(Editor's Note: This year Yellowstone National Park celebrates its 150th Birthday. In honor of that historic milestone we're bringing you a new series called "Yellowstone Revealed." These reports will offer a glimpse into the park's colorful history and stories that you've likely never heard before. The third installment - "Swans and Fish" - explores the delicate relationships among some of the wildlife in the world's first National Park.)
YELLOWSTONE NATIONAL PARK - What does gill netting for lake trout have to do with Trumpeter Swans? The answer is our country’s national bird: The Bald Eagle.
When Europeans first came to America, Trumpeter Swans, native water foul with eight-foot wingspans, lived all over the continent. Now a population of hundreds of trumpeters winter on two lakes in northern Arkansas. State biologists say they probably come south from Iowa, not Yellowstone.
Now there are around 63,000 Trumper Swans in the lower 48 states. But America’s swans were almost wiped out of the lower 48 by hunting and habitat loss by 1930. At that time only 70 swans survived in Yellowstone.
Now, park biologists have observed a new threat to Yellowstone swans: a newcomer to Yellowstone Lake.
Non-native Lake Trout were discovered in Yellowstone Lake in the mid-nineties. The voracious deep-water predators ate the native cutthroat trout, cutting their populations by an estimated 90% in tributaries to Yellowstone Lake.
So park management started gill netting lake trout and have so far killed almost four million of the non-native fish. But the cutthroat populations, while growing, are still depressed and animals that eat cutthroat, like grizzlies and bald eagles, are affected.
Yellowstone Park Senior Wildlife Biologist Doug Smith said in 2016: “Bald eagles have very much changed their feeding habits due to the loss of cutthroat. But they also take loon chicks and swan cygnets, and we don’t have a lot of those to spare.”
Anglers catch and kill as many lake trout as they can, while the gill netting continues to dent the predator population. Smith hopes the cutthroat populations revive to feed bears, osprey, and bald eagles.
But what’s ahead for the swans?
In 2019, biologists counted only 27 resident trumpeter swans in Yellowstone.
The 2022 Yellowstone Resources and Issues handbook says decades of drought and warmer weather are drying up the wetlands where swans would previously breed. While more swans migrate down to the park during the winter, the Trumpeter Swans are a species of concern in Yellowstone.