Title: Wildlife in Peril: Human Activity Threatens Grizzlies’ Vital Food Source
Subtitle: The army cutworm moth plays a crucial role in the grizzlies’ diet, but human interference and climate change pose risks
Date: Sun 8 Oct 2023 15.00 CEST
Wyoming’s barren mountain slopes may appear inhospitable, but for grizzly bears, it becomes a high-calorie buffet during the summer months. Thanks to the arrival of the army cutworm moth, these rocky hillsides become a rich feeding ground for the giant carnivores. However, as humans increasingly encroach upon the moth’s habitat and the climate crisis affects their survival, the future of this vital food source hangs in the balance.
Measuring half the size of a thumb and covered in tan and brown geometric designs, the army cutworm moth makes a long migration to the mountain peaks of Wyoming each summer, numbering in the hundreds of millions. Known as “bear butter” due to their high fat content, these moths provide a significant source of nutrition for grizzly bears in the region. It’s estimated that around 200 bears each year feast on as many as 40,000 moths a day, providing them with a substantial calorie intake.
However, the increasing human presence at these moth sites has disrupted the feeding patterns of the grizzlies. Enthusiasts eager to witness the spectacle inadvertently scare away the bears, causing them to miss out on critical calories. Additionally, the climate crisis poses a threat to the lower-elevation fields where caterpillars hatch and feed on young plants, as well as the high-mountain ecosystems reliant on abundant wildflowers fed by deep snowpack.
To better understand the moths and their relationship with grizzly bears, scientists have embarked on a quest to study their life cycle, migratory routes, and overall health. Bob Peterson, an entomology professor at Montana State University, worked with graduate students to analyze moth heads buried in hundreds of piles of bear feces. Their findings revealed that the moths arrived in Wyoming from various regions, including the Great Plains, Montana, British Columbia, Alberta, and the southern Northwest Territories.
Miraculously, hundreds of millions of these moths with 40mm wingspans migrate long distances using preferential winds and navigate by moon and starlight. Although their routes remain relatively direct, they face risks from human interference and changes in their habitats. At present, the army cutworm moth population remains stable due to their ability to originate from multiple locations across the region.
Frances van Manen, a grizzly bear researcher, emphasizes that the bears’ diet is incredibly diverse, with over 266 kinds of food observed. Grizzlies are adaptable and will consume plants, mammals, fungi, and even dirt. Having successfully recovered their population in recent decades, grizzlies now face challenges regarding their food sources as they continue their journey towards complete recovery.
The inclusion of grizzly bears on the endangered species list has sparked debates over their delisting for hunting, with some arguing that they have sufficiently recovered, while others believe they still face threats. Understanding their food sources remains critical to their future, with the army cutworm moth being a significant part of their diet.
As the army cutworm moth’s fate intertwines with that of the grizzlies, it is crucial to address human activities that disrupt their feeding patterns. Additionally, efforts to combat climate change and protect the moths’ habitats are necessary to secure the long-term survival of both these remarkable creatures.