Shorter days and cooler nights mean Grand Teton’s wildlife are preparing for the long winter ahead. Many of
the animals have already begun their migrations to warmer climates, but because of the mild weather they are pausing along their migration paths to continue foraging at lower elevations in the park.
• Pronghorn generally migrate out of the Jackson Hole valley to the Upper Green River basin near Pinedale. Usually numbering 300-400 animals in the herd, nearly all pronghorn leave the valley in winter; although in some years, small numbers have remained on or near the National Elk Refuge. Park biologists are seeing increased numbers of pronghorn this fall—an encouraging sign that the herd is recovering from the 2022–2023 winter die-off due to a combination of disease and harsh weather. A minimum of 83 animals were counted in August on the park and refuge, indicating a slow but positive increase from last year.
• Elk will begin migrating as November temperatures cool and snow accumulates in the high country.
• Moose have started concentrating in the sagebrush/grassland areas at the south end of the park. They seek bitterbrush and other foods in these areas that provide fall nutrition.
• Park mule deer are migrating to distant wintering areas. Those that winter near Cody in the north and south forks of the Shoshone River began their migrations in early to mid-October, while those that winter in Idaho, near Dubois, or near the town of Jackson, migrate later in October or early in November. Mule deer coats have now turned from summer tawny brown to an elegant winter grey, one of the more visible examples of seasonal pelage changes in temperate climate ungulates.
• Bear sightings within the park's frontcountry increased early in the fall as bears entered hyperphagia, consuming as many calories as possible in preparation for winter hibernation. Bear activity within the Moose-Wilson corridor was significantly different this fall due to the widespread failure of the hawthorn berry crop. It is unclear why hawthorn berry production was poor—possibly due to the late freeze in June or summer drought conditions. Black bears congregated briefly within the corridor before moving on to other areas. Grizzly bears are occasionally sighted in northern areas of Grand Teton as they forage on available natural foods. As October comes to an end, bears are beginning to enter their winter dens. A trend that will continue into early December as snow begins to accumulate and natural foods become inaccessible. With bears focused on bulking up for their winter slumber, park visitors and locals can help protect bears by ensuring attractants are properly secured so that bears aren't tempted to linger around developed areas or become conditioned to human foods.
• Rough-legged hawks, long-distance migrants who spend their summers in the Arctic, usually arrive during November.
• The woods are notably quiet, as most migratory birds have left the valley for their wintering grounds. Gray jays, Clark’s nutcrackers, chickadees, ravens, great horned owls, bald eagles, pine grosbeaks, goldeneyes, and trumpeter swans are a few of the prominent birds that remain here year-round.
• Six bat species were common and widespread in the valley, including little brown, big brown, hoary, silver-haired, long-legged, and long-eared bats. Bat activity plummeted in mid-September, but a month later long-legged and silver-haired bats were still common, at much reduced levels.
• Native mountain whitefish have just recently begun to spawn in many of the park’s lakes and streams, while fall spawning among non-native brook, brown, and lake trout is about finished for the year. The mild temperatures this fall have been favorable for cold-water fish. As water levels in many streams and rivers approach basal flows, larger fish seek deeper pools of water to wait out the winter months, often migrating downstream. Researchers are studying how the management of water releases from Jackson Lake Dam impacts the Snake River's fishery.
Wildlife watching is a treat this time of year as animals are often found congregating in and/or moving through lower elevations. Remember to always keep a safe distance and respect our wild animals—if you notice that your presence is causing an animal to change its behavior, stop feeding, or even flee you are too close. On roadways in and out of the park—please be alert, reduce your speed, and watch for wildlife crossing, especially at night and in low light.