Sexual Size Dimorphism in Cetaceans

Sexual size dimorphism (SSD), the size difference between males and females within a species, is crucial in ecological and evolutionary research, highlighting how the sexes adapt to their environment. However, marine taxa, including cetaceans (whales and dolphins) - the largest animals ever to have lived - are underrepresented. Rensch’s rule, a frequently cited pattern in SSD, posits that in species where males are larger, SSD increases with body size, whereas in species where females are larger, SSD decreases. However, the rule is understudied, and lacks generality in species where females are larger, which is the case for 30% of cetacean species.The study aimed to test Rensch’s rule in cetaceans and identify ecological factors influencing SSD. It hypothesised that in female-biased species, females are larger due to higher reproductive energy demands, while smaller males are more agile in competition. To test this hypothesis, this dataset covering 97 authenticated cetacean species, encompassing 34 life-history characteristics, was compiled.The dataset is provided in an Excel workbook. The first worksheet provides metadata describing the dataset, and the second worksheet provides a list of variable names and definitions. The full dataset is provided in the 'data' worksheet, with each row representing data from a single cetacean species from a single source, across the full range of variables. The worksheet 'taxonomic info' provides full taxonomic information for each species in the dataset, according to the WoRMS taxonomy (www.marinespecies.org). The final worksheet is a list of the references used for collating the biological data.