Catalina and the other Channel Islands are bustling with life. Many endemic species have lived and evolved on the islands for millennia. The channel islands, like so many other islands, have never been connected to any mainland or continent, so how did all of the different plants and animals get to there in the first place? The for most common ways for plants and animals to spread to new lands can easily be remembered with what we refer to as the four W’s.
The first W stands for Wind. The first inhabitants of newly formed islands are plants. Plants, which live very stationary lives, have had to evolve methods for reproducing and spreading their genes over broad areas. Many plants have developed the ability to spread their genes through pollen or seeds that are designed to be carried through the air far away from the parent plant.
The second W is wings. This is by far the simplest method for immigrating to new places. Birds, bats, and insects that possess wings can simply fly to freshly formed islands, especially ones as close to the mainland as Catalina.
The next W stands for water. Many animals have swum great distances to increase their range. One example of this is the pygmy mammoth of the Northern Channel Islands. Some experts think that at the time the mammoths swam across the channel that the distance was about 10-12 miles. Some animals like the foxes and squirrels that still roam the islands that distance was too great to swim. What likely happened was that they ended up stranded on floating debris piles that drifted to the islands. Once they hit the islands or were close enough, they escaped the rafts and many eventually evolved into new endemic species.
The last W can stand for either Westerners, Warner Brothers, or Wrigley’s. No matter which one you prefer the method and results were still the same. Humans brought plants and animals to the island for various reasons. Some plants were brought over for function such as the eucalyptus trees for erosion while others were brought over for décor. Animals that were brought to the island include goats, deer, and pigs. The most renowned animal on Catalina is probably the bison. They were first brought to Catalina for a movie and then they were never returned.
However they got there, the animals of Catalina have and will continue to shape it’s unique ecosystem.
Islands can be pretty awesome places. From the volcanic islands of Hawai’i and the Galapagos, to the mangrove islands of the Florida Keys, to the sandy beaches of the Caribbean, and even the rocky desert islands off the coast of California, islands represent many different types of ecosystems. As different as islands can be, their natural inhabitants can be incredibly unique themselves.
Whenever animals become isolated on islands, they can undergo extreme changes in size. This is usually as a result of an increase or decrease in natural resources such as food or water as well as a decrease or increase in predators. This is known as the Island Rule and was first proposed by biologist J. Bristol Forster in 1964. Forster studied 116 different Species of island dwelling animals and published his findings in the scientific journal Nature. Forster’s studies revealed that in many cases, smaller animals such as rodents had become larger, but larger animals and most carnivores became smaller. In the case of carnivores and larger animals like elephants, the islands that they ended up on simply could not support animals of their sizes. The bigger the animal, the more resources it would need. The only way for a species to survive was to become smaller. Rodents, on the other hand, would be coming into a new environment much more suitable for animals of their stature. They would often find more food with less competition allowing more individuals to grow to their maximum potential.
The Channel Islands off of the California coast including Catalina have some perfect examples of the island rule. The three northern most Channel Islands San Miguel, Santa Rosa, and Santa Cruz, all contain remains of pygmy mammoths. Pygmy mammoths were believed to have been Columbian mammoths that swam across the channel and shrank due to lack of water and vegetation. Pygmy mammoths like their mainland cousins all went extinct thousands of years ago.
Some living examples of the island rule are the channel island fox and Catalina California ground squirrel. The Channel Island fox is a direct descendant of the North American gray fox but like the pygmy mammoth, it shrank due to lack of resources. Channel Island foxes are only half the size of gray foxes found on the mainland. However, when Catalina California ground squirrels arrived to the island, they found themselves not only with an abundance of food but also a lack of competition. They were and are currently the only species of squirrel on the island. No other species of squirrel are around to divide the natural resources and only a fraction of their natural predators exist on the island to limit their population. These factors have led the Catalina California ground squirrel to grow larger than all other regional populations of the same species.
So next time you spot some island wildlife, think about the unique challenges the species faced when it became detached from its cousins in a larger environment, and the tradeoffs it had to make to become better suited to a smaller space and scrappier pool of resources. We can all marvel that while a tortoise towering over a fox might seem strange today, who knows… in a few more million years, or a ground squirrel might be the same size a mammoth once was… now that thought makes us a little squirrelly!
Hummingbirds rank among some of the smallest bird species on Earth. They get their name from the sound their wings make as they rapidly beat them 50 times a second to keep their bodies aloft! Their wings rotate in a figure eight pattern, which allows the bird to hover or fly backwards if it needs to. Because they move so quickly, they also burn through energy quickly, so they constantly have to feed on nectar and insects throughout the day. At night they hibernate, slowing their ultrafast metabolisms down to a torporific state. During this time they also slow their heart rates from 1200 to 50 beats per minute.
Catalina Island is home to three species of this tiny bird: the Anna’s Hummingbird, the migratory Allen’s Hummingbird, and the Channel Islands Allen’s Hummingbird. Male Allen’s Hummingbirds have bright, iridescent red-orange throats, and Anna’s Hummingbirds have magenta plumage on their throat and head. Both species can be found zooming around Catalina’s blossoming bushes and eucalyptus trees, feeding on nectar they find in the flowers. The Channel Islands Allen’s Hummingbird is endemic to all the Channel Islands except for Santa Barbara, and it is a permanent resident on Catalina. The migratory Allen’s Hummingbird winters in central Mexico and then works its way up the coast to spend its summers in California. Anna’s Hummingbirds can be found on Catalina all year round.
At 3 to 3.5 inches in length, these hummingbirds may be small, but don’t let that cause you to underestimate them! Male Allen’s Hummingbirds can be quite aggressive when they are defending their territory, and some have even been known to chase away red-tailed hawks! If you look at a tree buzzing with hummingbirds, you will soon notice several intense battles being waged, with the males sitting on conspicuous branches and quickly darting at anyone that tries to get near them. Male hummingbirds also put on a show when they mate, performing a courtship dance that includes a high-speed dive of 100 feet or more. With their dynamic flight patterns and brightly-colored bodies, these little hummingbirds are truly the feisty, speedy acrobats of the bird world.
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