Channel Islands Field Guide (Melissa Savage)
Reviewed By:
Melissa Savage- Biology Instructor GHCHS
Location:
Off the Coast of Ventura:
Latitude, Longitude - WGS 84 (NAD 83)
D: 34.00417, -119.39639
DM: 34° 0.2502', -119° 23.7834'
DMS: 34° 0' 15.012", -119° 23' 47.004"
UTM: 11S 278685.03534646 3765207.6005317
Biology Standards:
Ecology
6. Stability in an ecosystem is a balance between competing effects. As a basis for understanding this concept:
a. Students know bio diversity is the sum total of different kinds of organisms and is affected by alterations of habitats.
b. Students know how to analyze changes in an ecosystem resulting from changes in climate, human activity, introduction of nonnative species, or changes in population size.
c. Students know how fluctuations in population size in an ecosystem are determined by the relative rates of birth, immigration, emigration, and death.
e. Students know a vital part of an ecosystem is the stability of its producers and decomposers.
g. Students know how to distinguish between the accommodation of an individual organism to its environment and the gradual adaptation of a lineage of organisms through genetic change.
Evolution
7. The frequency of an allele in a gene pool of a population depends on many factors and may be stable or unstable over time. As a basis for understanding this concept:
a. Students know why natural selection acts on the phenotype rather than the genotype of an organism.
d. Students know variation within a species increases the likelihood that at least some members of a species will survive under changed environmental conditions.
8. Evolution is the result of genetic changes that occur in constantly changing environments. As a basis for understanding this concept:
a. Students know how natural selection determines the differential survival of groups of organisms.
b. Students know a great diversity of species increases the chance that at least some organisms survive major changes in the environment.
c. Students know the effects of genetic drift on the diversity of organisms in a population.
d. Students know reproductive or geographic isolation affects speciation.
Earth Science Standards:
5d. Students know properties of ocean water, such as temperature and salinity, can be used to explain the layered structure of the oceans, the generation of horizontal and vertical ocean currents, and the geographic distribution of marine organisms.
Channel Islands Intro
Channel Islands National Park encompasses five islands running east to west off the California coast near Ventura. Never part of the mainland, each has a different geography, character and its own endemic plants and animals, so many of them that I like to call it California's Galapagos.
Most visitors make their way out to the islands using one of the boat or air services that act as concessionaires for the National Park Service. Others arrive by private boat. More intrepid visitors can bring along camping gear and food and stay in one of the primitive campgrounds. There are no food concessions once you leave the mainland, so bring enough water and food to last for the trip.
Anacapa: A narrow, windswept rock with annual rainfall less than 10 inches and no trees, Anacapa shelters the world's largest gull-breeding colony, the rare Anacapa deer mouse, and eight species of songbirds. It's nearest the mainland and thus a good place for a first visit. Because of its steep cliffs, there's no boat dock, and visitors have to climb a metal ladder up the cliffside from their boat. Once ashore, you can view exhibits and take an easy hike around the island.
Santa Cruz: A large portion of this island is owned by the Nature Conservancy and the National Park Service owns the rest, which is open to the public. This largest of the Channel Islands has been much changed by human habitation and ranching, but efforts are underway to return it to its natural state. Of the Channel Islands' 85 native plant species, nine occur only on Santa Cruz.
Santa Rosa: The only island accessible by air, Santa Rosa is home to over 195 species of birds and the endemic spotted skunk.
San Miguel: The westernmost and flattest island, San Miguel has a ghostly caliche forest (standing sand casts of long-gone plant roots and trunks). In winter, it's home to an estimated 50,000 elephant seals, who breed and pup here.
Pygmy Mammoth
Mammoths have always fascinated people. From the creators of the earliest known cave painting and carvings to 20th century practitioners of modern art and even to today's tourists, humans have tried to grasp the essence of this magnificent creature – its enormous size, strength and beauty and its coexistence with and importance to humans. In 1994, paleontologists made the remarkable discovery of a pygmy mammoth on Santa Rosa Island, the most complete collection of its kind in the world.
Found only on the California Channel Islands and nowhere else in the world, the pygmy mammoth was probably a small form of the Columbian mammoth found on the mainland. Pygmy mammoths varied from 4.5 to 7 feet high at the shoulders and may have weighed only about 2,000 pounds, compared to the 14-foot tall, 20,000 pound Columbian mammoth. In other respects, they were probably similar, with short fur, a typical mammoth body form, and a relatively large head.
The first remains of "elephants" on Santa Rosa Island were reported in 1873. Additional excavations over the years have given a basic understanding of a population of mammoths on the islands which became smaller in body size through time and which perished as the Pleistocene ended. Paleontological excavations on Santa Rosa Island in 1927 and 1928 resulted in the retrieval of a significant collection of a new species described as Mammuthus exilis. Philip Orr of the Santa Barbara Museum of Natural History recovered additional materials during archeological and geological work on Santa Rosa Island during the 1940s and 1950s.
Remains of mammoths are most common on Santa Rosa and San MiguelIslands, with smaller numbers recovered from Santa Cruz Island and from San Nicolas Island, outside the park. The recovered specimens range in size from 4 to 8 feet at the shoulder, compared to the 12 to 14 foot height of mainland mammoths.
The Journey to the Islands
Approximately 40,000 to 20,000 years ago, a small group of 14-foot tall, 20,000-pound Columbian mammoths embarked on a journey that would eventually end in the development of a new species—the Channel Islands pygmy mammoth. Leaving the heavily grazed mainland behind, these Columbian mammoths swam towards the scents of abundant vegetation from the huge, mountainous island of Santarosae.
Approximately 20,000 years ago when sea level was about 300 feet lower than it is today, the four northern islands joined together to form an Ice Age “superisland” known as Santarosae. This island was only 6 miles from the mainland at its closest distance. As the ice sheets and glaciers melted and the sea level rose, only the highest parts of Santarosae remained as modern islands.
But how did they reach the island? With their snorkel-like trunk and buoyant mass, elephants, living relatives of mammoths, are considered excellent distance swimmers, among the best of all land mammals, and skilled at crossing watergaps. Documented accounts demonstrate that Asian elephant swim to islands they cannot even see – some up to 23 miles away—guided by the odor of ripening fruit and vegetation. There is no reason that Pleistocene mammoths were not just as seaworthy, and just as good at swimming.
Evolving into a New Species
Once on the island, the population of mammoths increased and, eventually, the food supply became scarce as the island decreased in size due to climatic changes – glaciers and ice sheets melting, and sea levels rising. Those mammoths that were smaller and could survive with less food and water were at an advantage, especially in times of seasonal shortages. Over time, smaller animals that required fewer resources became the norm. In addition, the absence of predators on the islands also may have contributed to this downsizing: large size was no longer needed for predator avoidance and defense.Within less than 20,000 years, natural selection favored smaller-sized mammoths that stood less than 6.5 feet tall at the shoulder, less than half the height of their mainland ancestor. Thus, the small mammoths became a new species, the Channel Islands pygmy mammoth.
The pygmy mammoth is an extinct member of an ancient and unique group of mammals collectively known as probiscideans. This name comes from the Greek word probiscis and refers to the large or extended noses. While the fossil history of this group spans over 55 million years and more than 160 different species, today’s elephants are the last survivors of this widespread group of animals.
Extinction
After 200,000 years as one of Earth's most dominant species, mammoths, which once thrived across Europe, Asia and North American, became extinct nearly 10,000 years ago. The extinction of the mammoths was also part of the much wider phenomenon of disappearance of the world's larger mammals, which started about 40,000 years ago and reached its peak between 12,000 and 10,000 years ago. Just what caused the demise of this Pleistocene megafauna is still unknown: nearly 30 years of research and testing has not yet provided an answer that is universally convincing.
Special Islands
Mammoth finds are by no means rare. Complete skeletons to cave paintings have been discovered on four continents in a wide variety of locations: an engraving of a mammoth on mammoth ivory found in a rock shelter southwestern France; a preserved frozen carcass of a baby male mammoth in the permafrost of Siberia; a sinkhole with more than 100 mammoth remains in Hot Springs, South Dakota; and, of course, our own mammoth find right here in our backyard, within Channel Islands National Park – the discovery of the world's first virtually complete pygmy mammoth skeleton in 1994.
Studying the pygmy mammoth reveals how important the Channel Islands are in illuminating the mysteries of evolution. The isolation of the islands have made them natural laboratories of evolutionary extravagance, as seen not only in the pygmy mammoth, but also in the extinct giant mouse, the diminutive island fox, the munchkin dudleya, and the giant, bright blue Island Jay. Isolated from their mainland relations and exposed to unique environmental conditions, the ancestors of these plants and animals, along with over 70 others, responded by becoming new species unique to the island – found nowhere else on earth.
Videos on Pygmy Mammoth
CHANNEL ISLANDS NATIONAL PARK
A cast of the pygmy mammoth skeleton is displayed in the Visitor Center.