New Monitoring Efforts Track Pollinator Populations at John Muir National Historic Site

By Natural Resources Intern Hannah Blank, John Muir National Historic Site

American Conservation Experience (ACE) interns conducting milkweed and blooming plant survey on Mt. Wanda.

NPS

This summer, the Natural Resources Management (NRM) team at John Muir National Historic Site began two new exciting wildlife monitoring projects involving beloved native pollinators: monarch butterflies and bumble bees.

A 5th instar monarch larva on narrowleaf milkweed.

NPS / Hannah Blank

In collaboration with the Monarch Joint Venture and the Integrated Monarch Monitoring Program, the NRM team began collecting monarch and milkweed data on Mt. Wanda. The goal is to learn how monarchs interact with the habitat there and track their population over time. The monarch (Danaus plexippus) is a candidate for listing under the Endangered Species Act and the migratory subspecies, D. p. plexippus, was recently listed as an endangered species on the IUCN Red List, emphasizing the need to focus on this species.

NRM interns began milkweed and blooming plant surveys in April, but narrowleaf milkweed (Asclepias fascicularis) did not appear on Mt. Wanda until June. The NRM team started weekly monitoring for monarch eggs and larvae in June, then switched to monitoring once per month in August and September. Despite the abundance of narrowleaf milkweed near the summit of Mt. Wanda, no monarchs were found within the milkweed survey plot. However, the team found one larva and chrysalis on narrowleaf milkweed plants outside of the plot in August and September, respectively. Another larva was found on showy milkweed (Asclepias speciosa) in the Visitor Center’s native plant garden in September, suggesting the NRM team may have focused their efforts looking for monarchs too early. The few sightings were unsurprising given that North American Butterfly Association annual butterfly counts identified only eight monarchs on Mt. Wanda since 2003. But these counts usually occur in June. If monarchs appear later in the summer on Mt. Wanda, that could explain their absence in these counts. The team plans to continue monarch monitoring in future years to gain a clearer understanding of their presence on Mt. Wanda.

A bumble bee sitting atop the flowers of Santa Cruz Island Buckwheat (Eriogonum arboresens) in the native plant garden.

NPS / Bell Goines

Additionally, the NRM team began collecting data for the California Bumble Bee Atlas, a new community science effort launched in 2022 to conserve native bumble bees. During their first survey in June they caught six bumble bees via net, carefully transferred them to glass vials, and placed the vials in a chilled cooler to temporarily slow them down. Then team members quickly photographed the sluggish bees from different angles for later identification before they warmed up and flew away. The team conducted three more surveys in July, catching only one bumble bee per survey, possibly due to the lack of flowering plants later in the summer. In the future, the NRM team may decide to start bumble bee monitoring earlier to increase their bumble bee encounters.

What the NRM team learns from these monitoring projects will provide decision-makers with important insights when it comes to protecting the natural resources that monarchs and bees rely on. Additionally, these community science programs offered park interns the opportunity to gain valuable field work experience.

For more information

• Contact John Muir Natural Resource Specialist Tori Seher

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