By Dr. Becker
Komodo dragons have roamed Indonesian islands for millions of years. They remain largely unchanged from their ancient ancestors, perhaps because their two-pronged approach to catching prey has proved to be so efficient.
Despite their bulky and seemingly awkward body shape, Komodo dragons are able hunters, lying in wait — sometimes for hours — before attacking large animals like deer, boar and goats.
If the prey manages to escape, venom and bacteria (up to 50 different strains) in their saliva will complete the job, causing a combination of factors, including potential blood infection, that kill the animal in a matter of days. The dragons, with their keen sense of smell, follow the wounded animals, waiting patiently to feed.1
The microbial characteristics of Komodo dragons have also recently caught researchers’ attention, including those from the University of California San Diego, the University of Colorado-Boulder, the University of Chicago and the U.S. Department of Energy's (DOE's) Argonne National Laboratory, who are using them to understand health in captive animals.
Komodo Dragon Microbiome Studied to Explore Microbial Diversity in Captive Animals
Animals, including humans, have a complex relationship with the microbial organisms present in their environment.
The researchers were interested in determining what effect spending time in captivity — a relatively recent phenomenon — had on microbial life both residing on/in animals and in their environment. The researchers wrote in mSystems:2
“A full characterization of host-microbe sharing in both closed and open environments will provide crucial information that may enable the improvement of health in humans and in captive animals, both of which experience a greater incidence of disease (including chronic illness) than counterparts living under more ecologically natural conditions.”
They started by collecting samples of microbial communities from the saliva, skin and feces of 37 Komodo dragons living in 12 U.S. zoos.
They also sampled microbes from two of the dragons’ living spaces. Upon analysis, the researchers described the animals’ microbial exchange as “circular in nature” in that the dragons both contribute and reacquire microbes to and from their environment.3
Similar to the pets living in your home (another example of a relatively closed environment), Komodo dragons are a significant source of contribution to the microbes in their environment. This isn’t necessarily the case for animals living in the wild, however. According to the study:4
“We additionally compared host-environment microbiome sharing between captive Komodo dragons and their enclosures, humans and pets and their homes, and wild amphibians and their environments.
We observed similar host-environment microbiome sharing patterns among humans and their pets and Komodo dragons, with high levels of human/pet- and Komodo dragon-associated microbes on home and enclosure surfaces.
In contrast, only small amounts of amphibian-associated microbes were detected in the animals’ environments.”
Helping Explain Why Captive Animals Face Unique Disease Risks
Study author Jack Gilbert of the Argonne National Laboratory explained that the exchange of microbes between an animal and its environment can have significant health ramifications, including changing the host’s immune system for better or worse. He told Science Daily:5
"The problem is that the degree of exposure becomes limited when you put a host in captivity, and this change has unknown consequences on health, which is exactly why we're trying to learn more about it."
Animals (including humans) living in captivity have a greater incidence of chronic diseases than their wild counterparts.
Reduced exposure to a diverse variety of microbes may be one reason why, and the researchers hope that by studying microbiome interactions in captive animal models, it may yield clues about the microbial health of humans as well.
Komodo Dragons Kill Prey Using Venom, Too
While it’s long been said that bacteria were responsible for Komodo dragons’ deadly bites, newer research revealed the lizards also have venom glands that inject their victims with toxins that lower blood pressure and prevent blood clotting leading to massive bleeding and shock.6
Study author Bryan Fry, an associate professor of biology at the University of Queensland in Australia, told Live Science, "The role of the venom is to exaggerate the blood loss and shock-inducing mechanical damage caused by the bite.”7
When Fry compared the bacteria in Komodo dragons’ mouths with that of other animals, he didn’t find anything unusually deadly. He told National Geographic that Komodos are even “clean:”8
“The levels of bacteria in the mouth are lower than you’d get for a captive mammalian carnivore, such as a lion or Tasmanian devil … Komodos are actually remarkably clean animals. This is another nail in the coffin to the idea of them using bacteria as a weapon.”
The idea that Komodo dragons kill prey primarily via bacterial means is still widespread, but, as Fry’s research shows, there’s still a lot that remains to be discovered about these interesting lizards.
Whether or not we’re able to continue to learn from them depends on protecting these creatures in their natural environment. While there are about 3,000 to 5,000 Komodo dragons living on several Indonesian islands, due to poaching, loss of habitat and natural disasters, they are currently endangered.9