Researchers Complete First Season of Point Reyes Mountain Beaver Habitat Surveys

By Science Communication Specialist Jessica Weinberg McClosky and Wildlife Biologist Taylor Ellis, San Francisco Bay Area Inventory & Monitoring Network

Wildlife Biologists Taylor Ellis (pictured) and Matt Lau just completed their first season of surveys as a part of a 2-year mountain beaver habitat modeling project in collaboration with UC Berkeley.

NPS / MATT LAU

March 2023 - The Point Reyes mountain beaver—a primitive rodent that isn’t a beaver—is a sort of mythical creature at Point Reyes National Seashore. Almost no one has seen one in-person with their own eyes. Not even National Park Service Wildlife Biologists Taylor Ellis and Matt Lau, who just completed their first season of surveys as a part of a 2-year mountain beaver habitat modeling project in collaboration with UC Berkeley. Still, the survey season was a great success.

Mountain beavers frequently leave clippings of fresh herbs at the entrances to their burrows, signaling to biologists that this burrow is occupied.

NPS / TAYLOR ELLIS

With the Point Reyes mountain beavers (Aplodontia rufa phaea) being so elusive, Ellis and Lau surveyed for something slightly easier to find: mountain beaver burrows. They searched random plots throughout forested areas of the park and in ranch lands north to Tomales Point (excluding the outer point). With lots of steep slopes and dense vegetation, it was difficult, painstaking work. But surveying in the winter when some vegetation has died back allowed them to more easily see the ground to identify burrow entrances.

These surveys are the first of note for Point Reyes mountain beavers since the 1990s, and much broader in scope. Already they're significantly improving our understanding of the species' distribution. For example, Ellis and Lau are finding disparate areas—like shady drainages with abundant coffeeberry, sword fern, and blackberry—that have large mountain beaver colonies. Data about which subplots do/do not have burrows will be fed into a complex habitat model to predict the likelihood of mountain beaver presence throughout the park.

Point Reyes mountain beavers are vulnerable due to their limited range—they exist almost exclusively in the Seashore—and their constant need for water. Climate change, and more frequent drought and wildfire, is likely exacerbating those vulnerabilities. But with a new, clear picture of their habitat, the park will be much better equipped to protect them.

Staff at UC Berkeley will be able to test-run the habitat model soon with the first season's data. Next winter, surveys will resume for a final season of data collection before the model is finalized. In the meantime, Ellis and Lau are hoping to get some good photos of the mysterious mountain beavers from camera traps placed around some of the burrows they've found!

For more information

• Point Reyes National Seashore mountain beaver webpage
• Contact Wildlife Biologists Taylor Ellis or Matt Lau

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