Explore your world with Birch Aquarium at Scripps Executive Director Nigella Hillgarth -- Something big is surfacing off the coast of San Diego these days.

This time every year, gray whales make their annual epic journey from their frigid feeding grounds in the Bering Strait to tranquil lagoons near Baja California, where they breed and give birth. Nearly 20,000 gray whales make the 10,000-mile round-trip journey, the longest mammal migration in the world!

It's quite a sight to see these majestic animals in the open ocean. An average adult gray whale weighs about the same as 10 large elephants, so often they are bigger than your boat. Their eating habits are unique since gray whales have no teeth. Instead, they eat by using baleen, a bristly plate that lets the whales strain swarms of zooplankton and other animals from the ocean floor.

Here are a few other facts about gray whales:

- Some scientists think gray whales swim on "autopilot" when they sleep during their annual migration south.

- An adult gray whale can stay underwater up to 15 minutes without breathing.

- Within three hours of birth, a calf can keep itself afloat and swim on a steady course.

- Gray whales can swim nearly 100 miles a day.

Gray whales are protected by law so humans can't hunt them anymore, but the animals still face threats. Ocean pollution, huge fishing nets, shipping and other human activities endanger them.

You can celebrate the final stretch of gray whale season with Birch Aquarium at Scripps. Now through March 31, we offer daily whale watching cruises through San Diego Harbor Excursion. We also have a new traveling exhibit on whale sounds at the aquarium.

Come join the adventure!