There are several types of grizzly attacks. It's possible you will survive an attack due to random encounter, or an attack by a mother with cubs, if the cubs run away - playing dead may help there, as the bear seeks only to teach you a lesson. If an attack by a mother whose cubs tree near her, or if yearling cubs are involved and they attack also, the attack will be fatal unless you can stop it. Predatory attacks are fatal. if you stumble onto a grizzly food cache, you are dead, unless you can kill the bear. Playing dead isn't a top option.
This info gleaned from a couple of books by a man (forgot name, maybe kendall) who conducted bear safety courses for gov't and private industry in BC in the 70s, 80s, and 90s. He was a lifetime observer of bears and a lifetime interviewer of bear attack survivors and witnesses. He differs from Herrero in a number of key points. He attributes the differences to Herrero's use of broad statistics that include "attacks" by bears near human establishments. This man's work centers on bear attacks in wild country. He ran shooting courses for those who might encounter a bear attack. His writing and his experience base are compelling.
He doesn't reject spray out of hand, just notes that it is often ineffective - remember that the bear may well come back after being sprayed, so carry two cans. If you think about it, spraying the bear's fur isn't going to do much of anything, you need to get the spray into eyes or mouth, if mouth, preferably when bear is inhaling. Even then it may only discourage the bear momentarily. Note that he taught a firearms course, not a bear spray course.
I notice his books have disappeared from Amazon, dropped in favor of more touchy-feely or sensationalistic stuff.
