La Trobe
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Cassowary casques act as thermal windows

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journal contribution
posted on 25.08.2021, 01:27 by Danielle EastickDanielle Eastick, Glenn J Tattersall, Simon J Watson, John LeskuJohn Lesku, Kylie RobertKylie Robert
Many ideas have been put forward for the adaptive value of the cassowary casque; and yet, its purpose remains speculative. Homeothermic animals elevate body temperature through metabolic heat production. Heat gain must be offset by heat loss to maintain internal temperatures within a range for optimal performance. Living in a tropical climate, cassowaries, being large bodied, dark feathered birds, are under thermal pressure to offload heat. We tested the original hypothesis that the casque acts as a thermal window. With infrared thermographic analyses of living cassowaries over an expansive range of ambient temperatures, we provide evidence that the casque acts as a thermal radiator, offloading heat at high temperatures and restricting heat loss at low temperatures. Interestingly, at intermediate temperatures, the casque appears thermally heterogeneous, with the posterior of the casque heating up before the front half. These findings might have implications for the function of similar structures in avian and non-avian dinosaurs.

Funding

This research was supported by several Zoological Parks that gave us access to their cassowaries: Australia Zoo, Birdworld Kuranda, Cairns Tropical Zoo, Currumbin Wildlife Sanctuary, David Fleay Wildlife Park, Halls Gap Zoo, Hartley's Crocodile Adventures, Healesville Sanctuary, Melbourne Zoo, Rainforestation Wildlife Park and Wildlife Habitat. M. Symonds kindly provided advice, B. Eastick sketched the cassowary heads accompanying Fig. 4. The Peter Rawlinson award and the Richard Zann Bursary to D.E. and internal funding from La Trobe University Department of Ecology, Environment and Evolution to D.E., and K.R. and J.L. funded the project.

History

Publication Date

01/01/2019

Journal

Scientific Reports

Volume

9

Issue

1

Article Number

1966

Pagination

7p.

Publisher

Springer Nature

ISSN

2045-2322

Rights Statement

The Author reserves all moral rights over the deposited text and must be credited if any re-use occurs. Documents deposited in OPAL are the Open Access versions of outputs published elsewhere. Changes resulting from the publishing process may therefore not be reflected in this document. The final published version may be obtained via the publisher’s DOI. Please note that additional copyright and access restrictions may apply to the published version.