# Facts from feces revisited > In the Brenta mountains of Italy, nobody had seen the last brown bears, yet their droppings told researchers how isolated they were, that both males and females survived, and what they had eaten. This 1997 review shows how DNA from scat can reveal species, individuals, sex, diet, disease and family ties, and why scat may be the best clue we have to rare and elusive mammals. Summary by Kersey Lawrence, Original Wisdom. Updated 9 November 2026. Page: https://www.originalwisdom.com/tracking-literature/1997-kohn-wayne-facts-feces-revisited/ ## Citation and access - **Authors:** Michael H. Kohn and Robert K. Wayne - **Year published:** 1997 - **Journal or source:** Trends in Ecology and Evolution - **Full citation:** Kohn, M. H. and Wayne, R. K. 1997. Facts from feces revisited. Trends in Ecology and Evolution 12(6): 223–227. - **DOI:** 10.1016/S0169-5347(97)01050-1 - **Access status:** Publisher link only - **Where to find it:** https://doi.org/10.1016/S0169-5347(97)01050-1 ## Tags - **Species:** Mammals > Brown bear - **Tracking:** Scat; Tracking - **Behaviour and ecology:** Behaviour; Feeding; Home range - **Methods and technology:** DNA; Literature review - **Data type:** Review - **Observer qualification:** Not needed - **Discipline:** Behaviour and ecology; Wildlife tracking - **Year published:** 1997 ## Detailed keywords - **Species:** Main worked example: brown bear (Ursus arctos) in the Brenta mountains of northern Italy, with comparison populations in Slovenia, Croatia and Bosnia; bear diet included plants of the genus Photinia (which the paper calls the hawthorn genus). Other species whose feces had yielded DNA in studies the authors review: Indian elephant (Elephas maximus), European bison (Bison bonasus), polar bear (Ursus maritimus), dugong (Dugong dugong), wild baboons (Papio cynocephalus), bonobos (Pan paniscus) and pinnipeds (seals). Parasite example: tapeworm (Echinococcus multilocularis) in feces of red foxes (Vulpes vulpes). Kinship example: wild-caught house mice (Mus musculus). - **Location and habitat:** No study area of their own. Examples from the Brenta mountains, northern Italy; Slovenia; Croatia; Bosnia. Authors based at the University of California, Los Angeles, United States. - **Topics:** molecular scatology; non-invasive genetic sampling; DNA from feces (scat); species identification from scat; individual identification (“genetic fingerprinting”); sex determination; diet; parasites and pathogens; fecal hormones and reproductive status; kinship and paternity; census population size; effective population size; home range and territory size from scat genotypes; genetic variation; phylogeography and gene flow; reintroduction source populations; technical problems (inhibition, inconsistency, specificity, contamination). - **Statistics or models:** None - **Data type:** Review of published studies (Trends in Ecology and Evolution “Reviews” section, June 1997). No new field data. The Box 2 figure that scats are assigned to the right species in only about 50 to 66% of cases is cited from a mammal tracking field guide (Halfpenny and Biesot 1986). ## Synopsis ### 1. What they did In 1984 Putman wrote a review called “Facts from Faeces”, noting that dung may be the easiest source of information for a field biologist whose study animals are hard to see. Kohn and Wayne return to that idea thirteen years later. Many mammals are becoming rarer and harder to observe, and capturing them is expensive, needs many permits and can change the very things a researcher wants to measure. The authors review how new genetic techniques can be applied to feces, a field they call molecular scatology. DNA is purified from a scat sample and short stretches of it are copied many times with the polymerase chain reaction (PCR), so they can be read. They set out: - The genetic markers that can be used (Box 1), and what they reveal. - Conventional (non-DNA) studies of feces (Box 2). - Early studies of fecal DNA, with a worked example of brown bears in Italy. - The technical problems still to be solved (Box 3). - The kinds of information feces can give: behaviour, population size, home range, effective population size, genetic variation, population history, diet and disease. ### 2. What they found What a single scat can tell you DNA from one fecal sample can show which species left it, which individual (a “genetic fingerprint”), whether it was male or female, which diseases and parasites it carried, and what it ate (Fig. 1). The animal’s own DNA comes from cells shed from the lining of the gut. The Brenta bears A small, endangered brown bear population survived in the Brenta mountains of northern Italy, but no one knew how many bears there were or their sex. Using feces alone: - A single mitochondrial DNA type was found, suggesting the population was small and isolated. The same type was common in bears from Slovenia, Croatia and Bosnia, so the Brenta bears were once in contact with those populations. - A Y-chromosome marker showed at least one male and one female were present, leaving open the possibility that the population could grow. - Plant DNA in the feces showed that the bears had eaten plants of the genus Photinia in late summer. - The results suggested that bears for any reintroduction should come from the Slovenian population. The bears were never seen during the study. Other early successes DNA had been taken from the feces of Indian elephants, European bison, polar bears and dugongs. Four studies had identified individuals from their feces (baboons, bonobos, brown bears and seals). Conventional scat studies (Box 2) - Mammal species can often be identified from their feces, but without extra information feces are assigned to the right species in only about 50 to 66% of cases, because related species leave scats of overlapping size. - Scat counts have been used to estimate abundance and population size, but the same individual can be counted more than once. - Scat abundance has been used to study habitat use and range size, and scat piles can mark territory boundaries. These studies often required animals to eat coloured plastic markers or radioactive bait so their feces could be told apart. - Undigested prey and plant remains show diet, though with shortcomings. Fecal hormones show reproductive status, stress, sex and age; feces also show parasites, gut bacteria and pollutants. What fecal DNA could add - Behaviour: kinship and paternity, to see which behaviours lead to breeding success. About 20 microsatellite loci (highly variable DNA markers) may be needed, and more in small, inbred populations. - Population size: many large mammals leave feces along roads, trails and territory boundaries, which can be sampled again and again. When collecting more feces over a large area turns up no new individuals, everyone has probably been sampled. For animals that scatter feces more evenly, transects can be used. Fecal DNA may be the only way to prove that a cryptic, rare or supposedly extinct species is present. - Home range and territory: mapping where each individual’s feces are found, with methods like those used for radio-tracking data. - Effective population size, genetic variation and population history: the number and sex of breeding animals, monitored over time without handling them. - Diet and disease: finding a food’s DNA proves it was eaten, but not finding it does not prove it was not eaten, and DNA cannot easily show how much of each food was eaten. Looking at food remains by eye may be better for amounts. Technical problems (Box 3) Substances in feces can block PCR; DNA in feces is scarce and degraded, which can lead to individuals being typed wrongly; markers must be carefully chosen and the results checked; and samples are easily contaminated. Repeating extractions and tests on each sample is recommended. ### 3. What they concluded - Relief from “sampling despair” has come from an unexpected source: feces. - Combining conventional scat analysis (reproductive cycles, pathogens, diet) with the new DNA methods (paternity, kinship, sex ratios, population size, gene flow and population history) may give a much fuller picture of the hidden lives of elusive and rare mammals. - The lack of genetic, demographic and life history data has been a notorious problem in conservation management, and non-invasive sampling could solve it. - The challenge is to develop better methods for dealing with inhibition, inconsistency, specificity and contamination, so that molecular scatology can be used routinely on large numbers of samples. ### 4. How tracking was or was not used This is a review and no field tracking was done. The whole paper rests on scat, one of the most common signs trackers find. It points out that identifying the species from a scat’s appearance alone is right only about half to two thirds of the time (citing a mammal tracking field guide), and that DNA can confirm species, individual and sex. It also notes that many large mammals leave feces along roads, trails and territory boundaries, where they can be collected repeatedly. ### 6. Other technologies, skills or innovations - Polymerase chain reaction (PCR) to copy DNA from small, degraded samples. - Mitochondrial DNA (cytochrome b for species identification; the control region for differences within a species), microsatellites for individual fingerprints and kinship, the SRY gene on the Y chromosome for sex, and chloroplast DNA (rbcL) for plant foods. - Fecal steroid hormone analysis for reproductive status, stress, sex and age. ### 7. Implications for conservation (from the paper) - Fecal DNA lets researchers study endangered and elusive mammals without seeing, capturing or handling them, avoiding cost, permits and disturbance. - For the Brenta bears, fecal DNA showed that both sexes remained and pointed to Slovenia as the source for reintroduction. - For endangered species, any evidence of breeding is very important, and fecal DNA can provide it. It may be the only way to prove that a rare or supposedly extinct species is present. - Monitoring genetic variation over time from feces can help programmes that aim to keep a certain share of a population’s genetic variation. ### 8. Implications for tracking (Original Wisdom's observations) _These are Original Wisdom's observations, not the authors'._ - Scat collection for DNA depends on finding scat and knowing where animals leave it (roads, trails, territory boundaries, latrines). Tracking skill is the first step in this kind of study. - The 50 to 66% figure for identifying species from scat appearance alone is a reminder that scat identification benefits from supporting evidence such as associated tracks, and that DNA can be used to test it. ## Cite this summary Lawrence, K. 2026. Summary of: Facts from feces revisited (Kohn and Wayne, 1997). Original Wisdom, Tracking Literature. https://www.originalwisdom.com/tracking-literature/1997-kohn-wayne-facts-feces-revisited/