A MOTHER’S JOURNEY: PROTECTING THE NEXT GENERATION OF WHALES

In the open ocean, a mother humpback keeps her voice low.

Her calf – only a few days old – stays close, within a few body lengths. It can swim on its own but is still entirely dependent on her. For the first year of its life, it relies on her for everything – milk, protection and guidance through the ocean.

Rather than the powerful songs humpbacks are known for, mother whales use something quieter: short, low-volume calls that travel only a short distance – just far enough for her calf to hear.

The volume of these calls is deliberate. By keeping them quiet, the pair reduce the chance of attracting unwanted attention from nearby male humpbacks or predators like orcas.

But this communication system is delicate. Even brief disruptions can interfere with the connection between mother and calf.

And when a mother-calf pair lose contact, the calf’s chances of survival drop sharply.

How mother humpbacks guide calves through migration

For humpback whales along Australia’s coast, life begins in warmer northern waters.

After migrating thousands of kilometres from Antarctic feeding grounds, mothers give birth in relatively calm, shallow areas such as the Great Barrier Reef and the Kimberley. Here, calves take their first breaths and begin nursing on rich milk that fuels rapid growth.

The energy transfer during the early weeks is remarkable. The mother must draw heavily on her fat reserves while her calf suckles for much of the day and rapidly gains weight. Often, the calf feeds by positioning itself almost motionless beneath its mother while she rests. The calm waters of the north make this possible.

But this is a brief window of time. The pair will soon begin the long journey south, sometimes within weeks.

The migration back to colder feeding waters is slower for mothers with calves, as calves cannot sustain long dives, travel quickly or surface often. These pairs also travel closer to shore to avoid unnecessary exertion while the calf grows, builds strength and learns to swim efficiently. When available, mothers and calves make use of sheltered coastal bays and inlets; the reduced wave action allows them to conserve precious energy while helping the calf feed more efficiently.

The mother whale must carefully manage every stage of the journey – adjusting speed, direction and movement to keep her calf close and protected.

And throughout it all, the mother uses sound to guide her calf and keep it on track.

How mother whales stay connected with their calves

In the ocean, visibility is limited. Light fades quickly with depth and distance. But sound travels efficiently through water and is the primary way whales experience and navigate their environment.

The long, complex songs often associated with humpbacks are produced mainly by males to attract and find females during the breeding season. These calls can travel very large distances.

Mothers and calves communicate differently. Studies suggest these sounds are a form of ‘contact calls’ – simple vocalisations used to coordinate movement and surfacing while navigating the journey south. It is a constant two-way exchange; the mother whale quietly calls, the calf responds with soft squeaks and grunts, and together they adjust their pace and direction to remain connected.

These quiet calls have a very small active space – often around 100 metres – so the pair must stay close enough to hear each other. But this also means there is very little margin for error. Even small disruptions – such as background noise, a slight increase in distance or interference from other whales – can compromise this already fragile communication system.

If that communication breaks down, and the calf becomes separated from its mother, it is at serious risk.

Why mother whales keep their calls quiet

Scientists think mother-calf calls are kept quiet to avoid attracting unwanted attention from male humpbacks or detection by predators. Even when mothers become separated from their calves, they do not appear to increase the volume of their calls, suggesting that remaining difficult to detect is a priority.

Certain species of orcas, such as transient orcas, are of the few natural predators known to hunt large whales. These highly intelligent, toothed whales rely heavily on sound to hunt, navigate and socialise and they can target vulnerable whale calves, which are smaller, slower and unable to dive or manoeuvre as easily as adult humpbacks.

Attention from humpback males can also be risky. During breeding season, male humpbacks may begin following mother-calf pairs if they notice them, to try and gain reproductive access to the female. This opportunistic mating behaviour is not thought to be an attempt to harm the calf, but it can still disrupt the pair and increase the risk of separation. Increased activity around the mother and calf may interrupt essential resting or nursing, crowd the calf or cause it to become disoriented. It can also force the mother to change speed or direction suddenly, making it harder for the calf to stay close to its mother.

The reliance on quiet, short-range communication is why underwater noise pollution in our oceans is particularly problematic for mothers and their calves. If the pair cannot hear each other and lose contact, reuniting can be difficult. And, as underwater noise levels rise, the risk of this happening increases. Without its mother for protection, guidance and nourishment, a young calf is extremely vulnerable.

A noisier ocean is not just a disturbance. It can disrupt the mother-calf bond that is essential for a calf’s survival.

Why the ocean is becoming noisier

The ocean is no longer as quiet as it once was.

Human activity has introduced unprecedented underwater noise into marine environments, and these sounds frequently overlap with whale migratory routes, feeding and breeding grounds. Commercial ships, tourist and recreational boats, drilling and pile driving during offshore construction, seismic surveys used in oil and gas exploration and naval sonar combine to create a cacophony of human-made noise in our oceans.

And ocean noise is likely to keep increasing. Shipping is growing steadily worldwide and offshore development looks likely to continue to expand in Australia and globally.

Commercial shipping produces a constant low-frequency hum that can travel long distances. It is the largest source of chronic underwater noise in the world's oceans – over 80% of goods traded globally are transported by ship. Commercial shipping vessels increased from around 109,000 vessels in 2024 to 112,500 vessels in 2025, adding thousands more ships to the ocean in a single year. Tourist vessels are also increasing in some regions. In the Southern Ocean, for example, tourist voyages tripled between 1999 and 2019, and this number continues to rise.

Offshore development, including oil and gas exploration, offshore energy projects and marine construction, can add substantial noise to the ocean. Drilling during construction projects creates ongoing low-frequency noise and vibration, while pile driving – hammering large foundation piles into the seabed – produces powerful bursts of underwater sound. Seismic surveys, used extensively in Australian waters to search for oil and gas deposits, release repeated, high-intensity pulses across large areas of ocean.

One of the most intense human-made noises marine animals encounter is naval sonar. These systems use powerful acoustic signals to navigate and detect objects underwater and travel vast distances.

What happens when mother-calf communication is disrupted

For humpback and southern right whale mothers and calves, increased underwater noise may drown out quiet contact calls, reducing the distance over which mothers and calves can hear each other.

This can have immediate consequences. If communication becomes more difficult, the mother-calf pair may need to compensate by staying closer together or calling more frequently to maintain contact.

Having to stay closer together can leave the pair with less flexibility to respond to nearby boats or other whales. At the same time, noise can mask the sound of approaching ships, reducing how early whales detect them. With less warning time, the need to stay closely coordinated, and a calf that cannot dive as deeply or stay underwater for long, mother-calf pairs have fewer options for responding safely to danger.

Calling more frequently also comes at a cost. Migrating mothers are producing large quantities of milk while travelling thousands of kilometres between breeding and feeding grounds, while their calves are growing and developing rapidly and undertaking their first long migration. It is an energy-intensive process for both animals and one of the most demanding stages of a whale’s life. The additional burden of calling more often can leave fewer reserves available for nursing, growth and the long journey ahead.

How noise affects resting and nursing

For whale mothers and calves, taking time to rest, nurse and recover is an important part of the migration journey. Southern right whales spend extended periods in the calm, sheltered nursery areas along Australia's southern coastline, while humpbacks use protected bays and inlets along the east and west coasts. These breaks allow mothers to conserve energy while giving young whales the space to nurse and build strength during the early stages of life.

However, these shallow areas – and large parts of the migratory routes along Australia’s east and west coasts – overlap significantly with where recreational and tourism vessels operate. Noise from boats doesn’t just interfere with communication. Scientists believe it may be perceived as a potential threat or disturbance, prompting mothers to be more vigilant or discouraging them from using these important resting areas.

As a result, mothers and calves may spend more time moving and remaining alert to nearby activity rather than resting and recovering. One study found that high vessel noise caused humpback whale mothers to spend 30% less time resting, double their breathing rate and increase their swimming speed by 37%.

When mother-calf pairs spend more time responding to nearby vessels and less time resting, fewer energy reserves remain available for milk production, nursing and the long migration south. It is thought that repeated disturbances could affect calf development and leave mothers with reduced capacity to support their calves on this journey.

Why ocean noise matters for all whales

Unfortunately, the impact of human-generated underwater noise extends far beyond these vulnerable whale mothers and calves. Sound plays an important role in how all species of whale communicate, navigate, find food, avoid danger and stay connected with their young. While different species rely on sound in different ways, the underlying problem is the same: whales live in an acoustic world. When that world becomes noisier, these essential behaviours can become more difficult.

Studies have shown underwater noise affects baleen whales – including humpback, southern right, blue, fin and minke whales – as well as toothed whales – such as beaked whales, sperm whales and orcas. For toothed whales, which use echolocation for hunting, navigation and sensing their surroundings, increased underwater noise is especially problematic as it interferes with how they detect prey and move safely through the ocean.

Relentless shipping noise can mask whale calls and other vocalisations, reducing the distance over which they can be heard. This makes it harder for whales to locate mates and maintain social connections. It can also make it harder for whales to interpret the acoustic cues they rely on, interfering with navigation and increasing the risk of disorientation.

Intense noise from seismic surveys and poorly planned offshore construction can drive whales away from important habitat, including feeding grounds, breeding areas or migration routes. These sounds can also disrupt feeding behaviour directly by causing whales to spend less time feeding or altering their diving patterns.

Naval sonar, seismic airguns and pile driving have been found to cause hearing damage or worse, particularly for toothed whales. Sonar has been linked to abnormal diving behaviour in beaked whales, which can cause decompression-like injuries, internal haemorrhage and mass strandings.

Scientists are increasingly concerned about the cumulative effects of noise pollution. Frequent or prolonged exposure to ocean noise is thought to increase vigilance and trigger stress responses, causing whales to spend more time responding to the disturbance and less time on important natural behaviours.

Over time, human-generated underwater noise is likely to interfere with almost every aspect of a whale's life. The combined effects of disrupted communication, reduced feeding opportunities, navigational challenges, increased stress and avoidance of important habitat, can affect a whale’s health, reproductive success and even survival.

It’s clear that noise pollution not just something whales hear. It can shape where they go, how they behave, how much they feed and how safely they move through the ocean.

Why protecting mothers and calves matters for the next generation

For whale populations, every calf matters.

The journey from birth to independence is one of the most vulnerable periods in a whale's life. Calves must learn to navigate the ocean, find food, avoid danger and complete long migrations while remaining closely connected to their mothers. Some will not survive this precarious period.

Whales are also long-lived animals that reproduce slowly. Many species do not have their first calf until later in life, and mothers invest enormous amounts of time and energy raising each young whale. Because of this, even small changes in calf survival can influence how quickly populations recover and grow.

Protecting mothers and calves during these early stages – from noise pollution as well as from other threats in our oceans – helps ensure more young whales survive to adulthood. In a changing ocean, giving calves the best possible start is about more than protecting individual animals. It is an investment in the future of whale populations and the oceans they help sustain.

You can help us protect whales and their calves from noise pollution and other threats in our oceans by adopting a whale mother and calf.

What WWF is doing to reduce ocean noise

The good news is that ocean noise pollution is one of the more manageable threats facing whales.

WWF and partners have developed the world-first Blue Corridors Interactive Map. This conservation tool identifies key migration routes, habitats and locations of major threats to whales, including underwater noise hotspots. This scientific evidence helps inform conservation policy and action, including measures to reduce underwater noise in areas whales rely on most. As the government works towards its commitment to protect 30% of Australia’s oceans as marine sanctuaries by 2030, we are urging decision-makers to safeguard critical whale habitat and keep ships and other noisy industrial activity out of these areas.

You can help reduce noise and disturbance in whale feeding, breeding and nursery habitats by signing the petition for marine sanctuaries in 30% of Australia’s oceans.

WWF-Australia is also advocating for the implementation of practical measures that reduce noise at its source and stronger approval conditions for future offshore development, such as wind farms. Through initiatives such as the Blueprint for Australian Oceans Leadership and government consultation processes, WWF supports noise-reduction measures, including ship speed limits, whale-safe shipping routes and the use of technologies such as bubble curtains (walls of air bubbles that reduce how far underwater noise travels) during pile driving. We also recommend careful site placement and planning for offshore construction to avoid important habitats and sensitive migration and calving periods, as well as whale monitoring prior to high-noise activities.

Protecting whales and the ocean pathways they depend on takes science, advocacy and long-term conservation action. With your support, WWF can continue working to reduce threats such as underwater noise, protect critical whale habitat and help ensure future generations of whales can complete their journeys safely.