Conservation & Ecology
marten (Martes martes) has a positive correlation with the population crash in the Irish Midlands of the grey squirrel, whilst the native red squirrel population is increasing in these areas. It is thought that the red squirrel, being smaller, can escape to the furthest branches, whereas the grey squirrel falls victim to the attentions of a native predator. We are beginning to understand that
ecosystems are complex structures and predators such as pine martens have a place; by eradicating them from an area, we upset the natural balance that has been achieved over time. By introducing non-native species, we also upset the balance. In the long term, the grey squirrel may be the nail in the coffin of the red squirrel, it may only be a temporary guest or it may come to share,
Helen McRobie, senior lecturer in Biomedical Science at Anglia Ruskin University, said: “If you look closely at grey squirrel hairs, they are not actually grey at all but are a combination of white, black and orange stripes. However, the hairs of black squirrels have no stripes; they are just plain black.”
“Our research shows that one hormone turns the switch on to make black fur, and a different hormone turns the switch off to make orange and white fur.”
“So in the grey squirrel, as the fur is growing, the switch turns on and off to make the stripes.
“However, in the black squirrel, because there is a piece of DNA missing, a piece of the switch is also missing.”
“The first hormone that switches it on still works and black fur is made, but the second hormone that should switch off, actually switches on as well. The off switch fails and the black fur continues to grow.”
The black squirrel is the same species as the grey squirrel and poses no threat to the variety. Black squirrels can mate with greys and, if this happens, offspring will have a combination of
equitably, a place in our landscape. Whatever happens, they will always have a welcome at my bird table and I’ll always be amused at the look of bewildered consternation on Sidbury’s face. References:
British Broadcasting Corporation. (2006). Jamie ‘must back squirrel-eating’. Available:
http://news.bbc.co.uk/1/hi/uk/4835690.stm.
Broome and Johnson. (2001). An Evaluation of the Costs of Grey Squirrel Bark-Stripping Damage in British Woodlands. Forestry Commission.
Macdonald, D. and Burnham, D. (2011). The state of Britain’s mammals a focus on invasive species. People’s Trust for Endangered Species.
MAF. 1943. Memorandum to executive officers of County War Agricultural Executive Committees in England and Wales, destruction of grey squirrels: Grey Squirrels Order. MAF 44/45
Newson, S., Rexstad, E., Baillie, S., Buckland, S. & Aebischer, N. (2010). Population changes of avian
predators and grey squirrels in England: is there evidence for an impact on avian prey populations? Journal of Applied Ecology.
Parliamentary publications. (23rd Jan 2008). Column 221 House of Lords. Available:
http://www.publications.parliament.uk/pa/ld200708/ldha nsrd/text/
80123-0001.htm.
Rotherham, I. and Lambert, R. (2011). Invasive and Introduced Plants and Animals: Human Perceptions, Attitudes and Approaches to Management. London: Earthscan. p44.
Sheehy, E. & Lawton, C. (2014). Population crash in an invasive species following the recovery of a native predator: the case of the American grey squirrel and the European pine marten in Ireland. Biodiversity Conservation. 7 (23), 753-774.
The main article was first commissioned and published by Fair Acre Press for the Arts Council England funded poetry-writing project: Maligned Species
http://fairacrepress.co.uk/projects/maligned-species- project/
faulty and fully working genes, giving them a brown-black coat.
There have been around 6,100 sightings of black squirrels living in the UK.
Both are a threat to the red squirrel and can carry a pox which can kill reds and damage trees.
McRobie, who leads the black squirrel project at Anglia Ruskin University, said she now plans to study the other effects of the DNA mutation to determine whether this helps the black variety survive by giving them competitive advantages.
It has been reported that the black mutations have more testosterone, making them more aggressive and attractive to females, but there is little current evidence to support this.
A similar mutation occurs in the black jaguar and McRobie predicts this is caused by the same faulty gene.
She added: “This gene is found in other places in the body. It is also found in white blood cells and could have other effects. It is not yet known how it is going to affect the squirrel. In some animals it does affect immunity and can
make their immunity better.”
The black squirrel was first spotted in Bedfordshire in 1912 and has been seen in South West England, Wales and Southern Scotland in the last two years.
Anglia Ruskin University’s The Black Squirrel Project aims to gather data on the geographical range of the black squirrel within the UK.
Visit
http://www.blacksquirrelproject.org/ for further information
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