An experimental study of microhabitat selection and microhabitat shifts in European tadpoles

The presence or absence of heterospecific tadpoles or of vegetation and changes in population density influenced the microhabitat distribution of 5 sympatric tadpole species in laboratory experiments. Most species, except Hyla a. arborea, occupied the bottom of the aquaria. In some experiments the presence of vegetation caused a significant shift in the tadpole distribution towards the water surface. The presence of Pelobates fuscus, especially under higher density had a similar effect on tadpole distributions. In most species-combination tests one or both species shifted their distribution pattern due to the presence of the other species. In many cases this behaviour can be interpreted as spatial avoidance reaction especially in species which feed in the same water column in the field (Loschenkohl, 1986). The significance of microhabitat shifts as a mechanism to avoid competition is discussed.