Marcelo Aranda: Memorias sobre un naturalista

1. What they did

After Marcelo Aranda died on 4 April 2026, the editors invited his family, friends, colleagues and students to share their memories of him. The book gathers 47 contributions with his drawings and photographs, an introduction by the editors, a list of his main publications and indexes.

This entry is based on the summary, preface and introduction, and on ten contributions most focused on tracking (Barraza; Cabrera; Guevara and colleagues; Méndez Saint Martin; March Mifsut, three pieces; Sánchez-Cordero; Sosa Escalante; Sosa Fernández; Velázquez Montes), not on a full reading of all 47.

2. What they found

• Marcelo Aranda taught several generations of biologists to interpret the tracks and signs of wild mammals, through field courses (including his course on wild mammal signs at UNAM and 30 years of short courses), supervised theses, talks and work directly in the field.
• At 13 he had made his own pocket track guide. His books include “Rastros de los Mamíferos Silvestres de México” (1981), “Huellas y otros rastros de los mamíferos grandes y medianos de México” (2000) and the “Manual para el rastreo de mamíferos silvestres de México” (2012). Ten of his publications are mainly about tracks and signs; of 18 on wild cats, 8 are on the jaguar.
• In 1984 he donated plaster track casts, with a written catalogue, to the National Mammal Collection at UNAM. They stayed in storage for four decades, then were curated and formally opened in May 2025. He kept a still larger collection at home in Mérida, and helped build a reference collection of track casts for the Yucatán Peninsula, now at the Autonomous University of Yucatán.
• By Ignacio March’s account, he could tell female from male jaguars by their tracks, and on fine clay mud sometimes tell individuals apart from the position of a toe or a scar on a pad.
• In the field he showed students the features that identify each track, how the distance between tracks shows whether an animal walked or ran, and how to cast tracks in plaster. He stressed measuring tracks, pads and track patterns precisely, since many Yucatán species are smaller than elsewhere in the Neotropics.
• On iNaturalist he identified more than 89,000 observations. He patiently corrected misidentified tracks and said plainly when a track could not be identified from a photo.
• On a trip to El Cuyo in March 2025, the group cast tracks of 11 species in two days, including jaguar. He explained that on ideal ground a good tracker can identify many species in a short time, while camera traps must be left out for a set time.
• He held that tracks and signs and camera trapping complement each other rather than replace one another.

3. What they concluded

The contributors see his books, his track collections and the students he trained as a lasting legacy for the study and conservation of Mexico’s wild mammals. Ignacio March writes that tracks and signs identification remains a low-cost method that will not become obsolete, despite camera trapping and new technology.

The editors note that his photographs, drawings, skulls, casts and field diaries are still to be added to collections, and offer rich material for future research on natural history and on the history of science in Mexico.

4. How tracking was or was not used

Tracking is the subject of the book: tracks and signs identification, casting and measuring tracks, scat, hair and other signs, taught in the field and in reference collections.

5. Tracker or observer certification

Reported but not validated. The contributors describe Marcelo Aranda as a master tracker, but the book reports no certification or test of his skill. Kim Cabrera writes that she spoke about CyberTracker certification at a 2021 online tracking course where he also spoke, that he was interested, and that the first CyberTracker certification in Mexico was held recently.

6. Other technologies, skills or innovations

• Plaster casting and reference collections of tracks.
• Scientific illustration in ink and in colour.
• Black and white wildlife photography.
• Identifying tracks and camera-trap photos online on iNaturalist.
• A 1993 course of his was recorded on VHS video.
• Laura Barraza used what she learned on his course to build teaching materials on mammal signs for primary-school children.

7. Implications for conservation (from the paper)

• He raised concern about habitat destruction and the illegal trade in skins, especially of wild cats, and supported a 2020 study of jaguar trafficking in the Maya forest corridor.
• He held that conservation means involving local people, as at El Capulín.
• Contributors see tracking as a low-cost way to study remote populations.