Did you know? Sea otters eat a quarter of their body weight each day. [VID: How do sea otters protect their ecosystem? Sea otters play a crucial role in their marine habitat. They need to eat a lot to keep warm in the chilly water they live in. They eat a quarter of their body weight each day. Sea urchins are among their favorite foods. Sea otters keep sea urchin populations in check in marine protected areas. However, outside these protected areas, sea urchins thrive. Sea urchins are voracious