Nitrate affects courting and breathing but not escape performance in adult newts

The increasing spread of contaminants in the environment affects the behaviour of individuals and can be predicted to modify population characteristics in the long run. It is thus crucial to investigate the effect of contaminants on fitness-related traits. Nitrate is a major pollutant that disrupts oxygen fixation and steroid metabolism and is expected to affect adult behaviour. In water breeding newts, reduced oxygen supply may increase predation risk by elevating surfacing rate and limiting the capacity to evade a predator. It may also reduce mating success by altering sexual behaviour. We assessed the effect of nitrate on fitness-related behavioural traits in male palmate newts Lissotriton helveticus. We measured courtship and breathing during sexual encounters and escape performance in exposed and non-exposed adults. Unexpectedly, exposed males courted females more often than control males. Body size and breathing rate were also positively related in control males but not in exposed males. Results only partially support the hypothesis of oxygen transfer disruption. Alternatively, exposed males seem to compensate their reduced olfactory attractiveness by decreasing surfacing and increasing courtship frequency. Surprisingly, nitrate did not affect escape performance possibly because anaerobic respiration supplies most of energy during unsustainable activity. Nitrate exposure altered time budget in exposed adults and shifted behavioural trade-offs between competing activities like breathing and courting. Ecological and evolutionary consequences, driven by changes on predation risk or sexual selection regimes, can be expected. This study calls for more attention on amphibian adult stages and the evolutionary response of populations in contaminated environments.