Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Bat responses to aridity

Auteur : Conenna, Irene

Université de soutenance : University of Helsinki,

Grade : Doctoral dissertation (article-based) // Doctoral Programme in Wildlife Biology 2021

Résumé
Due to the perceived low biodiversity of arid environments, species inhabiting these regions have received less research compared to tropical areas and biodiversity hotspots. However, arid conditions are predicted to characterise a larger number of regions globally and there is a greater need to identify strategies that allow species to survive in these harsh environments. Bats occupy a wide variety of habitats, including some of the most arid habitats on Earth, thanks also to their nocturnal habits, ability of powered flight and species-specific physiological adaptations. However, knowledge of the mechanisms in place to face the variety of stressors linked with aridity is still relatively scarce, particularly concerning behaviour and in the light of the diversity characterising bats as a group.

In this thesis, I investigate further the responses and strategies that bats employ to cope with aridity, with a particular focus on the role of functional traits and movement. First, I model functional trait variation of bat assemblages to identify trends along the gradient of aridity globally. Bat assemblages inhabiting conditions of higher aridity display morphological and echolocation features more suitable to move in open habitats thanks to the greater speed and cost efficiency of flight. Additionally, larger body sizes appear to be favoured at these conditions, potentially as an advantage to reduce the exposure to cutaneous evaporative water loss by retaining a lower surface-to-volume ratio.

Despite these general trends, bat communities in arid environments still retain functional diversity, with manoeuvrable species taking benefit from their ability to hunt in the vicinity of the vegetation. Therefore, I then investigate how a low-mobility species, Lavia frons, copes with seasonal changes in aridity and the associated reduction in resources by following its movement using miniaturised GPS devices across a rainy and a dry season. Despite the overall low mobility observed, L. frons appears to respond to seasonal increases in aridity by moving over larger areas and for extended periods of time, supporting the role of movement as a strategy to offset for low prey densities during harsh periods

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