In the vast ocean, cold water tends to sink due to its higher density compared to warm water, creating these thermoclines. Placed between these layers lies the thermocline itself, a region where temperatures rapidly decrease. This zone tends to be rich in nutrients, attracting large amounts of fish, creating a perfect hotspot for penguins to feed. The secret lies in the behaviour of the fish and the thermal barrier created by the thermocline. Fish, much like their reptilian counterparts, are cold-blooded creatures. When they venture from the thermocline into the cooler waters below, their metabolic processes slow down. This decrease in activity makes them more sluggish and easier targets for hungry penguins. The separation created by the thermocline acts as a thermal barrier, enabling penguins to capitalise on this advantage without having to dive to extreme depths to catch their aquatic prey.

As the Little Penguins navigate these temperature gradients, they strategically position themselves to maximise their fishing success. By leveraging the presence of thermoclines and the behaviour of fish, the resourceful penguins optimise their foraging efforts, securing a bountiful feast while expending less energy. Under climate change, thermoclines disappear during severe El Niño. Our long-term data has been vital to monitor understanding how penguins adapt to environmental changes given that the water temperature in the southern-east corner of Australia is increasing four times faster than the global average. We have learned about penguins and thermoclines thanks to our long-term Little Penguin tracking studies.

By Andre Chiaradia, Marine/Penguin Scientist

Phillip Island Nature Parks