Wednesday, June 30, 2010

The Pygmy Shrew

The pygmy shrew (Sorex minutus) the smallest mammal in UK & Ireland favours hedgerows, field borders and woodlands. It continually searches for insects, snails and spiders and its tails is two-thirds that of its body length, 6cm. Yes, 6cm! (Complete British Wildlife, P. Skerry, HarperCollinsPublishers Ltd., 1997).

Pygmy shrew (Sorex minutus)

I found the dead animal back in April, on a pathway high in a woods in Hebden Bridge. I am not the one who is holding it mind you. I let a braver soul take this honour.

Note the size

Sorex minutus is a small (2.9-5.0 g) endotherm at the theoretical size limit for continuous endothermy and like other soricine shrews, stays active throughout the winter. But the pygmy shrew is more restricted in the range of behavioural and morphological strategies that may be used to conserve energy in winter compared to most rodent species. The strategy of short-term daily torpor as a means of reducing overall energy use is common among most winter-active homeotherms but not so for members of the soricine subfamily. One morphological strategy that is used by soricine shrews is an active winter regression in skeleton and internal organ mass, which also reduces total energy expenditure. Behaviourally, winter acclimatized S. minutus maintain a significantly lower RMR (Resting Meatabolic Rate) than other seasonal cohorts. McDevitt and Andrews suggest that the overwintering strategy of S. minutus is one of minimising energy expenditure wherever possible, by reducing mass and RMR, and by demonstrating an increasing reliance on behavioural thermoregulation. (Regina McDevitt, J. F. Andrews, Seasonal variation in the metabolic rate of the Pygmy shrew, Sorex minutus: Can resting metabolic rate be measured in post-absorptive shrews?, Journal of Thermal Biology, Volume 20, Issue 3, June 1995, Pages 255-261).

Although this fellow made it through the winter it looks like his luck ran out.

On a totally unrelated topic, I visited Sylvia Platt's grave that day too.



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