'Dinosaur' bird's unusual call could shape vital cassowary conservation
'Dinosaur' bird's unusual call could shape vital cassowary conservation
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Keepers and scientists at Chester Zoo have recorded a cassowary call that may be previously unknown to science
Female cassowaries in different zoos have now been observed making a 'booming' noise
The call, which is discussed in a major new podcast, is sometimes too deep for the human ear to hear
This discovery could help support cassowary conservation breeding
Keepers and scientists at Chester Zoo have recorded an unusual bird call, an infrasonic sound which could help safeguard an entire species.
This week, episode two of the zoo’s new podcast, Abi Clarke: Zookeeper in Training dropped on Spotify and other major podcast platforms. It featured Zoë Sweetman, team manager of parrots and penguins at the zoo talking all things cassowary – a remarkable flightless bird species found in Australasia.
This is the first time the cassowary call project has been made public.
Zoë Sweetman explained: “It all started when I burst into the science office and said: ‘the female cassowary is doing something unusual’. We’d spotted that she’d changed her behaviour around the male, so we set up cameras. That’s where we saw her making a vocal posture, but didn’t know what that meant at the time.
“I searched through the scientific literature to find out what the behaviour might mean, but there was pretty much nothing.
“My colleague Mark Vercoe, general manager of the birds department, recalled a few studies from the 2000s that suggested cassowaries communicate in infrasound – in frequencies below the threshold of human hearing – but aside from these, there is not much information about that, either.”
Zoë and her colleagues wondered whether the cassowary’s poses might accompany a call that the keepers could not hear, so they installed sound recorders.
Sure enough, the huge bird – whose ancestors have walked the earth for millions of years - was making a deep boom.
For now, the recordings and data are being kept top secret as they will be the centre of a forthcoming scientific paper.
“We realised this was something worth researching,” said Zoë, “because it’s a lot of effort for the females to make this strange, low sound. They must be doing it for a reason. This became a full study which formed part of my Master’s.
“We needed to make sure this call wasn’t just a one-off to Chester Zoo birds, so I expanded the study to BirdLand in Cheltenham and Avifauna in the Netherlands. We found the females there made the same call.”
These findings may improve our understanding of cassowary behaviour and aid their conservation. Existing cassowary subspecies, including the southern cassowaries living at Chester Zoo, face intense environmental pressures in Papua New Guinea, where land is being cleared for farming.
“Cassowaries are quite difficult to breed because they can be territorial outside the breeding season, which can lead to aggression between individuals,” said Rebecca Lewis, conservation scientist in population biology at Chester Zoo. “These are birds you look at and instinctively think: dinosaurs! They have long claws, and I remember watching a TV show when I was young where a cassowary kicked a hole through a thick piece of MDF.
“We’re pretty confident the sound is related to mating. Breeding success is limited in zoos and poor timing of mixes resulting in conflict is a common issue. Understanding the calls of these birds and the part they play in courtship might help time mixes more accurately, taking the guesswork out of when to pair birds.”
Cassowaries are unusual even within a group of flightless birds that include emus, rheas and ostriches.
Zoë said: “The females are polyandrous. They pair with a male, lay eggs, and then go off to find another mate, leaving the male to care for the clutch. This is extremely rare in birds, and we think the call might relate to this, alerting males that the female is ready to mate again.
“As a species they are secretive. Even though they’re quite large, and they have brightly coloured neck wattles and a tall structure called a ‘casque’ on the top of their heads, they are surprisingly hard to spot.
“They look fearsome, but they prefer to creep off into the undergrowth rather than fight, though they are quite capable of defending themselves, and males can be aggressive if they are guarding a nest or chicks.
“After watching thousands of hours of cassowary footage, I’ve realised that they shouldn’t be underestimated. I think they are a lot smarter than they are given credit for.”
The study included physiological and endocrinological elements where scientists tested hormones in the birds’ faeces to see whether the hormones peaked in synch with their behaviours, but this was inconclusive and requires further research.
Since taking part in this study, a pair of cassowaries at Birdland have successfully hatched and reared a chick.
Scientists discover surprising language ‘shortcuts’ in birdsong – just like humans
Scientists have uncovered a hidden pattern in birdsong that mirrors a core rule of human language.
A new study, led by researchers at The University of Manchester, in collaboration with Chester Zoo, found that birds appear to follow Zipf’s Law of Abbreviation (ZLA) – the idea that more frequently used sounds tend to be shorter. This rule, found in all human languages, helps make communication more efficient.
The findings, published in the journal PLoS Computational Biology today, offer new insight into how animals communicate and provide a new foundation for researchers exploring whether birds, like humans, shape their vocal signals according to the 'principle of least effort'.
Lead author Dr Tucker Gilman, Senior Lecturer at The University of Manchester said: “In human language, if we say something a lot, we tend to shorten it – like saying ‘TV’ instead of ‘television’. It turns out that the same pattern exists in birdsong.
“We know that birds and humans share similarities in the genes and brain structures involved in learning to communicate but this is the first time we’ve been able to detect a consistent pattern of ZLA across multiple bird species. There’s still a lot more work to be done but this is an exciting development.”
Although previous studies hinted that animal communication might follow ZLA – including in penguins – it has been difficult to find clear evidence of ZLA in birdsong. That’s partly because most birds have much smaller repertoires compared to humans. While humans use thousands of words, birds may only produce a few dozen distinct sounds.
To tackle this, the researchers developed new method for studying ZLA in birdsong that focuses on how often individual birds use certain note types and how long those notes last allowing them to examine communication at an individual rather than population level.
They then applied this method using a new open-source computational tool called ZLAvian, which compares real-world observed patterns to simulated ones to determine if ZLA is present.
Using ZLAvian, the team analysed more than 600 songs from 11 bird populations spanning seven different species. They found that while individual populations didn’t always show clear signs of ZLA, a stronger pattern emerged when the data was combined, showing more frequently used birdsong phrases were shorter on average.
Co-author Dr Rebecca Lewis, Conservation Scientist at Chester Zoo, said: “Studying ZLA in birdsong is far more complex than in human language. Birds often have very few note types, individuals even within the same species can vary widely in their repertoires, and classifying notes is tricky too. Our research has taught that it’s important to look across a wide range of species when looking for language patterns and we hope ZLAvian will make it easier for other researchers to explore these patterns in more birds but also other animals in the future.”
The team says that further studies are needed across a broader set of bird species to confirm their findings.
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