Agriculture

Gavilan STEM student studies threats to Monarch Butterfly

From 1994 to 2018, the monarch butterfly population has declined by more than 80 percent. Gavilan College students research the causes alongside San Jose State University professors.
Researcher Mariam Hernandez. Photo courtesy of Mariam Hernandez.
Monarch Butterflies. Photo courtesy of Christine Candelaria.

This article was contributed by community member Mariam Hernandez.

In 2018 I spent the summer as a research assistant for entomology Professor Jeffrey Honda at San Jose State University (SJSU). Along with fellow students, we sought answers to explain the dramatic decline in the number of monarch butterflies at the university and the California Fish and Wildlife Cañada de los Osos (Canyon of the Bears), six miles east of Gilroy at the southern edge of Henry Coe State Park. We participated in the Gavilan College program for science, technology, engineering, and mathematics, or STEM. If a STEM internship interests you, the deadline for  Gavilan College STEM 2019 Summer Internship is March 28.

Monarchs (danaus plexippus) thrive on milkweed, so we surveyed the plants using colored flags to mark their locations, saving the coordinates in a Garmin GPS to yield an overview of their presence in the reserve. Once done, we were able to return to the milkweeds and measure their length every two days. We slowly twirled the plants to look for monarch eggs and other predators such as coccinellids (ladybugs), aphids, spiders, and milkweed bugs.

To learn more about monarch predators, such as ladybugs, we recorded everything on data sheets, identifying the types of bugs found at SJSU and Cañada de los Osos. By doing so, we were able to document the most popular beetles found on the West Coast. For any beetles that could not be identified on site, we captured them and looked them up in the educational center or at the university with Dr. Honda.

Unfortunately, our results indicated a high mortality rate for monarch eggs, instars (a growth phase) and adult monarch butterflies. Throughout the months of research, we found only 11 eggs and one larva; none of these survived. Some of the most common predators we found in Cañada de los Osos Reserve were spiders, ants, coccinellids, parasites, aphids, and milkweed bugs.

As researchers we knew that predators were eating the monarch eggs. To prove our hypothesis, we placed a camera in front of a milkweed plant loaded with monarch eggs, with the goal of taking many photographs throughout the day. Approximately 20 minutes after we set up the camera and the eggs, predators started approaching the milkweed plant; and within 30 seconds the predators started eating the eggs, leaving nothing behind. We now have evidence that predators play a major role in the decline of monarchs.

As interns, we had various responsibilities, for example posting weekly updates on Google+, completing 160 hours of field and lab work combined, preparing a poster presentation for the Gavilan College STEM Symposium in late summer. The team members commuted to the field sites two times per week over three consecutive months, working from 9 a.m. to 5 p.m. We also had to commute to SJSU once a week to do lab work and collect data on the campus.

Fellow student Kimberly Leyva, describing her intern experience, said she “learned how to collect data, how to follow a cohort, work with a team, and connect with mentors.” Kimberly also said the internship gave her a chance to “take a closer look at a real lab experience.”

I asked Dr. Honda about his experience with the Gavilan-SJSU program. He told me, “As a scientist, I enjoy solving ecological questions. I also love the opportunity to be outdoors, and mentoring students. I find it very rewarding seeing former students become researchers themselves. STEM is very important; I highly promote it for it develops critical thinking. In today’s world, innovation and science literacy require STEM education.”

Monarchs cannot survive without milkweed. You can help by planting a butterfly favorite asclepias incarnata that provides “milk” for the hungry hatched larvae. Monarchs lay their eggs on the leaves and the caterpillars eat the leaves. A successful butterfly garden has plants that meet their needs during all four life stages: the egg, caterpillar, chrysalis, and adult. Most milkweeds prefer sunny dry areas. You can learn more at Monarch Watch and Save Our Monarchs.

The application deadline comes up soon on March 28, but there is still time to apply. Go to Gavilan College STEM 2019 Summer Internship.

The 2018 Gavilan College STEM research team included Jeffrey Honda, professor of entomology at SJSU; Urzula Holzmann, SJSU graduate student; Bob Clement and Henry Coletto, managers of Cañada de los Osos; Jorge ZaragozaCathelina Her, Maggie Wong, Manae Matsubara, David Wang, Kimberly Leyva, and Mariam Hernandez.

Special thanks for a successful STEM experience go to Jeffrey Honda and Urzula Holzmann at SJSU; Eduardo Cervantes, Rey Morales, and Marla Dresch at Gavilan College; and Bob Clement and Henry Coletto at Cañada de los Osos.

 

BenitoLink Staff