An Eerie Scene from the Camera Traps
One night in 2023, deep in the Peruvian Amazon, a camera trap at the Cocha Cashu Biological Station—originally set up to study birds—captured something that left scientists speechless when they reviewed the footage.
An ocelot (*Leopardus pardalis*) was walking unhurriedly along a forest trail. Nothing unusual there—ocelots are among the most common small-to-medium cats in Central and South America: nocturnal, solitary, feeding on rodents, birds, and reptiles.
The strange part: less than two meters behind it walked a common opossum (*Didelphis marsupialis*).
The two animals moved one after the other, in step, at a relaxed pace. No chasing, no wariness—none of the tension millions of years of evolution built between predator and prey. The opossum showed no panic, despite theoretically being ocelot dinner. The ocelot never looked back, as if the furry creature behind it were an old friend.
Lead researcher Isabel Damas-Moreira, a behavioral ecologist at Bielefeld University, later told *The New York Times*: "Like two old friends walking home from the bar."
Nor was it a one-off. Between 2019 and 2023, the team independently recorded the same scene four times at four different Peruvian Amazon sites—always opossum in front, ocelot trailing, sometimes returning along the same path together minutes later.
In June 2025, the paper appeared in *Ecosphere*: "Beyond predator and prey: First evidence of an association between ocelot and opossum individuals." It opened a fascinating puzzle: why would an animal that should eat another walk alongside it?
A Discovery Born at a Conference
The discovery has two origin stories. In Peru, Ettore Camerlenghi (ETH Zurich) and colleagues set up camera traps at Cocha Cashu for bird research, then noticed the strange footage and heard of similar sightings elsewhere in Peru.
In Panama, Dumas Gálvez of the Smithsonian Tropical Research Institute was studying how agoutis (*Dasyprocta punctata*) disperse seeds. He hypothesized agoutis avoid places smelling of ocelot urine. He placed cloth strips treated with ocelot urine, puma urine, and controls before camera traps.
The agoutis did avoid ocelot scent. But surprisingly, opossums showed strong attraction to ocelot scent—approaching, sniffing, rubbing their bodies against the cloth, even biting it. They visited puma scent only once and ignored the controls.
The two threads converged at a 2024 behavioral ecology conference in Melbourne, where Camerlenghi met Gálvez at a poster session. One had behavioral evidence of "walking together"; the other, experimental evidence of "scent preference." Their collaboration produced the *Ecosphere* paper.
Damas-Moreira reflected: "It's a great example of how science often advances through serendipity, curiosity, and collaboration."
The Ancient Script of Predator and Prey
The textbook relationship is clear: ocelots (7–15 kg, nocturnal ambush hunters) eat opossums (1–2 kg marsupials that survive mainly by playing dead and tolerating snake venom). By any account, opossums are on the menu.
But nature's menu is not absolute. A classic counterexample is the coyote–badger hunting alliance in North America: badgers dig out prey hiding underground; coyotes catch prey fleeing from other exits. Together, their hunting success far exceeds solo efforts. The U.S. Fish and Wildlife Service famously photographed a coyote and badger traveling—and even sharing a culvert—together. Research at the National Elk Refuge in Wyoming found 90% of coyote–badger joint hunts are one-on-one; only about 1% involve one badger with three coyotes.
But the ocelot–opossum case is stranger. Coyotes and badgers are both carnivores of similar size that can't eat each other. An ocelot could easily kill an opossum—so why tolerate a potential meal trailing behind?
Three Hypotheses: Who Is Using Whom?
Hypothesis 1: The Opossum's Chemical Camouflage
The most intuitive idea: the opossum exploits ocelot scent for protection. The Amazon teems with predators—jaguars, pumas, anacondas, caimans, raptors. If an opossum smells like an ocelot, other predators may avoid the area, believing an ocelot is nearby.
It's like walking through a dangerous neighborhood alongside the local crime boss—nobody dares touch you for fear of him.
Supporting evidence: opossums actively approach ocelot scent and rub against it, and rubbing a scent onto the body is typically a form of scent transfer in mammals.
Hypothesis 2: The Ocelot's Reverse Chemical Camouflage
Or it may be the reverse. Gálvez proposed a bolder idea: perhaps the ocelot exploits the opossum's stench.
Opossums are famously smelly—musky gland secretions plus scavenging habits. The ocelot's main prey (rodents and small marsupials) are extremely scent-sensitive and flee at predator odors. But walking beside a stinky opossum could mask the ocelot's own scent: prey smells "a harmless opossum passing," not "a cat approaching."
This is reverse chemical camouflage: not prey disguised as predator, but predator disguised as a harmless neighbor.
Hypothesis 3: Cooperative Hunting
The third hypothesis is more radical: they may hunt together.
Opossums possess an ability ocelots lack—natural immunity to snake venom. Their blood contains an 11-amino-acid peptide that neutralizes toxins from rattlesnakes and other pit vipers. With a venom-proof opossum leading the way, an ocelot could more safely hunt dangerous snakes.
No direct evidence yet—no cooperative snake hunting has been filmed—but it is the most tantalizing possibility: a felid and a marsupial forming a cross-class hunting alliance based on complementary abilities.
The Olfactory Arms Race
Whichever hypothesis holds, the phenomenon points to something long underestimated: smell plays a far more complex role in animal relationships than we imagine.
Humans are visual; most mammals navigate primarily by odor. Every tree, stone, and trail in the rainforest is saturated with chemical information—an invisible map animals read day and night. On that map, scent is not just an identity card but a tool that can be borrowed, forged, and weaponized.
Puff adders achieve "chemical crypsis" by suppressing their own scent; some parasitoid wasps mimic host ants' odors to infiltrate nests. Now we may add: opossum and ocelot possibly "borrow" each other's scent, each benefiting.
How Much Are We Missing?
The most sobering point comes from Gálvez:
> "I wonder how many of these weird interactions are happening that we're unaware of because they're difficult to record in the field."
Ocelots and opossums are among the most common mid-sized animals in the Amazon, roaming near villages and passing camera traps countless times. Yet only in 2025 was this behavior first systematically documented.
If we miss interactions between the most common animals, what about rare species, the deep sea, the rainforest canopy? How much of our food webs and ecosystem maps rests on incomplete observation?
Lessons for Cross-Species Cooperation
Seen more broadly, this is a story about heterogeneous cooperation: different capabilities—ocelot's speed and power, opossum's venom immunity and low threat profile—complementing each other's weaknesses.
This mirrors questions in multi-agent systems research: how do agents with different abilities form effective cooperation? Real-world cooperation—human or natural—is almost always heterogeneous. The coyote–badger alliance works because one chases while the other digs.
This suggests: cooperation may not require trust, language, or long-term bonds—only mutual non-harm plus complementary capabilities. In AI, breakthroughs may lie not in ever-larger single models, but in letting different models, tools, and humans form "ocelot–opossum-style" complementary partnerships—no shared objective function required, just walking together being better than walking alone.
Open Questions
The researchers are cautious, claiming only an "association," not cooperation or symbiosis. Unknowns include:
- Is this behavior individual-level (specific individuals) or population-level?
- Does the opossum actively choose to follow, or is it coincidence?
- What benefit does the ocelot actually gain?
- How widespread is this—across the whole Amazon basin?
- Camerlenghi, E., Gálvez, D., Ketola, C., Piga, A., Holmes, N., Mena, J.L., Tobler, M.W., Rayan, F., & Damas-Moreira, I. (2025). Beyond predator and prey: First evidence of an association between ocelot and opossum individuals. *Ecosphere*, 16(6). https://doi.org/10.1002/ecs2.70322
- Coverage: Smithsonian Magazine, Mongabay, The Wildlife Society, Bielefeld University
Gálvez's next step is a control experiment on Coiba Island, Panama, which has opossums but no ocelots or other large predators. Do opossums that have never encountered ocelots still prefer their scent? If yes, the preference is innate; if no, it is learned. The experiment directly probes a core question: is cross-species "cooperation" instinct or culture?
Epilogue
In the camera trap images, a spotted felid and a gray marsupial walk one after another down a trail worn by countless animals, into the rainforest's depths. They don't know they're being recorded, or that they may be overturning our understanding of predator–prey relations. They are just walking.
Perhaps the opossum borrows the ocelot's fearsome reputation. Perhaps the ocelot borrows the opossum's stench as cover. Perhaps each is using the other, owing nothing. Perhaps it is four coincidences.
But in those moments, in the Amazonian night, the line between predator and prey blurred—not erased, but briefly suspended by a subtler, older logic: on this night, walking together beats walking alone.
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