www.nature.com/nsu/020204/020204-5.html
The greys' pilfering of their fellow animals' food stores could have fuelled their rise and red squirrels' concomitant demise. In Britain, North American grey squirrels (Sciurus carolinensis) have all but replaced the native European reds (S. In Italy things are heading the same way: greys have been thriving since 1948, when a politician brought four back from America. A preliminary study showed that the parapoxvirus, known to kill red squirrels in the United Kingdom, is not present in Italy. So behavioural ecologists at the University of Insubria in Varese, Italy, investigated other possible mechanisms, such as aggression or competition for food or habitat. The scientists saw grey squirrels stealing from reds' seed hoards. Indeed when greys' home territory overlaps reds', reds recoup only two-thirds of their nut caches and subsequently lose weight during the winter. Reds rely on stashed food for 50% of their winter energy needs 18 ^1. This is potentially a very elegant explanation of the replacement of reds by greys Steven Rushton, University of Newcastle upon Tyne For females in particular, wasting in winter damages their chances of breeding in spring, says Luc Wauters of the Insubria team. Robbed of food, their reproductive output can decline to just one.
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