'Dinosaur' bird's unusual call could shape vital cassowary conservation
Chester Zoo recordings could help safeguard a species.
At Chester Zoo, keepers and scientists have recorded an unusual bird call – an infrasonic sound that could hold the key to safeguarding a critically endangered species.
This week, episode two of our podcast, Abi Clarke: Zookeeper in Training, dropped on Spotify and other major platforms. In this episode, Zoë Sweetman, our team manager of parrots and penguins, takes listeners behind the scenes to discuss the remarkable cassowary, a flightless bird from Australasia.
This is the first time the cassowary call project has been made public.
It all started when I burst into the science office and said, ‘The female cassowary is doing something unusual.’ We noticed a change in her behaviour around the male, so we set up cameras. That’s when we saw her making a vocal posture, but we didn’t know what that meant at the time.
Zoe Sweetman, Team Manager of Parrots and Penguins
She continued: "I searched through scientific literature to find out more, but there was almost nothing about it. My colleague, Mark Vercoe, recalled a few studies from the 2000s suggesting cassowaries communicate using infrasound – sound below the threshold of human hearing – but there wasn’t much information beyond that."
Zoë and her team decided to investigate further, wondering if the cassowary’s poses might accompany an inaudible call. They set up sound recorders, and sure enough, they captured a deep, resonant boom from the bird – one of the oldest species on Earth.
For now, these recordings remain top secret, as they will form the foundation of a forthcoming scientific paper.
“We realised this was worth researching,” Zoë adds. “Making that low sound takes a lot of effort from the female, so it must have a purpose. This became part of my Master’s research.”
The study expanded to include other zoos, including BirdLand in Cheltenham and Avifauna in the Netherlands. They found that female cassowaries in these zoos also made the same call.
These findings could improve our understanding of cassowary behaviour and aid in their conservation. With a growing threat of habitat loss in Papua New Guinea, where land is cleared for farming, these birds face increased pressures.
Cassowaries are challenging to breed because they can be territorial outside the breeding season, which leads to aggression. They’re often compared to dinosaurs. They have long claws, and I remember a TV show where a cassowary kicked a hole through a thick piece of MDF. We think the sound is related to mating, as poor timing in pairings often leads to conflict.
Rebecca Lewis, Conservation Scientist in Population Biology at Chester Zoo
Zoë continues, "What makes cassowaries even more interesting is that they’re polyandrous. The females mate with a male, lay eggs, then leave him to care for the clutch while she mates with another. This is rare in birds, and we think the call could alert the male that the female is ready to mate again."
Despite their imposing appearance, cassowaries are secretive. "They look fearsome, but they prefer to creep into the undergrowth rather than fight. However, they can be aggressive if guarding a nest or chicks," Zoë adds. "After watching hours of footage, I’ve realised they’re much smarter than they get credit for."
The study also included physiological and endocrinological tests, where scientists tested hormones in the birds' faeces to see if they matched the behaviours, though the results were inconclusive.
Since the study began, a pair of cassowaries at Birdland successfully hatched and raised a chick – a promising step in the right direction for the species.
