Courtship and underwater communication in the Sunda gharial (Tomistoma schlegelii)

ABSTRACT

Many threatened crocodilians are shy and difficult to observe in the wild, limiting the current knowledge of their behaviour and ecology. Although acoustic communication is commonly used by adults during courtship and territory defence, the signals produced vary between taxa. Here we provide the first classification of adult vocalisations in Tomistoma schlegelii – a rare gavialid inhabiting swamp forests in Southeast Asia – and describe the behaviour produced during courtship. Using video and passive underwater acoustic monitoring we recorded a breeding captive pair of T. schlegelii housed indoors, as well as monitored 12 captive adults kept in a semi-natural outdoor enclosure over a period of two months. Courtship behaviour during 18 recorded mating events followed that observed in other crocodilians, but acoustic signals were restricted to mating activity and were only recorded in the two animals housed indoors. We identified seven signal types produced by T. schlegelii, which differed in duration, dominant frequency, and the presence of harmonic structure. These results suggest the species uses short-range, underwater acoustic signals during courtship and mating, with little vocal activity outside of those events, and provide foundation for future studies of this rare crocodilian.

KEYWORDS:

• False gharial
• acoustic communication
• crocodylians
• mating

Acknowledgements

We thank Johnson Jong, Rob Stuebing, the staff of Crocodiles of the World Zoo, Jong’s Crocodile Farm and Sarawak Forestry Corporation. The study was carried out with the support of Virginia Aquarium, Los Angeles Zoo, The Explorers Club and the University of Bristol Alumni Foundation.

Disclosure statement

No potential conflict of interest was reported by the authors.

Ethics

The use of animals has been approved by the University of Bristol Ethical Review Group (UIN number: UB/16/005).

Supplementary material

Supplemental data for this article can be accessed here.