Wildlife Can Benefit From Well-Designed Fish Passage Structures


California Essential Habitat Connectivity Project (.pdf)


Caltrans integrates both fish and wildlife considerations into the design of their state highway structures to improve habitat connectivity for native fish and wildlife species. Crossing features, such as animal detection and driver warning systems, undercrossings provided by span bridges, overpasses that create land bridges, and wildlife exclusion and lateral escape measures, greatly enhance wildlife connectivity and survivability along the state highway system. Best practices for multi-purpose design include early coordination with stakeholders, assessing existing water conveyance features, incorporating maintenance measures to keep passageways clear and unobstructed, and making smart use of fencing to ensure additional barriers to movement are not created. The result of sound planning, design and implementation is a suite of aquatic and terrestrial species that benefit from connected ecosystems, and safer drivers that have fewer wildlife-vehicle encounters.


wildlife in fish passage wildlife in fish passage
wildlife in fish passage wildlife in fish passage
These photos capture a variety of terrestrial wildlife using dry culverts along Hwy 89 in Sierra County during different times of year.

Arch-Style road Crossing Structure from Relative Movement Rates of Large Mammals
by A.Z. Andis, M.P. Huijser, and L. Broberg. 2017. Frontiers in Ecology and Evolution. (5):1-13
ABSTRACT - In recent decades, an increasing number of highway construction and reconstruction projects have included mitigation measures aimed at reducing wildlife-vehicle collisions and maintaining habitat connectivity for wildlife. The most effective and robust measures include wildlife fences combined with wildlife underpasses and overpasses. The 39 wildlife crossing structures included along a 90 km stretch of US Highway 93 on the Flathead Indian Reservation in western Montana represent one of the most extensive of such projects. We measured movements of large mammal species at 15 elliptical arch-style wildlife underpasses and adjacent habitat between April and November 2015. We investigated if the movements of large mammals through the underpasses were similar to large mammal movements in the adjacent habitat. Across all structures, large mammals (all species combined) were more likely to move through the structures than pass at a random location in the surrounding habitat. At the species level, white-tailed deer (Odocoileus virginianus) and mule deer (O. hemionus) used the underpasses significantly more than could be expected based on their movement through the surrounding habitat. However, carnivorous species such as, black bear (Ursus americanus) and coyote (Canis latrans) moved through the underpasses in similar numbers compared to the surrounding habitat.
For a copy of the complete article, click here.

Caltrans Wildlife Connectivity Opportunity Areas and Fish Passage
Click on the map or here for a high resolution .pdf of the Caltrans Wildlife Connectivity Opportunity Areas Map
Desert Tortoise Front Desert Tortoise back