Tapeworms

  • Common issue
  • Tapeworms are very prevalent among Alaskan bears.
  • Both black bears and brown bears often harbor them.

Frequently observed

  • Katmai National Park live bear cams often show dangling tapeworms.
  • Many amateur videos show bears trailing tapeworms.
  • Part of salmon ecosystem
  • Tapeworms remain an overlooked but ever-present part of the salmon lifecycle that feeds much of Alaska’s wildlife.

Tapeworms in Other Species

Bears Tapeworms

Over 10,000 tapeworm species exist globally. All have similar lifestyles.

  • Many species affected
  • Tapeworms affect numerous animal species in addition to bears.
  • This includes around 40% of all animal life.
  • Humans also at risk
  • Eating raw or undercooked fish can transfer tapeworms to humans through sushi.
  • Many human tapeworm cases cause minimal symptoms.
  • But some cases result in unpleasant intestinal issues.

Why Tapeworms Matter


  • Although often unappreciated, parasites like tapeworms are an integral part of global biodiversity.
  • Their evolutionary development is complex and fascinating.

Ecosystem awareness

  • Tapeworms illustrate the interconnectivity of ecological systems.
  • They showcase how species rely on one another, both positively and negatively.

Improved understanding
By observing the role of parasites like tapeworms, we can better understand the lifestyle and health issues facing species like Alaskan bears.

Bears Tapeworms

The presence of tapeworms in Alaskan bears may seem disturbing initially. But parasite-host relationships are far more common than many people realize. Tapeworms play an integral role across Alaska’s wilderness by distributing salmon nutrients to other species. And despite temporary discomfort for bears, the parasites rarely pose major long-term health consequences. By shedding light on this overlooked aspect of Alaska’s ecosystems, we can grow to better appreciate the interconnectivity and resilience of nature. Even when parasite-host relationships take visually unpleasant turns.