Because the beaver isn't just an animal; it's an ecosystem!

The Martinez Beavers

The real sign of the beaver!

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Beavers create scent mounds which act as sentinels and sign posts, alerting beaver passersby that the nearby pond is occupied. (Mary Holland photograph)
Beavers create scent mounds which act as sentinels and sign posts, alerting beaver passersby that the nearby pond is occupied. (Mary Holland photograph)

Naturally Curious: Scented Signposts

Mary Holland

When they disperse, most young beavers go downstream to look for unoccupied territory. Ideally they come upon an old, abandoned beaver pond that has regrown a good supply of aspens, willows and birches — a beaver’s preferred diet. However, young beavers are rarely that lucky. It’s not beyond the realm of possibility for these young upstarts to attempt to move into an inhabited pond site, so resident beavers take measures to alertthese youngsters that the pond is spoken for.

In an attempt to discourage young beavers from lingering, one of the first things adult beavers do in the spring is to mark the perimeter of their territory. They do so by gathering mud and leaves from the bottom of their pond and making piles, or “scent mounds” to advertise their presence as well as ownership to any beavers passing by. They deposit castoreum, a secretion that conveys information such as the beaver’s age and sex, on each mound by straddling it, everting their castoreum sacs and dragging them across the mound. Scent mounds vary in size, from a height of just a few inches, to three feet or so and they are usually located within two feet from the water’s edge. The pheromones in the castoreum are broadcast far and wide from these mounds. An encroaching 2-year-old beaver detects the odor, and, if it is smart, continues on its way. If a stray male beaver deposits some of his own scent on a resident’s scent mound, or stops to feed, the resident male drives him off by hissing loudly, and if that doesn’t work, he attacks the interloper.

This is a nice article about a little appreciated beaver behavior that really only gets talked about at all if we’re complaining that castoreum is used in strawberry flavoring, or some such nonsense. Scent marking is essential to beaver survival and indirectly lead to the success of the fur trade – since even once metal traps were invented, trappers had no idea what to bait them with, until someone accidentally tried castoreum! Wham! Instant beaver!

We have been avidly looking for scent mounds in Martinez, but never spotted any. We’ve even asked visiting beaver experts to hunt them down with no avail. Where ever our beavers are marking their territory, we it’s a secret we haven’t yet uncovered. Mary’s article is on the Valley news site and definitely worth a read, but the paper has an impolite subscription policy that might not let you come back so just between us shhh.


Late-breaking news: our friend Malcom Kenton of Washington D.C. was inspired enough by beavers to write his own ballad and he’s looking for a musician! Here’s a taste but you really should go read the rest of it!

Many of fur and fin and feather all would gather ’round
Where pools of still, deep water were plenty to be found,
Made by a flat-tailed engineer whose works helped shape the land.
The beaver, steward of the continent’s streams, made ponds and wetlands so grand.

Inspired yet? Cheryl took this photo last night of some hard working-stewardship happening at the secondary dam!

Beaver Mudding: Cheryl Reynolds