California Condors: Little Things, Big Effects

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Condors have excellent vision, but some threats are too small for even these birds to see.

Condors have excellent vision, but some threats are too small for even these birds to see.

In spring of 2011, I served as a summer research fellow at the San Diego Zoo Institute for Conservation Research. Here I learned that I could contribute to the conservation of endangered species in a way I never dreamed possible: on a molecular level! To say this was a stretch for me is an understatement. Freshman year of undergrad I distinctly remember the shock when I was handed back my first BIO 101 exam: it was the first “D” I ever received at any time as a student. I turned to my friend and proclaimed, “I will NEVER work with something I cannot see,” (referencing biological materials such as DNA, RNA, and proteins), conclusively announcing “All I want to do is work with animals.”

Despite my initial frustration, I stuck with the biology major, tagged on an animal science minor, and got a keeper internship at my local zoo. The internship turned into a part-time job working hands-on with exotic animals, a dream come true! While zookeeping was a very gratifying job, reproductive physiology had caught my attention not only in the classroom but through my experience at the zoo. I was amazed at how reproductive techniques such as semen collection, artificial insemination, and hormone monitoring could inform animal managers and scientists of a broader picture not always seen by the naked eye. My interest and enthusiasm landed me an internship in the Reproductive Physiology Division at the Institute and, eventually, a permanent position as a research technician. We work on traditional gamete preservation, hormone monitoring, and the exciting new field in the zoo world: environmental toxicology. This research combines molecular techniques and endocrinology to explore the effects of chemicals found in the environment on the development and reproduction of captive and wild animals.

I am now a graduate from the University of Missouri’s animal science master’s program with a thesis describing the molecular interactions of environmental chemicals and hormone receptors of a critically endangered species, the California condor. Needless to say, I have changed my stance on working with biological materials that are not visible to the naked eye!

HEK cells (seen here at 100 times their actual size) are used as concor receptor factories to study the effects of environmental contaminants on reproduction. Photo by Rachel Felton

HEK cells (seen here at 100 times their actual size) are used as condor receptor factories to study the effects of environmental contaminants on reproduction.

In the Lab
In my previous post DDT: Another Challenge for California Condor, I explained our first investigations of the effects of environmental chemicals on California condor reproduction. In the lab, we were able to develop an assay to screen condor estrogen receptors (ERs) with chemicals found circulating in the blood of condors living along California’s coast to detect activation of these hormone receptors. Determining which chemicals mimic (activate ERs) or block (deactivate ERs) signaling of the endogenous hormone estrogen will be an important step in better understanding the endocrine-disrupting potential of chemicals found in the condor’s coastal environment.

Chemical concentrations circulating in condor blood activated condor estrogen receptors in the lab. This discovery lead us to speculate that in the wild, coastal condors are being exposed to levels of chemicals that may cause developmental and/or reproductive harm. The chemical load in condors today is similar to that found in other birds of prey along the California coast such as the bald eagle and peregrine falcon. These species have experienced eggshell thinning in the past. Unfortunately, eggshell thinning is already compromising the coastal condor population.

Relocating California condors to coastline habitats reduces chances of lead poisoning but may pose other risks.

Relocating California condors to coastline habitats reduces chances of lead poisoning but may contain other, unseen threats.

In the Field
What does this mean for free-flying condors? The cliffs along the Southern California coast may not be the ideal escape from the threats of lead poisoning. If chronic exposure and the production of thin eggshells continue in the population, there is the potential for long-term effects since coastal condors are sensitive at the molecular level to contaminants found in their diets. In Oregon and Washington, condor reintroduction was put on hold due to elevated levels of chemicals in the blubber of marine mammals.

In Baja California, Mexico, the wild condor population may have to be moved to the coast of Mexico. Conservation managers are hoping to wean condors off expensive supplemental feedings and toward a diet composed of beached marine mammals. But before relocation of this population occurs, chemical compositions of beached marine mammals at the potential release sites will be evaluated in the lab for endocrine-disrupting capabilities. Our goal is to move condors away from lead and intensive management practices, but not into another health-compromising situation.

Rachel Felton is a senior research technician at the San Diego Zoo Institute for Conservation Research.

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