River otters need permanent, fish-rich water year-round, and Yellowstone National Park’s rivers and lakes carry 63 of Wyoming’s 193 records, by far the strongest concentration, with Grand Teton and Bridger-Teton National Forest extending the pattern across the same Yellowstone-Teton headwater system.
Records build through summer to a September peak, more than nine times the April low, a pattern that likely tracks otters ranging more widely as fish move and increased visibility on open water before ice-up. NatureServe ranks the species S3, vulnerable, in Wyoming, a more cautious state-level read than its secure global status, and its playful, highly social behavior makes it one of the more distinctive waterway mammals to spot when conditions line up.
