Winter 2014-2015

Pantone Beaver

This gland is your gland

Rachel Poliquin

In 1999, Frank Rosell and Lixing Sun uncovered an improbable fact of beaver biology: the animals can be distinguished by the hue and viscosity of their anal scent gland secretions. The discovery was not just chromatically intriguing, but offered an ingenious system for identifying and eradicating invading beavers.

You see, there are not one but two beavers: the Eurasian beaver (Castor fiber) and the North American beaver (Castor canadensis). Separated at least eight million years ago, the two beavers nevertheless remain virtually identical in size, shape, and behavior. Although Heinrich Kuhl declared North American beavers to be a separate species in 1820, and Frédéric Cuvier point out differences in their skulls in 1825, the two beavers were not positively confirmed as distinct species until chromosomal testing in the 1970s discovered Eurasian beavers had forty-eight chromosomes while North American beavers had only forty.

Castor fiber once occupied much of the Eurasian continent from Wales to Mongolia and from Norway to the Turkish coast of the Black Sea. But for millennia, beavers were hunted for their fur and their extraordinarily pungent scent. Pious monks declared their tails to be fish and ate them during Lenten abstinence. By 1900, barely 1,200 Eurasian beavers remained. North American beavers fared only slightly better. From the tens of millions of beavers that once roamed the continent, perhaps 100,000 survived the obliteration resulting from the fur trade. Trappers and naturalists on both continents had long lamented dwindling beaver populations without expending much effort to stop the eradication. In 1836, Canada’s Hudson’s Bay Company established the world’s first beaver sanctuary, and Norway passed Europe’s earliest beaver protection law in 1845, an act which likely saved the Scandinavian population, but most countries were hardly so enlightened. Sweden banned beaver hunting in 1873, two years after Swedish beavers were already extinct.

However, the early twentieth century witnessed rising global conservationist concerns for failing beaver populations. Across North America and Europe, wildlife agents began live-trapping beavers from isolated pockets and relocating them to their former habitats. Between 1901 and 1907, thirty-four beavers were transplanted into the Adirondacks. In 1949, in one of the strangest acts of conservation, the Fish and Game Department of Idaho air-dropped seventy-six beavers in crates equipped with parachutes into beaver-bereft parts of the state.

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