While the true meaning behind the vocalisations of much of the animal kingdom is still shrouded in mystery, there are some conclusions we can draw pretty much universally: babies like burping and asking their mothers for food. And humpback whale calves, it would seem, are no exception. 

A new study has emerged, this week, to suggest that humpback whale calves strike a particular tone when on the prowl for a feeding time, by ‘barking’ and making ‘burping’ sounds at their matriarchs for food, proving there really is no love like that of a mother’s.

When humpback whale calves are born after an 11-month gestation period, they already weigh between one and two tonnes and measure 13-16 feet. It therefore seems no wonder that these giant babies immediately need a large amount of food to grow and get strong. They tend to nurse on their mother’s milk which is high in fat for up to a year. In the first few weeks of their lives, they can gain over 45kg of weight per day while drinking hundreds of litres of milk.

To ensure that they receive the needed amount of milk, researchers have now suggested that humpback whale calves beg for food – much like human babies do.

A new study, published in Proceedings of the Royal Society B: Biological Sciences, argues that humpback whale calves produce specific low-frequency vocalisations to signal that they’re hungry to their mothers. These noises, according to the researchers involved in the study, sound much like barks, snorts and burps and are the first-ever recorded sounds of begging-like behaviour in baleen whales.

Maevatiana Ratsimbazafindranahaka, lead author of the study which was part of his phD research, said in an interview with Oceanographic: “First, we knew little about the role and significance of vocalisations in mother-calf interactions in baleen whales. Past studies often focused on groups of adults and males. While the vocal repertoire of humpback whale mother-calf pairs has been more extensively described over the past decade, we were still far from understanding how specific types of social calls are linked to behaviours.

“Our study finally provides a glimpse into how particular call types are associated with the mother-calf activities, especially nursing behaviour – something that’s difficult to observe. Humpback whales are known to have a complex communication systems, and it’s fascinating to see that the different calls they use serve specific roles.”

Male and female humpback whales can make calls from a young age and as adults, they produce complex sounds that can travel thousands of miles across the ocean. Scientists have recently learned that these sounds can change over time and across different groups from different parts of the world.

While only the males sing, females and calves use different sounds, such as low-frequency grunts. With each other, they communicate with whale ‘whisper’, a complex sound that is quiet enough to not get picked up by predators.

Listen to a humpback whale calf whisper here:

Ratsimbazafindranahaka’s main aim behind the research, conducted by researchers from the Acoustic Communications team at the Paris-Saclay Institute of Neuroscience (CNRS/Paris-Saclay University), France, the Cétamada Association of Madagascar, and the University of Antananarivo of Madagascar, was to find out more about the interactions between mother and calf humpback whales as relatively little is known about this area of whale vocalisations.

The study represents the culmination of long-term collaboration and fieldwork in Sainte Marie, Madagascar, an important breeding area in the South-Western Indian Ocean.

“Since whales spend most of their time at depths beyond our reach, tags are the most effective way to reconstruct their underwater behavior and gain insights into their activities,” explained Ratsimbazafindranahaka. “For this study, we used data from eight calves collected during the winter of 2022 off Sainte Marie, totalling about 33 hours of exploitable video and sensor data.”

After analysing the video and audio files, the researchers identified behavioural states such as suckling sessions and added the corresponding audio spurs. The study recognised over 500 social calls, and found that the calves were quieter when milling, resting and travelling, while they were louder when playing at the surface and suckling.

“Suckling sessions were mainly associated with two sets of low-frequency calls corresponding to previously described burping, barking and snorting sounds. Surface play sessions featured mid-frequency calls with whoop-like sounds and other call types,” the study read which surprised the involved researchers. 

“Perhaps the most surprising finding was that, among the variety of calls we described, ranging from low to high frequency, it was the low-frequency calls – resembling barking or burping sounds – that were associated with nursing, so they’re likely begging calls used by the calf to ask for milk,” Ratsimbazafindranahaka told Oceanographic.

Begging behaviour is common in the animal kingdom, and Ratsimbazafindranahaka thinks that other baleen whales might also use begging behaviour.

One of the videos from the calf’s perspective, involved in the research: The calf surfaces to breathe, produces subtle, short low-frequency calls, and then suckles. For optimal appreciation, headphones with good bass response are recommended:

The new research reveals important insights into mother-calf interactions in baleen whales, and enhances our understanding of their communication systems.

As oceans become busier and noisier due to increased shipping traffic, seismic testing and other factors, whales might be able to communicate less, urges Ratsimbazafindranahaka: “It’s crucial to deepen our understanding of their biology and behaviour to assess how our actions and activities might affect them.

“In the context of rising noise pollution, knowledge of their communication systems is especially vital. We need to identify the specific noises we should minimise to avoid disrupting their communication. For example, reducing noise that may mask the low-frequency calls of mother-calf pairs is critical, as it could interfere with the initiation of nursing behaviour, which is vital for the calf during its early life stages.”

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