these pictographs (paintings versus images chipped into rock)
are considered made by the Fremont people and are
approximately 1,000 years old.

someone has outlined the two large and one small
images (upper left side) with white chalk.

(use of chalk is considered inappropriate and discouraged)

there are few good explanations for this style of rock art.
Mine are:
-- mescaline
-- aliens from outer space
-- mystical priests with animal robes
-- none of the above