Essential Science Indicators from
Reuters recently named the Zoological Society of
San Diego a
Rising Star in the field of Plant & Animal
Science, meaning that the Zoo had the highest percent
increase in total citations in this field from August
to October 2008. The Zoo's current record in this field
includes 228 papers cited a total of 1,545 times
between January 1, 1999 and February 28, 2009.
In this first of a two-part series,
ScienceWatch.com's Jennifer Minnick takes a
virtual tour of the Zoo and its various research projects
and conservation efforts.
The Zoo was founded in 1916, and today consists of three main branches: the
San Diego Zoo itself, the San Diego Wild Animal Park, and the Institute for
Conservation Research. The Zoo proper sits on 100 acres of land, and houses
more than 4,000 animals from more than 800 species and subspecies, many of
which are rare or endangered. The Wild Animal Park houses over 3,500
animals from over 400 species and subspecies on 1,800 acres of land. The
Institute for Conservation Research employs over 150 scientists, who
participate in studies and projects related to the conservation of animals,
plants, and their habitats in 35 countries worldwide.
San Diego Zoo
San Diego Wild Animal Park
Institute for Conservation
Conservation Research at the San Diego Zoo is composed of eight research-
and education-centered divisions: Field Programs, Applied Animal Ecology,
Applied Plant Ecology, Behavioral Biology, Genetics, Reproductive
Physiology, Wildlife Disease Laboratories, and Conservation Education.
Heading up the whole shebang is Dr. Allison Alberts. Dr. Alberts came to
the Zoo in 1991 and has never left, working her way up the ranks from
postdoctoral research fellow to associate scientist, to division head, to
her current title as the Zoological Society's Chief Conservation Officer
and Benirschke Chair of Research.
Conservation Research has an extensive reach, far beyond the boundaries of
the Zoo and Wildlife Park. Internally, there are currently over 100
research projects going on, either in the collection or out in the wild. In
terms of external partnerships, the various divisions are involved in over
These projects range in size from small-scale, in which the Zoo's role is
only one aspect of a bigger plan, to larger, strategic, long-term projects,
such as their many partnerships with the US Fish and Wildlife Service
(FWS). The Zoo's relationship with FWS has its origins in the very
successful project of recovering the California condor population, which
started in the 1980s. More recently, the Zoo partnered with FWS to work on
the long-term preservation of the desert tortoise.
Internal cooperation is a hallmark of the Zoo's work. "We've had a big push
in recent years to work more collaboratively across divisions, and I can't
think of any project that doesn't touch on at least more than one
scientific discipline," Alberts explains. "We've found that working
together is how we get our scientific innovations and our big
breakthroughs. Everything's multifaceted and seems to involve almost
everyone. When you talk about these large-scale recovery projects, like
that for the California condor, we have every division contributing their
piece of the puzzle to the whole, and I think that's why we've been as
successful as we have."
When asked about a typical day in the life of an administrator, Alberts
replied that there really isn't such a thing as a typical day, that each
day is different, whether dealing with meetings on the various projects,
raising awareness in the public, visiting in the field, etc.—her job
is large of scope and high on variety.
The Difference between Survival and
Even with administrative duties taking up much of her days, Alberts still
makes time for her own research interests, which concern endangered
reptiles ranging from the Caribbean and South Pacific to native California
species. She finds reptiles fascinating. "They have a reputation for being
ugly and not so intelligent," she says, "but when you begin to research
them, you'll find that have amazing memories, terrific longevity, complex
social structures, and are incredibly well adapted to their environments."
One of Alberts's projects involves a "headstarting" program for Caribbean
rock iguanas, laid out in the paper "Behavioral considerations of
headstarting as a conservation strategy for endangered Caribbean rock
iguanas" (Applied Animal Behaviour Science 102[3-4]: 380-91,
February 2007). These iguanas are highly endangered. On island ecologies,
introduced species can spell disaster for native species, which have no
natural defenses against these new predators.
Although the iguanas are the largest native vertebrate still alive today on
the islands, when they're babies, their small size—maybe six to eight
inches long—makes them vulnerable to introduced predators on the
islands like cats, dogs, and mongooses. "You can go to certain islands in
the Caribbean a month after the breeding season takes place, and you
won’t be able to find a baby iguana; they're just all gone," Alberts
Caribbean Rock Iguana
The solution? The "headstarting" program. Under this program, the babies
born on the islands are brought into captivity and reared there until they
are three to four years of age, when they're large enough that they're no
longer vulnerable to the introduced species. Then they are released back
into the wild to give the population a boost.
This project is conducted in-country with the full and enthusiastic
cooperation of the island people and local governments and conservation
groups. The baby iguanas are raised at centers on the islands, rather than
being brought to California. Keeping them on the island just makes sense,
because moving them to the Zoo would bring unnecessary stress and increase
the potential for introducing exotic diseases.
For four out of the nine species of Caribbean iguanas, the headstarting
programs have meant the difference between survival and extinction. "It's
really kind of a Band-Aid approach, though," Alberts stresses. "It's not
going to solve the problem forever and you can't headstart animals forever,
but it buys you time to be able to deal with the introduced-species problem
in the wild."
The fact is, such Band-Aid approaches are completely necessary, and not
just with Caribbean rock iguanas. As Alberts says, "Some species do already
live only in captivity, and if you look at what's happening globally,
unfortunately, at least in the near term, that number's only going to
increase, but hopefully in the long term, we can change that by taking
captive-bred animals and reintroducing them to the wild once we get a
handle on the environmental problems there." The captive breeding and
reintroduction of the California condor over the '80s and '90s is one of
the Zoo's better-known success stories, but there are many other such
projects on the Zoo's roster.
The Case of the Disappearing Frogs
Captive breeding programs are now being considered for the frogs of the
world. All over the world, many species of frogs and salamanders have been
falling prey to a fungal skin infection, chytridiomycosis, or chytrid for
short, caused by the fungus Batrachochytrium dendrobatidis. Dr.
Rebecca Papendick, Senior Scientist in the Wildlife Disease Laboratories
division, has been involved with the global frog crisis from almost the
African bullfrog being tested by scientists for
chytrid fungus (this is part of a new procedure
that San Diego Zoo scientists have developed to
screen for the disease).
"It's one of those serendipitous stories," she relates. "I was doing my
residency in pathology at the University of Florida at the time. My husband
is a herpetologist, and one of his grad students, Dr. Karen Lips, was doing
her dissertation research in Costa Rica. She encountered mass die-offs of
frogs. It was known that frog populations were on the decline, but I think
Karen was one of the first to get her hands on some fairly freshly dead
frogs. My husband called me up and asked me to take a look at the specimens
and see if I could figure out what was killing them. I found the organism
that is now known as the chytrid, but I had no idea what it was and didn't
realize the significance of it—and neither did other people at the
But discovering the cause of the disease is only a small part of the
battle. Today, chytrid is still a serious cause of population decline and
species extinction worldwide. The Wildlife Disease Laboratories and other
people within the Zoo are currently very involved in trying to develop
protocols and standards for creating survival assurance colonies.
"This is a last-ditch effort to bring some of these animals that are on the
verge of extinction into captivity, raise them in a chytrid-free
environment, and keep the species going while we try to figure out what
else can be done, how to help in the wild," Papendick explains. "Is there
something we can do to help the frogs fight it off; can we find species
that are immune? But we need to do what we can to preserve the species that
we have right now. So that's a big push of our division at this point. It's
a two-pronged approach, to save the species in captivity while trying to
figure out what's going on with them in the wild. We can't wait until we
know more because they're disappearing now."
Frogs aren't Papendick's only focus. As a board-certified veterinary
diagnostic pathologist, she works on animal diseases throughout the Zoo and
Wildlife Park, as well as in the Conservation Research programs around the
world, and for various external partners.
Looking After Our Feathered Friends
Papendick and Dr. Bruce Rideout, the Associate Director of Conservation
Research and head of the Wildlife Disease Laboratories, are also very
involved in research dealing with avian mycobacteriosis (more commonly but
less accurately known as avian tuberculosis). This project, though still in
progress, has been groundbreaking in its discoveries so far.
California condor flying free in Northern
"When you talk about these
large-scale recovery projects, like that for
the California condor, we have every division
contributing their piece of the puzzle to the
whole, and I think that's why we've been as
successful as we have." ~Allison
Avian mycobacteriosis has been a huge management problem in captive
situations for decades. To begin with, diagnosis in a living bird is almost
impossible to obtain, because as a whole animals tend to hide problems.
It's a survival instinct: sickly animals can be kicked out of their social
groups or picked off by predators. Because of what is known about human
tuberculosis, which is highly contagious, when a bird in an enclosure was
diagnosed (usually post-mortem) with mycobacteriosis, it would set off a
panic—a rush to quarantine and test other birds that had been housed
with the infected bird. Elaborate clinical workups of living
birds—involving blood chemistry panels, fecal analyses, and sometimes
liver biopsies—were not only expensive but also extremely stressful
to the bird, especially since Zoo birds aren't trained to be handled by
The Wildlife Disease Laboratories groups, including Rideout, Papendick,
epidemiologist Carmel Witte, and others, decided to explore the
transmission of the disease. "As it turned out, all of the dogma about
avian mycobacteriosis being contagious was just that—dogma. We were
able to show that in the vast majority of cases studied, the birds acquired
the disease from the environment, not from other birds," Rideout states.
Although the team is still looking into what environmental factors cause
avian mycobacteriosis—whether water, soil, or food—and is also
exploring better ante-mortem diagnostic techniques, just the discovery that
avian mycobacteriosis isn't contagious has been an enormous step in the
right direction, and it has great practical significance.
First of all, infected birds don't need to be quarantined, but are instead
carefully monitored in their regular enclosure, causing less stress. "Now
when we diagnose a bird with the disease, people don't go into a panic,"
Papendick says. Even more valuable, Rideout points out, if a particularly
endangered bird gets infected, it can still be a part of a breeding program
without worrying about infecting its mate.
The Wildlife Disease Laboratories are also investigating Johne's disease in
exotic hoofed animals, as well as West Nile virus in California condors.
Because of the long-term commitment to the reintroduction of condors into
the wild, the populations are carefully monitored and managed. When they
are tested for lead poisoning (a well-known problem, stemming from
ingesting lead-shot carcasses), they also get tested and vaccinated against
Rideout is also involved in other key projects with birds, both in
captivity and in the wild. In captivity, he and his team helped to show
that the antiparasitic drugs fenbendazole and albendazole, which are widely
used in veterinary medicine, have a much narrower margin of safety than
previously imagined. "What happened," Rideout relates, "is that I noticed a
cluster of a few cases of cormorants that looked like they had viral
enteritis, but when I investigated them I couldn't find any viruses. Then
we had to backtrack and think of what other things cause intestinal lesions
that might look like a virus but are actually something else. One of the
things that can do that is drugs and toxins. So then we started looking
back in the history of the birds, and found that in all the cases, they had
been treated in previous weeks with these drugs."
"What made it difficult for people to realize this connection earlier,"
Rideout continues, "is that it takes weeks for this effect to happen. You
treat the birds for the parasites, which clear, and things seem to be going
great, then two to four weeks later, the bird dies. And nobody made the
connection that the birds are dying two to four weeks after this drug
treatment. So we did the work to show there actually was a connection and
to try to alert vets all over the world. The drugs can still be used, but
because of the much narrower margin of safety, we recommend that much lower
doses of the drugs be employed."
Sign at the entrance of the San Diego
"Interestingly," he adds, "after we published on this, other people started
looking at similar effects in other species, and found that these drugs
also have a much narrower margin of safety in other species—they
caused toxicity problems in dogs and cats and other exotic animals."
In the wild, Rideout has worked on projects investigating veterinary-drug
poisoning in vultures in Asia and toxoplasmosis in the Hawaiian crow, the
'Alala. In both cases, the bird populations were in severe decline, but the
underlying problems as well as the solutions in these cases were vastly
In the past decade, the vulture populations in Asia have declined by
upwards of 98%, with some species on the verge of extinction. This decline
was a dramatic change for birds that were once abundant across Asia.
Rideout was invited to be part of a team put together by The Peregrine
Fund, led by a colleague at Washington State University, to discover why
the vultures were dying out.
"We took a very systematic approach to our investigation and kept a much
more open mind than a lot of other groups, and the end result was that we
were able to show that the cause of the decline was the overuse of this
veterinary drug, diclofenac," Rideout explains. "It's sold over the counter
all across Asia and it has this amazing ability to take cattle that are
sick for whatever cause and make them feel really good, so they'll stand up
and appear to be better. It seems like a miracle drug, whereas it doesn't
cure anything. Ultimately, these cattle will die and they'll have high
levels of this drug in their bodies. Across most of Asia, when cattle die,
they're just left out for the vultures. So then the vultures eat the
carcasses and get a toxic dose of the drug themselves."
What was so significant about this study is that no one had ever shown that
a veterinary drug could cause such a widespread decline in a free-ranging
species. Rideout emphasizes that what the study really revealed is the
close connection between human activities and wildlife, analogous to the
DDT work done in the '60s.
As for what's being done about the problem, policymakers are working with
the governments to have diclofenac removed from the market. Other teams are
also researching new drugs that might be safer. "It's always best that
instead of just taking something away from people you give them something
to replace it with," Rideout remarks.
In the case of the 'Alala of Hawaii, the solution was more immediate and
more drastic. These birds were part of a reintroduction program on the
islands. A big problem for Hawaiian forest birds is becoming infected with
malaria or pox viruses, thanks to mosquitos, which had been introduced to
the islands in the 1880s. Many of the forest birds live at higher
elevations, above the mosquito line, but not the crows. They were found to
be able to survive pox and malaria infections, but the populations were
"It's a two-pronged approach, to
save the species in captivity while trying to
figure out what's going on with them in the
wild. We can't wait until we know more
because they're disappearing
The team outfitted the birds with radio transmitters that came equipped
with a mortality signal so that they could do post-mortem exams, which
revealed that the birds had toxoplasmosis from Toxoplasma gondii.
The disease vector was found to be feral cats—the crows would forage
in the cats' feces, even treating the feces as a food item.
The solution here was to bring all the birds back into the captive breeding
centers in order to beef up their numbers, and the plan is to reintroduce
them to the wild once scientists can figure out a way to do so safely,
without the birds being exposed to toxoplasmosis.
Tending to the Big Cats
Rideout doesn't just deal with birds. In a June 2007 paper, he and his
coauthors discuss a health problem in tigers that, through their case
studies, they discovered is more common than originally thought (Sykes JM,
et al., "Oral eosinophilic granulomas in tigers [Panthera
tigris]—a collection of 16 cases," Journal of Zoo and
Wildlife Medicine 38: 300-8, June 2007). "No one really knows what
the cause is. Tigers develop these raised lesions in their mouths, and
sometimes they can ulcerate. The animals won't want to eat because their
mouths are sore. They can get secondary infections. It's not usually a
life-threatening disease in itself, but it can really cause a lot of impact
on the animals. It's a very frustrating disease to treat," Rideout relates.
Though no closer to finding the cause, the paper explored potential
treatments, the most promising of which is corticosteroids. The fact that
steroids work may indicate an immunologic root of the problem. However,
steroid treatment is not without risks, particularly in terms of secondary
Next Month: Behavior, Reproduction, and Education
The health of the collections at the Zoo and Wild Animal Park, as well as
in the wild, is paramount to the scientists at the Institute for
Conservation Research. But the mental well-being and health of the animals
are also important for both keeping them engaged and stimulated and for
aiding in captive breeding programs. Next month, we'll talk with the teams
who are focused on animal behavior and reproduction, as well as the
education efforts of all the teams.