The “all-purpose killing machine” that is the Komodo dragon has long fascinated puny humans. For herpetologists, much of that fascination lies in the lizard’s fearsome saliva, which enables a Komodo to take down a deer, water buffalo or human in one devastating strike. For decades, researchers argued that Komodo dragons used septic bacteria to poison their prey—but in recent years, more have come to believe that deadly venom is the key to their success.
Yet even if bacteria isn’t the secret to their spit, Komodo dragons still rely mightily on the bacterial partners they carry around with them. New research in the journal mSystems finds that captive Komodos share their skin and oral microbiomes with their built environment. The paper notes just how similar captive Komodos are to humans in this regard—a quality that could make them the perfect model organism for studying our own microbiome.
As we’ve learned in recent years, microbiome diversity is crucial to health and function. Antibiotics and sterile urban environments are believed to be linked to a rise in allergies and other health problems, because they reduce that crucial diversity. But organisms can also affect the bacterial health of their environments: The new paper notes that humans have a tendency to colonize their surroundings with their microbiome, citing a study that found that within 24 hours of moving into a hotel room, one family’s microbes “overtook” the room.
For the study, researchers swabbed the skin and saliva of 37 Komodo dragons in 12 zoos across the country, as well as the surfaces of some of their enclosures. They found that in captive environments, Komodo dragons significantly share bacteria with their environments. For researchers interested in understanding the impact of urban environments on animal microbiomes, that could make these dragons the ideal organism for future studies.
“This study reflects a growing trend of trying to connect the microbiomes on various plants and animals to the microbiomes of the human built environments in which these organisms reside,” says Jonathan Eisen, a biology professor at the University of California at Davis who was not involved in the new research. “We need to start to study this in more detail in order to better understand how to optimize the built environment to promote the health of residents—whether human, other animals, plant, or other.”
Another quality that makes the Komodo an attractive research animal is their formidable size. Komodo dragons are large-bodied animals, which made them a “clear choice in terms of being readily available to sample at the zoo [and] practically safer than some other choices like gorillas or tigers,” says co-author Valerie McKenzie, a professor in the department of ecology and evolutionary biology at the University of Colorado at Boulder. “You expect large-bodied animals to have more biomass sharing back and forth, so you can detect stronger signals.”
Moreover, they’re conveniently solitary. In zoos, the animals are typically housed alone and are rarely transported to new environments; they may occasionally be brought together to mate, but adult animals don’t live well together. For researchers, that means fewer variables to parse through when studying the interactions between an animal and its environment. “In the wild, they may feed in groups, but they each have their dens where they go and sleep,” says Embriette Hyde, lead author on the study and a microbiome researcher at the University of California San Diego School of Medicine. “The level of isolation with Komodos is extreme.”
As Joe Mendelson, director of research at Zoo Atlanta and another author on the paper, puts it: “These conditions are not common across most other species in zoos, so it seemed a perfect study-system for Dr. Hyde’s angle of host-environment sharing of microbiomes.”
Our growing understanding of Komodo microbiomes also suggests that isolation could have unforeseen consequences for Komodo dragons—revealing how much we have yet to learn about keeping these animals in built environments. "On the scale of evolutionary time, vertebrates have only relatively recently begun to regularly interact with artificially built environments," the study authors note. Wild Komodos appear to have far greater bacterial diversity than captive dragons, a factor that could be key in maintaining health. A previous study found that wild Komodos had 46 percent more unique bacterial species in their mouths than their captive counterparts.
Already, Komodo dragon keepers consider a number of key variables to maintain the health of these animals in captivity. “Some of the priorities when building a Komodo dragon exhibit include space, temperature, humidity, deep substrate for nesting and a water feature,” says Lauren Augustine, a reptile keeper at the National Zoo. “It’s vital for an animal’s enclosure to offer choices, particularly when it comes to temperature for reptiles.” Yet as the new study shows, zookeepers may also need to take into account previously unforeseen variables, such as bacterial conditions.
In the meantime, Mendelson of Zoo Atlanta views their research as a step in the right direction toward better health for Komodo dragons in zoos and other captive animals. “I saw this as a great opportunity to collect baseline data to inform the best-possible care for our Komodo dragon at Zoo Atlanta,” he says.
Editor's Note, September 7, 2016: A previous version of this article misstated one of the study’s findings. Captive Komodo dragons were not found to colonize their built environments. They were found to share bacteria with their built environments.