# Scat removal: a source of bias in feces-related studies

> Scats are a favourite tool for studying what carnivores eat, but what if the evidence gets eaten first? On a Kansas army base, researchers set bobcat and coyote scats on sifted tracking plots and read the tracks every day. Up to half the scats vanished within days in summer, mostly where opossums had visited, and others were buried, dug over, cached by a woodrat or washed away by rain.

Summary by Kersey Lawrence, Original Wisdom. Updated 9 November 2026. Page: https://www.originalwisdom.com/tracking-literature/2005-livingston-gipson-scat-removal-source-bias/

## Citation and access

- **Authors:** Troy R. Livingston, Philip S. Gipson, Warren B. Ballard, Dana M. Sanchez and Paul R. Krausman
- **Year published:** 2005
- **Journal or source:** Wildlife Society Bulletin
- **Full citation:** Livingston, T. R., Gipson, P. S., Ballard, W. B., Sanchez, D. M. and Krausman, P. R. 2005. Scat removal: a source of bias in feces-related studies. Wildlife Society Bulletin 33(1): 172–178.
- **DOI:** 10.2193/0091-7648(2005)33[172:SRASOB]2.0.CO;2
- **Access status:** Publisher link only
- **Where to find it:** https://doi.org/10.2193/0091-7648(2005)33%5B172:SRASOB%5D2.0.CO;2

## Tags

- **Species:** Mammals > Bobcat; Mammals > Coyote; Mammals > Domestic dog; Mammals > Eastern cottontail; Mammals > Eastern woodrat; Mammals > Elk; Mammals > Raccoon; Birds > Ring-necked pheasant; Mammals > Virginia opossum; Mammals > White-tailed deer; Birds > Wild turkey
- **Region:** North America > United States
- **Tracking:** Caches; Feeding signs; Scat; Tracking; Tracks; Tracks and signs identification
- **Behaviour and ecology:** Behaviour; Feeding; Food caching
- **Data type:** New field data
- **Observer qualification:** Not reported
- **Discipline:** Behaviour and ecology; Wildlife tracking
- **Year published:** 2005

## Detailed keywords

- **Species:** Studied: scat removal of feces from captive bobcats (Lynx rufus), captive coyotes (Canis latrans) and free-ranging coyotes, and the animals visiting the scats, above all opossums (Didelphis virginiana). Recorded at the stations by their tracks: small birds, bobcat, coyote, deer (white-tailed deer, Odocoileus virginianus), dog, elk (Cervus elaphus), fox, insects, opossum, pheasant (Phasianus colchicus), rabbit (cottontail, Sylvilagus floridanus), raccoon (Procyon lotor), skunk, small rodents (all rodent tracks pooled) and turkey (Meleagris gallopavo). Eastern woodrat (Neotoma floridana): one woodrat cached coyote feces at a nearby den. Other predators in the study area: red fox (Vulpes vulpes), striped skunk (Mephitis mephitis), mink (Mustela vison), badger (Taxidea taxus), feral dogs and feral cats. Discussed: Allegheny woodrat (Neotoma magister) and raccoon roundworm (Baylisascaris procyonis).
- **Location and habitat:** Fort Riley Military Reservation, a 40,273 ha United States Army training area in the Flint Hills of Geary, Riley and Clay counties, northeastern Kansas, United States. Steep slopes, shallow limestone soils, tallgrass and mixed-grass prairie with wooded ravines and riverside forest (bur oak, chinquapin oak, American elm, red mulberry, black walnut, green ash, hackberry, honey locust); about 80 cm of rain a year. Stations were split evenly between forest and prairie.
- **Topics:** coprophagy (eating feces), scat removal and disappearance, bias in scat-based diet studies, bias in scat counts for presence and relative abundance, caching of feces by woodrats, territorial scent marking (removing a scat and depositing fresh feces), rain washing scats away, seasonal differences, forest versus prairie, parasite and disease transmission through feces, comparison of older stomach-based and newer scat-based coyote diet studies in Kansas.
- **Statistics or models:** Generalized linear model with binomial error and logit link (SAS), run separately for each season, testing habitat (forest or prairie), feces type and their interaction; percentages; average days to removal with standard errors (Figure 1). Inconsistencies in the paper: (1) the abstract gives the lowest removal rate as 7% in spring, but the results give 4 of 60 removed in winter (about 7%) and 9 of 58 in spring (about 16%); (2) the text reports 125 visits to baited stations in spring, but the spring columns of Table 1 add up to 115 (the other seasons match: 140, 176 and 271); (3) the conclusions describe removal rates as “<50%”, although summer removal was 50%; (4) the discussion says woodrat tracks were often present where scat was removed, but woodrats are not listed separately in Table 1 (all rodents were pooled as “small rodent”); (5) the number of scats placed in autumn is not given (19 were removed).
- **Data type:** New field data, collected January to December 2000 (winter 4 January to 19 March, spring 20 March to 20 June, summer 21 June to 21 September, autumn 22 September to 20 December), with monitoring on more than 30 days each season. The discussion also draws on two published coyote diet studies from Kansas (1948 to 1957, and 1990 to 1991).

## Synopsis

### 1. What they did

Scats are cheap and easy to collect, and researchers use them to study diet, to tell which species are present, to estimate relative numbers and even to identify individuals from DNA. All of this assumes that the scats found are a fair sample of what animals left behind. The authors asked how often scats simply disappear, and what takes them.

The study ran through 2000 on Fort Riley, a United States Army training area in the Flint Hills of northeastern Kansas, in both forest and prairie.

- Tracking stations. They cleared circles 1 m across, smoothed the ground and sifted sand and soil over them so that the tracks of visiting animals would show clearly.

- Scats. Each station got one scat, chosen at random, from one of three sources: free-ranging coyotes (collected fresh along dirt roads on the base), captive coyotes fed dog food, and captive bobcats fed a commercial cat diet (both from zoos). For each type they set 20 stations at least 0.5 km apart, half in forest and half in prairie, plus 12 stations with no scat as controls. Scats were frozen and thawed 24 hours before use.

- Checking. They read the stations every 24 hours, recorded and identified the tracks of visitors where possible, noted whether the scat had gone or been disturbed, then smoothed the surface again. They kept checking until the scat was removed or broke down from rain, drying or wind, over more than 30 days in each season.

- Analysis. For each season they tested whether removal depended on habitat, on the type of scat, or on the two together.

### 2. What they found

How many scats disappeared

- Winter: 4 of 60 scats were removed (2 bobcat, 1 captive coyote, 1 free-ranging coyote), 3 of them in forest. Too few to test.

- Spring: 9 of 58 were removed, 6 of them coyote scats. Removal depended on the combination of scat type and habitat, but not on either alone.

- Summer: 30 of 60 (50%) were removed and appeared to have been eaten. Removal was higher in forest (67% of removals) than prairie (33%). Scat type made no difference.

- Autumn: 19 scats were removed, nearly three times more often in forest than in prairie; 15 of the 19 were coyote scats, although scat type alone was not significant.

- Scats went quickly: on average in about 1.5 days in summer and about 2.5 to 3 days in the other seasons (read from Figure 1).

Who visited

- Baited stations had 140 visits in winter, 125 in spring, 176 in summer and 271 in autumn. Control stations with no scat were hardly visited: one deer in spring and one rabbit each in summer and autumn.

- Opossums were the most frequent visitors where scats were removed: at 2 of the 3 forest removals in winter, 33% of removal stations in spring, half of them in summer and 37% in autumn.

- Coyotes, bobcats, raccoons, deer, rabbits, small rodents and insects were also present at stations where scats disappeared.

Other ways scats disappeared

- A bobcat buried the study scat and defecated on the station in spring; in autumn a bobcat did the same with a captive bobcat’s scat.

- At 2 spring stations, coyote tracks were present, the scat was gone and the station had been dug up and covered with fresh urine and feces.

- A woodrat removed a coyote scat and cached it at a nearby den.

- Heavy spring rains washed scats away more than once.

The species that removed a scat could be named for certain only when a single species’ tracks were on the station. Where several species had visited, the authors listed them all but could not say which took the scat. Leftover pieces often showed tooth marks and small fragments, suggesting the scat had been eaten.

Comparing diet studies

An older study of 1190 coyote stomachs from Kansas (1948 to 1957) found rabbits and hares in 57% and hoofed animals (mostly livestock) in 38%, against rodents in 36%. A later study of 1389 coyote scats (1990 to 1991) found rodents in 86%, rabbits and hares in only 20% and hoofed animals in about 6%. The authors suggest that animals selectively eating scats holding partly digested rabbit and deer could explain part of the difference, alongside changes in prey and differences in method.

### 3. What they concluded

- Eating feces and other behaviours that remove scats can bias studies based on scats. Removal rates like those at Fort Riley could distort diet studies if scat contents are taken to represent what animals ate.

- Scat counts used to show presence or relative abundance could also be biased by scats being eaten, cached or removed during territorial marking.

- Scats may be an important seasonal food for opossums, perhaps because of the protein-rich insects on them in summer, and may supplement the diet of other species. Scats from large prey may be richer in protein because large prey are less completely digested.

- Eating or carrying feces may spread parasites and disease, as with the raccoon roundworm and the Allegheny woodrat.

- More physiological and behavioural studies of coprophagy are needed.

- Cameras or video would have identified the animals more surely, but theft and vandalism risks on a busy military base ruled them out.

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

Tracking was the main way the researchers learned what visited each scat. Each station was a patch of smoothed, sifted sand and soil, read every 24 hours, and the tracks of visitors were recorded and identified to species where possible. All rodent tracks were pooled as “small rodent” and small bird tracks as “small bird”. Tracks were also used to recognise territorial behaviour (a bobcat burying a scat and defecating; coyotes digging up stations and leaving fresh urine and feces). Leftover scat fragments were examined for tooth marks.

### 5. Tracker or observer certification

Not reported. The paper does not say who read the tracking stations or how their track identification skills were checked. This matters because which animals removed scats rests entirely on track identification.

### 6. Other technologies, skills or innovations

- Tracking stations (smoothed, sifted plots of sand and soil, 1 m across) used with scats as the bait, rather than scent.

- Comparison of scats from captive animals on known diets with scats from wild coyotes.

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

- Scat-based diet studies and population surveys, widely used because they are cheap and non-invasive, may be biased when scats are removed selectively, and removal varies with season and habitat.

- Woodrats foraging in latrines and caching feces may face a higher risk of parasites, which has been linked to the decline of the Allegheny woodrat.

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

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

- The study shows how much a simple tracking plot can reveal: tracks in sifted soil around a scat told the researchers which animals came, when scats disappeared and how (eaten, buried, dug over, cached or washed away).

- For trackers using scats, the find depends on what has happened since the scat was left. In summer at Fort Riley half the scats were gone within days, so the scats found on a survey may not be a fair sample of those deposited.

## Cite this summary

Lawrence, K. 2026. Summary of: Scat removal: a source of bias in feces-related studies (Livingston and Gipson et al., 2005). Original Wisdom, Tracking Literature. https://www.originalwisdom.com/tracking-literature/2005-livingston-gipson-scat-removal-source-bias/