On Sunday, a young southern right whale entered the Peel estuary, escorted out again by local dolphins, and now appears to be staying. It is a rare and confronting thing to witness. The Peel-Harvey system is not whale country. It is shallow, busy and heavily modified, yet this animal has chosen to come in and keep coming back.

It is a live example of how marine animals interact with our altered waterways, and what happens when a large, ocean-going species finds itself in a place that cannot really support it.

How shallow is the Peel estuary?

Southern right whales are known to rest in water around 5 metres deep. They can slow right down, drift or hold position, and conserve energy while conditions offshore are rough. The Peel–Harvey estuary, however, is extremely shallow by comparison.

Most of the natural estuary basins sit between about 0.5 and 2.5 metres deep. There are sandbars, broad shallow flats and only limited deeper pockets. The only genuinely deep water is in the engineered navigation channels, such as the Mandurah Entrance Channel and the Dawesville Channel, which have been dredged for boats, not whales.

In practical terms, that means a southern right whale cannot comfortably move around the estuary the way it would in coastal waters. It is restricted to the deeper dredged sections and risks grounding if it strays too far into the natural basins.

What does normal resting behaviour look like?

When southern right whales rest, it is usually short and purposeful. They may:

• Slow right down: reduce speed and drift in sheltered water
• Go still: float at the surface or just below, a behaviour called logging
• Resume movement: head back offshore once conditions improve

Typical resting periods are measured in tens of minutes to a few hours. Even a tired juvenile in rough weather would usually rest for hours, not days, before continuing along the coast.

A week of repeated entries into an estuary, followed by apparent lingering, is not standard resting behaviour. It suggests something more complex is going on.

Why a whale might keep coming back

The pattern described at Peel is striking. The whale comes in, is escorted out by dolphins, then returns again. Now it seems to be staying. That points to a behavioural change, and with southern right whales that usually means one of three broad possibilities.

Sheltering from ongoing rough conditions

If offshore seas remain uncomfortable, a juvenile may repeatedly seek shelter in calmer water. The estuary and entrance channels offer a break from swell and wind. However, a whole week of back and forth, followed by staying, is still unusual. Resting is normally short term.

Disorientation or fatigue

Complex, dredged waterways can confuse young whales. Strong currents, narrow channels and busy boat traffic create a very different environment to the open coast. A juvenile may:

• Become disoriented: lose its mental map of the exit route
• Rely on dolphins: follow local dolphins in or out as guides
• Struggle with currents: tire more quickly in confined water

The Peel system is not a natural whale environment. If the animal is tired or unsure of the way out, it may start using the estuary as a holding area, staying longer each time.

Injury or illness

When a whale remains in shallow or confined water for more than a day or two, wildlife authorities begin to consider the possibility of injury or illness. Whales that linger in estuaries often:

• Have minor injuries: from storms, predators or vessel interactions
• Are recovering: from a physically demanding event offshore
• Are compromised: enough to avoid deeper, rougher water

This does not automatically mean the whale is dying. Many animals recover. But it does mean the behaviour is not normal and warrants close monitoring.

The role of dolphins

One of the most striking parts of this story is the behaviour of the local dolphins. They have also been seen escorting a humpback whale out of the estuary. This is not random play. Dolphins are highly social and responsive to distress or unusual behaviour in other marine mammals.

When dolphins appear to shepherd a whale, it often means:

• They recognise something is off: the whale is not behaving like a confident traveller
• They are guiding: using their local knowledge of channels and exits
• They are responding: to acoustic or behavioural cues from the whale

If the whale stops following the dolphins, or no longer responds to their guidance, it may be too tired, too stressed or too confused to behave normally. That is when lingering begins.

What if the whale does not leave?

The hard question is this: what if he does not go? Southern right whales do not voluntarily remain in shallow estuarine systems for long periods. They need deep water, space to manoeuvre, quieter acoustic conditions and stable salinity. The Peel–Harvey estuary cannot provide those things.

If the whale stays beyond a few days, several risks increase:

• Grounding: on sandbars or shallow flats
• Boat strike: in busy navigation channels
• Stress: from vessel noise and close approaches
• Feeding difficulty: there is no suitable food for southern right whales in the estuary
• Declining condition: burning energy without replenishing it offshore

Whales cannot live in estuaries. If this animal does not leave, its health will eventually decline and intervention may become necessary.

What authorities usually do

When a large whale remains in an estuary or river system, wildlife and marine authorities typically:

• Monitor behaviour: watch surfacing patterns, movement and breathing rate
• Assess condition: look for visible injuries or signs of stress
• Manage risk: alert boaters and, if needed, restrict traffic
• Guide rather than force: use vessels and positioning to encourage the whale toward deeper water

The aim is always to support the animal to leave under its own power. Direct physical intervention is a last resort and carries its own risks.

This whale is a powerful reminder that our waterways are part of a much larger living system. The Peel-Harvey estuary is shaped by dredging, boat traffic and urban development, yet it still intersects with the life of a migratory whale and the local dolphin community.

Whether this young southern right whale leaves soon or needs help, his visit to the Peel estuary is a living case study in connection, stress and resilience along our marine corridors.