Red Squirrel Threats
The red squirrel faces three main threats to its survival in Scotland today:
- the spread of grey squirrels
- squirrelpox
- habitat fragmentation (the gradual loss of connection between areas of habitat)
Threat 1: the spread of grey squirrels
The rapid spread of the North American grey squirrel in Britain is the main threat to red squirrel survival. The arrival of grey squirrels in an area occupied by red squirrels causes reduced red squirrel breeding and survival rates, leading to a gradual decline in their numbers.
The North American grey squirrel is an invasive non-native squirrel species introduced to Britain around the turn of the Twentieth Century. Compared with red squirrels, grey squirrels are more robust as a species. They are physically larger and, unlike red squirrels, can feed on seeds with high tannin content, such as acorns, thanks to differences in digestive physiology. As a result, more food sources are available to greys and they tend to put on 20% in body weight over autumn, compared with 10% for reds. This gives grey squirrels an advantage in hard winters. These differences allow grey squirrels to compete more successfully than red squirrels for food and habitat. In areas where red and grey squirrels exist together; the presence of grey squirrels results in reduced survival rates amongst red squirrel young and reduced reproductive rates, causing the gradual decline in red squirrel populations over time. This effect can already be seen in Scotland’s central belt where grey squirrel spread has resulted in the almost complete disappearance of our native red squirrels.
Maps of red and grey squirrel distribution show how the spread of grey squirrels has resulted in the almost complete loss of red squirrels from England between 1940 and today, apart from remnant populations in northern England.
Maps of Scotland show how the spread of grey squirrels over the last ten years alone has significantly reduced red squirrel populations, particularly in central and south-western areas; continuation of this trend would threaten the survival of red squirrels in north Scotland.
While areas in north Scotland still remain grey squirrel free, Scotland is one of the only safe places left for red squirrels in Britain. Our red squirrels account for around 75% of the entire UK population. But grey squirrels are on the move! We must act now to protect our remaining red squirrels. If we do nothing, the red squirrel could become extinct on mainland Scotland.
Threat 2: squirrelpox
Grey squirrels can also bring another problem for red squirrels through the spread of the squirrelpox virus. This virus, carried by grey squirrels without causing them harm, is fatal to our native reds.
Often mistaken for myxomatosis, the virus lodges in red squirrels’ eyelids and mucous membranes, which become infected and swollen, and produces scabs in and around the eyes, nose, mouth, feet, ears and genitalia. The infected squirrel is very quickly unable to see or to feed properly and rapidly becomes malnourished. The disease is highly infectious to red squirrels and kills within 15 days of infection. Although the means of transmission is still being investigated, it is possible that the virus could be transmitted by secretions left on feeders, dreys (the nest of a squirrel) or branches. Squirrelpox is already present in south Scotland as grey squirrels, some carrying squirrelpox, spread northwards from England. Red Squirrels in South Scotland (RSSS), the sister project of SSRS, is working to set up a pox-free buffer zone to contain the spread of the virus. For more information, visit the official RSSS website at www.red-squirrels.org.uk.
Threat 3: habitat fragmentation
While grey squirrel spread is the main reason for the decline in red squirrel populations in Scotland today, habitat fragmentation is also a contributing factor.
Squirrel habitat fragmentation occurs when areas of woodland and forestry become segmented and separated by development and changing land-use. This leads to isolated areas which cannot sustain viable populations of wildlife, including red squirrels.
SSRS aims to directly address the factors contributing to red squirrel decline. This includes working with landowners to improve habitat conditions to help red squirrels thrive and increase in number as well as working to halt the decline of red squirrel populations in key areas of north Scotland through the prevention of further grey squirrel spread. Read more about Our Work for further details.
Read our FAQ's to find the answers to the commonly asked questions about the red squirrel's plight and SSRS the project.
