An assessment of red squirrels in Moyode Wood, Carughwell, Co Galway 

Dr Colin Lawton, Mammal Ecology Group, Zoology Dept, NUI Galway  

Introduction  

Red squirrels are a native species of Ireland, which means they predate human existence on the island. Throughout their history they have undergone fluctuations in both range and density. This can mostly be related to the woodland habitat available to the squirrels. Red squirrels all but disappeared from Ireland due to the major deforestation that occurred in the 17th and 18th centuries, and much of the current distribution is courtesy of a number of reintroductions that took place in the 19th century and the afforestation of the country in the last 150 years. 

A further threat to red squirrels in Ireland arrived in 1911, with the first and only introduction of grey squirrels to Ireland, at Castleforbes, Co Longford. This alien species became established and has spread through much of the eastern half of the island. This spread was mirrored by a loss of red squirrel distribution, predominantly caused by competition with the greys for resources, and by the spread of a pox virus, carried by grey squirrels but lethal to reds. 

The latest squirrel distribution survey in Ireland took place this year (Carey et al. 2007), and showed that grey squirrels had increased their distribution by 30% since the previous survey in the mid-90s, and that red squirrel distribution had dropped by 1% each year. Grey squirrels have still not moved into the west of Ireland, with the river Shannon acting as a barrier to their spread, and unsuitable habitat and corridors preventing movement by the squirrels. This, together with the situation in the rest of the country has heightened the importance of red squirrels in the west of Ireland, and in particular in a region covering east of Co Galway, and much of Co Clare, which represents what may become the last stronghold of red squirrels in the country. 

Red squirrels are protected in Ireland under the Wildlife Acts of 1976 and 2000, and are one of the few mammal species listed in the latest Irish Red Data Book due to their decreasing numbers leading to them being vulnerable to extinction on the island. An 'All-Ireland Squirrel Action Plan' was released in 2007 by the Dept. of Environment, Heritage and Local Government, and the Environment and Heritage Service of Northern Ireland, aimed at protecting the red squirrel and alleviating the problems caused by the grey. The squirrel situation in Ireland, Britain and Italy has increased its profile on a European stage also, with recent meetings held aiming at including the species in the EU Habitats Directive and tackling the overall problem. 

This report follows concerns raised by local residents over a possible sale of land at Moyode Woods, Co Galway, for use other than forestry, and the consequences that this may have for the red squirrel population therein. The woods were visited in December 2008, in order to make an estimate of the red squirrel population therein (based on habitat type, and known squirrel densities) and a consideration of the impact of the sale of part of the woods, and the loss of the habitat therein to the squirrel population.

Moyode wood 

The woodland is divided into four main compartments, each differing slightly in tree composition. These have been labelled 1 (most southerly compartment, closest to Craughwell), 2 (westerly of the middle two compartments), 3 (easterly of the middle two compartments) and 4 (most northerly compartment, closest to Athenry). The compartments under threat are numbers 2 and 3. 

In general the habitat is very suitable for red squirrels given the mature status of many of the tree stands. The predomination of Norway Spruce in the coniferous regions (compartments one, two and four), with broadleaved areas (mainly beech (some quite mature), ash and hazel) throughout and a large mature broadleaved area (compartment three) with mature beech and oak, and an understorey of ash and hazel. 

Squirrels were confirmed in the region through the presence of cone cores and hazel shells, which, when fed upon by squirrels, leave a core or broken shell that cannot be confused with the remains left behind by other mammal or bird species.

The populations estimated in the four compartments, and the total estimated population is listed in Table 1. 

Comp. No. Size (approx) Density

Source No. of Squirrels

1-- 41 0.34 Lurz et al. 1995 14

2 --50 0.34 Lurz et al. 1995 17

3 --60 0.9 Kenward et al. 1998 54

4 --41 0.34 Lurz et al. 1995 14

Total 192 n/a n/a 99 

Table 1: Estimates of squirrel density in Moyode wood, using known squirrel densities for habitat types. 

These numbers are obviously very rough as they are based on a habitat assessment and values from the known literature. An intensive study involving trapping and line transects would be required to obtain a reliable and accurate estimate of the population. However, as a rough estimate 100 squirrels can be expected to reside within Moyode wood currently. This is a healthy population size and represents a high overall density given the woodland size. It is likely that there would be a lot of movement of squirrels between compartments, with each compartment being within 250 metres of its neighbouring region. The relative densities in each compartment would fluctuate throughout the year as the squirrels move from one area to another to take advantage of seed crops coming in to season. For example, when hazel becomes available in July, most of the resident squirrels would move into area with large amounts of hazel trees. 

Conclusion

The proposed development as described by the local residents group would have a devastating impact upon the red squirrel population of Moyode wood. Not only would over half of the available habitat be lost, the habitat that promotes the highest squirrel density (compartment three) is one of the proposed development areas. There is also considerable concern that the population could be reduced to a level that goes below the minimum viable population size, with inbreeding and difficulty in finding a suitable mate becoming important factors in the prospects of the population. Furthermore the loss of the central two compartments would leave the remaining two compartments considerably isolated, with a distance of 1500 metres between them greatly reducing the movement between the two areas. If the intervening area is turned over to quarrying it can be expected that all movement between the two compartments by the red squirrels will cease. This would exacerbate the problems described by the reduced population size. 

As well as on a local level, the loss of Moyode woods could have an impact on the red squirrels in the region, and due to the importance of the region on a national level as well. Red squirrels, like the greys require suitable habitat through which to move, and given the lack of suitable corridors in the west of Ireland, the loss of a wood such as Moyode could further isolate neighbouring woods and prevent the gene transfer that occurs through the dispersal of young animals, that is crucial for the overall fitness of animal populations. 

References

Carey, M., Hamilton, G., Poole, A. & Lawton, C. (2007). The Irish Squirrel Survey 2007. COFORD, Dublin. 

Kenward, R. E., Hodder, K. H., Rose, R. J., Walls, C. A., Parish, T., Holm, J. L., Morris, P. A., Walls, S. S., and Doyle, F. I. (1998). Comparative demography of red squirrels (Sciurus vulgaris) and grey squirrels (Sciurus carolinensis) in deciduous and conifer woodland. Journal of Zoology 244: 7-21. 

Lurz, P. W. W., Garson, P. J., and Rushton, S. P. (1995). The ecology of squirrels in spruce dominated plantations: implications for forest management. Forest Ecology and Management: Kielder - The Ecology of a Man-Made Spruce Forest. 79:79-90