Sunday, December 30, 2012

Bighorn Sheep or Mountain Goat?- Yellowstone Reflections

Bighorn sheep climbing slopes high above the historic Roosevelt Arch of Yellowstone National Park
We saw a group of female and juvenile bighorn sheep browsing on the steep slopes above the Gardiner River canyon near the North Entrance to Yellowstone National Park. Bighorn sheep, especially females with young, prefer steep, open slopes where their nimbleness gives them the advantage to escape predators.

Still, they are cautious. As the group of approximately 15 ewes and lambs moved across the slope, the first adult would check over the edge.

Bighorn sheep ewe checking on the other side of a ridge.
And then the others would follow in a ragged line. If the other side was clear, it was okay to rest.

Lambs often followed the same path as the ewe.
Of the bighorn sheep we saw, most ewes had only one lamb.

On this warm day, lambs often reclined on the shady side of the ewe.
Some older juveniles practiced butting heads.

Bighorn sheep juveniles practicing head butting. Despite feet in the air, neither sheep was pushed very far.
One gray-colored ewe looked older and appeared to push the resting bighorn sheep forward.

Although steep slopes have their advantages regarding protection, vegetation can provide sparse browsing.
We also saw mountain goats on Barronette Peak near the Northeast Entrance to Yellowstone National Park but they were too far away to photograph. At first it was hard to distinguish the mountain goats from the high patches of snow, but if you watched closely enough, you could see the white patch move and then by carefully memorizing the distinct cuts and ledges in the rocky slope at that location, you could find the same spot in your binoculars, and it would take shape as a four-legged creature. It was a bit of a challenge, but I leaned my binocs on the top of the car and then it was easier to be patient watching the goats browse and appear and disappear among the sparse alpine shrubbery.

Fishermen stopped to see what we were looking at. As we described the mountain goats far up on the slope, at first they were disbelieving, then disinterested. They preferred the challenge of finding a fishing hole which wasn't already occupied by another fisherman and, at least for a little while, holding an elusive cutthroat trout in their own hands. In Yellowstone, fishermen are required to return native fish (including cutthroat trout, Arctic grayling and mountain whitefish) to the water immediately, but the nonnative brook, brown, lake and rainbow trout can be harvested, indeed in some cases, their removal from the water is required if a fisherman gets them on hook.

Fishing in Yellowstone National Park seems like a complicated sport. I preferred the sport of leaning on the car to watch mountain goats in binoculars. Mountain goats, originally introduced to surrounding mountain ranges for hunting purposes, moved into Yellowstone National Park probably sometime in the 1990s. In 2010, approximately 178 mountain goats were estimated to occupy alpine areas in the park. Research is being conducted to determine if they are competing with the native bighorn sheep or harming rare native alpine plants (Heinz).

The biologists who work in Yellowstone National Park have to make tough management decisions about native versus nonnative species, control of ecological forces like wildfires, and public recreation. I was feeling lucky that as a California park biologist, I only had to control invasive thistles in coastal grasslands or nonnative bullfrogs in ponds. So for the time being, I was going to stay on vacation and enjoy watching both the bighorn sheep and the mountain goats.

This is part of a series of posts on wildlife observed in Yellowstone National Park in September 2012. To see more posts, select "Yellowstone" in the Sightings box in the right column.

Bighorn sheep, Ovis canadensis
Mountain goat, Oreamnos americanus

Ranger George Heinz, Mountain Goats in Yellowstone, Episode 6, video on NPS website, May 15, 2012.

1 comment:

  1. Still trying to get a post out everyday for ten days during the holiday season. Which means sometimes I am writing late at night after all the relatives and guests have gone to bed. It is fun but I am making some errors. Thanks to you-know-who for catching the mistakes and gentle corrections. Last night when I posted this, I had some of the photos mislabeled. They are corrected now. The bighorn sheep are sheep and the mountain goats are goats.


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