Mice are eating monarch butterflies in Pismo Beach

A monarch butterfly lands on a plant
A recent study by University of Utah biologists conducted at Pismo State Beach Monarch Butterfly Grove found that mice actually eat monarch butterflies.
(K.C. Alfred / San Diego Union-Tribune)

Good morning, and welcome to the Essential California newsletter. It’s Thursday, Jan. 13. I’m Justin Ray.

Regular readers might recall our in-depth report about mysterious happenings involving clams at Pismo Beach. Well, I’m here to tell you about another strange thing happening in the area.

A recent study by University of Utah biologists found that mice have no problem chowing down on monarch butterflies there.

The study about the eating habits of the harvest mice was conducted at Pismo State Beach Monarch Butterfly Grove. The good news is, this diet is not believed to be contributing to the decline of monarchs. Instead, the biologists believe this behavior indicates how little we know about interactions in our ecosystem.

“One of the things that this really highlights is, here’s a butterfly, an insect that we’re all so familiar with, we all know about. Just about every school kid in California knows about its life cycle and knows about its toxins, and it’s in everybody’s yard. And yet, here’s an interaction that we had no idea existed,” Sara Weinstein, the postdoctoral researcher who helped author the study, said to the San Luis Obispo-Tribune.

How the study was conducted


So here’s an interesting thing to know about butterflies: Monarch butterflies have a “chemical armor,” the researchers explain. When they are caterpillars, they eat plants filled with toxic compounds (known as cardenolides). This makes them gross to eat for most — but not all — predators.

To see if mice would eat the butterflies, the researchers trapped the rodents in the grove in February 2020. They were eventually released, but their feces was kept and tested for monarch DNA — which was found in one sample. They performed the experiment in late winter, which was less than ideal because the insects were leaving, so there weren’t as many for the mice to eat.

The researchers intended to conduct the survey again the following fall, which would have been peak monarch season. But the butterfly population had crashed by then.

“At a site where 100,000 butterflies used to roost, in 2020 there were fewer than 200 monarchs. So, we had to change tactics,” Weinstein said, according to the release. “We tested whether rodents would feed on the butterflies using captive-reared monarchs.”

They put lab-reared monarch carcasses under camera traps and watched as the wild harvest mice ate the insects. They seemed to like dining on the “abdomen or thorax, high-calorie parts with fewer toxins,” the release says.

“Many rodent species are likely to have some resistance to cardenolides in monarchs, due to genetic changes at the site where these toxins bind,” Weinstein said in the release. “The Pismo Grove is one of hundreds of western monarch aggregation sites, and it seems likely that, at least in the past, rodents throughout the western monarch range may have supplemented their winter diets with monarchs. If you can handle the cardenolides in a monarch, their bodies are full of fat and offer a pretty good meal.”

The western monarch butterfly population has been decimated in the last 40 years. There will be an impact on the ecosystem, as many organisms depend on others for their survival.


And now, here’s what’s happening across California:

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‘I really thought I was gonna die.’ Patrisse Cullors is healing after quitting BLM. She explains to The Times that she had endured threats and criticism for years, but the turning point came in April 2021, when news outlets reported that Cullors had been on a personal “million-dollar real estate buying binge.” She denounced the reports as misleading, but the impact was brutal. Los Angeles Times

Patrisse Cullors
Patrisse Cullors at the Crenshaw Dairy Mart, an art gallery.
(Jason Armond / Los Angeles Times)

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‘He’s sitting on a massive budget surplus that is every politician’s dream.’ There seems to be nothing standing in the way of Gov. Gavin Newsom. Despite early concerns that the pandemic would weaken the state’s economy, another year of gushing tax revenue ensures that the politics of plenty will continue to define his first four years in office. But amid recent highly publicized smash-and-grab burglaries, a worsening homelessness crisis and other pressing issues, Newsom’s record as governor will hinge on whether he can make progress on the problems of today and meet the needs of tomorrow. Los Angeles Times


The positives of having two parties duking it out. It’s been a decade and a half since a Republican won statewide office in California and a quarter-century since the once-dominant GOP controlled either legislative chamber. Columnist Mark Z. Barabak says that’s not good. “Politicians and political parties need serious competition to hold them in check, keep them honest and avoid arrogance and overreach,” he writes. Los Angeles Times


The family of a 25-year-old man who was shot and killed by a Sacramento County sheriff’s gang unit detective in 2021 is suing the sheriff’s office and the county of Sacramento for $100 million in damages. Kershawn Geyger was shot and killed on Jan. 15, 2021. In a news conference, lawyers for Keshawn’s family said they felt compelled to file a lawsuit after receiving no response when asking authorities for more information on Geyger’s shooting death. When asked by The Times for comment, the sheriff’s office responded that, “the County of Sacramento and the Sacramento County Sheriff’s Office has a long standing policy not to comment on pending litigation.” KCRA

‘I fainted in front of my neighbors. I started screaming.’ A street musician spent years building a one-of-a-kind drum kit on wheels. Then, one morning, it was gone. Los Angeles Times

Anthony Sheriff, stage name Sheriff Drumman, plays drums
Anthony Sheriff, stage name Sheriff Drumman, plays the drums.
(Jason Armond / Los Angeles Times)

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Santa Barbara County firefighter paramedic killed in skiing accident. Joseph De Anda, 33, from San Luis Obispo died after visiting China Peak in Fresno County. De Anda struck a tree while skiing with a group of friends. He suffered serious injuries and died as a result of the crash, Fresno County Sheriff officials said. He had served as a firefighter paramedic with the Santa Barbara County Fire Department and also in various roles as a dispatcher and a paramedic with the Santa Barbara County Sheriff’s Office. KEYT


As an unprecedented wave of coronavirus infections washes over the region, Los Angeles County health officials are urging residents to postpone nonessential gatherings and avoid some activities — especially those with people who are unmasked, unvaccinated or at higher risk of severe COVID-19 illness. Los Angeles Times


A pair of alpacas went on a more than two-hour adventure through various neighborhoods when they escaped their enclosure in Oakland. Father and son alpacas Boogie and Woogie stopped drivers and bystanders in their tracks. Hundreds of people chimed in on Nextdoor, wondering if the dynamic animal duo had escaped from a nearby zoo. They were eventually caught by a homeowner, who then alerted the California Highway Patrol and animal control, who was able to reunite the alpacas with their owner. ABC 7 News

Ten books to help you understand inequality — and possible solutions. The systems that govern our lives have led to different ends for different people. We have compiled a list of works that will help you unpack the inequalities built into America’s economy. Los Angeles Times

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Los Angeles: Cloudy 71 San Diego: Cloudy 69 San Francisco: Overcast, 58 San Jose: 64 Fresno: Cloudy 62 Sacramento: 61. I love this cat, who growls instead of meowing. I can relate.


If you recall, I asked readers for music they listen to when they want some nostalgia in their lives. Here is a response from Kelly C. Richardson:

Anything from Kid Stuff Records & Tapes. An endless supply that never gets boring. When not able to thrift or uncover at garage sales during 2020 I was able to shop on Discogs and buy an album by Kid Stuff for less than the cost of shipping! Saved my sanity.


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