In 1864, the first living Mexican axolotls were brought from Mexico to Paris. On arrival, the 34 animals were divided up between the two zoos in Paris, the Ménagerie of the Muséum d'Histoire naturelle and the Jardin d'acclimatation. From there, the animals and their descendants spread around the world as zoo and laboratory specimens, as well as pets. Today, a population of hundreds of thousands of axolotls live in aquariums, zoos, and laboratories around the globe. The fate of the axolotls (...) in the Ménagerie and their subsequent proliferation open a unique window into the culture and practices of keeping unknown animals in Europe in the 19th century, and their relation to experimental zoology. During the early years, the challenges were to keep the axolotls alive and to bring them to reproduction. The surprising transformation of some of these normally aquatic animals into a land-dwelling form prompted further investigations of their living conditions and mode of reproduction. The example of the axolotl offers a detailed look into the practices of handling unknown species, the ways in which this handling became research, and the kinds of knowledge produced in this context. I pay particular attention to the role of the animal keepers and the infrastructures, and the ways in which practical knowledge about the animals' living conditions triggered experimental research. (shrink)