Longtime residents of Cape Cod are accustomed to the occasional beach strandings by sea critters, but this week has been at a whole new level. More than 400 turtles have washed ashore in recent days after getting stranded in Cape Cod Bay. Even now, experts say they can’t keep up with the number of turtles coming ashore, as many as 30 per tide.

WGBH News Science Editor Heather Goldstone explained what’s going on.