# On the origin of faeces: morphological versus molecular methods for surveying rare carnivores from their scats

> Can experienced naturalists tell a pine marten scat from a fox scat? DNA tests in Scotland, England and Wales showed they often cannot: nearly one in five Scottish “marten” scats came from foxes, and in England and Wales all but one did. The study is a striking reminder that identifications of rare animals from their signs need an independent check.

Summary by Kersey Lawrence, Original Wisdom. Updated 9 November 2026. Page: https://www.originalwisdom.com/tracking-literature/2002-davison-birks-origin-faeces-morphological-versus/

## Citation and access

- **Authors:** Angus Davison, Johnny D. S. Birks, Rachael C. Brookes, Tony C. Braithwaite and John E. Messenger
- **Year published:** 2002
- **Journal or source:** Journal of Zoology
- **Full citation:** Davison, A., Birks, J. D. S., Brookes, R. C., Braithwaite, T. C. and Messenger, J. E. 2002. On the origin of faeces: morphological versus molecular methods for surveying rare carnivores from their scats. Journal of Zoology 257(2): 141–143.
- **DOI:** 10.1017/S0952836902000730
- **Access status:** Hosted (freely available elsewhere)
- **PDF:** https://www.originalwisdom.com/wp-content/uploads/2026/11/2002_Davison_and_Birks_etal_on-the-origin-of-faeces.pdf

## Tags

- **Species:** Mammals > European polecat; Humans; Mammals > Pine marten; Mammals > Red fox
- **Region:** Europe > United Kingdom
- **Tracking:** Scat; Tracking; Tracks and signs identification
- **Behaviour and ecology:** Behaviour; Communication
- **Methods and technology:** Descriptive statistics; DNA; Observer reliability
- **Data type:** New field data
- **Observer qualification:** Other experienced trackers
- **Discipline:** Wildlife tracking
- **Year published:** 2002

## Detailed keywords

- **Species:** Studied: pine marten (Martes martes) and fox (Vulpes vulpes), through their scats; and humans (three experienced marten field workers and other naturalists whose scat identifications were tested). Also identified by DNA: one polecat (Mustela putorius) scat collected as “marten”. Captive pine martens supplied the scats for the exposure trial. Mentioned as other species monitored from their faeces in Britain: otter (Lutra lutra), mink (Mustela vison) and water vole (Arvicola terrestris).
- **Location and habitat:** Galloway, Scotland (a well-established pine marten and fox population), more widely in south-west Scotland, and a sample of 10 x 10 km squares in England and Wales where martens were probably present at low density. The one confirmed marten scat from England and Wales came from Caernarfonshire, Wales. United Kingdom. Habitat is not described.
- **Topics:** scat identification; observer accuracy; molecular scatology (DNA from scats); morphological versus DNA identification of scats; confidence scores (“possible”, “probable”, “certain”); presence surveys of rare and endangered carnivores; low-density populations; counter-marking of marten scats by foxes; DNA survival in scats left in the field; reintroduction decisions; multi-evidence monitoring (DNA, cast hairs, camera traps, sighting questionnaires); trained people or dogs to find scats; microarray screening.
- **Statistics or models:** Descriptive statistics only (percentages and counts). Species identified by sequencing a roughly 200 base pair section of mitochondrial DNA (control region) with carnivore-specific primers and comparing it with GenBank sequences. Possible inconsistency: 18% of 56 Scottish “marten” scats would be about 10 fox scats, but the text then refers to “eight fox scats from Galloway” when giving confidence scores; the paper does not explain the difference (perhaps only eight had confidence scores, or the others came from elsewhere in Scotland).
- **Data type:** New field data: scats collected 1999 to 2000; exposure trial with 30 captive marten scats (dates not given).

## Synopsis

### 1. What they did

In Britain, pine martens, foxes, otters, mink and water voles are monitored from their scats, and scats of martens and foxes have long been relied on to show where martens live. After a run of conflicting scat surveys, pine martens were argued to be effectively extinct in England and Wales, and a reintroduction was being considered. The authors used DNA to test whether experienced marten naturalists can really tell marten scats from fox scats in the field.

- Collecting scats (1999 to 2000). Three experienced marten field workers, kept anonymous, collected fresh “marten” scats along the same transects at different times in Galloway, Scotland, using standard methods. They noted size, shape and odour and gave each scat a confidence score: “possible”, “probable” or “certain” marten. One surveyor also collected more widely in south-west Scotland and in 10 x 10 km squares in England and Wales where martens were probably rare. Other naturalists sent in scats they believed might be from martens.

- Identifying the scats by DNA. Scats were air-dried and frozen. The team extracted DNA from a small scraping of each scat’s surface and sequenced a short piece of mitochondrial DNA to identify the species, with checks against contamination.

- Testing for counter-marking. To rule out foxes marking over marten scats and confusing identification, they placed 30 fresh scats from captive martens outside where foxes are common, 10 at a time, and collected them again at two-day intervals.

### 2. What they found

- DNA was extracted and amplified from 53% of the 163 scats.

- Scotland: 18% of the 56 scats identified as “marten” were actually from foxes. The three surveyors’ error rates were 9%, 29% and 19%.

- Confidence did not help: of eight fox scats from Galloway, three had been scored “certain” marten and two “probable”.

- England and Wales: only one scat was from a marten (from Caernarfonshire, Wales). All the other “marten” scats (97%) were from foxes (28) or a polecat (1).

- One surveyor correctly identified every marten scat in Galloway, yet was wrong every time (12 scats) in the low-density areas of England and Wales.

- All but one of the possible marten scats sent in by other naturalists in England and Wales were from foxes (18).

- Exposure trial: DNA identified the captive marten scats in 70%, 100% and 100% of cases in the three trials, after up to 20 days in the field (mean rainfall 40 mm). All amplified DNA was from martens, so fox counter-marking is unlikely to confuse identification.

### 3. What they concluded

- Pine marten scat surveys based on how scats look are unreliable: surveyors were wrongly confident that they could identify marten scats.

- The surveys failed completely where martens are endangered. This is partly because scats are harder to find when animals are scarce and stop marking territories, but also because surveyors’ judgement was much worse there.

- Because many studies of rare mammals rely on identifying scats, scat identification needs to be more stringent, especially for endangered species.

- Elusive mammals should be monitored with several kinds of evidence: DNA from scats, identification of cast hairs, camera traps and non-leading “sighting” questionnaires. For national surveys, screening many samples at once with microarrays may soon be cost-effective.

- Mitochondrial DNA can work even in fairly old, rain-washed scats, but only some scats ever yield usable DNA. Some scats in this study were more than a month old when collected, rain matters, and slugs have been seen eating nearly a whole scat within 24 hours.

- Field workers, or better, dogs, could perhaps be trained to identify scats, ideally using scats from wild animals identified by DNA, because captive animals’ diet may change the look and smell of their scats.

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

The study tested tracks and signs identification directly: experienced naturalists identified scats as pine marten from size, shape and odour, following standard field guides, and gave each a confidence score. DNA was then used to check every identification. No trailing was reported.

### 5. Tracker or observer certification

The three collectors are described as “experienced marten field workers”, and the other naturalists only as people who believed their scats might be from martens. No certification is reported. Their scat identification skill was tested in this study, by DNA, and was found unreliable, especially in low-density areas.

### 6. Other technologies, skills or innovations

- DNA extraction from scats with Nucleon phytopure kits (a plant DNA kit), scraping the scat’s outer surface to collect gut-lining cells.

- Sequencing of a roughly 200 base pair section of mitochondrial DNA with carnivore-specific primers designed for the study, compared with marten, fox and polecat sequences in the GenBank database.

- An exposure trial testing how long scats left in the field still give usable DNA.

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

- Decisions such as reintroducing pine martens to England and Wales, which are crucial and expensive, must rest on entirely reliable field data. International guidelines oppose reintroductions while remnant populations survive.

- Surveying from scat appearance is especially common in Britain but may spread elsewhere, because a carnivore that becomes rare is often protected by law and harder to survey by other means.

- Accurate scat identification also matters for diet studies.

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

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

- Confidence is not the same as accuracy: scats scored “certain” marten were sometimes from foxes. Testing identifications against an independent check, such as DNA, shows how reliable they really are.

- The same observer was accurate where martens were common and wrong every time where they were rare. Skill shown in one place or at one density may not carry over to another.

## Cite this summary

Lawrence, K. 2026. Summary of: On the origin of faeces: morphological versus molecular methods for surveying rare carnivores from their scats (Davison and Birks et al., 2002). Original Wisdom, Tracking Literature. https://www.originalwisdom.com/tracking-literature/2002-davison-birks-origin-faeces-morphological-versus/