They're big, brown and they're causing quite the stir at Folsom Lake. And, no, we're not talking about the bundles of driftwood.

"It's tarantula season at Folsom Lake," according to the official Folsom Lake State Recreation Area Twitter account.

Though it's uncommon, tarantulas can bite when agitated, officials warn. Though the large spiders have fangs and do carry poison, they are not considered a serious threat to humans.

The spiders move slowly, but park officials warn hikers they should not touch the large arachnids.