Abstract
The introduction of alien species is one of the major causes of current and global biodiversity loss. The introduction of fish can be a particular threat to native amphibian populations, which are declining worldwide. One way for amphibians to persist in such altered environments is to adopt anti-predator strategies especially at the behavioural level. However, although it has been shown that avoidance behaviour may decrease the probability of being detected by a potential predator, little is known on the consequences on sexual behaviour. In this study, we tested the hypothesis that adult Alpine newts (Ichthyosaura alpestris) use shelters more often and exhibit less sexual activity in the presence of goldfish (Carassius auratus) and that they reduce sexual activity more in risky micro-habitats than in safe environments. To this end, we assessed behavioural patterns of adult newts in a replicated laboratory design. Goldfish were present in direct contact with newts in half of the tanks. Consistently throughout the study period, significantly more newts used shelter in the presence of fish than in their absence. Newts also significantly decreased their sexual activity level overall, but specially outside the shelter when they were in direct contact with fish. These results show that fish presence can affect newts in complex ways, such as through inhibition of their reproduction. Our work highlights that integrating behaviour in conservation studies is essential to understanding the patterns of coexistence and exclusion between introduced fish and amphibians.
Highlights
Massive introductions of alien species can disrupt ecological equilibriums by creating novel contexts in which the responses of native species may be inadequate or costly [1]
There was a significant interaction between fish and habitat (Table 1): we found an effect of fish on the number of sexual activity events
We found that the goldfish, a species that is usually not a predator of adult amphibians such as the Alpine newt, affects them in complex behavioural ways, i.e. by involving a micro-habitat shift, and by inhibiting sexual behaviour, and this more in risky than in safe micro-habitats
Summary
Massive introductions of alien species can disrupt ecological equilibriums by creating novel contexts in which the responses of native species may be inadequate or costly [1]. Freshwater fish are often intentionally introduced into the wild by human activities for many reasons such as aquaculture, fisheries, biological control and ornamentation [7]. These introductions were identified as one of the main threats to amphibians [3], a class of vertebrates facing a massive decline worldwide, even recently reported as the sixth mass extinction [8,9]. The detrimental impact of fish introductions on pond-breeding amphibians is understandable since they typically evolved in aquatic habitats naturally devoid of fish [10,11,12]
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