Brainworms the Culprits Behind Minnesota’s Declining Moose Population

A bull moose. Moose population in MN has been declining because of brainwormsPhoto byWikimedia

Minnesota's moose population has been in steep decline in recent years, and scientists are now uncovering one of the main culprits behind this crisis: brainworms.

These parasites, scientifically known as Parelaphostrongylus tenuis, have infiltrated the state, and their impact on the moose population is becoming clearer.

Brainworms came to Minnesota through the brains of white-tailed deer, their primary host, where they're harmless.

But moose are defenseless against these parasites, which tunnel through their brains, leading to bizarre behaviors like circling and eventual death due to starvation or hypothermia.

Researchers suspected that moose were unintentionally ingesting brainworm larvae by consuming snails and slugs that had previously fed on infected deer feces while grazing on plant matter. Recent studies have shed light on this process. One study, published in the Journal of Wildlife Diseases, confirmed that moose consume snails and slugs which host brainworms.

There’s been a ton of research on the deer part of this (brainworm) cycle. But understanding the other pieces of the cycle, the slugs and snails, is helping explain how this is impacting moose- Tyler Garwood, Ecologist, University of Minnesota

Another study, in the journal Food Webs, revealed that moose encounter infected snails and slugs at mineral licks—areas rich in sodium and calcium that both moose and deer require for survival. Researchers used GPS data and trail cameras to observe these animals at these sites, where they discovered evidence of brainworm transmission.

Brainworms have become a leading cause of moose mortality in Minnesota, responsible for approximately 25 to 30 percent of deaths. Moose also face other threats such as predation by a growing gray wolf population, tick-related issues, and the impacts of climate change.

The moose population in Minnesota has plummeted from 8,000 individuals in 2009 to around 3,700 in recent years, posing a significant concern for indigenous communities and conservationists.

Efforts to save Minnesota's moose start with scientists and wildlife managers working to combat the brainworm threat and ensure the survival of these iconic creatures.