Manual para el rastreo de mamíferos silvestres de México

1. What they did

This book is a Spanish-language field manual for identifying and interpreting the tracks and signs of the medium and large wild mammals of Mexico. The author defines sign as any trace, mark or clue mammals leave during their activities, plus any remains of the animals themselves, and tracking as identifying and interpreting that sign. He compares learning to track with learning a language, and writes for hikers and other outdoor visitors as well as biologists.

The book has four parts:

• Basics of tracking. Limb anatomy and how it shapes tracks, track terms and measurements, the main gaits and the track patterns they leave, the influence of terrain, how weather changes sign over time, how to collect sign, and how to identify tracks.
• Species accounts. Family by family, from opossums to the paca, with taxonomy following Wilson and Reeder (2005). Each species (or group of species with similar sign) gets a description, distribution, natural history, then its tracks, scat, other signs, species with similar sign and notes, with ink drawings of right front and hind tracks, measurements and walking patterns. Where a family has many species with similar sign, a representative group is described.
• Practical applications. Tracking in education and in mammal research.
• Photographs of tracks and signs. 59 photographs of tracks, scats and other signs in natural conditions.

2. What they found

Reading tracks

• Tracks are usually the easiest sign to see and the most likely to be identified correctly, because the feet are closely tied to each species’ way of life and stay much the same among individuals.
• Knowing the number of toes, which toes are reduced, the shape of the pads and the claws or hooves is key. Rabbits and hares have no pads, only stiff hair.
• In overlapping tracks, the hind foot always lands on the front foot’s track.
• Four basic gaits are recognised: walk, trot, gallop and bound, each leaving typical patterns. For example, opossums walk with the hind track just behind the front track; deer, peccaries and cats often register the hind foot on the front track; raccoons leave tracks in pairs; large canids often trot with the body turned to one side; rabbits and some squirrels mostly use a half-bound; kangaroo rats hop on their hind feet only.
• Terrain changes the size, toe spread and clarity of tracks. Fine dry soil and soft shallow mud are best; coarse sand and deep mud lose detail; on slopes the toes and claws mark more going uphill and the pads more going downhill.
• To age sign, the author’s general rule is that the greater the difference between the ground inside a track and the ground around it, the fresher it is, because weather gradually evens them out. Rain, wind, cold and heat each change tracks in different ways.

Collecting sign

• Photograph the clearest sign with a scale such as a pen or ruler.
• Plaster casts: fine, fast-setting dental plaster works best, mixed in half a thick rubber ball; pour thin mixes on dry ground and let the plaster flow from the widest to the narrowest parts to avoid bubbles; a cast is set when hard, warm and does not mark the finger.
• Scats should be dried well against mould; those with hair need naphthalene against moths; soft ones can be coated with clear varnish or diluted glue.

Species accounts

• The accounts give typical track and scat sizes and how to separate similar species. For example, jaguar tracks are told from puma tracks by toes that do not taper to a point and a pad with a straight or convex top edge; jaguars do not cover large prey remains, unlike pumas; and jaguar and puma scats can be separated where they share an area by associated tracks, bile acids or DNA.
• Some signs other than tracks are described, such as the mounds of pocket gophers, whose tracks are almost never found because they live underground.

3. What they concluded

• Tracking is an enriching activity for anyone, and of great value for education and for research on mammals.
• As a research method it has drawbacks: it needs well-trained, experienced people; sign is not always easy to see or found everywhere, which makes random sampling hard; suitable ground varies between areas; data can be hard to interpret; and similar species, or individuals of the same species, can be hard to tell apart.
• Its advantages: it is cheap, needs no special equipment, and is non-invasive, causing no harm to animals and no risk to researchers, so trained volunteers can help.
• With so many species at risk, it is rarely justified to kill animals for information. For species whose tracks can be identified to species, recording and collecting tracks is a real alternative for keeping distribution records up to date.
• In the author’s opinion, building and keeping collections of track casts or digital photographs is a key task for knowing and conserving wild mammals. These can be curated like skins and skulls, as a complement to traditional collections, which hold little on medium and large mammals.

4. How tracking was or was not used

The whole book is about tracking: identifying and interpreting the tracks and signs of Mexican mammals, including footprints, gaits and track patterns, measurements, scats, feeding remains, burrows and mounds, claw marks, trails, and vocalisations. No trailing method is described, although the author notes that in snow animals can be followed over long distances and much of their activity read.

6. Other technologies, skills or innovations

• Plaster casting, with practical tips on mixing, pouring, reinforcing long casts with a stick, and setting on salty ground.
• Track photographs with a size reference, and ink drawings of an “ideal” track for each species, with the reminder that in the field one sees hollows in the ground, not drawings.
• Curating track casts and photographs as scientific collection specimens, following Ramírez-Pulido et al. (1989).

7. Implications for conservation (from the paper)

• Learning to read tracks and signs helps people see a place as an ecosystem rather than just scenery, and makes them more aware of the need to conserve natural areas and their biodiversity.
• Tracking is a non-invasive way to gain valuable information on species at risk, and track collections can provide current distribution records without killing animals.