A beach in Monterey turned red over the last couple of days, thanks to the brightly colored bodies of tuna crabs, also known as pelagic red crabs.

The species is normally found in the warmer waters off of Baja and the Gulf of California, but hundreds of thousands washed ashore after they made their way up the coast.

Marine Biologists note that this happens during El Niño weather patterns, and the appearance of the crabs is a signal of the warmer water. There have been mass strandings of the crabs in Monterey several times, including 1859, 1959, 1969, 1982-83 and now in 2015-2016. Right now, the water around Monterey Bay is around 10 degrees higher than usual, which has caused some local wildlife to migrate north looking for cooler water while wildlife from farther south has moved up the coast, including tuna crabs.

The tiny crabs are actually a species of squat lobster and only grow up to about 5 inches long. They are harmless, and while they aren't safe for humans to eat, birds, dolphins and many other species feast on the crabs when they appear.

Dan Albro, a senior guest experience trainer with the Monterey Bay Aquarium, told the Mercury News that the appearance of the tuna crabs may be why as many as 20 blue whales were spotted near Monterey Bay last weekend, as the krill-eating whales will also dine on these tiny crabs.

While not an unusual event, it is one that grabs the attention of beach-goers and biologists alike. Around this time last year, southern California's beaches were experiencing the same blankets of tuna crabs thanks to a warming pattern.

Here's what these little guys look like while alive and well in the water:


Jaymi Heimbuch ( @jaymiheimbuch ) focuses on wildlife conservation and animal news from her home base in San Francisco.