When in larval development does the smooth newt ( <i>Lissotriton vulgaris</i> ) learn the native pond odor?

Amphibians can learn the odor of the environment in which they have undergone larval stages and use this information for orientation. For anurans, it was shown that learning does not occur throughout development, but only at certain stages that can be described as sensitive periods. However, no similar studies have been carried out for Urodela. Therefore, we investigated whether a sensitive period exists in the smooth newt (Lissotriton vulgaris) by rearing larvae in a chemically marked water. Two experimental and one control groups were formed: first reared in 10−7 mol/L morpholine solution from egg laying to stage 40 of development (inclusively) [1, 40], second from stage 42 (inclusively) until the juveniles emerged onto land [42, 56], and a control group that developed all stages in tap water without a marker. After metamorphosis, juveniles were tested in a T-maze for chemical marker odor recognition response. A statistically significant preference for morpholine was found only in the first group [1, 40], in other cases, the distribution did not differ from the random one. However, at higher temperatures, the response to the odor may change from preference to avoidance.