Have you ever been to a San Diego Zoo Safari Park and had the Africa Tram driver warn parents of little ones that it is that time of year when the animals are breeding and their kids might have some questions about what they saw after the ride? This usually gets adults chuckling, and maybe even leads to a few “birds-and-the-bees conversations.” Well, imagine your job is to help in the reproduction of endangered species and that every person you meet eventually asks, “So, what you do for a living?” As a laboratory researcher in the Reproductive Physiology Division of the San Diego Zoo Institute for Conservation Research, I’ve learned to say, “Think of us as a fertility clinic for animals.” Here are a few examples I use to explain this idea:
One of our lab’s greatest achievements was the birth of Hua Mei, the first panda cub to be born at the San Diego Zoo. While her birth was due to a large-scale collaboration of many people from all over the Zoo, including scientists, curators, veterinarians, and keepers, our greatest contribution was the insemination. It became clear that male panda Shi Shi was not going to naturally breed female Bai Yun and that human intervention would be necessary. Barbara Durrant, the director of our division, was able to collect semen from Shi Shi and use it to artificially inseminate Bai Yun, resulting in the birth of Hua Mei.
Estrous cycle monitoring
Often when women are trying to conceive, doctors monitor their cycle using techniques to predict when ovulation will occur. Many of these techniques are not feasible to apply to our collection animals because they would require sedation. Instead, in addition to urine and fecal hormone monitoring, we collect vaginal cells and monitor changes using a modified Papanicolau stain and some good, old-fashioned microscopy work. The cells in many mammalian species have been found to change in color and shape as estrus progresses. Unlike the Pap smear women are familiar with, which checks for cervical cancer, we monitor the changes in vaginal cells, which requires a far less invasive method of collection. These cells can be obtained with operant conditioning or positive reinforcement training of the animal. It’s amazing what a sun bear will do for some honey water!
An example of a success achieved using this method is the birth of our first Bornean sun bear cub: Danum. A shift in vaginal cells from one dominant color to another, combined with behavioral observations by keepers and scientists, allowed us to pinpoint the right time to introduce the normally solitary male and female to each other with a decreased risk of aggression and increased chance of breeding.
In-vitro maturation (IVM), in-vitro fertilization (IVF), embryo development (ED)
Many of us remember the term “test tube babies.” Today, IVM, IVF, and ED techniques are being employed all around the world, enabling couples to have children despite a variety of fertility issues. Often a human female is given hormones to produce many oocytes (eggs) that are retrieved from her ovaries using ultrasound-guided aspiration. These oocytes are put into a medium specifically designed to help the oocyte mature (IVM) in preparation for fertilization. Sperm is then introduced to the egg in a petri dish (IVF) or by a procedure called intra-cytoplasmic sperm injection (ICSI).
The oocyte is then put back into the medium designed to promote embryonic growth in an incubator. That embryo is then implanted inside the female or frozen for future use. In our lab we are using these same techniques to try to produce embryos from endangered species. Our challenge is that we work with a variety of different species, all with their own special needs, and many of the oocytes we work with are from ovaries of animals that have passed away, leaving us one step behind in the maturation process. We have used these procedures on animals as common as cats and rabbits to animals as endangered as rhinos and polar bears.
It is no secret that the best part of this job for me is getting to see the fruits of my labor. I may be taking a petri dish that once contained oocytes and sperm out of the incubator and seeing a growing embryo, or standing in front of an exhibit watching an adorable sun bear cub climb up a tree stump, but the feeling of helping to create life is indescribable. My friends like to tell people I make babies. Well, if by babies they mean cubs, kittens, and pups, then I am happy to agree. It may not be the easiest job to explain to people, but I almost always get a response like, “That is so cool.” It is, and I finally found a way to tell people just how cool it is.
Nicole Ravida is a research coordinator for the Reproductive Physiology Division of the San Diego Zoo Institute for Conservation Research. Read her previous post, Creating a Sperm Atlas.