By David Williams, CNN
(CNN) -- The National Park Service has released a guide to safely petting bison after recent dangerous encounters between tourists and the giant animals.
The short version is: Don't.
The agency also posted a diagram on Facebook to go with its guide to smart wildlife watching.
It urges people to think before scratching a bison's back and warns that petting the shoulder area could be vacation-ending.
If you fancy a bison belly rub, check your insurance first.
Bison are the largest mammals in North America and a full-grown male can weigh 2,000 pounds -- not much less than a Mazda Miata convertible.
Last month, a bison gored a teenager at Theodore Roosevelt National Park in North Dakota. Officials said the 17-year-old was punctured in the thigh and tossed 6 feet.
A few days earlier, a 9-year-old girl was hurt at Yellowstone National Park when a bison charged her and threw her in the air.
The Park Service says visitors must give animals plenty of space.
It recommends staying at least 25 yards from bison and elk.
Yellowstone says to keep at least 100 yards between you and the park's wolves, black bears and grizzly bears.
The National Park Service also warns against stopping in the road to admire a bison or other critter. Traffic accidents are the most common cause of deaths and injuries at Yellowstone.