Mammalian Biology

, Volume 83, Issue 1, pp 78–80 | Cite as

Sexual-size dimorphism in two synanthropic rat species: Comparison and eco-evolutionary perspectives

  • Emiliano MoriEmail author
  • Angela Iacucci
  • Riccardo Castiglia
  • Luca Santini
Short communication


Sexual dimorphism is a common trait in many mammal species and sexual-size dimorphism (SSD) repre-sents its commonest form. Rattus rattus and Rattus norvegicus are two cosmopolitan, polygynous species, for which a male-biased SSD has been anecdotally reported, but never quantified. In this work, we assessed the occurrence of SSD in both species and we tested the hypothesis that R. norvegicus has a more evident SSD than R. rattus, in agreement with their body mass-testes size ratio, intra-male aggressive behaviour and mating system. We collected weight data of 40 (20 males and 20 females) adult R. rattus and 27 (13 males and 14 females) adult R. norvegicus from 4 localities in Italy characterized by different habitat typologies. We used a t-test based on Bayesian inference to compare the SSD in both species. The results were in line with our expectation supporting a higher SSD in R. norvegicus than in R. rattus. This study aimed to identify the eco-evolutionary drivers of SSD., and provides further support to well established life history theories on two widely distributed rodent species.


Black rat Brown rat Rattus rattus Rattus norvegicus Sexual-size dimorphism Body mass 


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Copyright information

© Deutsche Gesellschaft für Säugetierkunde, e. V. DGS 2017

Authors and Affiliations

  • Emiliano Mori
    • 1
    Email author
  • Angela Iacucci
    • 1
  • Riccardo Castiglia
    • 2
  • Luca Santini
    • 3
  1. 1.Research Unit of Behavioural Ecology, Ethology and Wildlife Management - Department of Life SciencesUniversity of SienaSienaItaly
  2. 2.Department of Biology and Biotechnology “Charles Darwin”University “La Sapienza”RomeItaly
  3. 3.Department of Environmental ScienceRadboud UniversityNijmegenThe Netherlands

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