Leiden University’s Carel ten Cate tracked down 34-year-old duck recordings—and the man who made them—to verify that musk ducks are capable of vocal learning, an ability that hadn’t been thought to exist in waterfowl.
If it walks like a duck and talks like a person, it’s probably a musk duck (Biziura lobata)—the only waterfowl species known that can learn sounds from other species. The Australian species’ facility for vocal learning had been mentioned anecdotally in the ornithological literature; now, a paper published September 6 in Philosophical Transactions of the Royal Society B reviews and discusses the evidence, which includes 34-year-old recordings made of a human-reared musk duck named Ripper engaging in an aggressive display while quacking “you bloody fool.”
The Scientist spoke with the lead author on the paper, Leiden University animal behavior researcher Carel ten Cate, to learn more about these unique ducks and what their unexpected ability reveals about the evolution of vocal learning.
The Scientist: What is vocal learning?
COURTESY OF CAREL TEN CATE
Carel ten Cate: Vocal learning, as it is used in this case, is that animals and humans, they learn their sounds from experience. So they learn from what they hear around them, which will usually be the parents, but it can also be other individuals. And if they don’t get that sort of exposure, then they will be unable to produce species-specific vocalizations, or in the human case, speech sounds and proper spoken language.
The Scientist spoke with the lead author on the paper, Leiden University animal behavior researcher Carel ten Cate, to learn more about these unique ducks and what their unexpected ability reveals about the evolution of vocal learning.
The Scientist: What is vocal learning?
COURTESY OF CAREL TEN CATE
Carel ten Cate: Vocal learning, as it is used in this case, is that animals and humans, they learn their sounds from experience. So they learn from what they hear around them, which will usually be the parents, but it can also be other individuals. And if they don’t get that sort of exposure, then they will be unable to produce species-specific vocalizations, or in the human case, speech sounds and proper spoken language.
TS: What drew you to studying vocal learning?
CtC: I’m interested in communication by sound by birds. That has been a major topic in my research over the years, and that also included how do sounds develop. There are bird groups in which sounds—vocalizations—develop without much experience, like pigeons, for instance. Also, ducks and geese are usually considered not to be [vocal] learners, in contrast to songbirds. In songbirds, there is clear evidence for many species that, if they don’t have experience at an early age, they don’t sing proper species-specific songs. I’m interested in why [there is] this difference, and what’s the advantage of learning your vocalizations, as opposed to developing them without any impact of learning.
TS: What can comparative studies of vocal learning in different animals teach us?
CtC: An important reason to study that has to do with the fact that we are vocal learners. But among primates, and great apes, we are the only species who are vocal learners. In other great apes, they don’t need experience to develop vocalizations. . . . It’s quite a special feature of us. In order to understand why that might have evolved, and how that might have evolved, you need comparative studies on other animal species where you can make this contrast between learners and nonlearners.
For both mammals and birds, there are only a limited number of examples of vocal learners. That is to say, all the songbirds are vocal learners, and all the parrots are vocal learners, but because their ancestor, the common ancestor of these groups, were vocal learners, all the later-appearing species—they got that trait from that ancestor. We can’t look back in the past deep enough to understand why it evolved in the ancestor of parrots or hummingbirds or songbirds. This duck is so interesting because there you may have relatives, relatively close relatives, which don’t show vocal learning, and others which do.
TS: That brings us to musk ducks and Ripper. When did you first learn about Ripper?
CtC: I’ve been doing a review on vocal learning in birds—of the type I just discussed, but also in some bird species, there’s evidence that they may modify existing vocalizations by reinforcement. . . . So I was working on the review and reading up all I could find about vocal development in birds of any kind. And then, in a book chapter, someone mentioned, well, there is a report about a duck imitating vocalizations. That triggered me because that would be highly unexpected. So then I started to trace the reference for that. Through a whole series of various steps and computations, I managed to find the source of that reference. And it turned out that the recordings related to that reference were actually in an Australian sound archive. I got in touch with them, and after a long exchange, they managed to send me some of these recordings. READ MORE
CtC: An important reason to study that has to do with the fact that we are vocal learners. But among primates, and great apes, we are the only species who are vocal learners. In other great apes, they don’t need experience to develop vocalizations. . . . It’s quite a special feature of us. In order to understand why that might have evolved, and how that might have evolved, you need comparative studies on other animal species where you can make this contrast between learners and nonlearners.
For both mammals and birds, there are only a limited number of examples of vocal learners. That is to say, all the songbirds are vocal learners, and all the parrots are vocal learners, but because their ancestor, the common ancestor of these groups, were vocal learners, all the later-appearing species—they got that trait from that ancestor. We can’t look back in the past deep enough to understand why it evolved in the ancestor of parrots or hummingbirds or songbirds. This duck is so interesting because there you may have relatives, relatively close relatives, which don’t show vocal learning, and others which do.
TS: That brings us to musk ducks and Ripper. When did you first learn about Ripper?
CtC: I’ve been doing a review on vocal learning in birds—of the type I just discussed, but also in some bird species, there’s evidence that they may modify existing vocalizations by reinforcement. . . . So I was working on the review and reading up all I could find about vocal development in birds of any kind. And then, in a book chapter, someone mentioned, well, there is a report about a duck imitating vocalizations. That triggered me because that would be highly unexpected. So then I started to trace the reference for that. Through a whole series of various steps and computations, I managed to find the source of that reference. And it turned out that the recordings related to that reference were actually in an Australian sound archive. I got in touch with them, and after a long exchange, they managed to send me some of these recordings. READ MORE
