Get Ready to Follow the Spring Migration in Real Time

If you haven’t been following the BlūMorpho tagged monarchs since they reached the overwintering sanctuaries in central Mexico in November, it is time to start watching again by using the free Project Monarch Science mobile app (download via your device’s app store). Monarchs typically start their northward migration from the overwintering sanctuaries in late February, with the first individuals reported in Texas in early to mid-March.

Update on BlūMorpho Tagged Monarchs
If you go back and read my previous blog posts (Nov. 7 and Nov. 17) about the 30 monarchs that we tagged with Blū+ tags in Lawrence, Kansas at the end of September, you will notice that I mentioned we had 9 monarchs that had been detected in Mexico. We were excited to increase that number to 10 when MW005 was detected at Cerro Pelón in early January. Prior to that, MW005 was last detected on October 31 near Matagorda Island, which is northeast of Corpus Christi, Texas.

Left: Track of MW005 showing the time and distance between detections in Texas and at the overwintering sanctuaries in central Mexico. Right: Tracks of the 10 “MW” monarchs that have been detected in Mexico.

In the Project Monarch Science app, 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”. We have 5 monarchs (MW001, MW005, MW020, MW024, MW026) that have been detected at the overwintering sanctuaries in February. Recall that Blū+ tags are solar-powered transmitters that use Bluetooth crowd-sourced location networks to increase the number of detections. This means that the tags have to be in the sun to be detected and a Bluetooth device or other receiver (e.g., Motus tower, Terra station) need to be nearby for a detection to occur. We will be checking frequently for any northward movement by the “MW” butterflies and others as we get closer to the end of February.

Locations of MW001, MW005, MW020, MW024, MW026 from 9-15 February.

We also recommend searching the Project Monarch Science app for monarchs labeled with the prefixes CHI, ROS, and MES, as these individuals were recently tagged by World Wildlife Fund – Mexico (WWF-MX), the National Commission of Natural Protected Areas (CONANP), Cape May Point Arts & Science Center (CMPASC), and Cellular Tracking Technologies (CTT) as part of the Project Monarch Collaboration. More than 25 organizations make up the Project Monarch Collaboration:

Logos of 2025 Project Monarch Partners.

Monarch Watch Tag Recoveries
We have also started receiving information about Monarch Watch tag recoveries, referring to our circular tags with unique letter and number codes that are applied to the hind wings of monarchs by community scientists to study the monarch’s fall migration. In contrast to the BlūMorpho tags, Monarch Watch tags rely on people to observe and report or recover tags. 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 look forward to sharing information about tag recoveries this spring, so please check our Monarch Watch Tagging Program page for updates.