Grey squirrels: is birth control the solution to Britain’s invasive species problem?

J. Gilchrist,  The Conversation,  2021.

There are thought to be 2.7 million grey squirrels in the UK, versus only 287,000 red squirrels. The invasive greys, brought to Britain and Ireland from North America in the 1870s, are blamed for the disappearance of the native red throughout much of England and Wales, due to the squirrel pox virus they transmit and the fact that they compete for food and habitat with their smaller relatives. As with the UK’s other invasive species, such as rabbits, signal crayfish and Japanese knotweed, introducing the grey squirrel has proved to be an expensive mistake. Not only do grey squirrels displace red squirrels, they strip bark from trees. A recent report estimated that this could cost commercial forestry and native woodlands £1.1 billion (US$1.5 billion) over the next 40 years, including revenue lost to damaged timber, reduced carbon storage, tree replacement costs and squirrel control. Despite efforts to kill grey squirrels over several decades, their populations remain large and widespread. So could government-backed plans for using oral contraceptives to control their breeding be the turning point?

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