Located near the west entrance to UC Santa Cruz, Cave Gulch has many charms. The majestic redwoods are the most obvious one and they set the stage. Their thick tall trunks, earthy smell and drooping boughs play with the sunlight and create a feel of enchantment. I often feel that a forest sprite might jump out at any moment. Read on as many of the unique treasures of Cave Gulch are revealed.

Karst Caves

There are many caves on the UCSC campus and most are along Cave Gulch (hence the name). The caves exists because of a Swiss cheese like nature of the bedrock beneath your feet – its called “karst” topography and it exists where you have rocks made of marble (basically cooked seashells) that have interacted with water. Over millions of years, slightly acidic ground water dissolves the calcium carbonate (CaCo3) from marble bedrock and creates deep fractures and holes. Over time the fractures can enlarge and create tunnels and sometimes really large spaces known, of course, as caves. The caves tend to form along fault zones, because the physical grinding along the fault makes it much easier for water to penetrate and start the process of dissolving the marble (chemical erosion). It turns out Cave Gulch has a a fault right in the areas where most of the caves are, in fact, the trace of the fault pretty much defines where the creek runs. So the famous HellHole and Porter Caves of UCSC partying lore exist thanks to faults moving within the larger San Andreas Fault System.

Stalactites and stalagmites used to be common in the caves but most have been destroyed or taken away by the curious. A few remain but if I told you where they were the forest sprites would smite me. The caves can be very dangerous especially in the rainy season. Rule of thumb: when it’s moist outside, it’s wet and slippery inside the caves. If you choose to explore please do so carefully, respectfully and responsibly.

If you’re visiting Cave Gulch in winter in a wet year you might see water flowing in the river bed. The bedrock in some places is not marble but made of metamorphosed (cooked) sediments called schist and granite. Unlike the fractured marble, they hold the water more like a canal. At some points the flow in the river abruptly disappears underground; this is where the schist or granite has hit a patch of marble rattled with cracks, holes and tunnels.

Drinking up the Fog

The tall Redwoods are very thirsty and require a lot of water, up to 130 gallons per day for the average tree. They survive our Mediterranean dry summers and droughts by harvesting fog-water with their leaves. Some of the water is absorbed through their leaves but most falls to the forest floor where their roots and other understory plants can drink it up. This availability of water to the forest floor is why redwood forests stay vibrantly green even throughout dry summer months.

The Forest Floor

Below the Redwood trees you’ll see many comparably smaller plants blanketing the forest floor. Clusters of ferns big and small scatter mosaically among the landscape of Cave Gulch. Wet mats of bright green moss cover rocks and tree trunks resembling scenes from “The Lord Of The Rings”. One of my favorite ground covers is Redwood Sorrel because it gives the imagination that fairies and hobbits could be living among the forest leaf litter.

In early spring, look out for the delicate Fetid Adder’s Tongue that smells of decayed mushrooms. Their undeniable beauty among the darkness of the Redwood forest would never indicate its offensive smell.

Critters On The Ground

One animal you can find year round is UCSC’s Mascot, the slimy Santa Cruz Banana Slug. They may look like a fallen yellowed Bay leaf but look closer and you will see four tentacles guiding a ripe banana peel colored slug with a snail trail following behind. Their eyes are located at the tip of the two upper most tentacles represented as tiny black specks. Their two lower tentacles, which both smell and feel, help navigate their slow journey across the forest floor. With tongues like conveyor belts, called radula, banana slugs are able to pulverize and eat anything from dead animals, to poop, to plants and mushrooms. Eating stuff on the forest floor is their specialty job.

Despite their tender look and charming color, banana slug slime packs a punch to any would-be predator. When threatened, this slug curls into a ball and secretes a white slimy mucus that makes any predator want to immediately spit it out. Surprisingly, some predators too hungry to let this stop them, such as Raccoons, have been seen on campus rolling banana slugs in dirt to buffer the slime and then gulping them down in one swallow. The Pacific Giant Salamander has also been witnessed choking down the slimy yellow mascot.

There are three main salamanders that find their homes in Cave Gulch. The earthworm sized Slender Salamander usually hangs out under rocks or fallen limbs along with their friend and fellow salamander, the Yellow Eyed Ensatina.

The coloring of the Yellow Eyed Ensatina (brown back, orange stomach, and yellow patches under the eyes) mimics that of the highly toxic Rough-Skinned Newt. Because of this adaptation, their coloring deters predators from snacking on their tasty non-toxic meat.

The Pacific Giant Salamander is rarely if ever seen but their larvae can be easily found in summer months swimming in perennial pools along Cave Gulch. The Giant Salamander is not only the heaviest terrestrial salamander in the world but they also have extremely sharp dagger-like teeth that give them hierarchy in the food web over other salamanders. Equipped with a deadly set of pearly whites, the Giant Salamander can eat crickets, shrews and even the tasty Yellow Eyed Ensatina.

Salamanders are very sensitive to any oils and salts that we naturally have on our hands so it’s best to admire without touching.

Birds in The Trees

There are many birds among the forests of Cave Gulch whose calls and songs are melodious to the avid birder and the occasional passerby alike. There are roughly 40 different species of birds that visit Cave Gulch yearly, some more commonly seen than others. The tiny brown and white Chestnut-backed Chickadee is found year round in the Gulch. It often chats in groups and occasionally hangs from the tips of branches while looking for seeds or bugs to munch on.

You may also hear the echo of the Hairy Woodpecker in a faraway tree. The call resembles the sound of a dog’s squeak toy. Usually seen pecking holes in tree trunks, those who catch a glimpse of the Hairy Woodpecker will never forget its exceptionally long beak, fuzzy nose and striking red cap.

Take the Self-Guided Mobile Tour

This piece is part of the UCSC Natural History Tour. Download the free app with many tours of the Santa Cruz area and beyond.