Current Expedition: Gulf of Guinea Islands: São Tomé and Príncipe
African Frog Calls
Robert Drewes has an abiding fascination with the continent of Africa, having conducted field research in 30 different African countries since 1969. He is interested in the comparative physiology of frogs and serves on the board of the Kenya Wildlife Service.
Bob Drewes is living proof that you can turn your childhood passions into a lifelong career. Drewes was born and raised about a mile from Steinhart Aquarium in Golden Gate Park. Throughout his childhood, his home was filled with things he had found under rocks or picked up at the beach.
“I have always been deeply fascinated by weird stuff,” Drewes said.
He remembers one Academy exhibit that first fired his imagination as a child: “Strangely, it was the rotating tray of rocks that would appear normal under incandescent light and then glow brightly as they rotated under fluorescent light. As a toddler, I always gravitated to it.”
But upon reflection, what really changed his life was African Hall: “I fell in love with Africa in part because of the beauty of that hall and in part because of the influence of my great-uncle, Norman B. Livermore, under whose guidance it was built.” Livermore was the Academy's Chairman of the Board of Trustees during the Depression and war years.
“Like many of my schoolmates from my part of the city, I was raised to be either a doctor, lawyer, or businessman,” Drewes said.
It was a prospect that made him deeply unhappy. He did very poorly in his early undergraduate period, attempting to pursue a more traditional career path. Finally, he left school and served a tour of duty with the army Special Forces, an experience he found maturing.
When he finished his tour, Drewes married Gail, his childhood sweetheart, and returned to school.
“At this point, I was studying psychology, a field I found intuitive and really easy. At the same time, our little apartment on Potrero Hill was full of critters—some reptiles, two monkeys, and a coatimundi. One night as Gail fed our marmoset, she asked me, 'Bob, why on earth are you studying psychology?' From that moment on, I never looked back.”
Drewes completed his undergraduate degree at San Francisco State and his Ph.D. in Biology at UCLA, focusing on the evolutionary relationships of the dominant tree frog family of Africa, Madagascar, and the Seychelles Islands. His graduate career at UCLA also instilled in him an ongoing fascination with environmental physiology, the study of how individual organisms physically interact with the environment.
Bob's ongoing research on the systematics, natural history, and behavior of African reptiles and amphibians began with a year-long trip to East Africa in 1969, which he undertook with Gail and their then 9-month-old son, Bart.
“We got off the plane, and I was in Africa. Bob was home,” recalled Gail.
Drewes has returned to Africa every year since then. Drewes' long association with the Academy has created “a perfect base for someone like me,” he said. “I have the freedom to work in remote, poorly-known wild regions of Africa and at the same time to ask and answer fundamental scientific questions. And we have a collection of nearly 300,000 reptiles and amphibians from all over the world. If I'm doing an anatomical or morphological study, I can just grab specimens of related species off the shelf for comparison.”
“Imagine getting a job doing what you love more than anything else within the most venerable scientific institution in your own city," Drewes said. "How can I describe that? I've had 38 years of adventures in the African bush observing and catching weird critters. And I've also experienced the unbelievable thrill of academic discovery. It's been a hell of a ride.”
Frog populations are vanishing before our eyes. From South America to Egypt, from sites high in the Sierras to pristine rainforests in Eastern Australia, frog populations are in sudden, dramatic decline.
“That's a scary proposition,” Drewes said. “Frogs serve as a model for environmental health. They lay their eggs in water and their gilled larvae, which we call tadpoles, spend a considerable amount of time in the aquatic environment. If there's something wrong with the water, there's probably going to be an impact on the development of frogs. Later after metamorphosis, they become land-dwelling, air-breathing adults that have moist, permeable skins. Thus, if there is something wrong with the terrestrial environment, adult frogs will be among the first terrestrial vertebrates affected.”
Frogs are an indicator species: their presence or absence can tell us a lot about the health of an ecosystem. Many are also considered keystone species, whose roles are critical in defining ecosystem structure. The disappearance of a keystone species can profoundly affect the way an ecosystem operates. Systematists like Drewes are on the front lines of the research surrounding the worldwide population decline of frogs.
“We provide the data that are vital to all other fields of biological endeavor," he said. "Our job is to determine what's there, to whom it is related, and how it got there. Armed with these data, the world at large can make informed environmental decisions. The least we can do is let them know what they stand to lose.”
According to Drewes, there are many possible reasons for the decline in frog populations. They range from acid rain, increased ultraviolet B radiation because of a decreased ozone layer, pH shifts in water, heavy metals leaching into the water, and widespread habitat degradation. Then there is also chytridiomycosis, a fungal infection that has wiped out entire species in a single month. The fungus appears to be one of the dominant influences on the disappearance of frogs in Central America.
When the public asks about the causes behind the frogs' disappearance, Drewes has a ready answer: “Look in the mirror."
São Tomé and Príncipe, two islands forming a single nation off the western equatorial coast of Africa, may be the last undisturbed paradise on earth. More than 17 and 31 million years old respectively, the sparsely inhabited islands are home to hundreds of species of flora and fauna found nowhere else in the world.
That's exactly why Drewes, who is the curator of herpetology at the Academy, has led two multidisciplinary Academy expeditions there in past years. Island biogeography presents a unique opportunity to witness evolutionary processes in microcosm. São Tomé and Príncipe, small and isolated as they are, represent a relatively simple way to uncover evolutionary relationships at work.
The islands are noteworthy for their geological age, and more importantly, for the fact that they've never been attached to the African mainland. Anything that's arrived there—plants, insects, and animals—had to cross significant ocean barriers. Drewes and his team are trying to find out how these colonizations occurred.
“The islands are noteworthy for their high endemicity—that is, the number of species that exist on the islands and nowhere else in the world," Drewes said. "Half of all the birds on São Tomé and Príncipe are found nowhere else.”
There are some perplexing relationships on the island, as well: “The amphibian fauna we find here is more closely related to East African species on the other side of the continent than to species of the West African coast a few hundred kilometers away.”
This is a pattern that Drewes and his colleagues are exploring. To investigate further, Drewes and another Academy team will return for more expeditions. Drewes invites scientists and grad students who represent fields that are poorly represented or understood on these islands. He finds the multidisciplinary approach stimulating and productive, “similar to the way field work was accomplished in the old days—like the Galapagos Islands Expedition of 1905-1906. We are all looking at different organisms but asking the same evolutionary questions.”
But the undisturbed biodiversity on the islands will change—and change fast—thanks to the discovery of oil offshore. The huge influx of oil money, along with the infrastructure of oil exploration and drilling rigs, will change the islands forever.
“That's why it makes it all the more important to document, describe, and inform the people who live there as quickly as we can," Drewes said. "We have to tell them what they've got, and what's unique about their islands so they can make informed decisions.”
Current Expedition: Gulf of Guinea Islands: São Tomé and Príncipe
African Frog Calls
Learn more about Dr. Drewes' research, publications, and current projects by visiting the research side of our website, home to the Academy's Institute for Science and Sustainability.
The Academy's Herpetology collection of amphibians and reptiles is one of the ten largest in the world, containing more than 309,000 cataloged specimens from 175 countries. Learn more about the department's staff, research, and expeditions.