Ice Age Mysteries of the Channel Islands, California By: Dr. Jim Mead
ISLANDS! You got to love them…surrounded by water, endless and often breath-taking views. As a kid with my science-oriented parents I lived a while in O’ahu, Hawaii. I quickly learned about field work, being methodical in my search, observations, and writing of notes. My dad was researching how the recently and accidentally introduced Giant African land snail (Achatina fulica) – which could easily be over a foot long while sliming over the forest floor – quickly spread over the entire island. BUT, interesting, its offspring quickly became smaller size. Apparently, according to dad, due to the population size and the limited resources on the island, this giant of a snail was becoming diminutive. Although the story about Achatina is slightly different than for insular mammals, some of the reactions of being on an island are the same. So often typically small animals develop into larger forms when restricted to islands, and conversely, typically large animals will become smaller forms. Remember that the largest living lizard, Komodo dragon or monitor (Varanus komodoensis), lives on an island. And the largest of tortoises live on islands too.
The Channel Islands off of California have the same effect on some mammals. Take for instance the extinct mouse Peromyscus nesodytes. Typically the peromyscine mice are very small, like the introduced house mice you might unfortunately have around the barn or house. But the Channel Islands mouse has developed into a larger form.
Now let’s take a look at the mammoth – Mammuthus. We all know that this extinct form of elephant was huge. The extinct woolly mammoth (M. primigenius) could stand up to 3.4 m (11 ft) high and weigh in at 4-6 tons – about the size of some living African elephants (Loxodonta africana). The extinct Columbian mammoth was even larger – up to 4 m (13 ft) tall, or higher, and weighed in at an estimated 10 tons! We also know that Columbian mammoths wandered all over North America including along the California coast.
Elephants we know can actually swim – that is how they got out to Sri Lanka from India, and we know that the Columbian mammoth, or its near-relative, swam out to the Channel Islands, which during the Ice Age was one large island called Santarosae. Those huge mammoths for whatever reason were restricted to Santarosae did just what the giant African snail did – successive generations became smaller! Pygmys actually! These insular mammoths were only about 2 m (6.5 ft) high!
The Channel Islands National Park off the coast from Ventura and The Mammoth Site in the Black Hills of South Dakota are collaborating to see just how all these mammoths transformed from HUGE to little (and certainly cute) insular herbivores. A crew of paleontologists from The Mammoth Site (Monica Bugbee and Justin Wilkins) joined retired archaeologist and Mammoth Site Crew Chief, Don Morris and others to understand a recently discovered mammoth skull emerging on Santa Rosa Island. This particular specimen is incredibly interesting – it is not the size of the typical pygmy mammoth (M. exilis) and certainly not the huge Columbian mammoth. It is an in-between size.
What we are investigating is very intriguing!! 1) When did mammoths venture onto Santarosae – how long ago? 2) When did they become diminutive? 3) How long did it take for successive generations to become pygmy? 4) How often did other large mainland forms swim out to Santarosae and interbreed with the insular pygmy? 5) And if they did – what did these offspring look like?
What the collaborative crews have found is intensely interesting. The preservation is outstanding, so we hope to not only get excellent linear measurements from the skull and teeth but we anticipate to be able to recover ancient DNA. We suspect that if we can isolate the DNA that it will indicate that we do indeed have a mixture of mainland and island forms….but who knows right now. We have lots to do … lots to investigate! … and the skull has to be helicoptered from its place of rest to a boat and then to the lab for preparation. I want to know all the answers NOW, but I will be patient and let our research progress be methodical just as my dad taught me.
Also here is a link to a news story about the recent discovery at the Channel Islands written by Cheri Carlson, courtesy of the Ventura County Star http://www.vcstar.com/longform/news/special-reports/outdoors/2016/09/14/clues-uncovered-life-long-extinct-mammoths-channel-islands/90306708/