# Are Scat Surveys a Reliable Method for Assessing Distribution and Population Status of Pine Martens?

> For decades, Britain judged the status of its pine martens by searching forest trails for their droppings. When DNA was used to check, experienced surveyors had mistaken fox scats for marten scats, and the most accurate of them got every sample from England and Wales wrong. This review explains why scat surveys can mislead, especially where an animal is scarce.

Summary by Kersey Lawrence, Original Wisdom. Updated 9 November 2026. Page: https://www.originalwisdom.com/tracking-literature/2005-birks-messenger-scat-surveys-reliable-method/

## Citation and access

- **Authors:** Johnny Birks, John Messenger, Tony Braithwaite, Angus Davison, Rachael Brookes and Chris Strachan
- **Year published:** 2005
- **Journal or source:** Martens and Fishers (Martes) in Human-Altered Environments: An International Perspective (book chapter, Springer)
- **Full citation:** Birks, J., Messenger, J., Braithwaite, T., Davison, A., Brookes, R. and Strachan, C. 2005. Are scat surveys a reliable method for assessing distribution and population status of pine martens? Pages 235-252 in Harrison, D. J., Fuller, A. K. and Proulx, G. (eds.), Martens and Fishers (Martes) in Human-Altered Environments: An International Perspective. Springer.
- **DOI:** 10.1007/0-387-22691-5_12
- **Access status:** Hosted (freely available elsewhere)
- **PDF:** https://www.originalwisdom.com/wp-content/uploads/2026/11/2005_Birks_and_Messenger_etal_are-scat-surveys-a-reliable-method-for-assessing-distribution-and-population-status-of-pine-martens.pdf

## Tags

- **Species:** Mammals > Pine marten; Mammals > Red fox
- **Region:** Europe > Spain; Europe > United Kingdom
- **Tracking:** Scat; Sign surveys; Tracking; Tracks; Tracks and signs identification
- **Behaviour and ecology:** Behaviour; Communication; Habitat selection
- **Methods and technology:** Detectability; Distribution mapping; DNA; Literature review; Observer reliability; Population trends
- **Data type:** Review
- **Observer qualification:** Other experienced trackers
- **Discipline:** Behaviour and ecology; Wildlife tracking
- **Year published:** 2005

## Detailed keywords

- **Species:** Studied: pine marten (Martes martes). Species whose scats can be mistaken for marten scats: red fox (Vulpes vulpes), polecat and polecat-ferret (Mustela putorius), American mink (Mustela vison), stoat (Mustela erminea), and, in one Spanish survey, weasel (Mustela nivalis) and feral cat (Felis catus). In the genetic study the paper reviews, the misidentified “marten” scats were from red foxes. Animals seen destroying or removing marten scats: foxes, dor beetles (Geotrupes sp.) and great black slugs (Arion ater). Also mentioned: Eurasian otter (Lutra lutra), whose spraint surveys inspired the marten method, and black woodpecker (Dryocopus martius), whose tree holes martens use as dens in the Netherlands.
- **Location and habitat:** Great Britain: Scotland (including Highland Region, Wester Ross, Inverness-shire, south-west Scotland and the Kielder Region on the England-Scotland border), northern England and Wales. One survey on Minorca and Majorca (Balearic Islands), Spain. The Netherlands mentioned for scat searches under woodpecker holes. Habitats surveyed: commercial conifer plantations, other woodland, pine and Holm oak woodland, moorland, pasture, rock outcrops, crags, scrub and coastal habitats.
- **Topics:** scat surveys and their assumptions; scat identification by smell, size and shape; observer error in scat identification; DNA verification of scat identity; scent marking (“signing”) on trails and trail intersections; transect length, placement and spacing; seasonal variation in scat numbers (most in summer, fewest in winter); false negatives and inferring absence; scat abundance as an index of population size or breeding status; scat loss to foxes, dor beetles and slugs; three-dimensional (tree-dwelling) lifestyle of martens; conflicting conclusions about marten status in England and Wales; alternative survey methods (sighting surveys, camera traps, tracker dogs, hair snagging stations, track plates).
- **Statistics or models:** None
- **Data type:** Review of 9 scat surveys (8 in Britain, 1 in Spain) carried out between 1980 and 1996, plus the authors’ own unpublished field observations in Wales on what happens to marten scats left on forest trails, and personal observations of captive martens.

## Synopsis

### 1. What they did

Pine martens are strictly protected in Britain and are scarce or absent outside Scotland. Since 1980 their status has been judged mainly by searching for their droppings (scats) along forest trails, a method adapted from otter surveys. Different surveys reached very different conclusions, which led to disagreement about what conservation action was needed.

The authors reviewed 9 scat surveys of pine martens, 8 in Britain and 1 in Spain, to ask three questions:

- Are the survey methods and objectives appropriate? They compared what each survey set out to do, where it searched, which habitats and trail types it chose, and how long and how far apart its transects were.

- Are scats correctly identified? They compared each survey’s identification rules and drew on a DNA study (Davison et al. 2002), on which several of them were authors, that tested how often experienced surveyors identified marten scats correctly.

- How do the patterns of scat abundance affect results? They looked at seasonal changes in scat numbers, at what surveys concluded when no scats were found, and at attempts to use scat numbers to judge whether martens were resident or breeding.

### 2. What they found

Survey design rests on untested assumptions

- Most surveys searched trails and paths because martens are believed to mark trails with their scats, especially where their own routes cross man-made trails or streams. Whether martens really leave scats mainly on man-made trails has never been tested.

- Surveys chose different habitats. Some covered many wooded and open habitats; others searched only 5 m wide trails in commercial conifer forest. Yet authors often drew conclusions about martens far beyond the habitats they sampled. There is plenty of anecdotal evidence of martens living in open, rocky country in Britain.

- Martens spend much of their time above ground. In the Netherlands, their scats gather on branches or at tree bases under dens in black woodpecker holes, so some scats may never be on the ground where surveyors look.

- Marking on trails may be strongest in territorial, dense populations. Where martens are few, they may hardly mark trails at all.

- Transect length varied from 0.5 to 2 km. Tests of how length affects the chance of finding a scat were done only in Scotland.

Scat identification is unreliable

- Fox, polecat, mink and stoat scats can look like marten scats. Surveys used different rules: some relied on the “sweet, musky” smell of fresh scats, some on size and shape, some needed several scats before accepting marten presence, and some gave no criteria at all.

- In one survey, 27 scats looked like marten scats but had no smell; the authors could not be sure what they were, while surveys with looser rules might have counted them.

- In the DNA study, 3 experienced surveyors misidentified 18% of 56 fresh “marten” scats collected in Scotland. The misidentified scats came from red foxes. Error rates for individual surveyors ranged from 9% to 29%, and 2 surveyors misidentified scats they had marked as “certain”.

- The most accurate surveyor in Scotland (9% error) misidentified all 12 scats collected from the sparser marten populations in England and Wales.

- DNA could be extracted from only 53% of the fresh scats collected.

Scat numbers are a poor guide to marten numbers

- Scat numbers change hugely with the season. On one set of forest trails they were more than 100 times higher in July (12 scats per km) than in January (0.1 scats per km), yet many surveys were done outside summer.

- Every survey had many transects with no marten scats (from about 39% to 100%; see the table in the paper). In one national survey, 32 squares in Scotland with no scats found still produced marten carcasses or sightings.

- In England and Wales very few scats were found, even where footprints, sightings and carcasses showed martens were present.

- In the authors’ own work in Wales, foxes destroyed scats from captive martens placed on forest trails by scratching at them, dor beetles removed and buried scats, and great black slugs ate fresh scats completely within as little as 48 hours.

- Some surveys used scat numbers to decide whether martens were breeding residents or just passing through, and set thresholds for presence or absence. There is no evidence linking scat numbers to marten numbers, and the same team used different thresholds in different places.

### 3. What they concluded

- Because experienced surveyors misidentify fresh marten scats, the authors say scat surveys should not be used for any purpose without DNA confirmation of what made the scats, especially where martens are scarce.

- Scat survey methods have never been tested across seasons, habitats and population levels, and never shown to work where martens are scarce. Practical and statistical testing should come before any future survey, and conclusions should be limited to the habitats sampled.

- It is unsafe to use scat numbers to estimate marten numbers or population trends. Where no scats are found, little can be concluded beyond the possibility that martens are scarce there.

- Even with DNA checks, scat counts could be meaningless unless seasonal changes in scat deposition are allowed for. That needs behaviour studies of martens across seasons, habitats and population levels.

- The earlier conclusions that no viable marten populations remained in England and Wales cannot be supported.

- Where martens are scarce, the authors recommend combining several methods: sighting surveys, camera traps, tracker dogs, hair snagging stations and track plates.

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

The whole paper is about one tracks and signs method: finding and identifying scats along transects. The surveys reviewed identified marten scats by smell, size, shape and freshness, and some also recorded other signs, such as clear footprints, as evidence of martens. No trailing was reported. The authors also mention snow tracking and track plates as other ways of detecting martens, but snow is too limited and unpredictable in most of Britain for snow tracking.

### 5. Tracker or observer certification

No certification is reported. The surveyors in the cited DNA study (Davison et al. 2002) are described as experienced, and their scat identification skill was tested against DNA: their error rates were 9% to 29% on fresh scats in Scotland, and the best of them misidentified all 12 scats from England and Wales. The authors note these error rates are conservative, because the surveyors were experienced and knew they were being tested. For the other surveys reviewed, nothing is said about the surveyors’ skills.

### 6. Other technologies, skills or innovations

- DNA analysis of scats to confirm which species left them, described as then too expensive to use widely, but useful for testing field methods.

- Trained dogs, which could search for scats more widely than people limited to trails.

- Hair snagging tubes and stations, with genetic analysis of the hairs.

- Camera traps and track plates, used on martens elsewhere but not in Britain at the time.

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

- Scat surveys have shaped national conservation policy and recovery programmes for pine martens in Britain, so their errors matter.

- The pessimistic conclusion that martens were close to extinction in England and Wales rested on scat data that cannot support it.

- Low-density populations are the hardest to detect and the most in need of better survey methods.

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

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

- Experienced surveyors misidentified scats they felt certain about, and the most accurate of them got every scat wrong in a region with fewer martens. Confidence and experience are not the same as tested accuracy, which is why skill testing matters for anyone identifying tracks and signs.

- Scats can disappear within two days to foxes, beetles and slugs, and an animal that lives partly in trees may leave few scats on the ground. Finding no sign does not show an animal is absent.

- Scat odour, size and shape vary with diet, freshness and season, so identification criteria worked out in one population or season may not hold in another.

## Cite this summary

Lawrence, K. 2026. Summary of: Are Scat Surveys a Reliable Method for Assessing Distribution and Population Status of Pine Martens? (Birks and Messenger et al., 2005). Original Wisdom, Tracking Literature. https://www.originalwisdom.com/tracking-literature/2005-birks-messenger-scat-surveys-reliable-method/