Even in Murky Waters, Choices Are Made with Care

In the murky canals of Xochimilco, where the water holds more shadow than light, the axolotl has learned to navigate a world that asks little of the eyes. These soft-bodied salamanders, famous for regrowing limbs and even parts of their brains, have long been studied for their regenerative gifts. Yet what goes on inside their frilly heads has remained largely a mystery—until now, when a simple experiment with doorways revealed something quietly remarkable.

Researchers at the National Autonomous University of Mexico and the National Institute of Psychiatry Ramón de la Fuente Muñiz designed a test that suited the axolotl's natural talents rather than its limitations. They placed a gray plastic divider in each tank with two circular holes, one larger than the other. Both were wide enough for the animals to pass through comfortably, but the axolotls were given a choice: which doorway would they take ?

The answer, observed over eighteen days, was remarkably consistent. Across six different size combinations, the axolotls preferred the larger opening. Every single one of the twenty-two animals active enough to be analyzed showed a statistically significant preference for the bigger doorway. The greater the difference between the two holes, the stronger that preference became .

But the most intriguing finding came when the lights went out. Axolotls are nocturnal, and their natural habitat offers little visibility even during the day. In complete darkness, the animals moved less frequently, yet when they did cross through the divider, their preference for the larger opening remained just as pronounced. Vision, it seemed, was not essential for this task .

The researchers were initially surprised. "This shows that vision is not always essential for such tasks, especially when it is limited for taxonomic or environmental reasons," animal behaviorist Oxána Bánszegi told ScienceAlert . Exactly how the axolotls perceive the difference without sight remains unclear. One possibility involves their lateral line system, a sensory network that detects water movements and subtle pressure changes. But the study was not designed to isolate which senses were at work .

What the findings do suggest is that the axolotl's cognitive life is richer than its reputation as a laboratory specimen might imply. Distinguishing between openings of different sizes serves a practical purpose in the wild. A soft-bodied animal squeezing through gaps in vegetation or rocks needs to judge whether it will fit—and whether it might get stuck .

The study, published in Animal Behaviour, does not claim that axolotls can count or perform abstract mathematics. It shows something simpler and perhaps more elegant: these creatures can perceive spatial differences and use that information to make choices. In a dark canal, where eyes serve little purpose, that ability may be the difference between safe passage and an uncomfortable squeeze

AI Image Disclaimer: The accompanying visual is AI-generated and does not depict a real axolotl or research setting.

Sources: ScienceAlert, Scinexx, WIRED en Español, Animal Behaviour (journal)