Journal archives for October 2019

October 01, 2019

Large Moth Bias

iNaturalist is a wonderful platform and I use it on a daily basis. I'm honestly driven by my own enjoyment, but I also take pride in knowing I am conducting Citizen Science - the idea that the observations I post can be a valuable tool for biologists. As with any data set, iNaturalist observations must be used with care, and my own choices impact the data set. Biases exist and scientists must take care to identify the biases so that they can minimize their impact.

One of these biases I would like to highlight in this post is what I'll call the "Large Moth Bias." On a daily basis the average adult living in Oklahoma probably passes in close proximity to at least a few moths. How many of those moths do you think the average Oklahoman is going to stop, photograph, and upload to iNaturalist? That's right, the number is so low it might as well be 0%. On the other hand, if the average Oklahoman walks by a large moth, say a Luna or a Polyphemus, how many of those people are going to stop and take notice? Yep, definitely more than 0. This isn't just true of moths, of course. Most anything unusual or more conspicuous is likely to be noticed more than the small, common, or inconspicuous.

Why does this matter with iNaturalist observations, you ask? Well, if you look at the Moths of Oklahoma project landing page you'll see that the most observed species in the state is the Luna Moth (153 observations). Three other moths in the top observed list are also moths that I would put in the "large and conspicuous" category - White-lined Sphinx (115 observations), Polyphemus Moth (98 observations), and Io Moth (94 observations).

If you were to have an accurate count of every single moth in the state of Oklahoma over the course of a year I don't think any of these three species would be in the top 10. I believe the Luna, Polyphemus, and Io have so many iNat observations because when people see them they take notice and feel compelled to share the photo and find out what it is. In general, people are less likely to care what species a moth is when it's small and brown and fits their informal definition of what a moth should look like. While looking at observation numbers I was struck by the low count for Oklahoma's other large moth, the Cecropia. There are only 33 observations of this species in the state. I think that tells us that the Cecropia is quite rare, given that it is actually the largest moth and very showy and has so few observations. That seems significant to me. Another explanation is that the Cecropia only has one brood per year so the amount of time that Cecropias are out flying around is much less than the 2-3 broods of the other large silk moths (Io, Polyphemus, and Luna).

In my opinion, the White-lined Sphinx is more common than the species listed above, but I think it too has been elevated by observation bias because it is often seen during daylight (or dusk) hours and is sort of large.

Another impact on these counts is that iNaturalist is configured to log individual observations of a single organism, whereas some other platforms (like eBird) are built around the idea of logging multiple individuals of the same species, and there are ways to see the quantity and frequency of different species. On eBird you can enter a checklist with each species of bird you saw and how many you saw of each species. For instance, 2 Northern Cardinals, 5 Blue Jays, 100 European Starlings, and 1 Bald Eagle. With iNaturalist you are unlikely to log 100 individual Bluegrass Webworm moths when you see them. In fact, you might not log any of them because you see them so often and have already logged one this week. In that way, even those of us who contribute many observations to iNaturalist are contributing to this bias.

In a future blog post I will highlight how population biases the geographic distribution of species so stay tuned. In the meantime, what are some biases you can think might impact observations in iNaturalist?

Posted on October 01, 2019 13:48 by zdufran zdufran | 0 comments | Leave a comment

October 17, 2019

New banner image!

Our new banner image is a Pandorus Sphinx (Eumorpha pandorus) caterpillar observed by @lmm3629 in Jenks! It is a beautiful caterpillar that is not often seen in Oklahoma. Click the image to see the observation.

Congrats @lmm3629 and keep up those observations!

We'll select a new banner image in mid-November.

Posted on October 17, 2019 19:48 by zdufran zdufran | 0 comments | Leave a comment

Population Bias (aka "The Tulsa Phenomenon")

Earlier this summer I wrote a blog post about the ranges of moths in Oklahoma. I finished that post by mentioning the "Tulsa range phenomenon." This relates to my recent post on observation biases.

When I was flipping through my field guide looking specifically at the range maps I noticed a trend - there were a lot of maps that showed the species occurring in the Tulsa area, but not in the rest of the state. Is there something special about Tulsa that results in a huge biodiversity that is not seen elsewhere in the state? I don't think so. True, Tulsa is in the wetter eastern part of the state where there is a higher species diversity among plants and that results in more species of insects, but the number of species in other eastern parts of Oklahoma should be comparable to Tulsa.

Here is a single example of a range map that displays the "Tulsa phenomenon." This is Lespedeza Webworm (Pococera scortealis), which is shown as only occurring in the northeast part of Oklahoma (Tulsa). However, we have spotted this species at two of our moth nights in Norman.

I believe what we're seeing with this range maps is simply a bias of where observations are being made. Not only is Tulsa the second most populous city in the state, but there have also been a few dedicated individuals making regular observations of Lepidoptera in the Tulsa metro area. In fact, the state keeper of Lepidoptera records lives in the Tulsa area and has been making observations there for many years. So when we see a bulls-eye of species biodiversity in the Tulsa area I think what we're seeing is a reflection of the number of days spent observing.

I was first exposed to this concept of observation bias when I was studying meteorology at the University of Oklahoma. We were looking at a United States map that showed the track of every known tornado observation and you could see there were more observations near populated areas. Why? Historically the reason is because there were people there to see them. Nowadays it is rare for a single tornado to go unnoticed in the United States because of the storm chaser/spotter community and the lead time provided for severe weather by weather models and forecasters. Tornado vortex signatures are detected by radar and there are hundreds of storm chasers roaming the country, scouting out every storm with the potential to rotate. Therefore, the data set is becoming much less biased towards population centers.

Do you think we could ever come to a day when moths, or at least certain moths, could be so well observed? Probably not, but one can dream...

Posted on October 17, 2019 21:08 by zdufran zdufran | 0 comments | Leave a comment

October 08, 2019

Oklahoma BioBlitz Moth Results

This year the Oklahoma BioBlitz was held at Sequoyah State Park on October 4-6. We had record attendance of 458 people, so the activities were packed with participants. It is a lot of fun to be surrounded by so many nature enthusiasts. Activities include bird, herp, plant, fossil, or general discovery walks, nature crafts, setting and checking mammal traps, mist netting and banding of birds and bats, and others. A lot of the activities are kid friendly, but there is something for everyone.

There are "taxa leaders" and "taxa experts" that help identify different living things that have been photographed or collected. This year I helped collect the Lepidoptera species list and turned that over to the terrestrial invertebrates leader to compile.

I set up lights on the night of Friday, October 4 to attract moths and other nocturnal insects. In addition to my two light setups, Ken Hobson, Associate Professor of Biology at the University of Oklahoma, also had a sheet setup with florescent blacklight bulbs.

I monitored the lights until about midnight, which is my usual schedule, and then went to bed. I got up around 3:45 and checked the lights again and found a few additional species. In all, it was kind of slow for moths and other insects, but during the 24 hour inventory period for the BioBlitz we did turn up more than 50 species of moths and 15-20 species of butterflies. Since then I've seen some additional species reported through iNaturalist that I wasn't aware of at the time we collected the species tally.

At the conclusion of the species tally there were 879 species of life observed in Sequoyah State Park, which is pretty good. According to coordinator Priscilla Crawford, when BioBlitz was scheduled during the month of September they would regularly eclipse 1000 species, but this was a pretty good tally.

Next year's BioBlitz will be held on October 2-4, 2020 at Roman Nose State Park. See you there!
Details should be added here as we get closer to the date.

Posted on October 08, 2019 17:08 by zdufran zdufran | 0 comments | Leave a comment

October 29, 2019

Annual Report

This project has been blossoming, so I thought it would be fun to do a little observation data filtering to see how the project has grown. It is great that iNaturalist makes this so easy. It probably took me 5-10 minutes to gather this information. The calendar year is not complete yet and there will be some more additions, but I don't expect the species number to change much between now and December 31. Without further ado, here are the numbers:

year observations observers species running species count new species for the year
pre-2017 1,222 141 357 357 -
2017 1,606 141 456 585 228
2018 3,875 357 629 816 231
2019 10,194 561 949 1149 333

Clearly we had a big swell in observations this year! It paid off with more new species added to the project this year than any past year. I suspect that even if we have more observers and more observations next year, we'll start to slow down on the species added as we asymptotically approach the true species count for the state. We honestly don't know what the number is, but I would venture to guess that we're around 3/4 of the way there.

Another contributor to our large number of observations this year is that we had TWELVE moth nights scheduled this year, ranging from early April through mid October. Most of these were at the same location in east Norman, but we also had the National Moth Week events in southwest and northeast Oklahoma and a moth night at the Oklahoma BioBlitz in eastern Oklahoma.

Some things I am excited about in the years to come are getting more people involved in the project and filling in the gaps around our state. There are certainly moths in every county, and yet the records in many counties are pretty sparse, both on iNaturalist and in the official state records. Let's fill 'em in!

Posted on October 29, 2019 13:10 by zdufran zdufran | 0 comments | Leave a comment