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Treebeard's Stumper Answer
6 September 2002

Catalina Crossings

Here is a link to my hard Catalina Crossings crossword puzzle for Dunn Middle School students to solve while they pack for our Catalina Island adventure next week. We will cross to Catalina by boat, but how did everything else get there? Current opinion is that the California Channel Islands have not been connected to the mainland since at least the Pleistocene age 1.5+ million years ago. Therefore every native plant and animal species that we see next week is a stumper. Endemic plants and animals that occur nowhere else are especially interesting. How did island plants and animals cross the ocean barrier?

Julie and I spent a week on Catalina Island last summer. We camped at the Isthmus for a few days of fabulous kayaking and snorkling and hiking. (We loved it so much that we bought our own ocean kayaks when we got home!) We then joined a volunteer weed survey with the Catalina Island Conservancy. I've collected more Catalina links on the DMS Catalina Research webpage. The first sight coming into the Isthmus harbor is Bird Rock. It's covered with a thick deposit of bird guano, like frosting on a cake. We kayaked out to Bird Rock, and the smell is "interesting," like a diaper pail. But the rock is alive with birds and interesting plants.

The plants growing from the guano on Bird Rock are a dense, low thicket of Malva Rose (Lavatera assurgentiflora), Giant Coreopsis (Coreopsis gigantea), and prickly pear cactus (Opuntia littoralis x O. oricola). It's remarkable that Malva Rose is an island endemic that only grows on Bird Rock and Indian Rock in nearby Emerald Bay. Other races of Malva Rose exist on other Channel Islands. This beautiful endemic is now in cultivation and sometimes escapes on the mainland. How did this rare shrub originally get to the Channel Islands?
There's no mystery how some plants and animals got to the islands. We saw this herd of bison in some unfortunate's campground at Little Harbor. Note the blue ice chest under the bison on the right. As I understand it, the Bison were introduced to Catalina in 1924 during the filming of a silent movie, "The Vanishing American". Fourteen animals were originally released. The bison population is now controlled at about 500, and "Buffalo Burgers" are available. The story is told at Robert Roy Jan van de Hoek's Pimu-Catalina Island Wild Nature page. However plants and animals originally got to the islands, they are still doing it with human aid. Invasive weeds and animals are an on-going management problem. But how did the original native plants and animals get to the islands without people and boats to carry them?
The most interesting Channel Island endemic might be the Pygmy Mammoth (Mammuthus exilis) fossils found on Santa Cruz Island in the Santa Barbara Channel. This photo shows the reconstructed skeleton mounted by Phil Orr at the Santa Barbara Museum of Natural History. (Photo by Wm. B. Dewey, used without permision.) There's more info in Larry D. Agenbroad's Pygmy (Dwarf) Mammoths of the Channel Islands of California (1998), available from the Mammoth Site Museum Shop. These head-high Mammoths lived on the Channel Islands just 12,000 years ago. The world is poorer without them. Pygmy Mammoths are a great oxymoron, but they are also part of the stumper about how plants and animals colonize islands.


One way or another, all native island life originally hitched a ride to the islands. It helps that sea level was lower during recent ice ages, and Santa Ana winds blow offshore towards the islands. Birds eat berries and might pass the seeds 26 miles across the sea. Maybe a single pregnant fox (and hitchhiking ticks) rafted across the channel on a driftwood log pushed by sundowner winds. These chance migrations continue. The spread of exotic plants and animals around "this island earth" is a global problem we are only beginning to face. Like that first island fox, life is tenacious!

Notes:

Here is the answer to my hard Catalina Crossings crossword puzzle. DMS students Brett, Lenora, Emily, Amanda, Alicia, and Chase were the first to finish.

An ecological island is a broader notion than just land surrounded by ocean. Any relatively small habitat (the island surrounded by a different habitat (the mainland) can be considered an island, and the stumper of how life got there remains. Hot springs and desert mountain peaks and lakes are also ecological islands in this broader sense. In general, all islands are settled in just two (or three) ways:

There are interesting endemic plants on the Channel Islands like Ironwood (Lyonothamnus floribundus) that occur only in the fossil record on the mainland. The cool, foggy, marine climate on the islands still has the "Pleistocene climate" they need to survive. This supports the last option. Life hitched an easy ride and then was isolated to go it's own way. It's not surprising that so many common island plants and animals are endemic subspecies of mainland forms.

The California Channel Islands have been isolated for over a million years, so all Channel Island life hitched a ride. My imagined scenario is that a fox rafted across the channel on a driftwood log, maybe propelled by a Santa Ana wind in the fall after a wildfire and a tropical rainstorm flushing the canyons, like Noah populating a new world. Sure it's not likely, but there's room in deep time for the chance event to happen. Catalina and the other Southern Channel Islands were never connected to the Northern Channel Islands, but island foxes occur on both. There are Spotted Skunks on the northern islands, but not on Catalina. We camped on Santa Cruz Island a few years ago, and I remember how tame the island foxes were, coming right into our campground at Prisoner's Harbor. Maybe the Chumash Native Americans carried the foxes between the islands on their tomol boats as pets. I understand why they left the skunks behind!
Island Fox

Of course that original tenacious fox was not the endemic Island Fox (Urocyon littoralis) that lives on the islands today. Evolution happens quickly in a small population isolated from preditors. "Small and friendly" are traits of island populations around the world, and their demise. Flightless geese on Hawaii and Dodo birds on Mauritius were easy dinners for Polynesian and European explorers.

The California Channel was different during the last ice age. Sea level was lower 20,000 years ago during the ice age. The Northern Channel Islands were connected into the single island of Santarosae, only about six miles (20 km) from the mainland. Full size elephants have been recorded swimming as far as 23 miles, so a six mile swim is more than possible. This photo from India is so cool! That elephant looks like Nessie, using it's trunk as a snorkel.

Elephant swimming near Kerala, India.
Photo by Roy Matthew.

"Pygmy Mammoth" is a great oxymoron like "jumbo shrimp". A nearly complete pygmy mammoth skeleton was found on Santa Cruz Island in 1994, and carbon-dated back to 12,840 years ago. The earliest fossil remains are dated to about 10,500 years ago, very close in time to the first human remains on the island, depending who you ask. Is that a coincidenc/e?

There is fossil evidence of small elephants/mammoths on other islands in Indonesia, the Mediterranean, and Wrangle Island in the Siberian Arctic. The last is especially interesting. There are remains of large Woolly Mammoths dated to 12,000 years ago, and dwarf mammoths (about 6ft high) lived on the island until as recently as 3500 to 4000 years ago. This is the youngest date for mammoths anywhere in the world. This is evidence that size-reduction in an isolated population can happen quickly (in geological time).

What a loss that there are no Pygmy Mammoths today. We were so close. It's hard not to think about cloning...

Today the Island Fox is threatened by another preditor rafting with human aid. People bring their dogs to Catalina by the ferry, and now canine distemper is decimating the Island Fox population. Introduced Fennel and other invasive weeds are taking over the native flora on the islands and here at home. Snakehead Fish, West Nile Virus, Killer Bees, and HIV/AIDS have all been in the news lately, and there are many more.

That bumper sticker slogan is good advice: "Think Globally, Act Locally." Clear the weeds from your property. And keep doing it, year after year. That's something we can each do to keep the world as rich as it is.

Whew, this is a big topic, and this is all I have time for. There's already lots of links on this page, and here are a few more for your own research:

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Copyright © 2002 by Marc Kummel / mkummel@rain.org