Dicamptodon aterrimus

Good (1989) examined genetic relationships and concluded that the genus Dicamptodon comprises 4 species: D. ensatus (west-central California), D. aterrimus (Rocky Mountains of Idaho and adjacent Montana; see also Daugherty et al. (1983), D. tenebrosus (southern British Columbia to northern California), and D. copei (Washington and northern Oregon). A previous study of morphological variation (Nussbaum 1976) concluded that Dicamptodon includes only 2 species, copei and ensatus (the latter including aterrimus and tenebrosus).

This species has a limited range in Idaho and a small area in adjacent Montana. There are many occurrences on conservation lands and the population appears stable. Many historical threats have been minimized by adopting more compatible land management practices.

The range includes northern Idaho and a small adjoining portion of extreme western Montana, from the South Fork of the Salmon River to the St. Regis drainage in Montana (Nussbaum et al. 1983, Petranka 1998, Werner et al. 2004, Mullen et al. 2010, Isaak et al. 2025). The elevational range extends to at least 2,135 meters. Range extent is estimated to be 26,605 km² (GBIF 2025, Isaak et al. 2025, RARECAT 2025).

Applying a 5 km separation distance to NatureServe (2025) occurrence records, 79 occurrences are estimated (RARECAT 2025).

The primary threat is loss, degradation, and, particularly, fragmentation of habitat (Fisher 1989, Hossack 1998, Lohman and Bury 2005). Habitat fragmentation interferes with natural metapopulation dynamics (Sepulveda and Lowe 2009, Mullen et al. 2010). Sepulveda and Lowe (2009) found that the probability of occurrence of this species was highest in unfragmented headwater drainages with few roads. They also found that this species was numerous in streams with a high proportion of embedded substrate and fine sediments, indicating that sedimentation is not necessarily a significant threat. Historical placer mining probably negatively affected some populations. This species readily recolonizes disturbed areas as they recover or are restored. Genetic structure of populations suggests that such recolonization is most likely to occur within catchments (Mullen et al. 2010). Many of these threats have been greatly reduced or minimized since the 1980s by the adoption of more sustainable and compatible forestry practices. While the creation of roads was a major historical threat causing habitat fragmentation and degradation, this threat has been minimized. At Nez Perce-Clearwater National Forests, which host over half of the occurrences for this species, 1,625 miles of roads have been decommissioned and 46 miles of new roads have been created to relocate them to less sensitive habitats (USFS 2025). Approximately 67% of riparian areas in Nez Perce-Clearwater National Forests are protected as designated wilderness or protected under the Roadless Rule (USFS 2025). Climate change is a potential threat because habitat could be lost or rendered less suitable as a result of drought or increased temperatures (Hinderer et al. 2024). Logging, while ongoing throughout the range, is generally conducted in a manner to minimize impacts on stream habitat critical to this species (USFS 2025).