Ringtails

Q: I’ve heard stories that ringtails were known to “shack up” with miners during the Gold Rush, yet in 20 years as a wildlife biologist in California with many night surveys in likely habitat, I have encountered two mountain lions, but no ringtails. Where are the ringtails? [Wendy, Martinez]

A: I, too, have wondered about the lack of ringtail sightings in my nocturnal forays. From historical accounts, you’d think every prospector’s cabin had its own family of ringtails, keeping lonely miners company and the area free of rodents. At only three pounds, these diminutive critters are smaller than a house cat, but they’re right up there with sea otters on the cuteness scale—9.9, I’d say. While commonly referred to as “cats,” they are actually related to raccoons and coatis and more distantly to pandas! And they behave much more like weasels than raccoons. Their short legs give them a feline look, but their heads resemble those of small foxes. Their scientific name, Bassariscus astutes, means “clever little fox.” And their namesake bushy tail, banded in black and white, is as long as their 12-inch body. Adapted for nocturnal foraging, ringtails have huge eyes, large ears, and a keen sense of smell. They also have sensitive whiskers called vibrissae that grow not only by their mouths but also above their eyes and on their wrists.

They’re elusive, but also very successful and widespread: ringtails are found from Oregon to Mexico and east to Oklahoma in many different habitats from sea level to 9,000 feet. Ringtails thrive anywhere they can find food. What’s food for a ringtail? Just about anything—fruit, small birds and mammals, leaves, nuts, eggs, and insects—the latter making up about 40 percent of their diet. They are superb hunters and accomplished climbers. They can rotate their back legs 270 degrees, which helps them scale steep cliffs and leap from tree to tree. Their primary predators are probably great horned owls, which hunt using both dim light and sound. So it’s not surprising that ringtails are incredibly quiet and stealthy. That helps them elude those hungry owls while also nabbing their own unfortunate prey.

David Wyatt, a biology professor at Sacramento City College, has been studying ringtails for years. He has live-trapped and radio-collared a number of them in the Sutter Buttes and in riparian areas in the northern Sacramento Valley. He says that sometimes when he’s picking up radio signals and knows a ringtail is right in front of him, he often still can’t see it. But his research and the research of others indicate that ringtails continue to be numerous, though we rarely see them.

So don’t feel too bad Wendy. At least you saw mountain lions!

Michael Ellis – Ask the Naturalist – Bay Nature Magazine

Waterfall Under Golden Gate Bridge

Q: Rumor has it there might have been a waterfall at the Golden Gate during the last ice age, when sea level was at its lowest. Is there any evidence for this? [Cisco, Oakland]

A: Well, there is no incontrovertible evidence for a “waterfall” at the Golden Gate, but there very well could have been one in the past. The earth has undergone a number of ice ages over the last 2.5 million years, when the cooler, wetter climate caused the for-mation of large sheets of ice in the polar regions and at higher elevation, followed by the melting of this ice. This oscillation has caused sea level to periodically rise and fall by as much as 200 to 400 feet over periods of several thousand years.

Some 20,000 years ago, the San Francisco Bay was not a bay, but a broad valley with a river, which we now call the Sacramento, draining the Central Valley through the Car-quinez Strait and heading out to the Pacific through the “Golden Gate.” Except it didn’t meet the ocean at the Golden Gate, as it does now. Instead, it ran for another 27 miles across a broad plain past a series of hills (now the Farallon Islands) before draining into the Pacific. In fact, the now-flooded San Francisco Bay is the exception; for most of its life, the “Bay” has been a river valley.

The deepest part of the Bay, at 350 feet or more, is just west of the Golden Gate Bridge. To the east, bedrock at Racoon Strait (sic) between Angel Island and Tiburon is only 140 feet deep. So in just over two miles, the ancient river dropped more than 200 vertical feet. This most likely would have created a series of cascades, if not a waterfall. And right under the bridge is an extraordinarily deep hole in the ancient river channel (download a colorful 3-d map of the Bay floor at bit.ly/BayFloorMap). The existence of the hole is a bit of a conundrum to geologists, some of whom suspect that a good-size waterfall may have created this large cavity in the bedrock. The sheer volume of water passing through this narrow cut in the Coast Range must have been immense. Today, runoff from nearly 40 percent of California’s land area drains out through the San Fran-cisco Bay. During ice ages, there would have been even more water in the river to carve out the canyon. Waterfall or no, these rushing waters would have been an impressive sight, and sound.

As sea level rose at the end of the last ice age about 8,000 years ago, seawater in-vaded this river valley, creating the modern San Francisco Bay. Evidence of the old riv-erbed can be seen during winter storms when large waves break over the Potato Patch, a four-fathom shoal made up of sand carried by the ancient Sacramento River on its way out to the Pacific some 30 miles to the west. 

Email your questions to atn@baynature.org.

Pelican Beaks

Q: Do you remember this old limerick?
A wonderful bird is the pelican,
His mouth can hold more than his belly can,
He can hold in his beak,
Enough food for a week!
I’m damned if I know how the hell he can!
—Dixon Lanier Merritt

So is it really true?

A: The pelican’s pouch, more properly referred to as the gular sac, has several different functions. The first and most obvious is to procure food. The brown pelican we see along our coast hunts by plunging into a school of fish from a few dozen feet in the air; the greatly distensible sac opens upon impact and two and a half gallons of water (and any fish nearby) are immediately sucked in. The bird closes its beak, hanging its head down and letting the water drain out the sides, and then flips the beak up and swallows the fish. Apparently the bird’s beak can hold three times as much as its stomach, but I doubt if one gulp will last it for a week. Nesting pelicans also carry partially digested fish in their pouch to feed their young. Finally pelicans, like all birds, cannot sweat but dissipate heat by rapidly vibrating their throat sacs. This is called gular fluttering.

There are eight species of pelicans, with some on every continent but Antarctica, but only two feed by plunge diving—the brown and the Peruvian pelican (formerly considered a subspecies of the brown pelican but now given full species status). These two are also strictly saltwater species. The other species of pelican we regularly see in the Bay Area is the American white pelican. But unlike the brown, white pelicans fish by floating along the surface, often in formation, and scooping small fish out of the water with their beaks and into their large gular sacs. These birds nest in northeastern California and at Pyramid Lake in Nevada and are here during the non-breeding time of year from August to March. Their claim to fame is their 9-1/2 foot wingspan, and they are often seen soaring high in formation with striking black and white wings.

The brown pelican used to commonly nest in the California but due to eggshell thinning (from DDT) and the collapse of sardine populations, they now mostly breed in Baja California, though small breeding colonies have recently appeared on Anacapa and Santa Barbara islands. The federal government recently announced that the brown pelican is no longer considered endangered—good news indeed and proof that the Endangered Species Act works, so it looks like we’ll get to watch those gular sacs gulping and fluttering for a long time to come.

Quicksand

Q–What is quicksand? Is there any in the Bay Area? Is it true that an earthquake can turn some land into quicksand? Has anyone ever been sucked into such soil? [Chantal, San Francisco]

I have had two personal encounters with quicksand and neither happened in the Bay Area. The first was along the Amargosa River near Death Valley and later on the bank of the Colorado River in the Grand Canyon. Fortunately like everyone else who steps in quicksand, I survived! Classic Western movies, of course, have portrayed an entirely different outcome. Usually bad guys are sucked down into the muck with only their black hat remaining on the surface as witness to their justifiable and righteous death.

“Quick” in this sense does not mean fast but means alive which is the original definition of the word. The use is similar to the word –quicksilver- for the metal mercury’s liveliness in the liquid state. Basically quicksand is made up of small particles (technically not sand but finer grains referred to as silt by geologists) that are saturated with water. The friction between the silt particles is so reduced that the entire mass is a semi-liquid that cannot support any weight. Most quicksand is only a few feet deep but if you happen to find yourself floundering in it, don’t panic (yeah, right). Your body is less dense than the quicksand and you can swim to the nearby bank. All of your movements should be slow and deliberate like you are swimming in a big vat of molasses.

However there is a closely related phenomenon, which is present in the San Francisco Bay area – liquefaction. You can demonstrate this on any beach. Find some wet but firm sand and jump up and down on it. Soon the entire mass will become more and more liquid and unstable as your feet sink down into it. You have just demonstrated what can happen in certain areas during an earthquake. Much of our infrastructure in the Bay area is built on fill or young sediment, which is very near the water table. During an earthquake the ground shakes and the underlying sediment can quickly become saturated with water. It becomes unstable and unable to support the overlying structures. Buildings, roads and bridges collapse just like we saw during the Loma Prieta earthquake in the Marina District. And this my friends, is not a movie.

Michael Ellis – Ask the Naturalist- Bay Nature Magazine

Longest Bird Migrators

Q: Which bird that migrates to or through the Bay Area travels the farthest to get here from its breeding grounds? Where does it come from and where does it go? [Jason, Oakland]

A: In October 1977, during my first pelagic birding trip in the middle of foggy Monterey Bay, I was carefully studying the drawing of a bird I had just seen (a south polar skua) when Rich Stallcup, the boat naturalist (now with PRBO Conservation Science), suddenly shouted something I couldn’t make out. “Did he say ‘comic’ tern?” I asked the elderly woman next to me. “Yep” she replied. Even Rich, one of California’s premier birders, could not distinguish at that foggy distance between the common and the arctic tern. They look a lot alike, especially in autumn plumage and from the deck of a rolling ship. So we had to make do with the combo “comic” tern. Not something to add to your life list, but I think of it as my first possible sighting of a champion migrator.

Terns are closely related to gulls. I like to think of gulls as basic Ford pick-up trucks—durable, tough, long lasting, but not too fancy. Terns are more delicate, can turn on a dime, and hover nicely in place, a bit more like Porsches. Like all terns, arctics mate for life and usually migrate together.

In the Bay Area, arctic terns are usually only seen far offshore and during the autumn. They fly south from nesting grounds well north of the Arctic Circle all the way to southern Chile, traveling as far as 15,000 miles. In its average 25-year life span, an individual arctic tern may fly over a half a million miles! (The Earth is only 25,000 miles around.) Arctic terns spend more time in daylight than any other species on earth and for many years were considered the premier migrators on the planet.

But in 2005 that changed. Research biologist Scott Shaffer and his colleagues at UC Santa Cruz outfitted some sooty shearwaters with radio tags and tracked them for over 200 days. The sootys (relatives of albatrosses) leave their New Zealand breeding colonies and travel all the way north to California to spend the austral winter in our summer. Here they feed just offshore on krill and squid in our nutrient-rich waters. They molt their flight feathers in the process (an energy-intensive event). In the fall they funnel back south to New Zealand, covering a total of more than 40,000 miles!

Arctic terns are too small to be electronically tagged, so we can only estimate the distance they migrate. Sooty shearwaters go the farthest but arctic terns still win the sunbathing contest. Your best chance of seeing either in California is on a pelagic bird or whale-watching trip, though sootys sometimes congregate in huge flocks resting on the water close to the coast.

Michael Ellis – Ask the Naturalist- Bay Nature Magazine

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