Context-dependent anti-predator behavioral responses of the lowland tapir (Tapirus terrestris) to free-ranging domestic dogs: evidence from opportunistic visual records

In the wild, the moment a predator appears, an animal's life often depends on a split-second decision: run, hide, fight, or freeze. This split-second calculus is known as anti-predator behavior, a survival strategy honed over millions of years. For large herbivores like the lowland tapir, the biggest land mammal in South America, these choices are complicated by the landscape itself. Water, for instance, is often a sanctuary; many animals that cannot swim well on land can move with surprising speed and safety in a pond or river, leaving terrestrial hunters behind. However, the rules change when the pursuer is a domestic dog. Unlike wild predators that may give up when the terrain shifts, free-ranging dogs often follow their prey into the water, turning a potential refuge into a trap. Understanding how these ancient animals react to this modern, persistent threat is crucial, especially as human settlements encroach on protected natural areas, bringing dogs into direct contact with vulnerable wildlife.

A new study brings clarity to this dangerous dynamic by piecing together a collection of rare, real-world encounters between lowland tapirs and free-ranging dogs. The researchers did not set out to stage these events; instead, they gathered existing visual records, ranging from footage captured by park rangers in Brasília National Park to videos uploaded by the public on social media. By analyzing these opportunistic clips, the team documented exactly how tapirs behave when chased, revealing a toolkit of responses that is far more varied than previously understood. The findings show that while tapirs frequently use water to escape, this strategy does not always stop the chase, and the animals may also resort to standing still, running into thick bushes, or even turning to face their pursuers.

The core of the evidence comes from a specific incident recorded by park rangers in Brasília National Park on a single afternoon. In the video, a tapir is seen sprinting from the dry forest into a pond while dogs bark and chase it. Once in the water, the tapir does not simply stop; it continues to swim, keeping its head and snout above the surface. The dogs, undeterred by the water, jump in and swim after it. The recording cuts away before the chase concludes, but a separate set of photographs taken at the same pond on a different day offers a grim follow-up. These images show a dog swimming after a tapir, followed by a shot of the tapir emerging from the water with a fresh, visible wound on its side. While the photos cannot prove exactly how the injury happened, they confirm that these aquatic pursuits can end in physical harm.

To broaden the picture, the researchers examined ten other videos found online, uploaded between 2016 and 2025. These clips captured interactions in various settings, from wetlands to forest edges and even pastures. In seven of these videos, the tapir was seen using water as a refuge, swimming while the dogs followed. However, the water was not always the final answer. In three other videos, the tapir fled toward dense vegetation, successfully using the thick cover to break the line of sight. One particularly striking clip showed a tapir in a small pond that stopped swimming, turned around, and advanced toward a single pursuing dog, causing the dog to retreat. Another video captured a young tapir that, after a long chase, stood completely still for a moment before fleeing again. These behaviors—swimming, running into bushes, freezing, and even counter-attacking—demonstrate that the tapir is not a passive victim but an animal making active, context-dependent choices based on the immediate situation.

The study emphasizes that these observations describe what was visible in the available footage, not necessarily how often each behavior happens in the wild. Because the videos were found by chance and vary in length and quality, the researchers cannot say that swimming is the most common response or that it always works. What they can say with certainty is that tapirs possess a flexible repertoire of defenses. They know how to use water, but they also know when to run into the forest or stand their ground. The presence of dogs in these environments, however, introduces a persistent risk. The footage confirms that dogs will often continue a pursuit into the water, and that these chases can result in injury, as seen in the photographs from Brasília.

Ultimately, this research highlights a complex and often overlooked interaction between wildlife and domestic animals. It shows that the simple act of a tapir entering a pond does not guarantee safety from a pack of dogs. For conservationists managing protected areas, this means that monitoring the presence of free-ranging dogs is critical, as their ability to pursue prey across different terrains poses a unique threat. The study does not offer a simple solution, but it provides a clear, visual record of the struggle, showing that these large, gentle animals are constantly navigating a landscape where the rules of survival are being rewritten by the presence of human companions.