‘Penguins just want to be heard’
Bioacoustics research sheds light on animal communication
● Penguins often get a bad rap in movies, where they are portrayed as tetchy and rude.
In fact the famous flightless birds are quite sensitive and spend a lot of their time braying for attention.
Bioacoustic research of the African penguin presented this week revealed more or less what the penguins are chatting about – and it’s quite impressive. Not only can they recognise their partners’ calls amid the cacophony of other familiar calls, they get quite agitated if their partners’ calls unexpectedly disappear.
Another impressive feature of penguin vocalisation is their broad range of sounds, which include an “ecstatic display song” during breeding season — fivesecond bursts of multiple-syllable sound, often sung in unison across much of the colony. The distinctive song, whose donkey-like sound earned the species the nickname “jackass penguin ”— is believed to also advertise nest occupancy.
“We observed that when a penguin performed the ecstatic display song it was frequently followed by many other members of the colony in chorus,” the authors say in their study, aspects of which were presented on Monday at the third African Bioacoustics Community Conference at Skukuza in the Kruger National Park.
Bioacoustics is a fast-growing field that allows humans to “listen in” on other animals by decoding the basic building blocks of their vocalisation. In the case of African penguins, research indicates four basic adult sounds and two distinct juvenile begging sounds. A survey of penguins at Stony Point colony in Betty’s Bay found penguins are chattiest early in the morning, between 4 and 8, and in the evenings from 5.30 to 9.30. And their calls conform to human linguistic rules — the most frequent sounds are shorter in length.
One of the most recent findings is that penguins, again like humans, have the ability for “cross-modal” recognition: they combine visual and auditory information to recognise each other in a way many other species can’t. It means penguins differentiate between a mate, an acquaintance and a stranger and retain this sensory knowledge in the same way humans can match a voice with a particular face.
“The ability to identify one’s friendly neighbours both visually and vocally may have evolved to help reduce unnecessary conflicts,” the authors said in a paper that was also referenced at the conference. “Cross-modal recognition may have proved valuable in the turbulent environment among the waves and rocks, where visual identifiers (that is, their unique pattern of black spots) may not be a reliable salient cue to recognise others.”
Livio Favaro of the department of life sciences and systems biology at the University of Turin in Italy said audio analysis could also identify individual penguin calls, thereby allowing for useful “passive monitoring” of penguin colonies. Wildlife authorities can now use recording devices to determine population size and growth. In this way the technology was assisting with muchneeded conservation activities. “Government is getting very strict in terms of letting people into penguin colonies because the species is more and more endangered. In one or two years they may switch to being critically endangered,” Favaro said.
Another species to benefit from bioacoustic intervention is the mongoose, which also featured at this week’s conference.
The conference heard how researchers have been broadcasting traffic noise close to groups of dwarf mongooses to see how they react and understand how human noise pollution affects them. Traffic noise designed to simulate the rumble of the R40 near Hoedspruit was broadcast via loudspeaker, disrupting the animals’ foraging behaviour. Mongooses were less likely to hear warning calls from “sentinels” tasked with watching for predators.
Other notable research findings included voice-mediated social interactions among hippos and a comparison of songbird courtship with human drumming.
The conference also featured a workshop on international efforts to protect whales from the harmful impacts of human activity in the oceans, where noise pollution is a growing concern, particularly in relation to oil and gas exploration.