Docents present characteristics of snakes and lizards, the differences between species, and the roles each serves in the Sonoran Desert, during an interactive presentation and walk at 10 a.m., every Friday, through July 27; $8, $6 senior, $5 active military, $4 student with ID, $2 child age 5 to 12, free member or child younger than 5, includes admission to the park. Call or visit tohonochulpark.org for information.