Copyright 2017 NPR. To see more, visit AUDIE CORNISH, HOST: At this time every year, northern elephant seals gather along the California coast. Will Huntsberry visited a colony of some 23,000 seals and sent this audio postcard. WILL HUNTSBERRY, BYLINE: At Piedras Blancas, it's the beginning of mating season. And the males are trying to figure out who's the strongest. (SOUNDBITE OF ELEPHANT SEALS GROWLING) HUNTSBERRY: That sound you hear isn't a diesel engine. It's the sound of war. Sexually mature males have enlarged, floppy noses that help them make the growl. The alphas can weigh 5,000 pounds and be as big as a car. When they fight, it's ugly. They lift their bulky bodies high in the air and then strike hard at each other with their teeth. (SOUNDBITE OF ELEPHANT SEALS GROWLING) HUNTSBERRY: The fighting has big consequences. Those who win will end up with harems of around 20 to 30 females. But... RON KAUTZ: Less than 2 percent of all the males born will ever mate. HUNTSBERRY: That's