Results: The World's Largest Sample of Indoor Organisms

You make an excellent point highlighting a weakness of the project that I wouldn’t have thought of otherwise. Not everyone around the world lives in dwellings that separate the outside from the inside as assiduously as we tend to. When I lived in Sri Lanka I was in a house that had an open central courtyard. My kitchen, office, living room, and ‘inside garden’ were not separated from the open courtyard. Only bedrooms and bathrooms had walls that separated them from the open-air courtyard. Birds, geckoes, and lizards regularly traveled over the roof to get inside the courtyard. I was even surprised one morning to see a civet of some sort in the kitchen.


We aren’t actively seeking out observations on iNat that haven’t been added yet, and then adding them, so if you have any more indoor observations, please add the observations! I just checked and I don’t see an anole observation that you have submitted, and I don’t think any curators have removed such an observation, to my knowledge. Please share it with us! Lizards seem to be one of the few vertebrate taxa that “want” to be inside.

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Very interesting project, I just finished adding my indoor observations :-)

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I spend my days designing and detailing houses and trying to meet the strict regulations for air-tightness in this country. Softening the transition between indoor and outdoor space is an architectural ideal that is hard to achieve here. In my lovely air-tight house we generally leave the windows open all year round though because modern houses are too stuffy for our taste.
I have bats living in the roof but I don’t count them as being inside the house. I’m not even sure I count the garage as inside the house. It’s easier here because the air-tight zone provides a strict boundary between human space and everything else.


I just checked and it’s there. The observation is from 7 years ago, so it looks like it shows up that far back in the timeline.


Congratulations on analyzing all of this data and sharing it! You reminded me about your project, and I realized I’d only noted two indoor critters. Just added three more, and will keep an eye out for more.

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one of my favourites


This is such a fun project! I just joined and added everything I could quickly find. Many of the spiders and moths I added are photos from outside, since I took them outside to let them go. They were all found inside tho. I should upload the observations of the raccoons and skunks that come in my back kitchen door to eat cat food :joy:

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Thanks for adding! For photos that you took outside, but which are of organisms you found inside, could you please note in the comments of each observation that the organism was originally found inside? We’ll be doing some data cleaning to remove observations that don’t appear to be indoors and we wouldn’t want to accidentally remove your observations!


I LOVE the idea of this project. I also have a question of definition of ‘inside a structure’.

I have a lot of observations from inside garden sheds but also from inside public park outdoor washrooms. It’s a spectrum of construction standards in that list. Particularly in stuff like ventilation screens (or even lack thereof).

Here in Canada, for instance, I can pretty confidently say that some of the park outhouses+ units go for many months without any human visits.

Except maybe other bug hunters like myself, of course.

Would or should these be included in the study?

I wonder about that, too. I regularly photo insects in outhouses. The insects are inside something – but does that count like a house?

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Now I’m a little sad I never took a picture of the enormous treefrog that lived in the bathroom sink of one of the wilderness cabins we used when I worked in California. We would just scoop her up and set her beside the sink whenever we needed to use it.


Are American alligators a species which are regularly living and reproducing unaided in people’s garages and other indoor spaces all the time?

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Even with camping there are a lot of variations. RV tent trailers for example. Sometimes parked all summer. Or even full-blown motorized campers. Hmm.

My friend’s house on the island of Nevis has the top floor open to the sky. So in the kitchen and living room you can sometimes see all kinds of usually outdoor critters.


Obviously not, but that doesn’t in any way exclude them from the project.

But my impression of this project is that this is clearly an instance of a less desirable transient. If it is stated in that observation’s notes as to where that particular gator likely came from, and that it was also seen in multiple places outside, then it is not really a good candidate for this project.

I love the thoughtfulness of these comments, which are getting at the inevitable squishiness of this project-- a squishiness that any study trying to draw black and white boxes around the delightfully chaotic lives of animals will run into. To corral this squishiness into the best boxes we can, let’s zoom out to the overarching goals of this study and see if we can deduce some more specific guidelines about what “counts.” If there are things you think we should add/change regarding the specifications below, please let me know! I’ll add this to the project rules later.

The goal of this project is to identify the (non captive/cultivated) species that seem to be exploiting a newly formed ecosystem: the interior of human habitations. “Seem to be exploiting” and “human habitations” are doing a lot of work here. I think anyone would agree that a cellar spider in a kitchen cupboard with a web full of fruit flies is “exploiting” the “indoors.” On the other end of the spectrum, I bet we can all agree that a Wood Thrush that accidentally flew through an open window, frantically flying in circles, is not “exploiting” the indoors, and a deer eating leaves in an urban botanical garden, or a snake under a piece of tin, are not “inside” a human habitation in any meaningful sense of the term. So how should we parse the observations in the middle of this spectrum?

Let’s start by drawing a box around “inside,” which I think is the easier of our two terms to define. Let’s say that “the interior of human habitations” requires the following:

  1. A habitation is any structure built by people with walls and a roof that, say, a rat-sized animal would not be able to enter easily. This definition requires that the structure not be open-air (i.e., a patio, porch, etc.) And it also means that the habitation must be relatively impermeable (i.e., a shed with gaping holes in the wall wouldn’t count). Since it’s a “habitation,” people have to be in it, at least occasionally, so structures that have been abandoned for years shouldn’t count (e.g., places that look like The Last of Us). At the same time, portions of habitations rarely entered by people but closely associated with places we do enter (the attic or crawlspace of a home, the space beneath floorboards etc.) should count. This definition should be inclusive of most traditional habitations (mud brick, thatch-roof, etc.) as well, which, while more permeable to the outside than drywall and shingles, are still mostly self-contained.
  2. “the interior” means the organism can’t just be on the exterior walls, or in close proximity to the structure. It has to be inside the threshold.

Moving on to “exploiting.” This is, unfortunatley, almost impossible to discern from a photograph. Did the dead flies on the windowsill crawl in through a crack in the wall, trapping themselves and losing access to the resources they needed to survive? Or did they pupate from fruit in the cupboard, mate, lay eggs on the fruit, and then die, having passed on their genes? Unless you saw the fly enter the house, AND knew that it experienced no fitness gains (avoided predators, ate some crumbs) during its time in the house, you can’t really know. We suspect that more organisms than most people think are deriving some value from the indoors. So we’ve decided that, rather than trying to make rather arbitrary decisions about which organisms we think “want” to be inside, that we should just include all indoor observations in the dataset. From there, we can consider specific taxa more closely, especially taxa that are seen most often indoors, as these would be most likely to be evolving some benefit from being inside (unless they are extremely abundant outside too, in which case their indoor population is instead a reflection of outside conditions). This strategy will inevitably lead to our dataset including many observations of these “transients” that don’t “want” to be inside. But we’d rather include those observations as inherent error in the dataset than imposing our biases, borne of very limited natural history knowledge of many of these organisms, of which species we think belong where. Thus, just about any non captive/cultivated organism that was seen inside should be added to the project, unless it was deliberately brought inside by people.

All that to say, we’re definitely open to suggestions for other, better ways to think about this, if anyone has ideas. Now, on to specific thoughts/questions.

@broacher and @sedgequeen: If the garden shed is reasonably secure (i.e., it’s not open to the sky, or has gaping holes in the walls) then this counts. I’m not sure what you mean by an “outdoor washroom.” If you just mean a bathroom like you would find at many remote parks in the US/Canada (four walls, a roof, a door and a pit toilet like this) then it would count. If it’s truly outdoors (more like this) then it wouldn’t count. Basically, we would absolutely count any organisms seen in unfinished basements, attics or crawl spaces, which are pretty similar to sheds/outhouses, so most of these should count. RVs count too, even if they’re rarely used.

@ericroscoe the requirement for the project isn’t that it’s regularly living in/reproducing in the indoors. Only that it was found indoors and not deliberately brought in by people. I would agree with you that this alligator is most likely a “transient,” that got trapped in the garage somehow. But I don’t think that’s a given. For example, the gator in the photo is young; perhaps it is not old enough to hold territory against larger rivals and so is wandering long distances on land looking for a pond of its own. For such a gator, getting to shelter in an unoccupied garage for a day or two would be a benefit, and so would represent an example of an organism exploiting the indoors.

Good questions everyone.


I never even thought of that as an observation!

Damn! I wish I knew about this project earlier. It seems I have a lot of work to do!