Pima County Government Logo
  • Increase font size
  • Decrease font size
  • Print
  • RSS
  • Paseo de las Iglesias ready to offer a royal welcome to migrating Monarchs

    Apr 19, 2019 | Read More News
    Share this page
    Photo credit: Southwest Monarch StudySome royal visitors will arrive this fall in Pima County. When they do, the Regional Flood Control District and the Natural Resources, Parks and Recreation Department will be ready with accommodations and plenty of delicious food, even though it would be toxic to humans. Recently, the District and NRPR joined an effort to plant some 300 milkweeds at three sites within the Paseo de las Iglesias section of the Santa Cruz River Park in anticipation of the annual migration of Monarch butterflies through Southern Arizona.

    Working with the Southwest Monarch Study, a group of citizen scientists who track the butterflies' migration and breeding patterns in Arizona and the Southwestern United States, the two County agencies transplanted desert and pineneedle milkweed along with other pollinator-attracting plants from the County's Native Plant Nursery in dozens of spots around three ramadas located on either side of the Santa Cruz south of Silverlake Road. The locations will serve as Monarch way stations. Funding for the project came from a National Fish and Wildlife Foundation’s Monarch Butterfly Conservation Fund grant to the SMS, with volunteers from the Arizona Conservation Corps, a branch of Americorps, working with NRPR maintenance staff to connect the plants to the existing drip irrigation system. Each cluster is protected by browser cages to prevent grazing by rodents and other animals.

    "It took a while for this to come together because there's a regulatory process overseen by the Fish and Wildlife Foundation," District Open Space Land Manager Marisa Rice said. “That delayed planting but eventually we were able to implement the project. We thought Paseo [de las Igelsias] would be a good site because the area had few shrubs and grasses and looked bare. The ramadas provide a shady place for people to sit and and enjoy the plants and butterflies."

    Monarchs live largely in two regions divided by the Rocky Mountains. Once believed to be separate populations, the two groups of Monarchs have been shown by studies to be genetically identical. Monarchs living east of the Rockies migrate from the northern and central United States and southern Canada to Mexico. Those living west of the Continental Divide generally overwinter in coastal California before heading for Oregon, Washington, and Idaho as the weather warms. Monarchs in Arizona migrate to both California and Mexico each fall and fly back through the state on their way north and east in the spring. A number also head for the mountains of Colorado and Utah or even the White Mountains of Eastern Arizona. Tagging efforts have found that some western Monarchs occasionally travel to Canada in springtime. 

    File: butterfly garden plantsMonarchs' life cycle follows the same pattern as other butterflies but they rely almost exclusively on milkweed plants to lay their eggs. Caterpillars hatch after three to five days, growing rapidly and molting five times in about two weeks at which point they form chrysalises where they spend another two weeks before emerging as adults with their trademark orange and black wings with white spots around the edges. Only about five percent of caterpillars make it to adulthood thanks to a host of predators, including ants, spiders, and beetles that are able to tolerate the toxins the larvae build up by dining exclusively on toxic milkweed.

    "Milkweed is the 'host plant' for monarchs," Morris said. "They aren't like painted lady butterflies which lay their eggs almost anywhere. They stick to milkweed."

    Grown Monarchs have a more varied diet, feeding on nectar from many plants, and while they retain some of the toxicity of their larval stage, a number of species such as mice and birds, including varieties of robins, cardinals, sparrows, jays, and orioles found in Pima County consider them palatable. Others learn the hard way that Monarchs aren't for them.

    "One morning during this most recent migration we saw some roadrunners plucking Monarchs off plants," Morris said. "They didn't come back the next day."

    The timing of the project, planting as the bulk of the butterflies left Pima County, will allow the milkweed to grow and flourish well ahead of the Monarchs' return to the region in September and October. However, prolonged cooler weather this spring allowed them to stay here longer than usual. Most years, they would be in areas around Sedona and Flagstaff by mid-April. So far, the SMS has recorded just one sighting as far north as Camp Verde with most of the population stalled just north of Phoenix.

    "Monarchs are symbolic. They mean many things for many people. As scientists, we can look at their incredible migration and they're kind of a harbinger of all the pollinator species. There are a couple of other pollinators who are in trouble now too," Morris said.  

    File: pineneedle milkweedMonarchs hold important cultural significance in Mexico, serving as heralds of La Dia de los Muertos because their arrival in the fir-clad Sierra Madre mountains coincides with the holiday, almost like clockwork. The faithful believe the orange-winged butterflies are the souls of departed loved ones returning for an annual visit. The celebrations took a major blow in 2017 when the Monarchs arrived late and in historically low numbers due to late winter storms and cold weather. Illegal logging, climate change, pesticide abuse, and poor land management also have combined to put pressure on their population.

    "That's what we're looking at right now. What's threatened is their migration. We'll always have Monarchs. There will always be little pockets of them. But the concern is how do we keep their migration alive. Whether it's in Mexico or California, we're worried what's happening in those sites" Morris said.

    The migrations are epic, multi-generational journeys that cover roughly 3,000 miles. Individuals that set off from the northern edges of the Monarchs’ range never reach their ultimate destination, their great-great-great-great grandchildren do. For reasons still unclear, the insects pass a genetic memory of their route that not only allows the kaleidoscope (or flutter) to return to Mexico but often brings them back to the same backyard gardens their ancestors visited the year before. When possible, they travel using upper air masses called thermals to conserve energy at speeds between 15 and 25 miles per hour. Monarchs making the trip north do so in about two generations.

    Pima County residents can expect the Monarchs to return just as the summer heat begins to loosen its grip, passing through in clusters until about mid-November. Some of the butterflies spend the winter in Tucson at other lower-elevation locations. The way stations established in Paseo de las Iglesias will help them along and also provide a little spectacle for neighbors and people who use the Chuck Huckelberry Loop.

    The Southwest Monarch Study provides education and conservation programs as well as training on how to tag and monitor monarch butterflies, caterpillars, and their pupae. To participate, contact the organization by email or online.