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PLoS One. 2013 Dec 11;8(12):e80872. doi: 10.1371/journal.pone.0080872. eCollection 2013.

The good, the bad, and the ugly: agonistic behaviour in juvenile crocodilians.

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Research Institute for the Environment and Livelihoods, Charles Darwin University, Darwin, NT, Australia ; Wildlife Management International Pty. Limited, Karama, NT, Australia.
Department of Fisheries, Wildlife and Conservation Biology, University of Minnesota, Saint Paul, Minnesota, United States of America.
Department of Wildlife, Madras Crocodile Bank Trust and Centre for Herpetology, Mamallapuram, Tamil Nadu, India.
Research Institute for the Environment and Livelihoods, Charles Darwin University, Darwin, NT, Australia.


We examined agonistic behaviour in seven species of hatchling and juvenile crocodilians held in small groups (Nā€Š=ā€Š4) under similar laboratory conditions. Agonistic interactions occurred in all seven species, typically involved two individuals, were short in duration (5-15 seconds), and occurred between 1600-2200 h in open water. The nature and extent of agonistic interactions, the behaviours displayed, and the level of conspecific tolerance varied among species. Discrete postures, non-contact and contact movements are described. Three of these were species-specific: push downs by C. johnstoni; inflated tail sweeping by C. novaeguineae; and, side head striking combined with tail wagging by C. porosus. The two long-snouted species (C. johnstoni and G. gangeticus) avoided contact involving the head and often raised the head up out of the way during agonistic interactions. Several behaviours not associated with aggression are also described, including snout rubbing, raising the head up high while at rest, and the use of vocalizations. The two most aggressive species (C. porosus, C. novaeguineae) appeared to form dominance hierarchies, whereas the less aggressive species did not. Interspecific differences in agonistic behaviour may reflect evolutionary divergence associated with morphology, ecology, general life history and responses to interspecific conflict in areas where multiple species have co-existed. Understanding species-specific traits in agonistic behaviour and social tolerance has implications for the controlled raising of different species of hatchlings for conservation, management or production purposes.

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