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2020 Schmid, Paul Lennart: Differences in habitat choice between melanistic and cryptic coloured adders (Vipera berus) A GIS-mediated habitat analysis based using LiDAR data

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Coloration is one of the most adaptive traits in animals, affecting various parts of the ecology of species. A common type of coloration-based adaptation in polymorphic ectotherms is melanism. The thermal melanism hypothesis (TMH) suggests, that darker coloured individuals heat up faster and reach higher temperatures as lighter coloured ones of the same species. One species that displays very high rates of melanism is the common adder, Vipera berus. For this species trade-off factors for melanism have been identified as thermoregulatory advantages linked to sexual selection opposed to a higher risk of predation.

In this study, a habitat analyses based on LiDAR data has examined possible differences in habitat choice between melanistic and cryptic coloured adder females in summer. Due to the availability of environmental variables and a well-studied population of V. berus this habitat analyses took place in the Black Forest National Park.

In total, eight of 25 environmental variables proved significant differences between the two colorations. On a multivariate approach the main factors for the microhabitat of V. berus were identified as the variance of vegetation height and the exposition with the two main PCs displaying significant differences between the coloration types.

These variables most likely relate to cover from above and therefore different amounts of protection from avian predators. Since melanistic females preferred more cover, habitat choice is likely linked to the compensation of the risk of predation. Because of their different reproductive strategies, predation bares a higher cost for females than it does for males, which are known to neglect compensations during mating season. The results of this study suggest that habitat choice in female adders is influenced by reproductive strategies, that are under strong pressure by natural selection.


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