• Andy Davis

How to increase the scientific value of your tagging data


It's early October already, and the monarch fall migration is midway-finished by now - maybe even winding down in some places. So this would actually be a good time to talk about monarch tagging data - that is, what to do with it, after you've finished for the season. By now, a lot of folks out there may be getting ready to send in their data to Monarch Watch, the organization that supplies the tags. As a scientist who routinely works with folks who have monarch tagging data, I can offer some advice for how to make that data more valuable to science. So before you send those data sheets, have a read...

First and foremost - you should MAKE A COPY of the data sheets before you send them - and do this every year. Either photocopy the finished sheets, take an Iphone image of them, or even better - enter the data onto your own computer. Don't just send the finished sheets in! I can tell you that all of all the taggers I've worked with to get their data published (there have been many), they all have been self-archiving their tagging data over many years, which increases their value tremendously. As a tagger, you need to remember, it's your data - you captured the monarchs, and you wrote down the information, on your data sheet. A lot of people think the data belongs to Monarch Watch - it doesn't, it's yours. So make copies for your own records. That's the absolute best advice I can give. If you do nothing else from the stuff I list below, at least do this.

The reason I'm stressing the copying thing so much here is because it provides many opportunities in the future to have that data be examined by scientists. A lot of people may think that this is what Monarch Watch does - that they will use the data to "help understand the monarch migration". I added quotes here because I hear that regurgitated line a lot from taggers. Well, that's not really true, at least not that I can tell. Quite simply, Monarch Watch has other priorities right now than to analyze data and to write scientific studies. I personally think this is a shame, since they are the ones who supply the tags, but the reality is, there simply have not been any real scientific studies on monarch tagging that have come from Monarch Watch. In a recent review paper on monarch research in the journal, BioScience (link here), Karen Oberhauser and Leslie Ries looked back at all of the studies where citizen science data were used, and they counted 7 publications where Monarch Watch data were used. I wrote 5 of these papers, completely independently from Monarch Watch. Basically, for each of those papers I teamed up with taggers who shared copies (COPIES!) of their tagging data with me. I should add that one of the 7 papers was also written by researchers completely independently of Monarch Watch. And the last one was a conference proceedings from back in 1999 - barely a scientific paper.

I don't mean to bash that organization here, since they do perform a valuable service in at least supplying the tags (even though the volunteers actually pay for them). It's just that analyzing the tagging data is simply not a priority for their staff, who are busy with habitat restoration, milkweed sales, or what-have-you. I actually have other opinions on this subject that I've been very public about, and won't go into them here.

OK, the second bit of advice for making tagging data more valuable is this: all taggers should consider collecting additional information on each monarch they catch while it is in hand. Typically people record the date of the capture and the sex of the monarch, but that's pretty much it. But that's only a small bit of information. Adding other measurements can really help. For example, adding a wing length measurement is a good start - and in a previous post I showed a link to a good paper describing wing length measurement. Knowing how large or small monarchs are tells us a lot about the conditions of the habitat around them, for example. Other metrics to take could be more subjective (and don't require any equipment), such as a wing wear score, or the presence of wing damage. The MonarchLab in Minnesota actually has a nice overview of 'monarch measurements' that people can take - link here.

Third bit of advice: try to catch your own tagged monarchs! Most people think that the only goal of tagging is to track the migration success, that is, to track how many monarchs make it to Mexico. So they merely tag the monarch, release it, and forget about it, hoping to one day get one of their monarchs recovered. But there is actually a lot we can learn about their migration habits by studying their 'stopover behavior'. For example, how long do monarchs stay at the site where you tagged it? Knowing that can tell us a lot about the migration, and the best way to get at this is to keep track of the monarchs you tagged and released at the site. In other words, don't just tag and release, make sure to re-capture and re-release those monarchs as much as possible. After a while you will start to accumulate data on 'stopover lengths' (the length of time between the date of capture and recapture) at your tagging site. If enough people did this, it would allow for interesting comparisons between sites, or years, etc.

I guess if anyone out there wanted to go even further, they could always do what Billy McCord (an ardent tagger from South Carolina) does - he does all of the above, plus he even records what the monarch was doing when he caught it! He's been doing this for many years and has built up an impressive data set, that he has shared with me often. His behavior notes allowed us to do some very interesting analyses of monarch behavior during stopover, which we published in the journal of insect behavior in 2010. One of the more interesting findings from that study was that monarchs captured while roosting appeared to have the lowest amount of wing wear (compared to monarchs flying or resting), indicating they are in better condition than everyone else.

So that's all of my advice to give to taggers. if you do all of these things, or even just a couple of them, you can increase the value of your tagging activities immensely. You never know, you may even be listed as a co-author on a scientific study about monarchs someday!

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The science of monarch butterflies

A blog about monarchs, written by a monarch scientist, for people who love monarchs