With my previous posts setting the tone for the adventure I had in Australia, I am going to use this third and final post about my “Koala Kwest” to discuss just how unique and important this little island population of koalas really is.
To have a better understanding of what we are looking at on St. Bees Island, we have to go back to the 1930s. Records show that is was around that time in the history of St. Bees, humans introduced a little over a dozen koalas and an undetermined amount of swamp wallabies to the island. As best as anyone knows, no more koalas were brought to the island after that initial group. Also since that time, St. Bees has had a few humans living on it, but at this time the island is part of Australia’s National Park system and is only inhabited by a caretaker. There are no roads, cars, or pets, and thus the human impact to the wildlife on the island is just about nonexistent. That said, the island has been home to cattle, horses, and goats since the early 1900s. And although the larger grazing animals were removed from the island by the late 1960s, the larger population of goats continued to reside on the island much longer. It wasn’t until the start of 2000 that strong action was taken by the government to remove the invasive goat population. Today there are only a few goats remaining; we did glimpse three or four every now and then while we were on the island.
All of this is important to take into account because today we see a koala population estimated to be around 200 to 300 in number and all from the original 1930s group. This, of course, begs the question about issues with inbreeding and all that we tend to see accompanying genetic weakness from a limited founding population. Interestingly enough, we see from the study site there on St. Bees a healthy population that seems to be doing quite well on many levels.
Thus, what we are looking at is an isolated population of koalas that is healthy and not influenced by human behavior. This means we have a great baseline model of wild koalas that we can compare to zoo populations. Also, as human population increases on mainland Australia, we see city growth, also known as urbanization, causing wildlife “islands” that isolate koala populations those of other animals. Studying the St. Bees Island population can help us better understand what we may or may not see in these mainland koala populations.
A side note to all of this is a very fascinating thing we have observed with the St. Bees Island koalas: they have very little tooth wear in comparison to other koala populations. You see, a koala’s life usually comes to an end around 12 to 15 years of age because their teeth have worn down from grinding eucalyptus leaves. Once the koala’s teeth have worn down and it can no longer chew the leaves of the eucalyptus, then life is no longer sustainable. Interestingly enough, for some reason the population on St. Bees seems to have exceptional teeth! It is believed that it may have something to do with genetics, but that is currently unproven and being looked into.
This is why on this trip we took photos and X rays of their teeth, documenting age by the known history of the animal (some on this site have ear tags and documented history or age) and looking at the teeth to compare to koalas of similar age not on the island. We also took blood to perhaps better understand if genetics may play a role in the unique tooth condition. And the follow up to all of this will be when we retrieve the radio collars from the koalas in the future. More blood can be taken, more photos and X rays of teeth can be taken, and we can start developing an even better database for this population.
Another part of this program is that the team from Queensland is hoping to use the data collected from the radio/satellite collars to better understand koala breeding and social behavior. Oddly enough, for a species that is adored by humans, little is really known about its behavior other than what is seen in general observations. That said, these general observations are quite limited due to the fact that koalas tend to sleep most of the day and have more activity at night.
In conclusion, as we strive to better understand koalas in the wild and in zoos, we begin to position our scientists, veterinarians, animal care staff, and global partners to be the leaders in koala conservation.
Rick Schwartz is a keeper and San Diego Zoo Global ambassador.