Grey squirrels in British woodlands: understanding bark stripping and reproductive biology.

Christopher Nichols writes about his recently started PhD project, “The economic cost to the GB forestry industry from bark stripping in beech, sycamore and oak is estimated at £10 million per year (Forestry Commission, 2004). The aims of this project are to discover the reasons why grey squirrels strip the bark from trees and to explore the development of commercial products (such as dietary supplements or deterrence devices) that could be developed to solve this problem. Whilst the underlying causes for this behaviour are probably multi-faceted, our working hypothesis is that grey squirrels are eating the phloem of trees to gain calcium. Trees are most vulnerable to bark stripping during the spring and summer, and it is plausible that juveniles and female adults may be prone to calcium deficiency at this time – juveniles because they have just passed through their main period of bone growth, and female adults because of post-partum rigours such as lactation. In addition, after a good mast year grey squirrels will have received an unsaturated fatty acid-enriched autumn feed, and may be prone to calcium deficit in subsequent months. Initially the project aims to test this hypothesis as well as gathering baseline physiological data with a view to aiding and informing ongoing research on the development of grey squirrel contraceptive agents, in the broader context of red squirrel conservation.” Christopher can be contacted by email at  Christopher.Nichols ‘at’

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