Annual survey on Maunakea shows wēkiu bug population boom

This year, survey teams find a more than seven-fold increase in wēkiu bugs on Maunakea compared to recent surveys. The increased abundance could be a function of increased precipitation on the mountain this past year. 

By Susan Enright

The population of the endemic wēkiu bug, which can only be found on puʻu (cinder cones) on the summit of Maunakea, remains healthy according to the insect captures recorded during the University of Hawaiʻi at Hilo Center for Maunakea Stewardship’s annual arthropod monitoring surveys this year.

This year, land managers from the center collected nearly 3,000 bugs from the live traps compared to about 400 bugs in the last two years. Survey teams note each bug’s life stage and gender. All life stages and sexes were captured during the 2021 survey, which means populations are growing and reproducing.

The increased abundance could be a function of increased precipitation on the mountain this past year, as moisture is a limiting factor in the alpine ecosystem.

“We’re monitoring puʻu in the summit region for wēkiu bug abundance, distribution and demography to understand if these insects are reproducing and growing,” says Jessica Kirkpatrick, natural resource specialist at the stewardship center. “We’re also trying to get a sense of different invasive species threats that could potentially threaten the bug, things like ants are actually a number one threat to both the flora and fauna on the mountain.”

 Jessica Kirkpatrick and Jesse Eiben with bug trapping equipment in rocky terrain on Maunakea.
In this file photo from 2016, then-UH Hilo graduate student Jessica Kirkpatrick (left) and adviser Prof. Jesse Eiben check wēkiu bug traps on Maunakea. Kirkpatrick now serves as the natural resource specialist at the Center for Maunakea Stewardship. The center, formerly known as the Office of Maunakea Management, has monitored the wēkiu bug since 2002. (Courtesy photo)

Kirkpatrick is a graduate of the UH Hilo tropical conservation biology and environmental science program. She conducted research on the native wēkiu bug during her studies. Her research, under the tutelage of Jesse Eiben, who was then an assistant professor of applied entomology at UH Hilo, involved understanding wēkiu bug habitat in order to provide information for possible habitat restoration following the scheduled decommissioning and removal of three observatories on Maunakea.

Kirkpatrick believes above average snow and rain events on Maunakea in 2020 and early 2021 could be a contributing factor to the increase in wēkiu bug abundance found during this year’s survey. Insect populations are extremely variable from year to year and the wēkiu bug shows this same trend.

“Nightly freezing temperatures are important for the insect, as the cold kills their prey,” Kirkpatrick explains.

Little brown bug on rocky rerrain.
Wēkiu perched on a rock on Maunakea. (UH System News)

“The wēkiu bug is a carnivorous scavenger that feeds on dead and dying insects that get blown up to the summit via wind processes. Non-resident insects are not adapted to the cold temperatures and eventually die and become food for the wēkiu bug and other endemic residents such as the noctuid caterpillar [and] moth Agrotis kuamauna. The snow can act as a natural refrigerator keeping the wind blown insect prey fresh until it thaws and can be consumed by other native residents.”

Annual surveys

The Center for Maunakea Stewardship, formerly known as the Office of Maunakea Management, has monitored the wēkiu bug since 2002

Every year, surveyors place a variety of traps at more than 100 sites on the mauna to assess native species population levels and detect possible threats. Some trap locations require researchers to climb cinder cones that are 200-feet high. Each bug, no bigger than a grain of rice, is counted by hand in the field before they are released.

In 2011, studies sponsored by the center determined that the wēkiu bug had a wider habitat range in the Alpine Stone Desert than previously known. The U.S. Fish and Wildlife Service removed the wēkiu from the candidate endangered species list that year after entomologists and others compiled years of research on the insect’s biology, genetics and habitat, assuring its conservation and protection.

In the Hawaiian language, wēkiu means summit or peak. The bugs are well-adapted to the mountain’s harsh environment that experience extreme temperature fluctuations each day, high ultraviolet radiation and low relative humidity associated with high-altitude environments.

Story on this year’s survey results at UH System News.

By Susan Enright, a public information specialist for the Office of the Chancellor and editor of UH Hilo Stories. She received her bachelor of arts in English and certificate in women’s studies from UH Hilo.