How strong are cassowaries

The curious cassowary: why is this bird wearing a helmet?

There are many theories around the purpose of the curious headdress of the cassowaries, a family of ratites that live in Australia, New Guinea and some islands in the South Pacific. Experts already suspected that the eye-catching helmet could protect them from falling fruits or amplify their loud calls, be a sex signal or even a weapon in combat. However, there is insufficient evidence for any of these hypotheses. Now a working group headed by Danielle L. Eastick from La Trobe University in Melbourne is presenting measurements that support one of the assumptions. As the team reported in "Scientific Reports" in February 2019, the helmet probably serves to regulate the body temperature of the birds.

This conjecture is one of the oldest, and the structure of the head comb is consistent with such a function. The organ consists of keratin and is covered with bare, well-perfused skin. At the same time cassowaries have an urgent need for thermoregulation. Not only are they covered in dark plumage, but they are also quite heavy, weighing up to 60 kilograms. Accordingly, it is difficult for them to radiate excess heat - especially since they live in tropical and subtropical regions. With the help of infrared measurements, the researcher's team showed that the structure on the animal's head behaves as one would expect an organ to regulate heat.

This article is included in Spectrum - The Week, 14/2019

According to this, the cassowary's helmet emits most of the energy from all body regions at high temperatures - and accounts for around eight percent of the total energy exchange, significantly more than the surface area. That changes drastically in cooler weather. At an ambient temperature of five degrees Celsius, the helmet is significantly cooler than the rest of the head. The bird loses much more heat here via the base of the beak and the neck. In the opinion of Eastick and her team, the results not only show what the helmet is for the cassowaries: they believe that such helmet-like structures could also do this in dinosaurs such as Corythoraptor or the often conspicuously helmeted pterosaurs.