FT 11: Big Wall Ecology in Yosemite

Trip Itinerary: Starting from a google earth 3-D image of Yosemite Valley in Yosemite National Park, we will “zoom in” on particular locations and features to highlight the variety of physical conditions and biota present on the wall. Each stop will include a pre-recorded video of a guest scientist speaking about a certain aspect of cliff ecology. We will try to film these from the cliffs themselves. Stops may also include slide shows of particular features or species of interest with voiceover. Stops may include: • Glacial process that formed the cliffs – Glacier Point. 2-3 million years ago the Sierra Nevada entrained glaciers which transported materials and carved granite cliffs nearly a thousand meters high.
• Geology of El Capitan – El Capitan. Variations in geology of El Capitan contribute to differences in exfoliation type and rate which produces the substrate for life on big walls.
• Lichens – Higher Cathedral Rock. Lichens form through a symbiotic relationship between an alga and a fungus. The alga performs photosynthesis while the fungus mines the rocks they grow on for minerals. Together they provide food and shelter for animals and, importantly, decompose rocks making minerals and sediments available for biologic processes.
• Plant communities – Royal Arches. Plants grow on ledges and in cracks and crevices where sediments have been deposited over time. They are watered from seeps or directly from rainfall. We see a vast diversity of plant life including large oaks and pines, tiny monkeyflower, and showy mountain pride. The plants are accompanied by pollinators like butterflies, moths, and bees which, in turn, provide food to aerial insectivores.
• Invertebrates – El Capitan. There are some strange invertebrates living in the vertical realm. We will visit with primitive silverfish, microscopic red mites, and stinging Manica ants.
• Reptiles and Amphibians – Five Open Books. Pacific chorus frogs, Sierra fence lizards, and king snakes are commonly found on ledges and in cracks. Even the snakes scale the vertical cliffs with ease searching for insect and small mammal prey.
• Peregrine Falcons, Ravens, and Swifts – The Rostrum. Peregrine falcons, ravens, and swifts all forage, court, and build their nests in the vertical ecosystem.
• Bats – Liberty Cap. We will visit a large Mexican free-tailed bat colony. We will listen for spotted and mastiff bats. If we are lucky, we may encounter scorpion-eating pallid bats.
• Mammals – Leaning Tower and Washington Column. Why is there urine all over the cliff? This ledge may be occupied by a wood rat nest. Wood rats use their urine to cement their stick nests onto ledges and into cracks. Who made this berry-laden scat? Ringtails move deftly through the night, hunting for fruits and berries, insects, and small vertebrates in the vertical terrain.

Special guests may include Dr. Greg Stock (Park Geologist), Sean Smith (Peregrine Observer), Diana Tataru (Botanist), Colleen Kamoroff (Herpetologist), Dr. Jessica Blois (Paleontologist), and Matthew Bernstein (Climbing Ranger). At the conclusion of the tour, Dr. Breezy Jackson will be available for a Q&A section with the audience members.