Social organization in ungulates: Revisiting Jarman’s hypotheses

Karola Szemán, András Liker, Tamás Székely

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Ungulates (antelopes, deer and relatives) have some of the most diverse social systems among mammals. To understand the evolution of ungulate social organization, Jarman (1974) proposed an ecological scenario of how distribution of resources, habitat and feeding style may have influenced social organization. Although Jarman's scenario makes intuitive sense and remains a textbook example of social evolution, it has not been scrutinized using modern phylogenetic comparative methods. Here we use 230 ungulate species from ten families to test Jarman's hypotheses using phylogenetic analyses. Consistent with Jarman's proposition, both habitat and feeding style predict group size, since grazing ungulates typically live in open habitats and form large herds. Group size, in turn, has a knock-on effect on mating systems and sexual size dimorphism, since ungulates that live in large herds exhibit polygamy and extensive sexual size dimorphism. Phylogenetic confirmatory path analyses suggest that evolutionary changes in habitat type, feeding style and body size directly (or indirectly) induce shifts in social organization. Taken together, these phylogenetic comparative analyses confirm Jarman's conjectures, although they also uncover novel relationships between ecology and social organization. Further studies are needed to explore the relevance of Jarman (1974) scenario for mammals beyond ungulates.

Original languageEnglish
Pages (from-to)604-613
Number of pages10
JournalJournal of Evolutionary Biology
Issue number4
Early online date11 Mar 2021
Publication statusPublished - 30 Apr 2021

Bibliographical note

Funding Information:
We thank Alejandro Gonzalez‐Voyer, Robert P. Freckleton and Zitan Song for their advice on phylogenetic path analyses. Francisco Javier Pérez‐Barbería provided data on body mass of some species of Suidae. We appreciate the comments of Balázs Vági, Zsolt Végvári, Jácint Tökölyi, Gergely Katona and two anonymous reviewers on the manuscript and data analyses. This study is a part of KS's PhD funded by University of Debrecen. TS was funded by the Royal Society (Wolfson Merit Award WM170050, APEX APX\R1\191045, the International Exchanges scheme CNRS‐ROYAL SOCIETY 2016) and by the National Research, Development and Innovation Office of Hungary, NKFIH (ÉLVONAL KKP‐126949, K‐116310). AL was funded by an NKFIH grant (KH 130430) and by the NKFIH's TKP2020‐IKA‐07 project financed under the 2020‐4.1.1‐TKP2020 Thematic Excellence Programme by the National Research, Development and Innovation Fund of Hungary.


  • artiodactyla
  • feeding style
  • group size
  • habitat
  • mating system
  • phylogenetic generalized least squares
  • phylogenetic path analysis
  • social evolution

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics


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