Marine biology gannets, and auks. Although they spend most of their lives in the ocean, species such as gulls can often be found thousands of miles inland. There are five main types of marine mammals, namely cetaceans (toothed whales and baleen whales); sirenians such as manatees; pinnipeds including seals and the walrus; sea otters; and the polar bear. All are air-breathing, and while some such as the sperm whale can dive for prolonged periods, all must return to the surface to breathe. Marine habitats can be divided into coastal and open ocean habitats. Coastal habitats are found in the area that extends
Double-toothed barbet the seeds of some fruits. These barbets can be found in pairs or small family groups with helpers; lone double-toothed barbets are rare. Their territories are large. Double-toothed barbets roost communally, as all the barbets in a group roost in the same hole. Nests are made by excavating a tree, often rotting, at above two meters. Both barbets in a pair will dig out the nesting hole, and both will defend it. The entrance the nest is circular, five or more centimeters across. Some nests have an entrance tunnel. At maximum, a nest is 46 centimeters deep. When a male