Arizona is a gateway for migrating monarchs flying through our region each Spring and Fall from both California and Mexico. From the floors of the lower deserts rising to the high Colorado plateau, monarchs encounter a multitude of climate zones, each with its own gifts of abundant milkweed species and nectar as well as many challenges. As Dr. Fred Urquhart once noted when studying monarchs in our state, Arizona is also a winter home to small numbers of monarchs in the lower deserts each year, some breeding, others nonbreeding.
Arizona is second only to Texas in the sheer number of approximately 30 native Asclepias (milkweed) species across our multiple elevations and climate zones. We are unique in hosting evergreen milkweeds in the lower deserts, always available to monarchs whenever they visit our way.
Monarchs are present in Arizona all year, but no single location has monarchs present throughout all twelve months. Every year monarchs leave the hotter desert locations in May as high temperatures soar above 100°F. They can still be found in the higher elevations of the state especially above 7,000 feet elevation during the summer months. We welcome their return to the middle and lower elevations each Fall.
Summer Breeding Season
The monarch summer breeding season began with hopes of a good year. They were quickly dashed as high temperatures shattered records, and we experienced prolonged heat spells across the region. To make conditions worse, we also endured record low rainfall during our annual summer monsoon season across the state.
This left milkweed condition poor and nectar resources limited. They were only in their prime for a short period. Arizona experienced the lowest summer breeding season for monarchs recorded since 2007 with only small numbers recorded in all monitored areas around the state.
Severe to extreme drought conditions continue to grip Arizona, challenging monarchs during their Fall migration. Migration sightings and tagging started slowly in September as temperatures continued to soar above seasonal norms in the northern half of Arizona. By mid-October there was an uptick in monarch sightings as they reached the lower deserts.
Although the main migration arrived about ten days later than usual in the lower deserts, monarchs began to appear across the central and Southern region. Monarch enthusiasts reported their activity both in riparian areas on public lands and home backyards.
The greater Phoenix area, Tucson, Willcox and Lake Havasu all watched monarchs soar through the region. The new arrivals were in mixed condition – some looked fresh and new while others had worn, frayed wings. As high temperatures remained above 90°F during much of this time period, there were many reports of monarchs mating and oviposition as well. Most breeding activity was reported on Desert (Rush) Milkweed, Asclepias subulata, and Arizona Milkweed, Asclepias angustfolia, both native evergreens.
It’s early in the season to hear about recoveries, or tagged monarch sightings, but we heard news of our first one on November 2. Omar Vega spotted Southwest Monarch Study tagged monarch AB026 at South Park in San Diego, California. Adriane Grimaldi tagged AB026 in Scottsdale, Arizona, on October 20, 2020. Even though AB026 was found deceased, his life offered valuable information about the Fall migration in Arizona. AB026 had flown 309 miles, WSW, before he was reported by Omar. Monarchs tagged in Arizona have been reported in both California and Mexico.
Most migrators to California are of live monarchs (to date this is only the second deceased tagged monarch) while those recovered in Mexico are mostly deceased (with only one live sighting to date.) If you are out and about this season, keep an eye out for tagged monarchs and use the requested contact information on the tag to report them!
When is it best to tag? To date, the latest tagged monarch to be seen in California or Mexico was tagged on November 19. Monarchs usually lose the urge to migrate around December 1st. By continuing to tag monarchs during the winter months, however, we are able to monitor their activity and longevity. Some tagged monarchs have been found still alive after 90 days, indicating they were not breeding for at least some of this time.
The Southwest Monarch Study is continuing their study of the small numbers of monarchs that spend the winter in the Sonoran Desert. Where do they come from and why do they stay here? Could these monarchs be adults that complete their life-cycle from eggs laid late in October and November that are observed each Fall in the lower deserts? We’ll let you know what we learn through the passion of Community Scientists watching their activity!
To keep up to date regarding sightings, visit our Facebook page: https://www.facebook.com/SouthwestMonarchStudy
We are happy to report the National Fish and Wildlife Federation (NFWF) extended the Southwest Monarch Study (SWMS) grant another year. Although environmental compliance was approved for several sites in Arizona, this extension was necessary due to the drought and Covid-19 restrictions that prevented successful plantings of native milkweed and native Common Sunflower, Helianthus annuus. The SWMS is looking forward to again partnering with the Gila Watershed Partnership to provide over 5,000 native milkweeds for this project.
In addition, we will also provide monarch biology signage to selected locations. Arizona Game and Fish, Arizona State Parks, Bill Williams NWR, and more will all benefit from this NFWF grant. We also have a new endeavor creating a Pollinator Garden with the North American Pollinator Protection Campaign (NAPPC) at two mine sites in Miami and Bisbee. Stay tuned for more information as this project unrolls!
Since 2007 monarch enthusiasts in Arizona have reported monarch sightings to Journey North. To help everyone understand the importance and movement of monarchs West of the Rocky Mountains we now partner with Journey North to provide Western Monarch News during the Spring and Fall Migrations.
You can learn more about this effort here: https://journeynorth.org/monarchs/resources/article/western-monarch-news-archive
If you live in the West and post sightings on Journey North, you can provide additional insights about your experience by contacting firstname.lastname@example.org. We are especially looking for sighting information of monarchs on native milkweed or on any nectar sources to learn more about their preferences.
News to Share?
Please contact Gail Morris at email@example.com if you have monarch news to share in Arizona for guidelines to submit for our next update.
Monarchs Arizona Facebook Page