September marks a season of transition for Grand Teton’s wildlife. Many ungulates (hoofed animals) are mating, birds are leaving territories for fall migrations, and all animals are preparing for the winter.
● By late September, elk, moose, and pronghorn are still breeding but their rut is winding down. Bighorn sheep and mule deer won’t begin breeding until November. September is the ideal time to listen to elk bugling on crisp mornings just before dawn or quiet evenings before dusk. Bull elk use bugling to communicate a variety of things: a single bugle calls cows back to his harem if they stray; a scream bugle warns rival bulls he will defend his harem; and the bull-to-bull scream bugle asserts dominance, often scaring off a subordinate bull before physical conflict.
● Forests, meadows, and shrublands are quieter as birds abandon breeding territories and migrate to distant wintering grounds. Songbirds depart instinctively before harsh weather starts. Canada geese differ: they gather into larger flocks, gorge on grain (grass seeds), and wait for cold weather, frozen water, and food to become scarce. Young geese learn migration routes from their parents and other adults. As heavy-bodied birds that use strong wingbeats to fly fast, over 30 mph. They avoid headwinds by flying at night when it is calmer or with a tailwind during the day. Their V formation conserves energy. It is a form of drafting that helps pull the trailing bird forward and provides lift. Mature adults take turns leading the point, shifting as they tire and allowing younger, less strong geese the advantage of flying behind.
● Pikas, small relatives of rabbits, do not hibernate. Instead, they prepare for the long winter by gathering and storing plant materials. By September, their drying piles of vegetation—called haystacks—become visible, tucked into crevices or beneath overhangs on talus slopes near their dens. Pikas are highly selective in what they collect, favoring plants with high nutritional content. Some chosen plants also contain antimicrobial compounds that help prevent the haystacks from rotting. While these plants may be poisonous when gathered, their toxins break down as they dry, making them safe to eat in winter.
● Black bears and grizzly bears are entering a phase known as “hyperphagia,” which literally means “over-eating.” Many will forage on whitebark pinecone seeds beginning in August and will continue seeking them out until the end of September. The large seeds, or nuts, of whitebark pine are a high-energy food rich in fats, carbohydrates, and protein, making them an important food source for bears building fat reserves in preparation for winter denning. Obtaining seeds is challenging for ground dwellers as whitebark pinecones do not split open to scatter seeds when they mature. Most bears seek out seeds harvested and stored on the ground by red squirrels. Bears will also access cones by pulling down branches (grizzly bears) or by climbing the trees (black and some grizzly bears). Hikers should be particularly watchful for bears and exercise caution in the whitebark pine zone this time of year—around 8,500 to 10,000 feet elevation in the Tetons.
● Wolf pups will now travel with their packs on foraging trips, having graduated from waiting at rendezvous sites in August or early September. They are getting to know their territories in the process.
● Native mountain whitefish and non-native lake, brook, and brown trout are moving to natal habitats to begin fall spawning activities. Water levels will drop as fall progresses into winter and as flows recedes large fish seek winter refuge. Cutthroat trout often move downstream to deeper pools.
