Scientists are dressing pigs in clothes and burying them in Mexico. Why?

SBS Australia

02-08-2025

For the past four years, Maribel Cedeño has been looking for her brother. He's one of an estimated 130,000 people who are missing in Mexico, part of a wave of disappearances that families say is systemic and authorities are unwilling to confront or recognise. Al Jazeera reported the case of Elba Rivas in 2024, whose husband had gone missing, prompting her to join organised protests with others whose loved ones had vanished. "That's why I'm here, demanding that the president tells us where all these people are who have supposedly been found - because my husband never returned." If the missing people are found - dead or alive - it is usually by their loved ones, who - guided by information from witnesses, parents and siblings - search for graves by walking through drug cartel territory, plunging a metal rod into the earth. Around 6,000 clandestine graves have been found since 2007, but tens of thousands of remains have yet to be identified. Now, science has come along to help. Part of the solution has been to introduce high tech tools in the search - like drones. Maribel says using a drone helps her and her family cover more ground. "Flying over, say, a hillside makes it quicker and easier to survey than doing it all on foot - which could take us a couple of days. With a drone, it's easier because it flags points of interest you can then go check."] But they've also turned to a surprising source in their quest: pigs, which resemble humans in size, fat distribution and the structure and thickness of skin. Luis Silvan is a scientist at CentroGeo, a federal research institute focused on geospatial information. He's coordinating a mapping project with Guadalajara University, Mexico's National Autonomous University, and the University of Oxford in England, alongside the Jalisco [[hu-lisk-oh]] Search Commission, using pigs to find the graves of the missing. "We conducted an experiment using animals as stand-ins for human bodies, which we buried in the field behind me. The burial techniques replicate those observed in the region." He says that to simulate real cases, they have buried pigs using the same techniques cartels do to dispose of human bodies—wrapping, burning, dismembering, and burying them in isolated areas. They then use satellite imagery, hyperspectral drone cameras, thermal sensors, and ground-scanning equipment to detect changes in soil, vegetation, and underground structures caused by decomposition. Tunuari Chávez is a researcher at the Jalisco Search Commission. "We're searching for those children alive—just not in the form of life their families last saw them, but in the form of life they might exist in now." Search collectives have long observed that certain flowers or soil patterns often indicate graves. Silvan says the scientists are also tracking chemical shifts, insect activity, and electrical currents to understand how graves evolve. One set of pig graves is even encased behind a pane of transparent acrylic, providing a window for scientists to observe the pigs' decomposition in real time. "Here, we're working on a project to understand how graves evolve and how they can be detected using technology... We can't see the buried bodies directly with this technology. What we see are the effects those bodies have on the soil and vegetation." While Silván and his colleagues have contributed knowledge about grave mapping techniques, Chávez's team has worked to combine the science with what they know about how the cartels operate. They discovered that disappearances in Jalisco commonly happened along cartel routes between Pacific ports, drug manufacturing facilities and the U.S. border, and that most of the missing are found in the same municipality where they disappeared. Chavez says that this insight - combined with the science - tells a story. "A grave is like a micro-ecosystem that evolves over time." The state of Jalisco, home to the Jalisco New Generation Cartel, has the largest number of people reported missing in Mexico: 15,500. Silvan says they may not know how well the technology works, where and when it can be used, or under what conditions, for at least three years. Whether such tools will even be adopted more widely remains uncertain too, limited by high costs and lack of institutional support at the higher levels of government. But he says understanding how to detect graves here could inform searches across the country, supplementing family efforts and witness testimony. "We interpret the data to understand how different types of graves look, and that information is useful for people who are searching." The knowledge flow goes both ways. Silvan says some family members have been able to identify pig burial sites on sight alone, because of the plants, soil placement, and the fact that graves are often found under trees whose roots grow vertically, so those digging the graves can remain in the shade. Maribel says she is glad to be helping with the research - which she hopes will help to find her brother. "After death, there is life. That's what happens in these cases—when bodies go unfound and remain buried for a long time, they give life."