Variation in Defensive Strategies of Brown Frogs against Conspecific and Heterospecific Alarm Cues

Abstract Chemical cues released upon injury play a crucial role in mediating antipredator responses in many aquatic species. Prey populations capable of exploiting information from different sources may enhance their fitness, although the factors determining this ability are not always clear. In this study, we investigated the antipredator responses to both conspecific and heterospecific injury cues (i.e., alarm cues) in three brown frog species: Rana dalmatina , Rana latastei , and Rana temporaria . We recorded two tadpole defensive behaviours: the proportion of time spent inactive and the distance covered. Responses to a native odonate predator were used as a positive control. Tadpoles of R. dalmatina showed a clear decrease in activity in response to both con- and heterospecific cues, similar to their reaction to predator cues. Tadpoles of R. latastei slightly decreased activity in response to alarm cues from both agile frog species but did not react to common frog cues. Finally, R. temporaria exhibited high sensitivity to conspecific cues and a weak response to heterospecific cues. The phylogenetic-relatedness hypothesis seems to explain the observations for both R. latastei and R. temporaria , while for R. dalmatina , the ecological coexistence hypothesis, given its overlapping distribution with the other two species, seems to better explain the data. However, since the invoked hypotheses are not mutually exclusive, further analysis of other populations of these species is necessary to confirm the generality of these findings and to better understand the role of environmental factors in shaping these antipredator responses.