Museum Home > UCSC Natural History > Nature Hike Podcasts>


Cave Gulch in Fall

Chris: Welcome to one of the most gorgeous university campuses in California – U.C. Santa Cruz.

Erica: In addition to the variety of classes this university offers, UCSC also has an amazing diversity of natural landscapes and hundreds of species that live within the campus boundary. This makes UCSC a unique treasure. So when you’re not in class go take a walk in the woods –

Chris: Or a meadow –

Erica: Or a even a cave –

Chris: And experience the natural diversity of our campus for yourself. This podcast is part of the UCSC Natural History Podcast series, courtesy of the Museum of Natural History Collections in the Environmental Studies department here at UCSC. I’m Chris, the curator of the museum.

Erica: And I’m Erica, a senior environmental studies student here at UCSC. These podcasts are designed for you to download along with a map and listen to as you take a guided tour through a part of this amazing campus. They’re also tailored to different seasons. For example, we have a ‘Fall in Cave Gulch’ podcast that describes what you might see there during October or November. However, don’t feel limited – some of the things we talk about are visible any time of year!

Chris: In addition, the scripts for these podcasts are online. Along with the text we’ve linked a bunch of photographs of the plants, animals and fungi covered in each podcast. So be sure to check that out before or after your walk.

Erica: And now, let’s go exploring!

Chris: Alright folks, we’re going over to Cave Gulch today – on the far west side of campus, it’s a steep ravine running behind Kresge and Porter colleges. Make sure to bring a flashlight, some clothes you can get dirty, and a pocketknife if you have one, because we’re going spelunking!

Erica: We’ll begin this tour at the point where Cave Gulch runs underneath Empire Grade. To get there, walk to Porter Meadow and descend into the forest on the northwest edge of the meadow. Follow one of several small trails in the forest that lead steeply downhill and to the right. You should quickly be able to see Empire Grade road beneath you. If you found the right trail, you should end up at the graffiti-covered concrete bridge spanning Empire Grade. Near this bridge on the same side of Empire Grade that you are on, look for a large concrete block with a hole broken though the top – this is where Empire Cave (more commonly known as Porter Cave) is located.

Chris: You are now standing in Cave Gulch, a large ravine originating on the Upper Campus and continuing all the way to the coast. Cave Gulch is named so because of the geology of this drainage, which causes caves to form. The bedrock here in lower Cave Gulch consists of marble, an ancient metamorphic rock that probably originated as a limestone sedimentation of shells in a tropical sea. After forming, this limestone was buried in the earth’s crust, where heat and pressure transformed it into marble.

Erica: The marble on campus is 97% calcite, a relatively soft mineral that readily dissolves with acid. You can test this for yourself with a pocketknife and a small bottle of diluted hydrochloric acid.

Chris: Ask any enthusiastic Earth Sciences major and they can help you get a hold of some hydrochloric acid!

Erica: Find an exposed rock near the cave entrance and scrape it with your pocketknife. Calcite is not as hard as the metal blade of your knife, so you should be able to scratch the marble. If you have hydrochloric acid, drip a few drops on the exposed rock and you’ll see the rock fizz.

Chris: That fizzing is the calcite dissolving. The same thing happens on a larger scale when acidic groundwater seeps into the bedrock marble along fractures, faults and joints. Over a long period of time, more and more of the calcite dissolves until the rock is a honeycombed network of tunnels and caves. Empire Cave is an example of one of these caves.

Erica: This geology of cave gulch is part of a larger campus phenomenon known as karst topography. Karst occurs in areas where the bedrock is marble or limestone – both of which are very water soluable – and is characterized by caves, sinkholes and springs- all three of which are found in abundance on the campus.

Chris: So let’s check out this karst topography for ourselves by heading into Empire Cave. As you climb the metal ladder down into the cave, stop and look at the rock ceiling for brown-colored twilight moths (Triphosa haesitata). These moths roost in the cave during the day, and forage for flower nectar outside at night.

Erica: You’re also likely to spot a cavemat harvestman (Leiobunum exilipes), sometimes called a daddy-long-legs, in the first room of the cave. These arachnids are similar to spiders, but have smaller bodies, much longer legs and no silk organs. Unlike the popular myth, harvestmen do not have fangs nor can they produce poison.

Chris: In fact, the harvestman is hunted by another arachnid – the Empire Cave spider (Meta dolloff). This spider can be 2-3 inches long, dark grey to black, with long legs and dull orange or yellow splotches on its abdomen. It is endemic to the Empire Cave system, which means that it only occurs in Cave Gulch. In addition, to this unique spider, there are many other fragile organisms that call this cave home. When you explore the cave, remember to be respectful of this very unique habitat by not touching any of the animals and never leaving trash.

Erica: Back outside of Empire Cave we’ll continue to walk downstream in Cave Gulch. Shortly after crossing Empire Grade stop for a minute and look for the stream. Where did the water go? The streambed here is dry during summer and early fall, but just a short ways upstream there’s water! What do you think is happening?

Chris: As we walk farther down Cave Gulch the marble bedrock gives way to schist, another prominent metamorphic rock on campus. You can tell schist apart from marble because it is reddish and softer, and if you break apart a piece of schist you can see little bits of mica crystals shining inside. The mica in schist weathers to form clay, which you can experience firsthand by exploring Cave Gulch during a rainy winter!

Erica: Cave Gulch is part of the redwood forest plant community, but you will also see a lot of California bay (Umbellularia californica) trees growing here. California bays have a smooth gray trunk and simple, non-serrated leaves. They are angiosperms which flower in midwinter, unlike the non-flowering gymnosperm redwoods. To positively identify the bay, pick one of their narrow, glossy, green, pointed leaves, rub it between your fingers and smell. Their very distinct smell is very similar to store-bought bay leaves. Though the leaves of the California Bay are too strong to put in spaghetti sauce, look for the small fleshy green fruits ripening on the surrounding bay trees. Pick a few to take home and lightly roast in an oven. They have a creamy consistency and are very tasty.

Chris: On many of the bay trees (both living and dead) are large, hard, leathery “shelves” that protrude from the side of the trunk. This fungus is called the artist’s conk mushroom (Ganoderma applanatum). An artist’s conk is roughly the shape of a semi-circle, with the diameter side attached to the tree trunk. It may easily be a foot wide, and the top surface is dark brown, with a creamy white underside.

Erica: If you are gentle, you can write on the under side of the conk. If you come back a few days later, new growth from will replace the spore-producing tubes that you rubbed off. If you don’t see one here in Cave Gulch, there is a large one behind Kresge Apartment Building 8.

Chris: As you’re walking along the dry streambed, keep an eye out for banana slugs (Ariolimax dolichophallus). In a couple months when it’s wetter they’ll be all over campus, but you can find our school mascot in Cave Gulch year-round. The banana slug that occurs in Santa Cruz is a species that is only found in the Monterey Bay region, and it is the largest slug in North America. It’s not at all unusual to see an eight-inch slug! Banana slugs protect themselves with thick, sticky mucus that also keeps their bodies moist. This mucus is nearly impossible to wash or wipe away, so I wouldn’t recommend getting too friendly with these slugs.

Erica: Banana slugs are also hermaphrodites, i.e. every individual has both male and female sex organs. During mating, two slugs approach each other, dance around for a while and then insert their penises into each other. The Latin name of this species, dolichophallus, translates to “long penis;” banana slugs, in fact, have the largest penis-to-body length ratio in the entire animal kingdom! After several hours the mating pair tries to disengage, however, often one or both of their penises will become stuck. As it turns out, a receiving slug has the ability to hold onto its partner’s penis. Sometimes a receiving slug will even try to chew off its partner’s penis – this behavior is called apophallation, and may be a strategy to prevent the other slug from mating again.

Chris: After walking about 10-15 minutes downstream from Empire Cave, keep a close eye on the streambed. Can you find where the water suddenly appears again? Karst topography, the same geologic phenomenon that created Empire Cave, is responsible for this trick: stream water disappears underground in subterranean rock passageways, then emerges at a later point.

Erica: The stream here is home to one of UCSC’s most charismatic amphibians – the California giant salamander (Dicamptodon ensatus). This salamander has a chunky body with a marbled brown and gray color and a white belly. It can be up to 17 cm long (not including tail), and it is the heaviest terrestrial salamander in the world!

Chris: Unlike most of the eight salamander species on campus, the giant salamander has a larval stage in its life cycle, and the larval salamanders are much easier to find than the mature individuals. As you walk down the gulch, stop at pools in the stream and look under floating debris and rocks for a plain brownish creature with a whitish belly, a tail fin and gills. The larvae can be over 11cm long (not including tail), so they aren’t difficult to find, especially in the late summer or early fall when the stream is running low. Adult giant salamanders have powerful jaws with sharp teeth, and are a formidable predator for smaller animals, like crickets, banana slugs, and even shrews! The chances of finding an adult are slim to none, though, especially this time of year. Your best bet would be to lurk along Cave Gulch creek on a rainy winter night.

Erica: Continue far enough down Cave Gulch and you’ll find old dams, small waterfalls, forests of stinging nettle, and, eventually, Wilder Ranch State Park and Highway 1. There are also more caves in Cave Gulch, although we aren’t saying where to find them!

Chris: If you’re ready to head back to campus, walk just a little farther down from where the stream reappears and you’ll come to a trail that crosses the water. Take this trail left and it will take you back to Porter Meadow. If you continue another 20 minutes down stream, you’ll intercept a large trail. Follow this left up the side of the canyon into Mima Meadow, which is just across Empire Grade from the West Entrance of campus.

Erica: To learn more about the natural history of Mima Meadow, check out our Mima Meadow podcast. Thanks for hiking with us!

Return to UCSC Natural History Podcast Series page