Leave It to Beavers – PBS (2014)

There are two species of beavers in the temperate zones of the world. North American (Castor canadensis) and Eurasian (Castor fiber) beavers were almost exterminated to extinction. These rodents are the largest after the tropical capybara that lives in wetlands of the South American tropics.

Now bouncing back from extinction beaver populations are recovering under protection. Beavers are being recognized as keystone species by ecologists and conservation biologists.

As habitat constructors and brilliant hydro-engineers, beavers can recharge water tables and restore life on damaged lands. Habitat restoration and expansion is important to mitigate negative consequences of global warming and climate change.

Benefits of Beaver Ponds – Leave It to Beavers – PBS (2014) from Nature Documentaries on Vimeo.

Presence and absence of keystone species in a biological community has significant cascading trophic effects. Sea otters in the Pacific coast control sea urchins which prevent kelps from overgrazing and allow them to form impressive underwater forests. Tropical fig trees form abundant food resources for many animals in times when the food resources are scarce. Bluechub fish in Eastern North American rivers construct rock nests which form a critical spawning area for many other fish in the same habitat. Beavers are also like that.

Perhaps the most drastic influence of beavers was observed soon after the re-introduction of wolves in the Yellowstone National Park. Wolves brought about an enormous change in Yellowstone. They reduced browsing and as a consequence there was more vegetation especially along the river banks which in turn resulted in a trophic cascade. Increasing willow abundance along rivers provided food and construction material for beavers. Beaver activity slowed down hydrology and enhanced water retention capacity of the ecosystem. Increased water table invigorates vegetation. At the same time reduced sun exposure of rivers allows cold water adapted fish to thrive. Cold waters in deeper layers of beaver ponds are particularly valuable rearing habitat for fish like Coho salmon.

Unexpected Results – Leave It to Beavers – PBS (2014) from Nature Documentaries on Vimeo.

Beavers’ iron-strengthened incisors are impressive structures. Not only do they help beavers fell the hundreds of trees they need to dam a river, they also come in handy for meals because beavers are vegetarians that gnaw through bark to eat the sugary layer underneath. Beavers also cut and stash willow branches underwater as food storage during winters. This survival strategy resembles to that of squirrels. Like a squirrel, they can swim under ice and recover these young twigs to consume in their lodges.



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