# The diet of pine martens (Martes martes) with reference to squirrel predation in Loch Lomond and The Trossachs National Park, Scotland

> Do recovering pine martens keep grey squirrels in check? Picking through 120 marten scats from four sites in a Scottish national park, researchers found plenty of voles, mice and autumn berries, but not a single squirrel. Chewed cones and hair tubes suggested why: there were hardly any squirrels left to eat.

Summary by Kersey Lawrence, Original Wisdom. Updated 9 November 2026. Page: https://www.originalwisdom.com/tracking-literature/2008-paterson-skipper-diet-pine-martens-martes/

## Citation and access

- **Authors:** William D. Paterson and Gavin Skipper
- **Year published:** 2008
- **Journal or source:** The Glasgow Naturalist
- **Full citation:** Paterson, W. D. and Skipper, G. 2008. The diet of pine martens (Martes martes) with reference to squirrel predation in Loch Lomond and The Trossachs National Park, Scotland. The Glasgow Naturalist 25(1): 75-82.
- **Access status:** Open access (CC BY-NC 3.0)
- **PDF:** https://www.originalwisdom.com/wp-content/uploads/2026/11/2008_Paterson_and_Skipper_the-diet-of-pine-martens-with-reference-to-squirrel-predation.pdf

## Tags

- **Species:** Mammals > Eastern grey squirrel; Mammals > Eurasian red squirrel; Mammals > Pine marten
- **Region:** Europe > United Kingdom
- **Tracking:** Feeding signs; Hair; Scat; Sign surveys; Tracking; Tracks and signs identification
- **Behaviour and ecology:** Behaviour; Feeding; Predation
- **Methods and technology:** Chi-square test; Global Positioning System (GPS); Hair sampling
- **Data type:** New field data
- **Observer qualification:** Not reported
- **Discipline:** Behaviour and ecology; Wildlife tracking
- **Year published:** 2008

## Detailed keywords

- **Species:** Studied: pine marten (Martes martes), red squirrel (Sciurus vulgaris) and grey squirrel (Sciurus carolinensis). Food remains found in scats: field vole (Microtus agrestis), bank vole (Clethrionomys glareolus), wood mouse (Apodemus sylvaticus), birds (not identified to species), dor beetles (family Geotrupidae), rowan berries (Sorbus aucuparia), other seeds, nuts and vegetation. No squirrel remains. Hair reference collection also included European rabbit (Oryctolagus cuniculus), brown hare (Lepus europaeus), common mole (Talpa europaea) and common shrew (Sorex araneus).
- **Location and habitat:** Four sites in Loch Lomond and The Trossachs National Park, Scotland, United Kingdom: Auchineden (NS 508804) and Sallochy (NS 389951), considered grey squirrel sites; Duke’s Pass (NN 515031) and Glenbranter (NS 113987), considered red squirrel sites. Scats were collected from forestry roads and paths. Sallochy is coniferous woodland near the Rowardennan oak woodland. Median scat altitudes: Duke’s Pass 268 m, Sallochy 135 m, Glenbranter 119 m.
- **Topics:** pine marten diet; scat analysis; predation on red and grey squirrels; pine martens as a possible natural check on grey squirrels; squirrel density from feeding signs (cone feeding transects, “squirreled” cones); hair tube surveys; microscopic hair identification (cuticle impressions and cross-sections); field voles as preferred prey; seasonal fruit and berry eating; altitude of scats; conflicting conservation goals for pine martens and red squirrels. Inconsistencies in the paper: some in-text citation years differ from the reference list (Holm 1987 in the text, 1994 in the references; Pepper and Patterson 1988 and 1998 in the text, 1998 in the references; Halliwell 1993 in the text, 1997 in the references). Glenbranter scats were collected from 14 November 2006 to 7 January 2007, but the discussion calls them “mid-November” scats. Figure 4 gives 41 scats with small mammals, while the mammal percentages for the three pooled sites (27%, 23% and 83% of 30 scats each) work out to about 40.
- **Statistics or models:** Chi-square tests (scat contents between sites; small mammal scats between altitude bands); Kruskal-Wallis tests (squirreled cone counts and scat altitudes between sites); squirrel density estimated from cone energy values following Gurnell et al. (2001).
- **Data type:** New field data. Scats collected at Auchineden in May 2005; Sallochy 24 to 29 October 2006; Duke’s Pass 5 to 12 November 2006; Glenbranter 14 November 2006 to 7 January 2007. 30 scats per site (120 in total). A final-year BSc Zoology dissertation at the University of Glasgow.

## Synopsis

### 1. What they did

Pine martens are recovering in Scotland, and in Loch Lomond and The Trossachs National Park they have come into contact with introduced grey squirrels for the first time in Britain. Studies in Finland, Sweden and Germany have shown that squirrels can make up a large share of a pine marten’s diet, and there is anecdotal evidence that martens take grey squirrels more readily than red squirrels. The authors set out to find out whether pine martens in the park eat squirrels, and whether that depends on how many squirrels are around.

- Scats. Guided by local knowledge, they collected 30 pine marten scats at each of four sites (Auchineden, Sallochy, Duke’s Pass and Glenbranter) from forestry roads and paths, identifying them with a tracks and signs field guide and recording each location with a handheld Global Positioning System (GPS) unit.

- Diet analysis. In the lab they picked out bones, teeth, hair, feathers, insect parts, seeds and berries under a microscope. Mammal hairs were identified from cuticle impressions and cross-sections, checked against a reference collection that included red and grey squirrel hair.

- Squirrel numbers. At three sites they walked 14 cone feeding transects each (42 in all), counting cones eaten by squirrels to estimate squirrel density.

- Which squirrel. At the same three sites they set 10 hair tubes each for two weeks to see which squirrel species was present.

### 2. What they found

Diet

- No squirrel remains were found in any scat at any site.

- Mammal remains were field voles, bank voles and wood mice. Field voles were the most frequent prey: in 47% of scats at Auchineden and 37% at Glenbranter, but only 10% at Sallochy and 7% at Duke’s Pass.

- Bank voles turned up in 43% of scats at Glenbranter and 17 to 20% at the other sites. Wood mice were in 10% of scats at Auchineden and Glenbranter and none at the other two.

- Plant material (including rowan berries, seeds and nuts) was in every scat from Sallochy and Duke’s Pass (collected in October and early November), 73% at Auchineden and 17% at Glenbranter.

- Bird feathers and dor beetles were also found.

Squirrels

- Feeding signs suggested no squirrels in the area studied at Sallochy, about 19 at Duke’s Pass (0.08 per hectare) and about 3 at Glenbranter (0.02 per hectare). These are low compared with 0.39 to 0.58 per hectare reported elsewhere in Europe.

- One hair tube at Glenbranter caught red squirrel hair. No grey squirrel hair was found anywhere. Other tubes caught wood mouse hair (Glenbranter) and pine marten hair (Duke’s Pass).

Where the scats were

- Scats containing small mammals were found mostly between 60 and 180 m above sea level.

### 3. What they concluded

- Pine martens did not appear to be eating squirrels at any of the study sites, in line with earlier Scottish studies. The likely reason is that squirrels were absent or very scarce, and local information suggests squirrel numbers in the west of Scotland had already declined before the study began.

- Field voles, the preferred prey of pine martens in Scotland, seemed plentiful enough that martens had no need to switch to squirrels, which take more energy to hunt. Berries, nuts and seeds may fill in when voles are scarce or when fruit is abundant in autumn.

- Grey squirrels at Sallochy may have retreated to nearby broadleaf woodland, or may have already been reduced by pine marten predation, as local experts have suggested.

- Future diet studies should estimate the numbers of all prey species alongside the diet, and a site where red and grey squirrels live together with pine martens could show whether martens prefer one squirrel species.

### 4. How tracking was or was not used

Tracks and signs were central to the study. Pine marten scats were found along forestry roads and paths and identified with a tracks and signs field guide (Bang and Dahlström 2001). Squirrel numbers were estimated from feeding signs: cones stripped by squirrels along transects. Hair left in hair tubes, and hair inside scats, was identified under the microscope. No trailing was reported.

### 5. Tracker or observer certification

Not reported. The paper does not say who identified the scats or how their skill was checked; the fieldwork was a student dissertation project. This matters because no DNA check was used, so the diet results rest on scats being correctly identified as pine marten. The hair identification method, by contrast, was checked against a reference collection of known hairs.

### 6. Other technologies, skills or innovations

- Handheld GPS (eTrex) to record scat locations.

- Microscopic hair identification: gelatine cuticle impressions viewed at 400x, and thin cross-sections cut from hairs set in glue on balsa wood, compared with museum and trapped reference specimens.

- Cone feeding transects and hair tubes, following Forestry Commission squirrel survey methods (Gurnell et al. 2001).

### 7. Implications for conservation (from the paper)

- Helping pine martens recover may conflict with red squirrel conservation. Martens eating grey squirrels would help red squirrels by removing a competitor and the risk of squirrel pox, but an earlier study found that where martens had been present for over ten years, red squirrel numbers and recruitment were lower.

- Keeping small mammal populations healthy, for example by including rough grassland or more open forest areas in land management plans, could give martens plenty of voles and possibly reduce the risk of them turning to red squirrels.

### 8. Implications for tracking (Original Wisdom's observations)

_These are Original Wisdom's observations, not the authors'._

- The whole study rests on signs: scats for diet, chewed cones for squirrel numbers, and hair for which species are present. It shows how much a carefully read set of signs can say about a predator and its prey without ever seeing either.

- Because the scats were identified by eye from a field guide, with no report of who did it or any check of their accuracy, the results depend on correct scat identification, a point worth keeping in mind with any scat-based diet study.

## Cite this summary

Lawrence, K. 2026. Summary of: The diet of pine martens (Martes martes) with reference to squirrel predation in Loch Lomond and The Trossachs National Park, Scotland (Paterson and Skipper, 2008). Original Wisdom, Tracking Literature. https://www.originalwisdom.com/tracking-literature/2008-paterson-skipper-diet-pine-martens-martes/