Terrestrial Mammal Feces: a Morphometric Summary and Description

1. What they did

Scats tell us which animals are present, what they eat, how they use their home range and territory, and what parasites they carry. Older scats preserved as coprolites (fossil scats) help researchers study ancient ecosystems. DNA and chemical tests can now identify scats more precisely, but the author argues that a first identification from shape and size is still the starting point that guides which later analyses to choose.

The author:

• Compiled published measurements of scat length, width or diameter, and shape for terrestrial mammals from Eastern and Southern Africa, North America and Europe. Most came from field guides, including Liebenberg (2000), Walker (1996) and Stuart and Stuart (1998).
• Added her own measurements of scats from 15 mammal species in the semi-arid northeast of Brazil, with drawings of their shapes.
• Sorted the scats into groups of similar shape, and compared these with the mammal groups they come from.

The introduction also reviews what affects how well tracks and signs are preserved and found, and how scats work as social signals.

2. What they found

Nine scat groups

• Group I: sausage-shaped scats with segments, tapered at one end: the carnivores. Cat scats are compact with clear segments and one especially tapered end.
• Group II: small, round, single pellets in small patches or large piles: hares and rabbits, hyraxes and aardvark. Only aardvark scats, full of termite, ant and larva remains, can be told apart.
• Group III: single, cylindrical pellets with two rounded ends, or one slightly tapered: all rodents, from tiny mouse and squirrel pellets to porcupine, beaver and paca.
• Group IV: like Group III but with a furrow along the length (coffee bean shape): African cane rats and, in northeastern Brazil, the rocky cavy and preá, which share a common origin.
• Group V: pellets pointed at one end and concave at the other: the even-toed hoofed mammals (deer, antelope, peccaries and others), except cattle, buffalo and bison. With fresh green food the pellets can clump into soft patties.
• Group VI: flat scats in circular piles: cattle, buffalo and bison.
• Group VII: single kidney-shaped scats: horses and zebras, and warthog.
• Group VIII: big, bar-like cylinders: elephants, hippopotamus, rhinoceroses and, in South America, anteaters.
• Group IX: mixed shapes and sizes with no shared features: opossums, primates, armadillos and insectivores. These can be identified only with other evidence, such as footprints, other signs or good knowledge of the local fauna.

Telling species apart

• Cats: in North America, cat scats wider than 2.5 cm come from jaguar or puma. In northeastern Brazil, a diameter over 2.1 cm separated jaguar and puma from the small cats. Nowhere in the Americas could jaguar and puma scats be told apart by measurements.
• Dogs: in North America, scats wider than 3 cm can be identified as wolf and smaller ones as coyote; only 4.9% of coyote scats were misidentified as wolf. In Europe, wolf and red fox scats can be separated by size. In Brazil, maned wolf scats are over 2.5 cm wide, with a characteristic smell, texture and fruit remains; one from Serra da Canastra National Park was 4.5 cm wide, larger than any cougar or jaguar scat. In Africa, the many medium and large carnivores could not be separated by measurements.
• Rodents: in northeastern Brazil, five small rodent species could be separated by scat diameter. Rocky cavy scats have the furrow on the concave side, preá scats on the convex side.
• Deer: the two brocket deer of northeastern Brazil could not be separated by shape or size, as with similar species in Africa, North America and Europe.
• Diet: white rhinoceros dung contains only grass; black rhinoceros dung is fibrous and woody. Large carnivore scats can be completely white from bone eating, and lion scats can be black from blood.

Scats as signals

Scats dropped at random show an animal’s or group’s home range. Small amounts placed on prominent spots, such as trail junctions, rocks, tree trunks or termite mounds, act as territorial marks. Hyenas and collared anteaters use discreet individual latrines; some antelopes, hyraxes and raccoon relatives use shared latrines, and rocky cavy latrines can be used for generations.

3. What they concluded

• Nine groups can be recognized by scat shape and size. Although scat size changes with age and diet, size limits can still be set for each group.
• In the author’s studies in northeastern Brazil, shape and diameter were better guides to species than length. Shape is the first clue to which animal left a scat.
• Measurements analysed statistically can separate species within the same group, as with the rodents of northeastern Brazil. Where the local diet is well known, scat contents can also separate species, as with African rhinoceroses and South American dogs.
• Scat shape groups may reflect mammal ancestry, in line with fossil evidence on how mammals evolved.
• Standard measurement patterns could help field studies of living animals and encourage DNA and other studies of coprolites.
• Studying scats starts in the field, by tracking animals or by archaeological digs. The observer’s sharp attention, together with laboratory results, lets us rebuild movements, ecosystems and relationships, and work out what happened when no one was watching.

4. How tracking was or was not used

The paper is a reference on one kind of sign: scats. It opens by describing tracking as probably the oldest science, a low-cost, non-invasive way to study rare, nocturnal and hard-to-see animals, though it needs well-trained, sharp observers. It notes that sandy and loamy soils keep footprints best, while stony, dry and frozen places keep scats best, and that signs are hard to read where animals are very dense. The new Brazilian measurements came from scats found in the field, but the paper does not describe how they were found or identified.

5. Tracker or observer certification

Not reported. The paper does not say who found or identified the Brazilian scats, or how their species was confirmed, which matters because the measurements depend on those identifications.

6. Other technologies, skills or innovations

• Drawings and photographs of scat shapes beside the measurements in each table, and a figure of scat shapes from northeastern Brazilian mammals.
• The paper points to chemical tests (bile acids, pH) and DNA from scats as follow-up tools once a scat has been sorted by shape and size.

7. Implications for conservation (from the paper)

• Information from scats, such as which species are present, their diet, territory and parasites, can be used in conservation projects.
• Tracking signs such as scats is a non-invasive tool for studying threatened species and animals that are hard to observe or trap.
• Scat counts have been used to estimate population size, but the method is still debated because of seasonal changes, uncertain daily defecation rates and unknown decay times.