A surprising pattern of Sexual Dimorphism in the Eurasian otter (Lutra lutra) in Sweden
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EnvixLab, Department of Biosciences and Territory, Università degli Studi del Molise, Pesche, Italy
Department of Earth Sciences, Environment and Resources, University of Naples Federico II, 80138 Naples, Italy
These authors had equal contribution to this work
Online publication date: 2023-03-31
Publication date: 2023-03-31
Corresponding author
Luca Francesco Russo   

EnvixLab, Department of Biosciences and Territory, Università degli Studi del Molise, Pesche, Italy
Hystrix It. J. Mamm. 2023;34(1):14-18
Sexual dimorphism is a very common strategy in polygamous mammals. In mustelids, sexual size dimorphism (SSD) is present in several species, while sexual shape dimorphism (SShD) is not as common. The Eurasian otter is a semiaquatic mustelid, exclusively feeding on aquatic prey, mainly fish, amphibians, and crustaceans. It is well-known that male otters tend to be larger, whereas information on SShD is contrasting. We used a 3D geometric morphometric approach to investigate SSD and SShD in three genetically distinct populations of otters located in Northern, Central and Southern Sweden. We analyzed 71 otter skulls (M=41, F=30), using photogrammetric techniques to produce 3D models of each skull, placing 30 3D landmarks on each model. We found that sexual dimorphism varies among populations. Neither SSD nor SShD occurred in the North, only SSD occurred in the Centre, and both SSD and SShD are present in the South of Sweden. Allometric trajectories of males and females from the North population differed from those of the other two populations. Our results highlighted a great variability in sexual dimorphism in Swedish Eurasian otters, that probably derives from different responses to prey availability and historical contingencies.
We are especially grateful to Daniela Kalthoff for her amazing assistance during the visit to the Swedish Museum of Natural History.
This research received support from the SYNTHESYS Project n. SYNTH_SE-TAF-6787  which is financed by European Community Research Infrastructure Action under the FP7 "Capacities" Program.
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