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November 2005

The Distribution of the Water Vole in Caithness
E Fraser, D Glass and S Hogg

Introduction & Method
Results Page One
Results Continued
Future Work - Acknowledgements - References


A total of 34 sites were surveyed, 19 (56%) of which were found to be occupied with water voles and the remaining 15 (44%) unoccupied. Occupied sites were found in 11 (64.7%) of the 17 10 km squares chosen for surveying. Table 1 shows the location of all survey sites along with the 10 km square that each survey site was located in and the extent of area surveyed at each site. Figure 3 shows the locations of all surveyed sites, as numbered in Table 1.

The survey sites were classified, in terms of habitat type, using the Caithness Habitat Map from the Caithness Biodiversity Action Plan (February 2003). The surveyed sites covered 4 main habitat types, bog and moorland (from now on referred to as peatland), farm and croftland, forest and woodland and urban and unclassified. In total, 44.1% (15/34) of the surveyed sites were peatland, 41.2% (14/34) were farm and croftland, 11.8% (4/34) were forest and woodland and 2.9% (1/34) were urban and unclassified (Figures 4 and 5). Of the occupied sites, 47.4% (9/19) were peatland, 36.8% (7/19) were farm and croftland and 15.8% (3/19) were forest and woodland. Forty percent (6/15) of unoccupied sites were in peatland, 46.7% (7/15) were farm and croftland, 6.7% (1/15) were forest and woodland and 6.7% (1/15) were urban and unclassified. In one case, a site was initially determined as unoccupied but was re-surveyed 3 weeks later and was found then to be occupied. This occurred at Loch Hollistan which has been classified as occupied in the analysis.

All occupied sites had a defined flow of water, such as a burn or ditch, except Newtonhill Community Woodland. Here, signs of occupancy were found in a marshy area with standing water. Bank vegetation was varied. In general, peatland areas had a high level of vegetation cover which was commonly a mix of tall grasses, sedges and rushes, for example Allt na Craoibhe (Figure 6). In areas of farm and croftland, where grazing had been allowed up to the water’s edge, vegetation was short with discrete tussocks of rushes or sedges (as found at the Little River, Tacher). In other areas of farm and croftland, grazing was not permitted near the water because of fencing. This had led to the area becoming densely overgrown, with plants other than grasses and rushes tending to dominate. An example of this is the area surveyed on Thrumster Estate. In forest and woodland areas, suitable habitat and positive occupancy were recorded in open areas where growth of ground vegetation was not restricted by tree cover, for example in Achairn forest. There was no positive occupancy in areas categorised as urban and unclassified. For a list of example plant species found in suitable and unsuitable habitat see Table 2.

This variety of vegetation found at occupied sites led to a further classification which divided suitable habitat. ‘Typical’ habitat had good vegetation cover of grasses, sedges and rushes, with few shrubby plants e.g. Allt na Craoibhe or Achairn Forest. ‘Poor’ habitat had adequate vegetation cover which was generally tall, but overgrown and dominated by plants such as meadow sweet, thistles and nettles. Grasses and rushes were present but commonly only near to the water’s edges. A higher proportion of stones/rocks in the water or intermittently on the banks was also characteristic of ‘poor’ habitat e.g. Thrumster estate or Achsinegar (Table 3). It should, however, also be noted that in positively occupied sites, the habitat was generally not continuously suitable across the complete length of the survey.

Unoccupied areas were also further classified in to 2 groups: sites that had suitable habitat but were unoccupied and sites that were unsuitable. Suitable habitat, such as Loch Garbh and Loch Saorach outlet burns, followed the same description as above. Habitat was classed as unsuitable if the river banks were continuously rocky, solid or high e.g. Thurso river and Dunbeath water, water was fast flowing, there was a permanently high water table e.g. Broubster Leans, and vegetation cover was minimal e.g. Rumster forest, and/or dominated by woody or shrubby plants and bushes such as heather or gorse (Figure 7).

Occupied sites were 73.7% (14/19) typical and 26.3% (5/19) poor habitat. Suitable habitat was also found at 53.3% (8/15) of unoccupied sites. At the remaining 46.8% (7/15) of unoccupied sites, habitat was unsuitable (Figures 8 and 9).

Estimates of abundance have, in the past, been predicted using a correlation between number of latrines and total population of adults and juveniles (3); however, this correlation may not be valid in all habitats, particularly if water vole populations are small and fragmented (3). Estimates of abundance have therefore not been attempted but instead each occupied site was assigned a crude level of occupancy according to the quantity and distribution of signs that were found. There were 3 categories: low, medium and high. Sites classified as having low occupancy were those where only a few, isolated signs were found, for example a couple of droppings up to 3 latrines. Medium occupancy was used to describe sites where signs were numerous but had a patchy distribution. High occupancy was determined by a continuous stretch of signs over a distance of at least 100m. The majority (57.9%) of occupied sites had a medium level of occupancy. 31.6% of occupied sites had a low level of occupancy and 10.5% were highly occupied (Figure 10).

Table 1: Survey site locations, showing the 10km square each site was located in,
the extent of area surveyed, in grid squares, and the result of the survey.

Survey site location 10km square Extent of area surveyed (grid squares) Positive occupancy?
1 Loch Hollistan NC 9060 NC 9264 yes
2 Loch Garbh NC 9060 NC 9360, 9361, 9362, 9462 no
3 Allt nam Beist ND 0040 ND 0842, 0843, 0844, 0943 yes
4 Loch Beg and Lochan Dubh ND 0040 ND 0896, 0946 yes
5 Torran Water ND 0050 ND 0452, 0552, 0553, 0554 no
6 Lower River Forss ND 0060 ND 0269, 0367, 0368, 0369, 0466, 0467 yes
7 Wolf Burn and Scrabster

Loch Burn

ND 0060 ND 0870, 0968, 0970, 1068,1069, no
8 Loch Saorach and Thormaid ND 0060 ND 0159, 0060, 0160, 0161, 0260 yes
9 Broubster Leans ND 0060 ND 0360, 0460 no
10 Allt na Craoibhe ND 1030 ND 1637, 1737 yes
11 Burn of Latheronwheel ND 1030 ND 1736 yes
12 Allt Chaiteag ND 1040 ND 1145, 1146, 1147, 1244, 1245 no
13 Allt nam Sealbhag ND 1040 ND 1245, 1246, 1247 no
14 Little River ND 1040 ND 1746, 1747 yes
15 Burn of Tacher ND 1040 ND 1746, 1846 yes
16 Allt Caol ND 1040 ND 1947 yes
17 Loop Burn and Burn of Aultachlevan ND 1040 ND 1642, 1741, 1742, yes
18 Dunbeath Water ND 1040 ND 1341, 1342, 1429, 1430, 1431, 1529, 1530, 1629, no
19 Loch Scarmclate ND 1050 & 1060 ND 1859 no
20 Lower River Thurso ND 1060 ND 1167, 1168 no
21 North Calder ND 1060 ND 0961, 1061, 1161 no
22 Rumster Forest ND 2030 ND 2036, 2037, 2038, 2137, 2139, 2140 no
23 Achsinegar ND 2030 ND 2235 yes
24 Munsary and Ballharn ND 2040 ND 2144, 2145, 2146, 2244, 2245, 2246 yes
25 Achairn Forest ND 2040 ND 2847, 2848, 2849, 2947 yes
26 Strath Burn ND 2050 ND 2453, 2552, 2454 no
27 Midsand Burn ND 2060 ND 2168, 2268, 2368, 2369 no
28 Sinigoe Burn ND 2070 ND 2174, 2175 no
29 Burn of Rattar ND 2070 ND 2573 yes
30 Newtonhill Community Woodland ND 3040 ND 3449 yes
31 Wick River ND 3050 ND 3151, 3152, 3251, 3252, 3352, 3452 no
32 Thrumster Estate ND 3040 ND 3145, 3244, 3245, 3345, 3346 yes
33 Biel of Duncansby ND 3070 ND 3870, 3871 yes
34 Gill Burn ND 3090 ND 3567, 3667 yes

© Crown Copyright. The Highland Council 2005. 100023369
Figure 3: Map of Caithness showing the location of all sites surveyed. The numbers relate to those in Table 1.

Figure 4: Percentage number of sites in each habitat type category.

Figure 5: Percentage number of sites in each habitat type category,
showing the division between occupied and unoccupied sites.

Figure 6: Example of suitable habitat at Allt na Craoibhe, Latheronwheel Estate.

Table 2: Examples of plant species found in (a) suitable habitat and (b) unsuitable habitat.




plant group


Rushes soft rush (Juncus effusus)
conglomerated rush (J. conglomeratus)
Grasses tufted hair-grass (Deschampsia caespitosa)
Yorkshire fog (Holcus lanatus)
Purple Moor-grass (Molinia caerulea)
Reeds Reed sweet-grass (Glyceria maxima)
Sedges Bottle sedge (Carex rostrata)
Common sedge (C. migra)


Water plants watercress (Nasturtium officinale)
Wetland/ edge plants cuckoo flower (Caramine amara)
meadowsweet (Filipendula ulmaria)
watermint (Mentha aquatica)
  brooklime (Veronica beccabunga)




Plant group



Table 3: Habitat type and suitability at each (a) occupied and (b) unoccupied site. Occupied sites also have an extra classification of occupancy level. Where there is more than one habitat type listed, the first in the list represents the majority of the habitat.

(a) Occupied Sites

Site name Habitat type Habitat suitability Signs
Allt na Craoibhe peatland typical high
Biel of Duncansby peatland typical medium
Munsary and Ballharn peatland typical medium
Allt nam Beist peatland typical medium
Loch Beg and Lochan Dubh peatland typical medium
Allt Caol peatland typical medium
Loop Burn and Burn of Aultachlevan peatland typical medium
Loch Hollistan peatland typical low
Gill Burn peatland poor medium
Burn of Tacher farm and croftland,


typical high
Little River farm and croftland typical low
Burn of Latheronwheel farm and croftland typical low
Thrumster farm and croftland poor medium
Lower River Forss farm and croftland poor low
Burn of Rattar farm and croftland poor low
Achsinegar farm and croftland poor low
Newtonhill Community Woodland forest and woodland typical medium
Achairn Forest forest and woodland typical medium
Loch Saorach and Thormaid forest and woodland typical medium
(b) Unoccupied Sites
Site name Habitat type Habitat suitability
Allt Chaiteag peatland suitable
Allt nam Sealbhag peatland suitable
Torran Water peatland suitable
Loch Garbh peatland suitable
Sinigoe Burn peatland suitable
Dunbeath Water peatland unsuitable
North Calder farm and croftland suitable
Strath Burn farm and croftland suitable
Midsand Burn farm and croftland unsuitable
Broubster Leans farm and croftland unsuitable
Wick River farm and croftland unsuitable
Loch Scarmclate farm and croftland unsuitable
Wolf Burn and Scrabster Loch Burn farm and croftland, urban and unclassified suitable
Rumster Forest forest and woodland unsuitable
Lower River Thurso urban and unclassified unsuitable

(a)  (b)

Figure 8: Percentage number of occupied sites with ‘typical’ and ‘poor’ habitat in each habitat type.

Figure 9: Percentage number of unoccupied sites with suitable and unsuitable habitat in each habitat type.

© Crown Copyright. The Highland Council 2005. 100023369

Figure 10: Map of Caithness showing the surveyed sites that are occupied and unoccupied.
Occupied sites also show level of occupancy.