An international team of scientists led by Flinders University has found evidence of prenatal auditory learning in embryos of three vocal learning species (superb fairy-wren, red-winged fairy-wren and Darwin’s small ground finch) and two vocal non-learning species (little penguin and Japanese quail).
Colombelli-Négrel et al. demonstrate a capacity to perceive and learn to recognize sounds in ovo, as evidenced by habituation, even in bird species that were previously assumed to have little, if any, vocal production learning. Image credit: Barbara Fraatz.
There are many forms of vocal learning but vocal production learning by far stands out as a hallmark achievement in just seven orders (primates, songbirds, parrots, hummingbirds, cetaceans, pinnipeds, bats), and among primates, only humans can do it.
As a result of the rarity of vocal production learning, animals have been grouped into so-called ‘vocal learners’ (those that learn to imitate a vocalization from a vocal tutor) and ‘vocal non-learners’ (animals that produce vocalizations without imitating a vocal tutor).
“Vocal production learning is only believed to occur in seven lineages of birds and mammals including humans,” said Professor Sonia Kleindorfer, a researcher in the College of Science and Engineering at Flinders University and the Faculty of Life Sciences at the University of Vienna.
“Our research will hopefully inspire more study into the remarkable capacity of animals to learn sound.”
“By moving the time window for sound learning to the prenatal stage, this research direction opens pathways to measure neurobiological downstream effects of early auditory experience on behavior and information processing.”
In the study, Professor Kleindorfer and colleagues measured the vocal learning concepts in embryo behavior and response to sound in ovo using change in heart rate as the response variable — well before birds hatch and start making complex calls or songs several months or even years after birth.
“By studying the capacity for sound learning in embryos, we are paving the way to new inroads into evolutionary and developmental timescales,” said Dr. Diane Colombelli-Négrel, a researcher in the Department of Animal Ecology & Physiology at Radboud University, the Department of Animal Ecology at the Netherlands Institute of Ecology, and the Division of Ecology and Evolution at the Australian National University.
“Long before actual vocalization, we found that these tiny songbirds were also discriminating towards non-specific sounds and capable of ‘non-associative’ (not from parents) sounds, building on the complexity of vocal learning in songbirds.”
“Future research could address changes in neural organization and gene expression pathways in embryos reared in sound-poor or -rich environments, identify how prenatal sound experience shapes phenotypic variation in vocalization characteristics, measure the effect of pre-hatch acoustical environment on individual attention to particular cues/signals/environments post-hatch, and quantify the strength of selection on adults to guide the prenatal sound experience of their offspring,” the authors concluded.
The study is published in the Philosophical Transactions of the Royal Society B: Biological Sciences.
Diane Colombelli-Négrel et al. 2021. Prenatal auditory learning in avian vocal learners and non-learners. Phil. Trans. R. Soc. B 376 (1836): 20200247; doi: 10.1098/rstb.2020.0247