Abstract:

The identification of animals through their tracks represents a basic skill for students of Bachelor's and Master's degrees where biodiversity is a key element. Acquiring this skill requires extensive field experience that is difficult to achieve in university courses when time is limited. At least in the Spanish universities, one of the most common procedures to identify animal tracks is through the use of field guides, attempting to memorize diagnostic elements of the typical tracks that each species produces (e.g., the morphology of a footprint, the usual appearance of a pellet). Although this approach can be very useful, the actual tracks in nature are often incomplete, variable or ambiguous. These cases defy classificatory expectations and can hardly be dealt with through pattern matching (i.e., the comparison of the specimen with a model shown, e.g., in a field guide, such as when attempting to identify birds). Here we describe a complementary method that, in our experience, could help identification of ambiguous tracks. Diagnosis of discard (DOD) is widely used in medicine when the patient's symptomatology is confuse, and consists of discarding options until the most probable disease is "isolated" based on symptoms.

The application of DOD to identify ambiguous animal tracks requires:
(1) asking an unusual key question (“Who has NOT produced this track?”);
(2) possessing a minimal background on the natural history of animals;
(3) having information on the potential fauna of the area where the track has been found; and
(4) using logic. We describe how this skill can be trained in the classroom for medium-sized groups (≤ 30 students) through identification-problem sessions.

The target are biology and environmental science students with a basic background in zoology. Students firstly receive an introductory lecture on tracking (2 h). In 4 subsequent sessions (2 h each) students work in pairs to solve problems based on DOD using photographs of dated and georeferenced tracks, having a minimum bibliography at their disposal. Students’ performance is assessed according to the putative diagnosis reached and, especially, based on steps followed to reach such diagnosis.

The application of this method showed that students:
(1) exhibit a clear cognitive resistance to applying DOD because it challenges their ingrained tendency to compare specimens with patterns;
(2) are able to reach reasonable identifications through DOD; and
(3) are aware of the importance of DOD when working in multiple geographical contexts.

Keywords:

Animal track, diagnosis of discard, biodiversity, field guide.