Threatened Alameda Whipsnake More Flexible in Habitat Use Than Previously Thought

A 1.3 m long Alameda Whipsnake (Masticophis lateralis euyxanthus) in a blue oak (Quercus douglasii) on Mt. Wanda, John Muir Historic Site, Martinez, California, in 2018.

Mt. View Sanitary District / Kelly A. Davidson

August 2021 - When a species is threatened, it’s important to know what kind of habitat it uses. What kind of plants support its prey species? What kind of physical structure does it use for shelter from predators? The answers to these questions become critical when land managers are deciding whether to maintain or restore certain habitats.

The threatened Alameda whipsnake (Masticophis lateralis euryxanthus) is generally thought to prefer habitat with chaparral or scrub plant communities. So when park scientists found Alameda whipsnakes in unexpected places at John Muir National Historic site, they realized that the snake may be using a broader range of habitats than previously thought. Their results could have significant implications for habitat management not only at John Muir, but across the entire known range for the Alameda whipsnake.

General habitat types and locations of trapping arrays for reptiles, including the Alameda Whipsnake (Masticophis lateralis euryxanthus) in 2018 at Mt. Wanda, John Muir Historic Site, Martinez, California.

NPS

While conducting catch and release reptile surveys at John Muir’s Mt. Wanda in 2018, researchers captured nine Alameda whipsnakes (35% of all captured whipsnakes) at a historic olive orchard. They also captured 16 Alameda whipsnakes (65% of all captured whipsnakes) in the transitional zone between small patches of coastal sagebrush scrub and blue oak (Quercus douglasii) woodlands.

Researchers suspect that the physical structure of habitat vegetation may be more important in determining whether an area will be suitable for the snakes than the actual species of plants in that habitat. Apart from the atypical vegetation type, the olive orchard on the Mt. Wanda site seemed to be suitable for the snakes. It had food available (i.e., three lizard species), basking sites (olive tree canopy), shelter sites (woody understory and low-lying shrubs) and seasonal retreat sites (rodent burrows). The olive orchard may provide similar physical structure to oak woodlands habitats. Alternatively, the snakes may be more flexible with the kind of habitat they can use than we thought they were.

Photo of the historic olive (Olea sp.) orchard at Mt. Wanda that was used by several Alameda Whipsnakes (Masticophis lateralis euyxanthus) in 2018.

NPS / Angel Sprague

The capture of Alameda whipsnakes in the extremely small patches of coastal scrub habitat surrounded by blue oak woodlands suggest that the snakes may be more capable of using smaller patches of scrub habitat than previously thought.They may be relying on surrounding oak woodland habitat for foraging or basking opportunities.

The results of this study suggest that any vegetation type structurally similar to chaparral, including orchards, ornamental gardens, and residential landscapes, may also provide suitable habitat for this threatened snake. The researchers hope that their findings will also help land managers prioritize protecting habitats next to chaparral and scrub. This broader understanding of how Alameda whipsnakes use habitat may prove critical for conserving this threatened species.

• Read the full publication: Alvarez, J., Davidson, K. A., Villalba, F., Amador, D., Sprague, A. 2021. Atypical habitat use by the threatened Alameda whipsnake in the eastern Bay Area of California. Western Wildlife 8:8–12.

• Questions? Contact John Muir Biological Science Technician Angel Sprague or Natural Resources Program Manager Tori Seher