Venom in the Preserve Educational Walk from Brown’s Ranch Trailhead.   Some reptiles and arthropods in the Sonoran Desert use venom or other poisons to defend themselves or subdue their prey. Learn how to recognize these animals that bite and sting and the effect of their venom.  Join Dr. Rich Cochran on an easy 1.5 hour walk.  Bathrooms at the trailhead.  Bring water for the trail.  No dogs please. Arrive 15 minutes before start of hike.