Greetings again! I am halfway through my summer internship at the koala barn at the San Diego Zoo and busy with all the data I am collecting. These past few weeks have increased my understanding of the interesting world of behavioral biology.

My two research projects are moving along quickly (see Maressa’s previous blog: Catnap, Koala Style). Cooladi (pictured above), the focal subject of my estrous project, has been very cooperative, and I have been able to collect many urine samples. This past week, I transferred all the frozen samples to the Endocrinology Lab at the Beckman Center for Conservation Research. I am interested in hormone levels present in the urine, specifically estradiol and progesterone, because these two hormones should help me figure out when Cooladi is in estrus, or heat. I am using a steroid radioimmunoassay (RIA) to track the hormones. Basically, I am “tagging” the hormones in the urine with harmless radioactive markers (the radioactivity levels are too low to harm and are very safe to handle). The radioactivity of the hormones makes them “visible” to special machines, so I can measure the amount of hormones present in each sample.

Scant information exists about urine analysis in female koalas regarding estrous cycles. Researchers in Australia have analyzed hormone levels from blood samples taken from female koalas and determined that their estrous cycles are about 35 days long. I hope that my project results will yield results that agree with the Australian researchers. I use urine samples to determine female hormone levels because collecting urine off the ground does not require the capture of a koala, so it is less stressful to the animal. Estrous cycles are species specific and the length of a cycle may vary greatly between animal species; for comparison, an average cycle of a domestic dog is six months. By collecting urine samples every day, I should be able to track at least two full estrous cycles, making koalas an ideal study subject for my summer project.

My second project has also been keeping me occupied. Another female, Orana (pictured at left), was introduced to the other three females living outdoors at the San Diego Zoo, and now the enclosure houses a content group of four. I am immensely enjoying my observation of “the girls” out on exhibit. Besides the usual sleeping and eating habits, they have shown me hiccups, yawns, social interactions, running (if you can believe a koala can run), and the most adorable mid-nap stretches. Although they seem like they would be very easy to spot, I sometimes find it challenging to record their behavior! The girls have quite a knack for hiding themselves in the eucalyptus browse provided by the keepers. Sometimes I only know a koala is in a perch because of a dainty paw sticking out of the leaves. Once I get all my data graphed and statistically analyzed, it will be very interesting to see if the girls prefer certain perches or places within the enclosure.

I will continue to happily watch and study my furry little charges. Please check in again toward the end of the summer for my research results! Perhaps I will be able to predict Cooladi’s next estrous cycle or the favorite perch of each of the girls.

Maressa Takahashi is a Neeper Summer Student Fellow in the Behavioral Biology Division/San Diego Zoo.

Listen to an iZoofari Chat with Maressa.

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