Dragon Guts in the City

Image Credit: Aravindhanp, CC BY-SA 3.0, Image Cropped

City life alters the gut microbiome and stable isotope profiling of the eastern water dragon (Intellagama lesueuriii) (2019) Littleford-Colquhoun, Weyrich, Kent & Frere, Molecular Ecology, https://doi.org/10.1111/mec.15240

The Crux

It’s a pretty fair call to assume that if you build a city on a species’ habitat, it might be a little miffed. Yet as human settlements expand worldwide, many species are showing that they’re able to make rapid changes to their biology to adapt to living around humans.

This includes their diet, of course. As diets shift, many other aspects of a species’ biology follows, including the microbes that live in a species’ gut. And gut microbes influence a huge range of factors, including immunology, development, and general health. The response of a gut microbe community (the gut microbiome) to a new diet can in turn affect an animal’s ability to adapt to that environment.

This week’s authors wanted to take a break from saving koalas from bushfires and explore whether there was a difference between the gut microbiome in water dragons in their native range and those that were living in urban environments.

What They Did

The researchers compared the diet and gut microbiome of two types of eastern water dragon (Intellagama lesueurii); those living in in isolated native habitat (native dragons) and those living in city parks (city dragons). Dragons were collected and their blood and faeces were sampled. These samples were then sent to the Australian Genome Research Facility to have their gut bacteria analysed. Carbon and nitrogen isotopes, which can tell us a great deal about the consistency and make-up of an individuals diet, were also analysed. The results were then compared to establish any differences between the two types of dragon.

Did You Know: The Frere Lab

That reference to saving koalas earlier wasn’t a joke. This week’s authors are members of Celine Frere’s lab at the University of the Sunshine Coast, who played a major role in monitoring koala populations along Australia’s east coast. You might have their trainee Bear the koala detection dog in the news over the past few weeks, a product of their Detection Dogs for Conservation program. I was actually lucky enough to meet Bear and his friends last year during a short stay with the lab. More on the koala crisis tomorrow though.


Whilst Eastern Water Dragons do seem to have changed their gut microbiomes, it’s too early to tell whether the changes will bring negative effects to other aspects of their biology (Image Credit: Stu’s Images, CC BY-SA 4.0)

What They Found

City dragons showed more diversity in both their gut microbiomes and stable isotopes than their native counterparts, though they lack some forms of bacteria. They also showed more diversity between individuals, as opposed to the natives, whose diets and microbiomes were more homogenous. City dragons also appear to be consuming more plant material, and may now have a diet that is higher in protein and fat.


There is a big jump between a dragon living in a city park and one living in a “natural” habitat. It makes it hard to quantify to what degree exposure to human activity affects dragon diet. Whilst looking at different measures of such exposure would no doubt yield interesting results, time and resources often mean that such binary conditions are the only possible solution.

So What?

The higher diversity in diet and gut microbiome of city dragons suggest that they are capable of quickly adapting to urban environments, which is encouraging. However it’s not quite true, as we simply don’t know what losing those forms of bacteria could mean for the dragons in the long term. Could they be more prone to disease? Could their growth rate differ? Regardless, it at least shows that the species is capable of rapid evolution, which may be useful heading further into the Anthropocene.

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