Marcelo Aranda (@marcelo_aranda) joined the iNaturalistMX platform on July 22, 2014. He immediately became the leading curator of mammal observations. Over a dozen years, he identified 83,935 photographs, becoming the principal curator of observations of white-tailed deer (3,780), raccoon (2,979), coyote (2,324), collared peccary (1,501), jaguar (1,030), ocelot (830), mule deer (671), margay (294), jaguarundi (262), tayra (143), kinkajou (103), red brocket deer (100), grison (100), Yucatán brown brocket deer (74), among many others.
His identifications were not limited to photos of the animals themselves but also included images of tracks, scat, and skulls. Despite extreme weakness during his final months, weeks, and days due to an aggressive cancer, he recorded his last 10 identifications just one day before his passing.
Marcelo, affectionately known as “el ruco” because of his prematurely gray hair, was a teacher and guide to many generations of biologists through his field courses, and to thousands more through his publications. In the Manual for Tracking Wild Mammals of Mexico (2012), a revised and expanded edition of earlier works, the skills he developed as a true autodidact come together—skills cultivated over a lifetime of engagement with nature: photography, scientific illustration, tracking, and research.
Accompanying Marcelo on a field excursion was a feast in the art of observation—it meant being transported to another level of perception: distinguishing deer trails within shrub vegetation, identifying tracks in mud, recognizing gait patterns of different species, knowing whether they walked slowly, trotted, or ran. It was entering an almost magical world, as he himself described it. All of this he learned by walking alone with unwavering persistence, guided by both science and art.
We all see the nature around us, but few truly observe it. Even among those of us dedicated to studying and observing nature, there are different “zip codes” of perception. From a very early age, long before beginning his undergraduate studies, Marcelo Aranda walked many kilometers through the forests of the Basin of Mexico, and he continued walking after graduating—through the jungles of Chiapas, Costa Rica, Campeche, the forests of Jalisco, and many other ecosystems. Marcelo developed the art and science of tracking as no one had done before in Mexico, and he has generously left us an invaluable legacy.
I had the immense opportunity to meet, share time, and walk with Marcelo Aranda since the late 1970s, when we were both students. The footprints of this exceptional naturalist are not ephemeral, like most of the tracks he studied; rather, they are deeply etched in the hearts of countless naturalists.
