The helmeted hornbill can withstand high-impact collisions

New research has revealed how the unique internal anatomy of the helmeted hornbill’s casque helps it withstand damage during aerial jousting battles. This understanding may aid in conserving this critically endangered species and developing impact-resistant materials.

“When I started in Hong Kong, I visited City University of Hong Kong (CityU)’s conservation forensics group to chat about their research and they introduced me to this amazing bird, to its bizarre cranial anatomy, and to the threats posed to the species by the illegal wildlife trade,” said Mason Dean, an associate professor of comparative anatomy at CityU.

The unique headgear of the helmeted hornbill

The helmeted hornbill is targeted in the illegal wildlife trade for its distinctive casque. While casques are common among hornbills, their function varies by species. In the helmeted hornbill, the casque has a thick keratin layer and a dense network of bone. 

“As I learned more about this species, I discovered a cross-section of a dried skull in a museum, revealing a shocking trainwreck of trabeculae in the casque,” Dean said. “When I heard that individuals are known to ram their casques together in mid-air displays, I just had to know more about the functional morphology.”

Trabeculae are inter-connected struts inside bones that provide strength and resistance to buckling. “Understanding hornbill anatomy and how it allows for this jousting behavior can therefore give us clues about this elusive animal’s ecology and fundamental aspects of its life history and health,” Dean explained.

Skull support during high-impact collisions 

The study revealed that the casque’s dense trabeculae support the structure during high-impact collisions. The team used microCT to analyze the casque’s internal structure. 

“We have been focused on understanding the hierarchical architectures of the skull, uniting biology, materials science, and engineering techniques,” Dean said.

“We’ve been able to get a detailed and quantitative picture of how the casque is constructed, how the bone interacts with the keratin, and the intricate latticework of bone trabeculae supporting the skull’s impact surface.”

Surprising anatomy of the helmeted hornbill

The team found that the hornbill’s trabeculae were as thick as those in an elephant’s femur, despite the hornbill being much smaller. 

“I’ve used microCT to look at a big diversity of animal skeletons, but I have never seen bony trabeculae like the ones we’ve found in the hornbill,” Dean added.

The findings also show that the casque’s trabeculae channel back to the braincase, providing additional reinforcement. 

“That massive stand of trabeculae then channels back to the braincase, like a bundle of banyan tree prop roots, converging on a bony platform that’s far more reinforced than in other hornbills and relatives we’ve looked at.”

Need for increased awareness 

Illegal wildlife trade has driven the helmeted hornbill to become critically endangered. 

“The helmeted hornbill is one of the largest hornbill species in Asia, with the keratin fronting its casque historically a target for the art and antique market for carving into ornamental wildlife products,” Dean explained. “A large number of our skull specimens still contained the bullets that had likely killed the animal.”

“Since the species is elusive and hard to observe in the wild, there is a great need to improve knowledge of its biology, to preserve its habitat, protect dwindling wild populations, and to develop better tools to ID wildlife products.” 

“We hope projects like ours contribute to an understanding of species’ natural history and raise public awareness of the challenges facing biodiversity loss, while also ideally showing scientists that steps toward conservation need not solely come from conservation biologists!,” he concluded.

This study will be presented at the Society for Experimental Biology Annual Conference in Prague on July 2-5, 2024.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates.

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–