Microplastics found in blood of wild tapirs and anteaters across Brazil

Researchers have found microplastic particles in the blood of wild lowland tapirs and giant anteaters across three of Brazil's major ecosystems, including animals whose home ranges never came within tens of kilometers of a road, a farm or a town. The study, published this week in the journal Nature and first reported in English-language science press on Wednesday, is among the first to link satellite-tracked animal movement directly to blood-level plastic contamination in free-ranging terrestrial mammals, rather than in carcasses, feces or captive animals.

A team led by Marcia de Almeida Monteiro Melo Ferraz, a reproductive biologist with joint appointments at the University of British Columbia's Okanagan campus and Germany's Ludwig Maximilian University of Munich, drew blood from 26 lowland tapirs and 21 giant anteaters captured at three sites spanning the Amazon-Cerrado transition, the Cerrado grasslands and the Pantanal wetland between February 2021 and November 2022. Each animal was also fitted with a GPS tag, allowing the researchers to reconstruct exactly how much of its home range overlapped with roads, farmland, settlements and waste facilities. The senior author, movement ecologist Michael Noonan of UBC Okanagan, supplied the modeling framework used to turn those GPS tracks into a measure of each animal's lifetime exposure to human-altered land.

What the blood tests found

Of roughly 17,000 particles extracted from the samples and run through confocal Raman spectroscopy, which identifies a material by how it scatters laser light, 2,815 matched the signature of plastic polymers closely enough to count as microplastics. Those particles turned up in 43 of the 47 animals. Concentrations varied enormously, from none in a handful of individuals to more than 1,200 particles per milliliter in the most contaminated, with a mean of about 74 particles per milliliter across the sample. Tapirs carried roughly twice the median load of anteaters, though the difference between species fell just short of standard statistical significance.

The clearest pattern was with geography rather than species. Blood concentrations rose with the Human Footprint Index, a composite measure of built infrastructure, population density, cropland, pasture, roads and nighttime lighting, calculated for each animal's home range. They also rose as the distance to the nearest town or waste-management facility shrank. The statistical model found both relationships held even after accounting for an animal's sex, age, body weight and species, with the association to distance from development notably strong.

Measuring exposure without measuring every town

The Human Footprint Index the team relied on traces back two decades to mapping work originally produced with the Wildlife Conservation Society and catalogued through NASA's open data portal, which combined population counts, land cover, roads, railways, rivers and lighting into a single global grid of cumulative human pressure. Later updates to that index show just how fast the backdrop has shifted: the global mean footprint score rose roughly a quarter between 2001 and 2020, and Brazil's own mean footprint rose more than 40 percent over the same stretch, driven largely by the expansion of agriculture and infrastructure into the Amazon's southern and eastern fringes, an area ecologists call the Arc of Deforestation.

That context matters for interpreting the Pantanal results, which the authors describe as the most striking part of the dataset. Every animal sampled there carried microplastics, even individuals whose entire tracked range sat more than 65 kilometers from the nearest development and more than 110 kilometers from a waste facility. Concentrations in those remote Pantanal animals were markedly lower than in tapirs and anteaters living near farms or settlements elsewhere, but their statistical model, extrapolated to a theoretical home range with zero human footprint, still predicted a baseline level of contamination rather than zero. The authors interpret that as evidence that some microplastic exposure now travels through water, air, flooding or prey even where direct contact with human infrastructure is absent.

Who the findings reach

Both species are listed as vulnerable to extinction by international conservation assessments, and both are already the focus of long-running protection programs in Brazil: the Lowland Tapir Conservation Initiative, run by the Brazilian nonprofit Instituto de Pesquisas Ecológicas, and the giant anteater monitoring work carried out by the Wild Animal Conservation Institute, known in Brazil as ICAS, whose Anteaters and Highways Project also supplied animals and field data to the new study. Researchers from the Toronto Zoo, the Royal Zoological Society of Scotland and Germany's Helmholtz Centre for Environmental Research also contributed samples or analysis, reflecting how much international infrastructure now underpins Brazilian wildlife-health monitoring.

The implications extend beyond the two species sampled. Both animals sit in the middle of their food webs — tapirs as large herbivores and seed dispersers, anteaters as specialist predators of ants and termites — and both are frequently proposed by biologists as sentinel species whose health can signal broader ecosystem contamination. Because the particles were measured directly in blood rather than in digestive waste, the study offers firmer evidence that ingested or inhaled plastic is crossing into general circulation in a wild mammal, not simply passing through the gut.

"Our paper is the first to demonstrate this linkage for terrestrial mammals," said Justin Calabrese, a co-author who leads a research group at the Center for Advanced Systems Understanding, a Helmholtz Association institute in Görlitz, Germany, referring to the statistical tie between human land use and blood-borne plastic contamination.

What happens next

The authors frame their results as an argument for targeted, local interventions rather than only broad plastic-reduction campaigns. They point to improved waste collection and treatment around rural settlements, buffer zones between protected areas and nearby development, and the removal of specific point sources of plastic pollution — such as open dumps near reserve boundaries — as measures that could plausibly lower exposure for wildlife living nearby. Brazil's waste-management infrastructure has lagged behind the rapid growth of farming towns along the agricultural frontier, a gap the authors suggest is now showing up in animal bloodstreams.

Noonan's laboratory at UBC Okanagan has separately secured new funding this year through a joint competition run by Canada's Natural Sciences and Engineering Research Council and Environment and Climate Change Canada, which is backing a follow-up effort to map terrestrial microplastic exposure in wildlife across Canadian ecosystems using similar movement-tracking methods. The Brazilian dataset and the statistical code behind it have been released publicly, and the authors say they expect other groups to apply the same blood-and-GPS approach to additional species and regions, which would help establish whether the Pantanal's low but persistent baseline contamination is a Brazilian pattern or close to a global one.

For now, the study does not address what, if anything, the measured concentrations mean for the animals' health; the authors note they did not find a statistically robust relationship between microplastic load and body condition in this sample, and they caution against drawing clinical conclusions from blood particle counts alone. That question, they write, is the logical next phase of the work.