Which US state has the MOST ticks?

It is important to know where ticks are abundant before going out iNat-ing. They can spread serious diseases (and are totally gross :-p). There are many online lists of the worst places for ticks. But where do iNat-ers report the most ticks?

I used iNaturalist data to compare relative abundance of ticks (Ixodida) in several US states. iNaturalist observations can be easily summarized by state, county, or city in the Explore tab. However, some areas have many more people using iNaturalist, so it is important to standardize the data by dividing by the total number of observations in each area. This creates a metric of the relative abundance of tick observations compared to total observations.

Another potential confounder wound be if some people specifically tried to observe as many ticks as possible. This could skew the results if one state had someone obsessed with tick photography, and another state didn’t. I corrected for this by subtracting out the observations from the #1 tick observer in each state. Only one state (CA) had this problem. However, this correction did not substantially change the results in CA, or any state.

I didn’t look at every state or metro area, just the ones I’m likely to visit:

The state/area with the most reports of ticks was CA, but CA also had the greatest total number of observations of all life forms. When corrected for relative abundance, CA is near the middle of the distribution. Hartford, CT, famous for its tick abundance, topped the list. Arizona and Washington had the lowest relative abundance. Other top areas included MA, CT, ME, PA, and NY.

I hope this is helpful! Please let me know what you think of this approach to assess relative abundance?


This may be relevant to people who posted about ticks here before. What do you think? @sunguramy @mkkennedy @danaleeling


I think the approach in general is a reasonable one to using iNat data to estimate relative abundance (with all the usual caveats about using iNat data for this). The ratio column calculation looks a little off though unless I am missing something. Hartford should definitely be 0.1% I think.

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How are you deciding to list what species of ticks occur in which states?

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I was curious how my current location would compare: Austria: 730 Ixodida, 1,415,795 observations, so 0.05%. So about in the middle as well which sounds right!


I think it would make more sense to use some sort of grid (maybe the iNat auto obscure grid since it affects the data here) instead of state lines. My gut response was ‘Maine’ but i think it’s mostly southern Maine. I think the answer is coastal New England but since state lines don’t tend to follow ecoregions the question while interesting kind of obscures the real answer.


I think this method is good enough to determine the relative abundance of ticks per state. To refine the analysis, I would divide the dataset into groups: 1 for each species with at least 1 research grade observation in a given location + 1 for all genus-level or higher research grade observations in that same location. The main practical basis for that being that different species of ticks transmit different diseases (correct me if I’m wrong). Otherwise I would probably study the dataset by month, since ticks are less likely to be observed during winter in northern states.

Hartford is .08% because I subtracted the top Observer of Ixodida in each area. (To correct for the possibility of super-observers skewing the results.) So the relative ratio (abundance) is a bit lower.


@lothlin I just listed the most common species on the Species tab, based on totally subjective criteria. I was curious to subdivide the data but there aren’t enough observations to really do the analysis for each species….

I added the rest of the states in the high-tick area, and there’s a new winner! New Hampshire has the highest ratio of tick observations to total observations.

Interestingly, the other top states are now New Jersey, Oklahoma, and Missouri. These results are robust to include or exclude the top observer in each state. The Midwest states were a surprise to me, but a friend in Missouri confirms that she can’t go outside in the summer without getting ticks.

@charlie I did check just southern Maine, but its not much higher than the total for ME.



The Ozarks are infamous for our ticks. Nuttall even mentioned this in his naturalist journals investigating the Arkansas territory. This explains Missouri and Oklahoma, but Arkansas seems too low. Duct tape is necessary equipment for dealing with seed ticks when hiking here in the summer. I’m not sure I’m agreeing with this as a measure of abundance. Maybe we just find taking pictures of ticks a bit odd.


While I have visited Wisconsin which has ticks, I live on a tropical Pacific island where ticks are not an issue. :sweat_smile: Thanks for the tag!


for what’s it worth ticks were horrible down here last year in arkansas. And on the photo note with ticks it mostly get them off and throw them out the window if driving, or if at home and their dug in get them off and flushed so they won’t get on anyone else in the family.

I don’t post photos of ticks. Too busy trying to get them off. But I get into hundreds every year. So…Not sure using iNat is a great way to tell density…


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