January 13, 2012
Natural History of Catalina Island
The Channel Islands are a chain of eight islands in Southern California off the Santa Barbara Channel. Santa Catalina Island – often referred to as just “Catalina” – is located roughly 20 miles directly opposite Torrance and Palos Verdes and is one of the larger islands in the Channel Island chain (76 sq. mi.). Catalina exhibits a mild, sub-tropical climate year-round and is composed mainly of a quartz base. The vegetation resembles that of a desert/ chaparral climate, and noteworthy landmarks include Echo Lake and Black Jack Mountain.
California Channel Islands, from Wikipedia
Catalina is an oceanic island that was formed by tectonic activity as opposed to being a continental island that separated from the mainland many years ago. This marine history was proved by the presence of fossils from plankton skeleton called diatoms. The material created by the presence of diatoms, called diatomite, is white and looks somewhat chalky. Continental islands’ native species often evolved from ancestral species that occupied the land before it broke away from the mainland, but oceanic islands are populated by immigrating species. Catalina Island is relatively close to the mainland, and the island’s biodiversity reflects this proximity. This follows the theory that larger islands will have higher levels of biodiversity than smaller islands, and islands that are closer to the mainland will have higher levels of biodiversity than those that are far away. Over time, animals have rafted, flew, and swam across the channel to the island to populate Catalina and the other islands. Once there, many have evolved to adapt to their new habitats.
Geological records are not necessarily conclusive, but it is possible to estimate species’ introduction to the island via remains and chart their arrival and extinction. Additionally, researchers have noticed that many plant and animal species closely resembled species on the mainland, but their physical appearances differ slightly. When species are separated from the mainland, and competitors or predators are removed, different physical traits may be selected over features that proved successful previously.
There are varying theories regarding the means of transportation taken by founder species and the reasons that species have changed in physical appearance. The Island Fox, a species on six of the eight Channel Islands, is thought to have been introduced thousands of years ago when Native Americans brought them over as domesticated pets.
Island Fox, Photo: L. Collins
Present day feral cats and dogs were also introduced as pets, but are now wild. More recent introductions, such as the Bison, have persisted on Catalina and have adapted to island life by evolving into ‘dwarf bison.’ The origin of the bison on Catalina is a funny one. In the 1920s, fourteen bison were brought to Catalina for the filming of a movie. After the movie was finished, the crew left the bison on the Island and their population grew quickly, now amounting to almost 600 across the whole Island.
Bison on Catalina Island, Photo: L.Collins
The island fox also exhibits a similar case to the bison of dwarfism and appears smaller than the average mainland fox. The quail and squirrel, on the other hand, have become larger, exhibiting signs of gigantism. It has been proposed that some smaller animals were able to grow larger over generations due to the lack of stress presented by predators and competitors, while once-large animals became smaller because there were not sufficient resources to keep them well nourished. In addition, due to differences in environment and competition, some shrubs undergo ‘arborescence,’ which leads them to look more like trees after many generations. On Catalina, this is true of the Toyon and Island Scrub Oak. Species that can only be found in one place or region are called ‘endemic species,’ and Catalina Island contains eight such plant species and eight animal species as well as eight species of invertebrates. According to the Catalina Conservancy, which managed 88% of the island, two of the plant species are still under review regarding whether or not they are truly endemic. An interesting case study is that of the Island Ironwood trees. Many island endemics are often grouped as subspecies of mainland plants, but the Island Ironwood is the only species that is actually differentiated on the genus level from the parent species. The Santa Catalina Ironwood (Lyonothamnus floribundus, floribundus) differentiates from the Island Ironwood (Lyonothamnus floribundus, aspleniifolius) in that the Catalina Ironwoods have significantly longer and wider leaves.
This post was authored by Nina Gordon-Kirsch ’12 an Environmental Studies major (BS) with a minor in marketing; and Annie Guo ’12 an Environmental Studies major (BS) with a minor in International Relations.
For more information about Santa Catalina Island, feel free to visit the Catalina Island Conservancy’s website.
I am a California native, specifically from Los Angeles, and have lived in many of the diverse regions that make up Southern California. I’ve experienced life in the coastal cities, like San Diego and Santa Monica, urban parts of down town and east L.A., the mountains and foothills of La Crescenta and the Angeles Crest, and have even lived in the dreadful desert region of Palmdale, in the Antelope Valley. Having experienced many of the topographic regions of Southern California has allowed me to appreciate where I’m from all the more; and bonus there’s not only the mainland to boast about, but there are islands too.
As written in the blog posts of my colleagues, the chain of the California Channel Islands harbors a history rich with geological, biological, and ecological information that scientists and students have always been eager to explore. In and of themselves the islands are geologically fascinating to study. But as a byproduct of this exploration, scientists have also learned how species have immigrated and colonized on the islands, species endemism and variation among the different islands, the unique biodiversity of the different regions, and other substantial discoveries that have furthered the understanding of oceanic islands.
While the information mentioned above is indeed captivating, I ask that you please excuse the self-serving deviation for a moment. If you know me, then you’d know that I have done more than my fair share of world traveling. However, I have never been to any of the Channel Islands, something that I can hardly believe myself. Thus, it goes without saying, that I am very excited to visit Catalina and Santa Cruz islands this semester and have the opportunity to see first hand these unique islands that were formed by our friendly Southern California seismic activity. Additionally, I am rather fascinated by the phenomena of island dwarfism and gigantism, and am quite eager to see this in the bison and squirrels on the island, respectively. Furthermore, I like having the opportunity to apply some of the other concepts and ideas involving the Channel Islands that, up until this point, I have only read about in this class and in the blog posts of my classmates.
I’ve always been intrigued by the fact that dwarf bison live on Catalina Island and that they have been accepted as they have. Some people of course hope to see Catalina return to its natural state, and bison don’t fit into that image of Catalina. However, while pigs and goats have come and gone, and there are currently strong debates over the presence of feral cats, the bison have been able to safely remain on the island.
Fourteen were shipped over in 1924 as props for the old western film The Vanishing American, a number that later grew to about 500 in the 90s. I think it was very irresponsible for the filmmakers of The Vanishing American to leave the bison on the island when they wrapped shooting their movie. I doubt they considered the potential harm these nonnative animals could have done to the island and it’s native species, and I think the creators of the film just got lucky that the bison and island have simultaneously adapted to each other.
That being said, I actually really enjoy seeing bison when I’m visiting Catalina and am glad that the population has been able to survive in a habitat where they seem to live happily.
I found some supplementary information in the LA Times article found at this website: http://articles.latimes.com/2009/nov/20/local/la-me-catalina-bison20-2009nov20
Also, here’s a picture of the movie poster that the original bison starred in!
http://ecx.images-amazon.com/images/I/51PY4H06MML._SL500_AA300_.jpg
Now that we have visited both Catalina Island and Santa Cruz Island, I think it is interesting how there can be so many of the same flora and fauna found on both islands yet they have developed in different ways due to different factors.
For example, the population of native Island foxes decreased significantly on their respective islands. However, both decreases came as a result of different factors. The population of Catalina foxes decreased because of human introduction of animals such as dogs and raccoons which passed on the canine distemper virus onto the native fox populations, which caused them to decline greatly. The population of the Santa Cruz Island fix decreased due to hyper predation by golden eagles. The situation was exacerbated by having to face competition from wild pigs for resources.
The process by which the natural environment selects for certain traits that make for an evolutionarily better-adapted individual is well understood, and has produced a stunning array of fascinating adaptations in wild flora and fauna. Island gigantism and island dwarfism, related but opposite phenomena that similarly result from a change in habitat constraints (e.g., water, food resources, space), are obviously the result of the natural environment selecting for size. What fascinates me particularly about the island dwarfism seen in the bison population on Santa Catalina Island is the speed with which the population began to transition toward smaller individuals. If the bison were truly left on the island as recently as the 1920s after a film shoot (just another instance of the plight of the background actor in Hollywood), I’m appalled that the population would begin to experience a phenotypic shift that quickly. I’m not entirely sure how many generations a bison can go through in less than one century, but I have to imagine that this is a particularly accelerated case of natural selection.
Additionally, thanks to user “Addie Rowe” for the movie poster from the bisons’ breakout role: I’ll be adding “The Vanishing American” to my Netflix queue posthaste!
Now that I have visited Catalina Island I’m really glad I got to see the diversity first hand. Seeing a random bison grazing on a hill top and a fox cross our path was really beautiful. It was fascinating to see that what were once abandoned animal actors in 1924 have adapted and evolved so well to island life and have even helped the island a little by grazing on non-native grasses. Catalina island is a prime example of how human actions can alter the ecology of a natural area. In the case of bison the repercussions of introducing a non-native species was not as horrific as it could have been. For example, the apple snail was introduced to Taiwan with the hope of establishing an escargot industry but the snails became the carriers of dangerous parasite that can be deadly if ingested and they also ended up threatening rice production in the region. The snails spread to Indonesia, Thailand, Combodia, Hong Kong, and Southern Philippines. We also got to see the extensive fields of invasive fennel and learned about the growing problem of feral cats threatening native wildlife on the island.