Wednesday, December 26, 2012

Pronghorn Antelope - Yellowstone Reflections

Pronghorn antelope in Lamar Valley of Yellowstone National Park
Lamar Valley is a wide river plain of glacier-strewn sediments and grasses, so Lamar Valley is a land of herds and grazing animals, pronghorn antelopes and bison, flocks of sandhill cranes and Canada geese.

From the distance in September in Yellowstone National Park, I enjoyed spotting the white rumps of the pronghorn antelopes in the wide vistas of Lamar Valley. First I would see one white rump in the binoculars and then check for the oddly-shaped horns, head in profile and chest; then I would spot another white-rumped pronghorn; then many, even without the binocs.

Pronghorns usually rut (breed) from mid-September to early October, but we noticed some pronghorns in early September in Lamar Valley positioning themselves for rut-season success. We watched a large pronghorn male push his harem of females and juveniles along the river, therefore, he had one less side from which to deflect the advances of other males.

The smaller single male in the above photo may be looking for an opportunity to participate in the rut, but Feldhamer et al. says, "Males make serious attempts to breed starting at age 3 years and continue annually until death. However, roughly one half of the males in any cohort never breed." That's some tough statistics.

Once in hot summer when I was traveling around the rural northern side of the Great Salt Lake in Utah, I noticed a pronghorn antelope standing in the shadow of a telephone pole along the road. A few telephone poles further, I noticed another pronghorn standing in another long, narrow shadow, and then another pronghorn and another lined up in the pole shadows. Finally, I had to stop to see if my speeding eyes were deceiving me. As I got out of the car, the pronghorn dashed away from its shadow and was quickly joined by another medium sized pronghorn and then a smaller one from adjacent telephone pole shadows.

Pronghorn antelopes are much faster than other animals in the Rocky Mountains, and during the rut, the males may kill each other. These two traits are much different than the black-tail deer I observe in coastal California as the primary (only?) grazing wildlife animal, and I continue to ponder how these traits might help the pronghorns in creating their own unique ecological niche, and why the black-tail deer survive as more generalists.

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.

Pronghorn antelope, Antilocapra americana

Wild Mammals of North America: Biology, Management, and Conservation. George A. Feldhamer, Bruce C. Thompson, Joseph A. Chapman, editors. 2nd edition. John Hopkins University Press. 2003.

1 comment:

  1. The Lion Hunter provided some clarification about herd animals which pronghorn antelope and mule/blacktail deer really are NOT. I will be fixing that info tonight but some really interesting additional reflections on grazing ungulates and their niches and responses to predators. So cool having my own expert wildlife biologist touring national parks with me and then teaching me more as I sort through the observations.


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