Status of the red squirrel
The elusive red squirrel (Sciurus vulgaris) is an animal that is much spoken about but seldom seen. In the UK they are synonymous with the victims of invasive species and most people are aware of their plight. But just how threatened are they, and is it possible for them to recover with the right conservation measures?
The most recent comprehensive study of their numbers in Britain estimates the overall population to be at 161,000. 30,000 of these are in England, 121,000 in Scotland and 10,000 in Wales. However these statistics were accumulated in 1995, so it is uncertain how the population may have changed over the course of nearly two decades.
Red squirrels are thought to have arrived in Britain at the end of the last ice age roughly 10,000 years ago. There are records of them dating back to the 15th and 16th centuries, and even before the introduction of the grey squirrel (Sciurus carolinensis) between 1876 and 1929 there have been fluctuation in the population. Deforestation and subsequent reforestation in the 18th and 19th centuries caused their numbers to fall and then rise. In 1903 the Highland Squirrel Club was introduced to try and prevent the severe damage being caused to tree bark. 82,000 were killed up to the year 1933 by this organisation. Now it is competition from the American grey squirrel which poses the biggest threat. It is thought that red and grey squirrel populations can only co-exist together for about 20 years before the red squirrels numbers fall through competition and disease transmission.
The main source of competition amongst the red and grey varieties will come from food sources. Red squirrels are very poor at digesting acorn matter compared to their grey cousins, preferring instead hazel nuts. However grey squirrels can digest both, and eat the hazel crop before the acorn. As a result, red squirrels are unlikely to survive in areas with greater than 14% oak density. The abundance of oak in deciduous wood coupled with a post-war decline in coppiced hazel, demonstrates how the loss of food source is one of the main contributing factors in their decline. Taking this further, red squirrels only increase their weight by 10%, with grey squirrels increasing by 20%. Maintenance of weight over the winter is essential to reproduction, and as a result reductions in the population may be due to reduced reproductive success as opposed to reduced survival.
However it is not all doom and gloom. A study by conservation group Red Squirrels Northern England found that in the north of England their population had risen by 7% in Spring 2013 compared to Spring 2012. This is the first population increase after nearly 140 years of decline, and highlights how control of grey squirrels and habitat management can yield success.
The future of this iconic species is very much in the balance currently, and if grey squirrel numbers continue to rise we may not see them for much longer. However with a commitment to forest management and grey squirrel control we may be able to save the species. Conifer forests need to be spruce dominated, oak needs to make way for coppiced hazel, and grey squirrel numbers, especially those carrying pox disease, need to be controlled.
BBC News, (2013). Red squirrel population on the rise. [online] Available at: http://www.bbc.co.uk/news/uk-england-24124737 [Accessed 20 Dec. 2014].
DEFRA, (1995). A review of British mammals: population estimates and conservation status of British mammals other than cetaceans. pp.42-44.
Forestry.gov.uk, (2014). UK Red Squirrel Group – Red squirrel facts (Forest Research). [online] Available at: http://www.forestry.gov.uk/fr/INFD-8C8BHC [Accessed 20 Dec. 2014].
Image credit : Peter Trimming https://www.flickr.com/photos/peter-trimming/6583159839/
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