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Washington State University

SoE in National Geographic: How to Butter Up a Grizzly Bear

Posted by rdsayler | March 13, 2023
[Brown bear paws. Credit: National Park Service/Kaiti Critz. Photo in Public Domain.]


Our first suggestion for how to butter up a grizzly bear would be to be very nice and considerate, meaning be careful not to surprise them and don’t be intrusive or threatening. Our second suggestion for buttering up a grizzly bear would be to see some of the many science news stories on SoE researchers, including Drs. Dan Thornton, Charles T. Robbins, and colleagues and their work on bears, including a recent story by National Geographic on the seemingly strange phenomenon of grizzly bears foraging on moths in Glacier National Park.

National Geographic recently reported on what they call “The odd phenomenon of moth-eating bears – and the dangers they face“. The beautifully-illustrated story explores and explains how grizzly bears in the Northern Rockies will climb to high elevation talus slopes (steep sloping landscapes of rock fragments or “scree”) to turn over small rocks and forage on hiding army cutworm moths (Euxoa auxilliaris) or what are commonly called, miller moths.

Untold billions of army cutworm moths migrate to the Northern Rockies every summer from the plains below and live in the cool shade in the air spaces beneath the rocks and then emerge at night to feed on blooming alpine flowers. Gorging on this abundant floral nectar allows the insects to store tremendous amounts of body fat, up to about 75% of body weight, making them a high-value, high-energy food source for grizzly bears preparing for fasting during hibernation and winter.

Bear Butter

The moths store so much body fat that their body fat composition is approximately equivalent to the same amount of butter – hence the nickname “bear butter” given to the moths by former SoE graduate student,  Erik Peterson, and other bear researchers. This high fat content explains why it can be worth the energy expense and risk to grizzly bears to climb to these mountainous heights and search for moths, sometimes eating thousands in a day.

How to Butter Up a Grizzly Bear?

Now you see what we feel is the best answer for how to butter up a grizzly bear – conserve their natural food sources and habitats to support the insects, fish, trees and seeds (e.g. Whitebark pine nuts), grass, tubers, forbs, and the many animals and environmental resources that constitute their food webs along with space to avoid excessive human disturbance. In other words, conserve and live and let live.

To learn more about bear behavior and ecology we encourage you to see the National Geographic article below and then also explore two of our research labs and facilities in the School of the Environment that are conducting research on large carnivores and bears.

R. Sayler
School of the Environment

[Note: National Geographic may limit the number of free articles you may see without registering with an email or subscribing.]

To Learn More:

See: National Geographic – The odd phenomenon of moth-eating bears and the dangers they face

To Learn More About SoE Bear Research:
See – Dr. Dan Thornton – Mammal Spatial Ecology & Conservation Lab;  Dr. Charles T. Robbins – WSU Bear Center

See more stories @ SoE Science News