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Turtle University

by Margaret Rousser | June 28th, 2011

Newly hatched western pond turtle

Its turtling season at the Oakland Zoo again! Each summer our zookeepers team up with biologists and students from Sonoma State University to study the western pond turtle. Turtle nesting season is in full swing and California’s only native aquatic freshwater turtle has been an enigma to researchers for years. This is the fourth consecutive year that zookeepers have spent in Lake County and our knowledge of this species of special concern has increased exponentially. Here is just a short run down of a few of the things we have learned about western pond turtles through our collaborative research:
First, we were surprised to discover just how dry the nests were. Aquatic turtles are usually expected to have very moist nests, but not our western pond turtles. Based on our observations at the site, we created a very dry vermiculite mixture in which to incubate the eggs we collected. Several experts expressed concern about the lack of moisture in the mixture, but our guess was correct and we had a 90% hatch rate the first year.
One little known fact about many reptile species, western pond turtles included, is that the sex of the hatchling is determined by the temperature at which the egg is incubated. Along with our dry vermiculite mixture, we also set up five separate incubators at five different temperatures. The hatchlings were carefully marked with numbered dots so we knew exactly which clutch and incubator they came from. The hatchlings were then raised here at the zoo for about ten months, until they were big enough for a small endoscopic surgery to determine their sex. This data was then correlated with the incubation data and we now know the exact temperatures that produce male turtles versus female turtles.

Dr. Andrea Goodnight uses an endoscope to identify a turtle's sex.

As time went on, our project expanded and we also began to incubate nests in the field. This requires careful placement of high tech temperature and humidity sensors inside the nests and then covering the nests to secure them against predators. The wide range of temperatures in even a single day took us by surprise. Who would have guessed a difference of up to fifty degrees in one twenty-four hour period.
This is a project that is near and dear to our hearts, not only because it is a native species, but also because it is a project that zookeepers can be directly involved in. Just days ago, two keepers went to the lake to use telemetry equipment to track nesting females while other keepers were here at the zoo caring for last year’s hatchlings, who will be released at the end of this month. As we continue to progress in this conservation project, we hope to learn even more about this special animal.

Tags: Conservation, Oakland Zoo, Sonoma State University, turtle research, Turtles, Western Pond Turtle, ZooKeepers, zoos
Posted in Conservation, Veterinary Care, ZooKeepers No Comments »

Baby Otters!

by Margaret Rousser | May 11th, 2011

Otter pups at 1 day old

What’s more amazing than baby otters? Nothing! This year, our 4 year old female North American river otter gave birth to her first litter. First time moms often make keepers nervous since we never know how they will do, but Ginger has turned out to be a pro!
Ginger joined us here at the Oakland Zoo in 2008, when she was just one year old. North American River otters are not very prolific breeders, so AZA makes annual breeding recommendations. When Ginger came to us, she was still a bit too young to breed, but we knew that the AZA eventually wanted her to breed with our 12 year old male, Heath.
River otters are one of the few species that exhibit a phenomenon called delayed implantation. Essentially, otters breed in the spring but the fertilized egg doesn’t actually implant until fall! So how does one plan for such a unique pregnancy? As it turns out, hormone levels can be measured in otters’ feces! Our keepers collected samples from Ginger four times each week and mailed them off to Cincinnati to be tested. In December, we got the word that Ginger’s progesterone had spiked and that she was likely pregnant with a due date sometime between February 15th and 23rd.
Now the preparations really ramped up! The keepers had meetings with the vet staff to prepare for any and all possibilities. Cameras were set up in denning area. Supplies such as extra towels, an infant scale and thermometer, and data recording sheets were prepared and brought down to the night house. We also requested additional help from our Behavioral Observation Team, a group of dedicated volunteers who spent hours each week watching Ginger and observing her for any changes in her behavior. We also kept close tabs on Ginger’s weight and appetite at this time. The keepers had been training her to jump on a scale using positive reinforcement since she arrived, so they were able to monitor her weight several times each week and increase her food as necessary.
On February 15th, keepers arrived to find Ginger not only ravenous, but cranky as well! She wanted nothing to do with the two male otters with whom she shares her exhibit. A quick peek confirmed that she had given birth to TWO pups overnight (two to three is average for otters)! We quickly weighed them and put them back to cause as little disturbance as possible. The pups then had their first vet visit the following day where they were pronounced healthy!
The work doesn’t end there, however. Our otter observers now had to watch Ginger and the pups on a closed circuit monitor to ensure that Ginger was keeping them warm and that they were nursing. Otter pups are born blind and helpless, about the size of a stick of butter, so they depend on their mother for everything! Thankfully, Ginger is the best otter mom we could have hoped for and the pups quickly thrived under her care!

Twice each week, someone from the vet staff would come down to examine the pups. We monitored their temperatures, weight gain, hydration, respiration, and heart rates. Since Ginger had to be separated from the pups during the vet visits, we kept the checks down to no more than 10 minutes to minimize the stress on both the mother and the pups.
We are so happy to have healthy baby otter pups and we are so proud of Ginger. For more photos and video of our otter pups check out our otter webpage!