While quantity discrimination is generally considered advantageous, its expression varies based on the ecological requirements of each species. Amphibians remain notably under-represented in such research, primarily because their ecological background often makes it difficult to test them using traditional food or group size paradigms. The critically endangered Mexican axolotl, Ambystoma mexicanum , renowned for its regenerative abilities, is used frequently in developmental and biomedical research. Nevertheless, its cognitive capacities remain largely unknown. Axolotls frequently encounter physical obstacles in their underwater habitat, which they must navigate by accurately estimating the size of openings to avoid injury or entrapment. To mirror their natural ecology, we investigated whether axolotls could discriminate between differently sized holes. Over a 3-day observation period in a familiar environment, axolotls were presented with pairs of passable openings of different sizes. They consistently discriminated between them, with choices influenced by size difference and combined area. This suggests that axolotls possess basic quantitative abilities, thereby enhancing our understanding of amphibian cognition and ecological adaptability. These findings have potential implications for improving our understanding of ecologically relevant cognitive traits that may influence habitat use, movement patterns and species interactions.
Bánszegi et al. (Mon,) studied this question.