The end of summer marks the start of butterfly migration season. While some species of butterflies are flying to their summer homes, Don and Gayla Ohde of Cedar Rapids are concerned. Gayla saw just seven butterflies in their yard this summer, one black swallowtail and six monarchs.
In past years, the Ohdes have reared swallowtails and monarchs in their screened-in porch. This year, the took a break from housing the insects but they -- and other nature lovers they talk to -- are seeing fewer butterflies. The Ohdes turned to Curious Iowa, a Gazette series that answers readers' questions, to find out where the butterflies have gone.
We'll say upfront that we don't have an exact answer for this question. While butterflies are around, annual populations vary by species. The Gazette spoke with Iowa experts about their butterfly observations this season and what Iowans should know about them.
The data that measures butterfly populations in Iowa is collected by naturalists and citizen scientists. There are a variety of programs in the state that survey butterflies, but The Gazette used data from the Iowa Butterfly Survey Network (IBSN). IBSN requires that volunteers survey their assigned site at least six times to provide data on how butterflies are faring in that location. IBSN's chosen sites are areas that have butterfly habitat, like county parks.
Nathan Brockman, Director of Entomology at Reiman Gardens in Ames, said in early spring there was a "booming" population of red admirals, which had him excited about how the season would progress.
"And then as we were surveying, they just weren't there," Brockman said.
Even cabbage whites, an invasive butterfly, have had a lower population this year.
"It may just be because we were cooler and wetter which slows down development of things because they're all affected by temperature," Brockman said.
While populations were down during the summer months for most Iowa, some of the fall species are seeing an uptick, reaching numbers Brockman would expect to see.
"Some species are holding fine or we're still seeing really banner years. However, there are other species ... I would say the majority of Midwest states are seeing a decline in several of the Midwest skippers that would normally be found in the state," Brockman said. "Not all of the species, but I would say several offhand."
Johnson County Conservation education specialist Frances Owen has been conducting monarch tagging events at Kent Park in Oxford throughout the summer. These events involve netting fast flying monarchs and adhering small numbered stickers to their hind wings. The data is used by Project Monarch Watch at the University of Kansas to learn more about monarchs' migration. Throughout the migration season, community scientists capture monarchs and record data on the monarch and where it came from.
Owen said 29 monarch butterflies were tagged this season and about double have been sighted during tagging events. They will continue tagging until October. In past years, Owen remembers catching 30 butterflies between just herself and another person.
"It has been a slow season and this is kind of the time of year, around the first couple weeks of September, where, for our latitude, we should start really seeing them bunching up and coming in mass," Owen said. "Time will tell over the next couple weeks how that looks but it seems like it's going to be a low population."
The monarchs we see in Iowa are part of the Eastern monarch population, which refers to the population east of the Rockies. The Eastern and Western population have different migratory homes and do not typically mate, Augie Bergstrom, manager of the Monarch Research Station in Marion, said.
Bergstrom said it's no coincidence people aren't seeing the same volume of monarchs as years past. The Eastern Monarch population dropped by 59 percent this past year.
Fall drought conditions likely played a role, Bergstrom said, as it can reduce the number of flowering plants. Nectar is the insect's only source of nutrition.
"It's hard work migrating thousands of miles to Central Mexico and when you pair an already decreased monarch population with severe climate conditions, you unfortunately end up with the second lowest population numbers in recorded history," Bergstrom said.
We won't have a full picture of this year's monarch population until the World Wide Fund for Nature measures the population in Mexico between December and January. But Bergstrom provided insight into local efforts to rear monarchs in captivity. Earlier this summer, Monarch Research Project distributed more than 2,500 caterpillars to Monarch Zone host families. These volunteers rear monarchs from their porches, decks and backyards, supplying them with all the milkweed they can eat. Bergstrom estimated that about 2,000 butterflies will be released from monarch zones this year.
"Female monarchs released in the early summer months will lay hundreds of eggs each." Bergstrom said. "The hope is that subsequent generations will be larger and we will eventually end the season with a much larger local migratory population."
A variety of factors determine how butterfly populations fare each year. They include weather, food and habitat availability, predator loads and parasites.
Brockman pointed out that adult butterflies are what we typically notice in nature.
"We don't notice that there were 10,000 caterpillars possibly in an area, but if they get eaten or attacked by some sort of parasite, then they don't make it to adulthood."
When it comes to habitat and food availability, butterflies and other insects rely on grasses, trees and flowers. Just 0.1 percent of the 23.3 million acres of prairie Iowa had in the 1850s remains today. By growing host plants, like milkweed, parsley, oak trees or bee balm, your yard can become a buffet for caterpillars and butterflies alike. If you're able to plant species native to Iowa, like blazing star or foxglove beardtongue, even better. Feeding insects supports the greater food web, of which insects support the foundation of.
Monarch butterflies have one host plant: milkweed. Without milkweed availability, monarchs don't have a place to lay their eggs and caterpillars will go hungry.
"The best and easiest thing you can do for monarchs is to plant milkweed." Bergstrom said.
"There's evidence to show that ... pocket prairies are helpful for insects and for butterflies," Owen said. "So even if you have just a small 10-foot by 10-foot space that you can pack full of native grasses and flowering plants, then that's better than nothing."
There are about 118 species of butterflies in Iowa and 32 of those species are either listed as endangered, threatened or of special concern. That list was created in 2009.
Butterflies are a great indicator species. This means they can show if something in the environment has changed. They are widely surveyed, unlike flies or beetles, which are also in decline, Brockman said. He said it's important that we start looking closely at all insects.
"The loss of the insects and butterflies ... means that our habitats aren't functioning at the level they should be, which means our environment isn't doing as well as it should be or has historically," Brockman said. "I guess times change and the way we are using resources are different and so it's how do we continue to provide for the animals?"