The Henry’s Fork watershed is well documented as the home to significant populations of Grizzly and Black bears, migrating Rocky Mountain Elk, resident Shiras Moose, Pronghorn, Whitetail and Mule deer and to a growing population of Gray Wolves. However, it is also home to lesser-known mammals like River Otters, Long-Tailed Weasels, Northern Flying Squirrels and to no less than eight species of bats that are frequently seen feasting on the rich insect hatches of the Henry’s Fork River in late evening hours.

For more information on the mammals of Henry's Fork, click here.

Birdwatchers from across the world come to watch the feather filled skies of the Greater Yellowstone region with its 318 species of birds. The Henry’s Fork watershed is well noted for its predatory birds that readily feed on its rich fish populations, most notably Osprey, Great Blue Heron, majestic Bald and Golden Eagles, Pelicans, Cormorants and Mergansers. Red-Tailed and Swainson's hawks in addition to the occasional Peregrine falcon can also be seen hunting the more secluded canyon sections of the Teton, Fall and Bechler river drainages.

There are also lesser-seen birds like the Great Gray Owl of the caldera region, the largest North American owl, and Sandhill Cranes with a prehistoric call that pierces the serene silence during spring breeding season. The hundreds of species of ducks, geese, woodpeckers, jays, ravens, songbirds, crows and swallows can all be seen in pristine habitat that is virtually untouched by mankind. The Henry’s Fork Foundation is in place to ensure the grand and fragile ecosystem supporting these species remains the treasure it is today.

For more information on the birds of Henry's Fork, click here.

The Henry’s Fork watershed is home to a rich diversity of plant species. The caldera plateau is dominated by lodgepole pine forests with Engelmann spruce along the streams and stately Douglas fir scattered throughout. The forest is interspersed with lush meadows filled with brilliant wildflowers in summer. Sagebrush steppe habitats are also scattered on the plateau but are the dominant vegetation at the lower elevations. Sagebrush, bitterbrush, juniper, native bunchgrasses, and even prickly-pear cactus typify the sagebrush steppe habitat. The rivers and wetlands support abundant aquatic plant life. In all cases, the Henry’s Fork watershed is a rich and vibrant landscape filled with vegetation which supports a diversity of fish and wildlife.

In the midst of this diverse native plant life, there are also non-native species that threaten the delicate balance and health of the watershed. All HFF members and local communities must work together to stem this major threat. See Protect the River section for what you can do.

For more information on the plants of Henry's Fork, click here

Caldera rim and background

The Henry’s Fork region is a geological young terrain that is caused by volcanic activity, glacial retreat and the unique thermal influences of the Greater Yellowstone Region (which is the largest thermal area in the world). The Yellowstone caldera - a broad, oval depression about 40 by 60 kilometers in size- was formed about 600,000 years ago, at the climax of the last cycle of volcanism. Since that time, voluminous obsidian lava flows have covered much of the caldera floor. Sitting in the midst of this caldera region, Island Park, Idaho is a shallow volcanic caldera, partly filled with lava flows and sediment through which flows the upper reaches of the Henry’s Fork and Buffalo River as well as a large number of lakes and streams.

Mammoth Hot Springs

Today, the Greater Yellowstone region is the most seismically active region of North America, and thousands of earthquakes occur each year. The ground motion is undoubtedly important in maintaining the thermal activity of the region, since deep channels for hot fluids would quickly be sealed with mineral matter if not for the frequent earthquakes. Partly molten rock is believed to exist beneath the Yellowstone caldera at a depth of about 8 kilometers. As a result, the amount of heat flowing from the ground beneath Yellowstone is estimated to account for about 5 percent of the total heat flow from all of North America. This heat energy drives an enormous underground circulation system of hot water and steam, giving rise to the many geysers, hot springs and mud pots for which Yellowstone is famous.

Amongst the rarest of wildlife found in the Henry’s Fork region are the reptiles and amphibians. It is believed that the extraordinary cold and dry conditions limit the ideal habitat for these species.

In fact, only six reptiles are known to exist in the region. Five snakes, the only poisonous one being the Western rattlesnake found in the lower desert regions and frequently observed in the canyon section of the Teton river, and one lizard—the Sagebrush lizard.

A more common sight are the common garter snakes that frequent the Henry’s Fork drainage in general and the Bechler River specifically for the Western terrestrial garter snake. In fact, garter snakes have been observed hunting small trout and minnows, leeches and frogs in the Pinehaven and Box Canyon sections of the Henry’s Fork.

The same conditions that limit reptiles also limit the presence of amphibians. The Henry’s Fork drainage is home to only five amphibians—the Western chorus frog, Northern leopard frog and Spotted frog, Western toad and Tiger salamander.

For more information on the amphibians and reptiles of Henry's Fork, click here

The Henry’s Fork is renowned for its rich aquatic insect life that forms the basis for the claim of “the greatest fly fishing in the world.” The HFF has established standardized sampling sites and repeatable collection protocols in the ranch section of the river. The four years of analyzed data show aquatic insect densities to be about 4,000 individuals per square meter, with about 60 percent of those individuals being mayflies, stoneflies, or caddis.

How abundance and species have changed over the past 50 years is not well known. Anecdotal evidence suggests a decline in the quality of the insect life. This is one of the areas that HFF looks toward as a “canary in the coal mine” warning sign of the overall health of the entire watershed.

Click here for an insect hatch chart.