Tracking Individual Monarchs with Radio Tags as Part of the Project Monarch Collaboration

With today’s New York Times article (We Can Now Track Individual Monarch Butterflies. It’s a Revelation. 17 November 2025) and press release from Cellular Tracking Technologies (CTT) and the Cape May Point Arts & Science Center (CMPASC), we want to share more information about our participation in the Project Monarch Collaboration.

BlūMorpho Radio Tags

BlūMorpho solar-powered radio transmitters (also referred to as “tags”) provide an amazing opportunity to track the paths of individual monarch butterflies. In particular, the ultralight tags can use Bluetooth crowd-sourced location networks to increase the number of detections. Visit the CTT/CMPASC Project Monarch website to learn more about how the project started and how BlūMorpho tags work. In contrast to these radio tags, our Monarch Watch Tagging Program uses sticker tags and relies on people to observe and report or recover tags with unique letter and number codes. Both tagging approaches provide unique and complementary information about the monarch’s fall migration, as well as different ways for people to engage with monarchs. We are excited about the research questions that can be asked with the new technology and look forward to continuing to study the monarch’s fall migration with both the BlūMorpho tags and Monarch Watch sticker tags. We hope you will share our excitement!

Monarch Watch deployed a total of 30 BlūMorpho tags towards the end of September. Of the 30 monarchs that we tagged, 30% (9) have been detected in Mexico, 63% (19) in Texas, and 70% (21) in Oklahoma. Previous estimates (see Monarch Population Dynamics: Issues of scale) have suggested that 20% (or 1 out of 5) or fewer of monarchs that start the migration across the breeding range make it to the overwintering sanctuaries in central Mexico. While we do not know the origins of the wild-caught monarchs that we tagged with BlūMorpho tags in Kansas, we do know that they had many fewer miles left to fly (1370 miles) by the time we tagged them than those tagged by many of our colleagues and collaborators on this project. For example, those tagged in Long Point, Ontario, had to fly at least 1960 miles to reach the overwintering sanctuaries, while those tagged in Harrisonburg, Virginia, flew at least 1830 miles. Based on the preliminary results from this year and expected mortality during the migration, the success of the BlūMorpho tagged monarchs is very good.

Monarch Tracking Data Visualization

Using the free Project Monarch Science app (download via your device’s app store), you can view lots of information about many of the tagged individuals. You can find the monarchs tagged by Monarch Watch in the Data tab by selecting the monarch icon at the top of the screen then searching for “MW”. When you look at the map view, make sure to zoom in as far as you can so that you are not missing any monarchs.

We had some excitement on Nov. 9 when JMU004 was the first monarch to be detected at a known overwintering site (El Rosario), but MW026 was detected in the same location a couple of hours later, obscuring the view of JMU004, as you can see in the images captured from the app, below.

Monarch MW026 obscuring the view of monarch JMU004.

I mentioned in a previous blog post (Radio-tagged monarch MW001 arrives at the MBBR) that monarch movement was slow due to winds from the south. The BlūMorpho tags capture this in a way that was not possible before. Using MW026 as an example, some graphics below illustrate that point. Keep in mind that winds are reported based on the direction they are coming from. That means that North winds (those blowing north to south) help the monarchs move south when they are starting in Kansas, but South winds (those blowing south to north) make the migration more difficult.

Full tracking of monarch MW026 through 16 November 2025.

If you are looking for some monarchs to check out in the app, a good starting point might be MW026, XOKC006, NOK015, LPM093, and JMU004, which are grouped together (at least at the time I am writing this!) in the Monarch Butterfly Biosphere Reserve. There are also lots of other monarchs doing interesting and even unexpected things, so look around!

You could also check out the nine monarchs that we tagged that made it to Mexico: MW001, MW002, MW003, MW008, MW020, MW021, MW023, MW024, M026. Their tracks appear below.

Tracks of nine monarchs in Mexico, tagged and released by Monarch Watch.

Below are the tracks of all 30 monarchs that we tagged.

Tracks of 30 monarchs tagged and released by Monarch Watch.

Project Monarch Collaboration 2025

More than 25 research organizations make up the Project Monarch Collaboration this year (see logos below). Not only is this project an amazing contribution to science, but it has also been a lot of fun, in particular sharing the experience (including lots of ideas, information, questions, answers, etc.) with so many other dedicated scientists.

Logos of 2025 Project Monarch Partners.