Mendocino Land Trust

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Point Arena Mountain Beaver

What is a Mountain Beaver?
The curious Point Arena Mountain Beaver (Aplondontia rufa nigra) has a very misleading name. Affectionately known as PAMB, they are neither true aquatic beavers, nor do they live in craggy mountainous areas. Instead, this elusive creature is found above creek banks as well as in wet sand dunes near the City of Point Arena on the Mendocino Coast, so long as you know where to look with a keen eye.
So what exactly is a Mountain Beaver? Also known as 'Boomers,' Mountain Beavers are rodents about one foot long, weighing 2-4 pounds. They are not aquatic like true beavers, but rather spend most of their lives in elaborate underground burrows. Both types of beavers have small eyes and round ears, but instead of webbed feet, PAMB have long claws for digging and a stump for a tail rather than a paddle.
Protecting an Endangered Species
As a federally-listed endangered species, it is part of our mission to protect and conserve the Point Arena Mountain Beaver and its habitat. We were recently very excited to discover an active PAMB burrow at our Pelican Bluffs Preserve, providing us with an opportunity to play a pivotal role in endangered species habitat conservation. In fact, one of the greatest threats to PAMB is habitat loss due to development and grazing. By setting aside wild places where these animals can thrive, we preserve the unique biodiversity of the Mendocino Coast.
It is hard to know what role a species fulfills in its ecosystem until they are removed, at which point it is too late. The beavers are a food source for predators, they bring their forage down into their burrows which adds complexity to the soil, and the burrows themselves are deep an conveluted, allowing these creatures to spend most of their lives underground. There is still so much to learn about them and the role they play, so it is important to protect them before it's too late.
Restoring the True Beaver 
The other beaver, the North American or "true beaver," although not endangered is a keystone species. When it is not in the environment, many other animals and plants may cease to exist. Although currently rare in Mendocino County, it is thought that the aquatic North American Beaver were once plentiful here and helped shape the environment through their dams, which raise the water table and create abundant wetlands. They were almost hunted to extiction for their pelts in the 1800's, and they were only saved by the fact that the demand for 'beaver hats' had fallen out of fashion.

Over the past several years of drought, we must wonder how different the landscape might look if aquatic beavers were still abundant. Beavers add complexity to a stream, including ponds and marshes that provide habitat for salmon and other species. This beaver-created habitat may be particularly important to coho salmon (Oncorhynchus Kisutch), as the loss of beaver ponds and their ability to nurture juvenile salmon may have contributed to the reduction of our local coho population to near extinction.

One day, we might reintroduce the North American Beaver to the Northern California coast in degraded legacy forest lands. In time, they might restore river and stream habitats to a more natural state, and by doing so, help recover endangered coho salmon- perfectly illustrating how we don't always understand the role a single species plays in their ecosystem, until they are gone.

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