Moose are one of the most popular species in Jackson Hole, but despite our love of moose, their numbers have declined in the last 25 years. Moose prefer habitat near streams and ponds as they primarily eat willows in winter and aquatic plants in summer. They move from low elevation riparian shrub and aspen habitats in winter along regular migration routes to higher, cooler elevations with similar features in summer. They experience heat stress at temperatures above 57 F in summer and 23 F in winter. Exposure to heat stress has been linked to decreased body condition; this may be one of the reasons that moose have declined.
Moose have been in the Jackson Hole area for less than 150 years, arriving in the late 19th century, possibly arriving concurrently with settlers from the East.
From 1950 to the early 1990s, the Jackson moose population grew from roughly 600 to 3000-5000. Since then, the population has dropped significantly due to a variety of factors, including climate change, over-browsing, and the reduction of food due to wildfires. The current population is estimated to be about 500.
Carotid artery worms, spread through horseflies that also benefit from warmer conditions, substantially reduce blood flow to the brains of the moose they infect. This can cause blindness, difficulty eating, and nervous system damage. A survey in the 1970s found zero prevalence of carotid artery worm, whereas a 2009 survey found that nearly 50% of moose were infected.
Vehicles, especially around the Moose Wilson Road and Hwy 22 junction, are a source of moose mortality. Even though the total number is relatively small compared to other ungulate species, every death is consequential for this declining population.
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