"Since January, individuals have defaced the day-use and canyon area of Rattlesnake Canyon with graffiti, " the park said in a statement.

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In pictures released by the National Park Service, the words "oatmeal cookie" and "nature boy" appear to be painted or spray-painted on boulders in Rattlesnake Canyon.

WSJ: Outbreak of Graffiti Defaces a Beauty Spot

To limit the impact of vandalism on historic sites, park rangers closed 308 acres of Rattlesnake Canyon until the end of the month, citing the escalating problem.

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