About 17,000 seabirds nest in the Nga Motu–Sugar Loaf Islands Marine Protected Area. Shearwaters, petrels, terns, penguins, shags, and herons, some of them threatened species (the reef heron is one), nest and feed on and around these little islands. The islands are also a breeding colony and hauling grounds for New Zealand fur seals; in winter more than 400 seals congregate here. Dolphins, orca, and pilot whales frequent
the waters around the islands, and humpback whales migrate past in August and September.
Beneath the water's surface, caves, crevices, boulder fields, and sand flats, together with the merging of warm and cool sea currents, support a wealth of marine life. More than 80 species of fish have been recorded here, along with jewel and striped anemones, sponges, and rock lobsters.
On land, more than 80 different native plant species survive on the islands. Cook's scurvy grass, almost extinct on the mainland, grows on two of the islands. The palatable species is rich in vitamin C and was sought by early sailors to treat scurvy.