Stunning video shows sharks devouring sea urchins, spines and all

Heterodontus galeatus sharks eating various urchins - YouTube

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Long-spined sea urchins have emerged as an environmental issue off Australia's far south coast. Native to temperate waters around New South Wales, the urchins have expanded their range south as oceans warm. There, they devour kelp and invertebrates, leaving barren habitats in their wake.

Lobsters are widely accepted as sea urchins' key predator. In efforts to control urchin numbers, scientists have been researching this predator-prey relationship. And the latest research by my colleagues and I, released today, delivered an unexpected result.

We set up several cameras outside a lobster den and placed sea urchins in it. We filmed at night for almost a month. When we checked the footage, most sea urchins had been eaten — not by lobsters, but by sharks.

This suggests sharks have been overlooked as predators of sea urchins in NSW. Importantly, sharks seem to very easily consume these large, spiky creatures — sometimes in just a few gulps! Our findings suggest the diversity of predators eating large sea urchins is broader than we thought — and that could prove to be good news for protecting our kelp forests.

Related: 'It's like we opened a buffet': Sharks in Gulf of Mexico learn to steal food from fishing nets

A puzzling picture

The waters off Australia's south-east are warming at almost four times the global average. This has allowed long-spined sea urchins (Centrostephanus rodgersii) to extend their range from NSW into waters off Victoria and Tasmania.

Sea urchins feed on kelp and in their march south, have reduced kelp cover. This has added to pressure on kelp forests, which face many threats.