The Eurasian red squirrel is, in my opinion at least, one of the cutest additions to the Irish countryside. The little ear tufts of the red squirrel help differentiate it from the invasive grey squirrel, the North American competitor of the red squirrel introduced here about 100 years ago. Other features include the size difference, as the grey squirrel is quite a bit larger. You might think that it should be relatively easy to differentiate the species by colour, but colourations can vary considerably, and the two species can actually exhibit quite similar variations.
The grey squirrel has been linked to the decline of the red squirrel in Ireland and Britain due to competition for habitat and resources, and the spread of diseases such as squirrel pox-virus, a disease which the grey squirrel has immunity to, but is lethal to the red squirrel. To learn more about the history of squirrels in Ireland, check out this article I previously wrote for Ireland’s Wildlife.
How to look for squirrels
What are the signs you use to look for squirrels? Because the little Eurasian red squirrel can be particularly shy in comparison to its American counterpart, red squirrels are not always readily visible in a woodland (the most likely place to find a squirrel). Therefore, the best way to prove their presence (or absence) in an area is to build up a case of evidence.
One of the first signs to look for are feeding signs such as stripped pine cones and split hazelnuts. Squirrels strip the seeds from Sitka spruce and Scots pine, leaving a ragged cone core. Mice too enjoy eating pine cones, but they chew the cones to the core leaving a very neat finish. Hazelnuts are another favourite! Squirrels split the outer shell cleanly in half to remove the nut, while mice and voles gnaw a circular hole in the nut. Birds too enjoy hazelnuts, and remove the nut by cracking the shell off a rock, leaving knock marks on the surface of the shell, and shattering the shell into uneven pieces. While feeding signs are a useful way to find preliminary evidence of squirrels, feeding signs alone cannot be used to differentiate between red and grey squirrels, and further evidence must be collected.
Squirrels build a nest called a drey. They use this nest as a place to shelter and sleep. A single squirrel may have multiple dreys across its feeding area, and it may also have different dreys for daytime naps and night time sleeping. Squirrel dreys look a bit like a bird’s nest, but they tend to be quite spherical and they are also usually built quite close to the tree trunk. It can be difficult to spot a drey, especially in a dense woodland, but winter time can make it easier, particularly in areas with deciduous trees. Again, a drey on its own does not provide very conclusive evidence of the presence of a squirrel, and it is a good idea to collect more direct evidence.
Hair-tubes are a useful way to collect hair samples of squirrels, and can provide another line of evidence to inform their presence or absence at a particular site. The tube can be made from a section of PVC piping wired to a tree. It is then baited with nuts and seeds, and a sticky patch can be placed inside the tube that collects hair from the squirrel as it removes the bait. Both red and grey squirrels can have similar hair colour variations, with some red squirrels turning dark in winter and some grey squirrels also turning a ginger colour, making it difficult to identify the hair sample by eye. However, the hair sample can be accurately identified to species using hair follicle analysis and even DNA analysis.
If the DNA sample is of good enough quality it can be used for more in-depth DNA analysis to obtain a genetic fingerprint to identify individual squirrels, and the mitochondrial DNA haplotype (DNA strain) can be obtained to gain an insight into the history of the population. This kind of information is useful for conservation and reintroduction programmes.
I’ve had very mixed results using hair-tubes for squirrels. I find the best place to place a hair-tube transect is in an area where I have already identified squirrel feeding signs and other evidence such as dreys, and I tend to concentrate my efforts in these areas. During my PhD research, I found that the hair-tubes tended to work better the longer they were in place. As a result, I recommend a sampling period of 5 – 6 weeks with weekly tube checks and bait replacement.
As I previously discussed on this blog, camera traps are a great way to collect evidence of wildlife, and they also work well for squirrels. I have had good success using camera traps in combination with hair-tubes, as the tube makes a pretty good bait station. In the video below, you can see a red squirrel using a hair-tube.
Rob Strachan (2009). Mammal Detective (British Natural History Series) Whittet Books Ltd