They’re hard-working, tail-slapping, tree-cutting machines, and they’re one of the greatest wildlife recovery stories in North America: Castor canadensis, the North American beaver. And, as if all that weren’t enough, apparently their rear ends produce an oil that’s vanilla-scented. Join the guys as they keep their puns and innuendos in check and dive into beavers!

This episode was recorded on January 28, 2023 at the Beaver Meadow Audubon Center in North Java, NY.  

Episode Notes

Beaver anal glands – which gland is used for which? There was some confusion over the beaver’s anal glands and the oils they produce. Some sources stated that beavers have two anal glands that produce oil for waterproofing - the oil that smells like motor oil in male beavers and rancid cheese in females) and two more glands that produce oil (castoreum) for marking their scent mounds. Some sources, however, said the waterproofing oil was also used for scent marking. So, what gives?

With a little more research, Bill discovered that he misspoke during the episode. Beavers have two anal glands that produce the waterproofing oil, and two castor sacs (not glands, although they’re often referred to as such) that produce castoreum, the oil used for scent-marking. All four structures are located near each other, between the pelvis and the base of the tail.

Here’s a paper that explains it all. Click the “pdf viewer” tab for a format that is easier to read.

Steve recalled hearing how parts of whales were used in perfume production. He was right! “Ambergris [is] a solid waxy substance originating in the intestine of the sperm whale (Physeter catodon). In Eastern cultures ambergris is used for medicines and potions and as a spice; in the West it was used to stabilize the scent of fine perfumes.” From Britannica.com

When discussing the study that looked at how beaver dams fare during floods, Bill cited that, in one study, 70% of beaver dams remained intact during a flood event. Steve then pointed out that 30% of the dams failing seemed to lend at least some credence to the anecdotal records of beaver dams being unreliable at mitigating flood impacts. If Bill was a quicker thinker, he would have realized that he had JUST SAID that even though 30% of the dams in the study did not remain completely intact, the researchers found that many of them still helped reduce flood impacts downstream.

Do wetlands have lower biomass? Steve mentioned he thought this was true, but, after the episode, Bill did a search of general and academic sources and could not find a definitive answer. He was, however, rushing a bit, trying to get this episode released. If you find a source with a concrete answer to this question and send it in (thefieldguides@gmail.com), the guys would definitely give you a shout-out on a future episode!

Links

The Conversation: This is the website Bill mentioned that publishes science articles for the general public, written by academics and researchers.

The world’s largest beaver dam - 58.2722° N, 112.2521° W

A collection of Gerry Rising’s nature columns from the Buffalo News (1991-2015). More recently, he wrote for Buffalo Spree, and those articles can be found here.

Check out the Outside Chronicles website. You can also follow them on Facebook, YouTube, and Instagram.

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Works Cited

Aleksiuk, M., 1970. The function of the tail as a fat storage depot in the beaver (Castor canadensis). Journal of Mammalogy, 51(1), pp.145-148.

Lancia, R.A., Dodge, W.E. and Larson, J.S., 1982. Winter activity patterns of two radio-marked beaver colonies. Journal of Mammalogy, 63(4), pp.598-606.

Larsen, A., Larsen, J.R. and Lane, S.N., 2021. Dam builders and their works: Beaver influences on the structure and function of river corridor hydrology, geomorphology, biogeochemistry and ecosystems. Earth-Science Reviews, 218, p.103623.

Lazar, J.G., Addy, K., Gold, A.J., Groffman, P.M., McKinney, R.A. and Kellogg, D.Q., 2015. Beaver ponds: resurgent nitrogen sinks for rural watersheds in the northeastern United States. Journal of environmental quality, 44(5), pp.1684-1693.

Stephenson, A.B., 1969. Temperatures within a beaver lodge in winter. Journal of Mammalogy, 50(1), pp.134-136.

Tape, K.D., Clark, J.A., Jones, B.M., Kantner, S., Gaglioti, B.V., Grosse, G. and Nitze, I., 2022. Expanding beaver pond distribution in Arctic Alaska, 1949 to 2019. Scientific Reports, 12(1), pp.1-9.

Westbrook, C.J., Ronnquist, A. and Bedard‐Haughn, A., 2020. Hydrological functioning of a beaver dam sequence and regional dam persistence during an extreme rainstorm. Hydrological Processes, 34(18), pp.3726-3737.