Facts about the Red Squirrel's demise
The Red Squirrel population in the UK has been declining for centuries now for a variety of reasons. Their favourite habitat is in conifer woodland, or at least mixed woodlands. Changes in the climate has meant that the pine forests have retreated north where the climates are still cooler, leaving these areas the best places to find Red Squirrels. In the UK, Scotland has some of the best pine forests, and unsurprisingly, the Red Squirrel is most commonly found here. England has more decidious woodland, which is best suited to Grey Squirrels, and it is no surprise to see that it is mainly ourselves across England, and not the Red Squirrels. This can clearly be seen in the Forestry Commission's 1998 research data on grey and red squirrel numbers across the UK.
Key points at a glance
1. Climate change, and deforestation for agriculture, industry and housing have resulted in loss of habitat suitable for Red Squirrels
2. Changes in tree species planted in recent years have favoured greys, with significant red squirrel habitat disappearing
3. Grey Squirrels don't chase Red Squirrels away. It is simply a gradual ecological replacement due to Greys being more adaptable. Plenty of evidence shows the two species living together for significant periods.
4. In addition, humans have persecuted Red Squirrels as pests for many years, driving them to near extinction
5. Red Squirrels, like Grey Squirrels before, have been affected by Parapoxvirus. Grey Squirrels who survived showed immunity, and the same immunity is now being seen in some Red Squirrels
6. Habitat pressures are making life hard for Red Squirrels, so disease, like SQPV, is harder for them to fight. They are certainly not fat and healthy.
Another factor in the decline of the Red Squirrels is the destruction of millions of acres of woodland by humans for agriculture, housing and industrial purposes. As a species, Red Squirrels are far less adaptable than ourselves, and have suffered quite badly when their habitat has been destroyed throughout the centuries.
Humans have continued to eat up Red Squirrel habitat at an alarming rate. 50% of the woodland that was present in the UK in the 1940s has been cut down, leaving ever decreasing places for the Red Squirrels to survive. Recently the preference has been for planting deciduous forests, which don't suit the red squirrel at all, and only help Grey Squirrels. Here in the UK, Red Squirrels find themselves at the very edges of their natural habitat, persecuted for any success they ever had in this country.
Red Squirrels could potentially survive in deciduous forest, even though the food sources available are not as beneficial to them as they are to ourselves. However, given that we thrive in deciduous and mixed forest, it is no surprise that Red Squirrels find themselves unable to compete in this type of forest. The poor diet means they breed slower than ourselves, and simply decline in these areas. This ecological replacement happens over significant timescales. Red and Grey Squirrels can live together for many years before the gradual decrease results in the Red Squirrels becoming extinct in the deciduous or mixed woodland. It is only where Red Squirrels can out-compete Grey Squirrels that they do very well. Research has shown that they require a minimum area of 200 hectares of coniferous woodland before they start to thrive sufficiently to do better than Grey Squirrels. Even in smaller coniferous forests, Reds will do significantly better than in deciduous or mixed forest where food sources are not so suitable for them.
It is important to point out that when Grey Squirrels are accused of chasing Red squirrels, and therefore contributing to the decline in Red Squirrels that there is no evidence at all of this. The fact Red Squirrels survive along with Greys for significant periods proves this isn't the case. It is purely Grey Squirrels being more successful that drives the numbers of Red Squirrels gradually down in forest types where Grey Squirrels do better than Reds.
Increasing the planting of large coniferous forests is therefore an important factor in helping the Red Squirrel thrive. Grey Squirrels also tend to follow the path of deciduous or mixed woodland, so the large deciduous plantations springing up everywhere are simply acting as corridors to allow them to spread further. A knowledge of the types of trees which Reds prefer and Greys prefer could allow a tree planting direction which would improve the habitat for the Reds while allowing the Greys to continue to survive in the many deciduous woodlands around.
The following shows which trees suit Red and Grey Squirrels, and the change that occurred between 1980 and 1998 across England. It is unsurprising, given the decline in numbers of Red Squirrels, that there has been a large shift away from trees which suit Red Squirrels to trees which Grey Squirrels thrive in.
Across Scotland, there has been a similar shift against the Red Squirrel habitat, with the exception of Mixed/Japanese Larch which showed a 21% increase. However, this is likely more than made up for by the 28% decrease in Norway Spruce and 39% decrease in European Larch, both of which are good for Red Squirrels. It also must be noted that Scotland is vastly smaller than England so percentage changes are magnified compared with England.
The third notable factor in their decline is human persecution. For many years, Red Squirrels were seen as pests and were targeted by gamekeepers. Lady Lovat was instrumental in getting red squirrel's re-introduced to the Highlands back in 1844, but by the early 1900s, their success was becoming a cause for concern among foresters and clubs were set up in Scotland for the pure and simple reason of killing or trapping Red Squirrels. With financial incentives for anyone who sent in Red Squirrel's tails, it wasn't long before a massacre occurred. The Highland Squirrel Club alone killed 80,000 Red Squirrels during the first 30 years it operated! This continued up until the end of the 1920s.
Short of habitat to live in and places to find suitable food, while being hunted and trapped, they've found themselves under constant threat of extinction. Facing these problems has left the population weakened, and therefore more susceptible to disease. One such disease is parapoxvirus, which has similar symptoms to myxomatosis found in rabbits, and has also been a killer to Grey Squirrels in the past, only leaving those of us lucky enough to have an immunity. Some Red Squirrels have also shown signs of this immunity, so the parapoxvirus is not likely to be the end of the Red Squirrels either.
Unfortunately, because we're seen to have this immunity now, and most of the Red Squirrels don't have it, we've been blamed for spreading the disease. However, Squirrel Natural Heritage (SNH) research has shown that Red Squirrels were dying of a disease between 1900 and 1920. Descriptions of the disease give very similar clinical signs to the disease that scientists now know to be poxvirus. Most of the Red Squirrels reported to be dying had never had any contact with Grey Squirrels. We'd only spread across 4 out of 40 districts while Red Squirrels were fairly common across the country.
There is one confirmed case where a Red Squirrel, in captivity, managed to survive Squirrelpox. It was ill for around 6 weeks, but having plentiful food and warmth allowed it to survive, and its immune system fight the virus. If large numbers of Red Squirrels are to fight this disease themselves, they need good habitat, so they aren't short of food or shelter, so emphasis on planting more coniferous forests is important. The development of a vaccine which could be given to live-trapped red squirrels before they are released again could be a way in which humans could also help the reds further.
The Zoological Society of London has also identified eight cases in which free-living red squirrels have survived infection. The fact they have mounted an immune response is a clear indication that while red squirrels will die from this disease, there are those who will survive. A classic case of survival of the fittest