Viability selection on coat spot patterns correlates with temperature anomalies in Masai giraffes

Abstract

Phenotype-dependent demography may result from heterogeneous selection pressures, which can be altered by temperature anomalies. Understanding which phenotypes are best adapted to different temperatures could clarify how populations may adapt to climatic changes and guide effective conservation measures. Animal markings are heritable phenotypic traits that show variation within populations, which suggest they may be adaptive. Variation in marking shape and size may influence thermoregulation and lead to differing individual responses to temperature anomalies. Therefore, markings may affect survival in variable and changing environments and be important for adapting to climate change. Using resighting data from 810 wild giraffes over 8 years, we estimated viability selection on spot patterns and whether it was affected by temperature anomalies. Calves with smaller lobate and adult males with smaller lobate or larger polygonal spots survived better. Additionally, calves and adult males with larger (vs. smaller) spots that experienced anomalously low (vs. high) temperatures survived better. Spot patterns had a smaller effect on adult females, with individuals of all spot types having lower survival in anomalously high temperatures. Synthesis and applications. Spot patterns influenced giraffe survival and their effects were altered by temperature anomalies. In calves, spot size may help with thermoregulation while spot shape may conceal them from predators. In adults, sex-specific selection pressures suggest sex differences in heat tolerance and trade-off with different functions. Conservation management maintaining variation in spot patterns by facilitating genetic exchange (e.g. through habitat connectivity) may help giraffes to adapt to climate change. Markings may have fitness consequences in other mammalian species and be important for population adaptation.