There is no place like home: Larval habitat type and size affect risk‐taking behaviour in fire salamander larvae (Salamandra salamandra)

Abstract

Individual life histories are strongly influenced by early environmental conditions and experiences. They shape morphology as well as behaviour and can promote adaptive divergence and phenotypic plasticity with regard to different habitat types. The fire salamander (Salamandra salamandra) in the Kottenforst forest in Bonn, Germany, exhibits two genetically distinct ecotypes occurring in two larval habitats, either ponds or streams. In this study, we investigated whether both ecotypes differ in risk‐taking behaviour, measured as the behavioural response during a shelter‐emergence test and a shelter‐seeking test, and whether larval habitat type and size impact these behaviours. Our results revealed an influence of size as well as habitat type. Larger larvae of both habitats appear to be more risk‐prone, as they spent more time outside the starting shelter in the shelter‐emergence test. Irrespective of size, pond larvae sought shelter more often in the shelter‐seeking test and are thus considered to be less risk‐prone. These results indicate that larvae conform to a given niche by adjusting their behaviour. Future studies are needed to disentangle the role of genetic adaptation or phenotypic plasticity and to investigate long‐term consequences of the larval habitat for the adult phenotype. Thereby, efforts should be made to create a concise set of multiple tests assessing behavioural patterns.

Food level and light conditions affect the antipredator behavior in larvae of a stream-breeding amphibian

“…These results indicate that fire salamander larvae had the ability to modulate their behavior depending on immediate predation risk and past variation of environmental conditions. While Oswald et al (2020) showed that risk-taking behavior of salamander larvae depends on the predation risk in the natal habitat, the results presented in this study show that risk-taking behavior is complex and depends on multiple environmental conditions. More generally, while it is well understood that the growth/predation risk trade-off is determined by an interaction between food level and risk, our results indicate that the interactions with environmental factors may modulate the trade-off.…”

“…The aim of our study was to investigate the interactive effects of the long-term exposure to contrasting food levels and light conditions on the antipredator response in larvae of the fire salamander (Salamandra salamandra). We used the probability to emerge from the refuge and the distance moved outside the refuge as antipredator responses describing risk-taking behavior (Sih et al 1988, Anholt and Werner 1995, Oswald et al 2020. Specifically, we hypothesized that long-term exposure to low food levels coupled with longer photoperiod would decrease antipredator response in prey (i.e., larvae will emerge from the refuge more frequently and travel longer distances) when exposed to cues from a predator.…”

Size-related boldness is not altered by stomach flushing in a terrestrial salamander

“…These conditions impact small individuals more than larger individuals (Feder, 1983;Pastorelli et al, 2007), especially when these threats are combined (Rohr and Madison, 2003). Although body size has been associated with exploratory behaviour in amphibians (Keheller et al, 2017), to our knowledge, the present results provide one of the first evidences of a positive relationship between boldness and body size in salamanders (Oswald et al, 2020). This relationship has been already described in other heterothermic vertebrates with continuous body growth such as snakes (Maillet et al, 2015;Mayer et al, 2016) and fish (Harris et al, 2010).…”

“…Because there was a significant repeatability between trials, an individual mean "boldness" value was calculated as: [log(emergence time in trial 1) + log(emergence time in trial 2)]/2. These nonnormally distributed scores were correlated to individual body size (SVL) by means of Spearman's non-parametric rank test (Oswald et al, 2020). Statistical analyses were performed using Minitab software, version 17.0.…”

Behavioural responses to chemical cues of predators differ between fire salamander larvae from two different habitats

“…Salamanders from the two genetic clusters may have already evolved specific behavioural adaptations to their habitat (Weitere et al, 2004). For instance, females from the two clusters differed in their larval deposition behaviour (Caspers et al, 2015) and larvae from the two habitats differed in their risk-taking behaviour (Oswald, Tunnat, Hahn, & Caspers, 2020). Our study system allows to examine if and how individuals from two habitat types behave differently.…”