- Author: Kathy Keatley Garvey
It's New Year's Day and it's common for folks to turn over a new leaf.
What about the old leaves?
Sometimes if you turn over an old leaf this time of year in Solano and Yolo counties, you might find a monarch caterpillar. As of today, we have two monarchs munching away in our pollinator garden in Vacaville. They've survived through freezing temperatures, heavy winds and steady rain.
Back in the late summer and early fall, monarchs fluttered into our gardem to lay their eggs. We provide four species of milkweed. Every fall we cut back the milkweed, but not until all the 'cats are gone. This year the 'cats "weren't gone."
Monarchs surprise us. Some of our December/January sightings:
- A monarch in flight on Dec. 16, 2023 in west Vacaville
- A monarch in flight on Jan. 3, 2023 near Vacaville High School
- A monarch caterpillar munching Jan. 23, 2021 in our garden.
We remember UC Davis distinguished professor Art Shapiro (now emeritus) of the Department of Evolution and Ecology telling us that he recorded a monarch in flight on Jan. 19, 2020 in Sacramento, but even earlier than that--UC Davis professor Louie Yang of the Department of Entomology and Nematology spotted one flying Jan. 8, 2012 in east Davis.
Shapiro, who has monitored the butterfly populations of Central California since 1972, maintains esearch website at http://butterfly.ucdavis.edu/. His 10 sites stretch from the Sacramento River Delta through the Sacramento Valley and Sierra Nevada mountains to the high desert of the Western Great Basin. It's the largest and oldest database in North America, and was recently cited by British conservation biologist Chris Thomas in a worldwide study of insect biomass.
The monarch Shapiro saw on Jan. 29, 2020, however, wasn't in his research project. As he told it in an email to his posse: "We had a visitor today--a British journalist--who wanted to go on a site walk. Rancho Cordova was next up. We went in his rental car. We were on US 50, just passing the Tower Theater in Sacramento heading eastbound, when, at 10.30 a.m. (temperature in mid-upper 50s, light North wind, mostly sunny), a Monarch, sex unknown, flew across the freeway in front of us, 20-22' up, from SW to NE. There is no possibility of error, unless I am having visual hallucinations."
And the monarch caterpillar we saw in our garden on Jan. 23, 2021? "Evidence of inland winter breeding," Shapiro told us. "Nothing surprises me any more..."
- Author: Kathy Keatley Garvey
It's almost time for the Art Shapiro's annual "Beer-for-a-Butterfly" contest that he's sponsored since 1972. The person who finds the first-of-the-year cabbage white butterfly, Pieris rapae, in the three-county area of Yolo, Sacramento and Solano, wins a beer--or its equivalent.
And bragging rights!
Shapiro, UC Davis distinguished professor emeritus, Department of Evolution and Ecology, is retired, but not from his research and not from sponsoring the annual “Beer-for-a-Butterfly” contest.
Beginning Jan. 1, 2024, Shapiro will be collaborating with the Bohart Museum of Entomology, the "dropping off point," for the entries. Bohart curator and collections manager Brennen Dyer will be accepting the entries.
Shapiro launched the contest a half a century ago as part of his scientific research to determine the first flight of the year in the three-county area. His research involves long-term studies of butterfly life cycles and climate change.
Shapiro says P. rapae is emerging earlier and earlier as the regional climate has warmed. "Since 1972, the first flight of the cabbage white butterfly has varied from Jan. 1 to Feb. 22, averaging about Jan. 20."
Shapiro, who maintains a research website at http://butterfly.ucdavis.edu/, says the point of the contest "is to get the earliest possible flight date for statistical purposes. The rules require that the animal be captured and brought in alive to be verified. That way no one can falsely claim to have seen one or misidentify something else as a cabbage white."
The contest rules include:
- It must be an adult (no caterpillars or pupae) and be captured outdoors.
- It must be brought in alive to the Bohart Museum of Entomology, located in Room 1124, Academic Surge Building, 455 Crocker Lane, UC Davis campus, during work hours, from 8 a.m. to noon, and from 1 to 5 p.m., Monday through Friday. It must include full data (exact time, date and location of the capture) and the contact information of the collector (address, phone number and/or e-mail.) Brennen Dyer will certify that it is alive and refrigerate it. (If it's collected on a weekend or holiday, it can be kept in the refrigerator for a few days--do not freeze it, Shapiro says.)
- Shapiro is the sole judge.
Feb 8 was "the 11th latest first rapae day since 1972,” he said, detailing the 10 later finds: Feb. 26, 1972 (“which is probably too late, since I hadn't yet learned where to look for them first!”); Feb. 22, 1992 (“I fully believe that one”); Feb. 18, 1978 and 1986; Feb. 17, 1979; Feb. 16, 1975; Feb. 14, 1981; Feb. 13, 1983 and 1985; and Feb. 10, 1980. “Note that most of these are from the '80s,” he said. “There has indeed been a trend to earlier emergence, though this year is an outlier!”
Shapiro, who monitors butterfly populations in the field for more than 200 days of the year, participates in his own contest. He has been defeated only four times and those were by UC Davis graduate students. Adam Porter won in 1983; Sherri Graves and Rick VanBuskirk each won in the late 1990s; and Jacob Montgomery in 2016. The first three were his own graduate students.
Shapiro nets many of the winners in mustard patches near railroad tracks in West Sacramento, Yolo County
Recent Beer-for-a-Butterfly Contest statistics:
- 2023: Art Shapiro recorded the first butterfly of the year at 11:22 a.m., Feb 8 in West Sacramento County, Yolo County. He did not collect the specimen and no one can forth with a winner.
- 2022: No official contest due to the COVID pandemic, but Shapiro recorded his first-of-the-year P. rapae at 1:25 p.m. on Jan. 19 in West Sacramento, Yolo County
- 2021: No official contest due to the COVID pandemic, but Shapiro collected his first-of-the-year at 1:55 p.m. Jan. 16 on the UC Davis campus, Yolo County
- 2020: Technically, no winner, as Shapiro did not collect the one he spotted in Winters, Yolo County at 11:16 a.m. on Jan. 30 at the Putah Creek Nature Park. "It flew back and forth across Putah Creek and then departed the area, flying out of reach above the trees," he noted. He waited around for 90 minutes to see if it would return. It did not.
- 2019: Shapiro collected the first cabbage white butterfly near the Suisun Yacht Club, Suisun City, Solano County, at 1:12 p.m., Friday, Jan. 25. "It was the earliest recorded in Suisun City in 47 seasons."
- 2018: Art Shapiro collected the winner in West Sacramento
- 2017: Jan. 19: Art Shapiro collected the winner on the UC Davis campus
- 2016: Jan. 16: Jacob Montgomery collected the winner in west Davis
- 2015: Jan. 26: Shapiro collected the winner in West Sacramento
- 2014: Jan. 14: Shapiro collected the winner in West Sacramento
- 2013: Jan. 21: Shapiro collected the winner in West Sacramento
- 2012: Jan. 8: Shapiro collected the winner in West Sacramento
- 2011: Jan. 31: Shapiro collected the winner in Suisun
- 2010: Jan. 27: Shapiro collected the winner in West Sacramento
A fellow of the American Association for the Advancement of Science, the Royal Entomological Society and the California Academy of Sciences, Shapiro is the author of A Field Guide to Butterflies of the San Francisco Bay and Sacramento Valley Regions, illustrated by Tim Manolis and published in 2007 by the University of California Press.
Collaborating with Shapiro on butterfly research projects is Foundation Professor Matthew Forister, the Trevor J. McMinn Endowed Research Professor in Biology, University of Nevada. Forister received his doctorate from UC Davis, studying with Shapiro, his major professor.
Pest of Cole Crops. As a caterpillar, the insect is a pest of cole crops such as cabbage. UC Statewide Integrated Pest Management Program (UC IPM) says the cabbageworm is active throughout the year in California. "Cabbageworm larvae chew large, irregular holes in leaves, bore into heads, and drop greenish brown fecal pellets that may contaminate the marketed product. Seedlings may be damaged, but most losses are due to damage to marketed parts of the plant," according to the UC IPM website.
The Bohart Museum of Entomology is directed by UC Davis distinguished professor Lynn Kimsey. Entomologist Jeff Smith curates the Lepidoptera collection, a global collection of some 500,000 moths and butterflies.
- Author: Kathy Keatley Garvey
Roll call of monarch caterpillars today in a milkweed bed in a Vacaville pollinator garden.
Secretary: "Caterpillar No. 1!"
"Present."
Secretary: "Caterpillar No. 2!"
"Present!"
Secretary: "Caterpillar No. 3!"
"Present!"
Secretary: "Caterpillar No. 4!"
"Here!"
Secretary: "Caterpillar No. 5!"
"Ditto!"
Secretary: "Roll call complete. All present and accounted for. At ease, 'cats!"
Winter begins Dec. 21, but it seems like winter right now, what with the freezing cold, rain and wind. Meanwhile, the monarch fall breeding has ended, and it's doubtful these 'cats will make it to chrysalids.
"The suppression of reproductive diapause, which I hypothesize is due to warming in autumn, especially at night, will spread winter breeding inland anywhere where host plants are available in winter!" observes UC Davis distinguished professor emeritus Art Shapiro of the Department of Evolution and Ecology. He's been monitoring butterfly populations in California since 1972 and maintains a research website at https://butterfly.ucdavis.edu.
How many 'cats will be present for the next roll call?
- Author: Kathy Keatley Garvey
Where do Western monarchs go after leaving their overwintering sites along coastal California in February?
An observation: They didn't stop in the spring or summer to deposit eggs on any of our four species of milkweed in our Vacaville pollinator garden.
Spring? Zero. Zilch. Nada.
Summer? Zero. Zilch. Nada.
Fall? Yes.
Why not spring and summer? Did the monarchs passing through Vacaville opt for "a better habitat" in the cooler Pacific Northwest and beyond (British Columbia)?
"I wish I knew," commented UC Davis distinguished professor emeritus Art Shapiro, who has monitored the butterfly populations of Central California since 1972 and maintains a research website, Art's Butterfly World.
Beginning in September, as many five monarchs a day began fluttering into our garden. Some laid eggs.
To date, we've spotted some 20 eggs and caterpillars.
"This is generally consistent with the pattern we've seen in previous years," said UC Davis Department of Entomology and Nematology professor Louie Yang, who researches monarchs. "Even in Davis, we've been seeing more caterpillars in the late summer/fall. I think this is probably because some are stopping to lay eggs on the return migration, and the fall population is much larger than the spring migration population. Looking very carefully, we did also see eggs in the spring each year, but very few of them developed into large caterpillars." See the Louie Yang et al, research paper, "Different Factors Limit Early- and Late-Season Windows of Opportunity for Monarch Development," published in July 2022 in the journal, Evolution and Ecology.
The availability of food resources, such as tropical milkweed (Asclepias curassavica) that can overwinter in warmer climates, doesn't deter them from migrating, said UC Davis emeritus professor Hugh Dingle of the Department of Entomology and Nematology. Dingle, an internationally known expert on animal migration who has studied monarchs for more than two decades, said: "Migration and the diapause that accompanies it in the fall are determined by shortening photoperiod and temperature (warm temps can override short days hence the issue with climate change)."
Said UC Davis professor Elizabeth Crone of the Department of Evolution and Ecology: "Monarchs may behave similarly in spring, but the spring population is probably much smaller than the fall one, so they are less likely to happen across your garden. Our estimate is that the population increases 2-3x each generation (so it's about 100-200x larger in Fall than Spring), then resets each year due to mortality during Fall migration and overwintering. There is some research from Sonia Altizer's lab in Georgia showing that monarch butterflies that encounter milkweeds during fall migration will leave reproductive diapause and breed. It is unknown whether these monarchs are effectively lost from the migratory population, or whether they or their offspring (the caterpillars in your yard) will continue on to the overwintering sites."
"The egg-laying females you are seeing now are likely migrants that have eschewed reproductive dormancy for reproduction," says entomologist David James, an associate professor at Washington State University who researches migratory monarchs. "This has probably always happened to some extent but is likely more significant now because of warmer falls."
"The lack of activity in summer in Vacaville was probably a function of most of the population having dispersed further east and north, maybe more than usual? They surely did pass through Vacaville in spring on their way north but clearly didn't stop to use your milkweeds. It does seem that some years they are more prone to frequent stopping/oviposition on their way north and east, yet in others they just keep flying. There's evidence that the latter was the case this year... with as many migrants making it to BC as to Washington... Normally they stop in Washington and only a handful make it to BC."
"The many mysteries of monarchs," James added.
James is the author of a newly published book, The Lives of Butterflies: A Natural History of Our Planet's Butterfly Life (Princeton University) with colleague David Lohman of the City College of New York. The book, released in the UK on Oct. 3, 2023, will be available in the United States starting Jan. 9, 2024.
Irish scientist Éanna Ní Lamhna recently interviewed the WSU entomologist in a podcast on RTÉ, or Raidió Teilifís Éireann. The book, she said, "showcases extraordinary diversity of world's butterflies, while exploring their life histories, behavior, conservation and other aspects of these most fascinating and beguiling insects." (See Bug Squad blog)
Listen to the butterfly podcast here: https://www.rte.ie/radio/radio1/clips/22294525/
Meanwhile, are you seeing fall breeding and egg-laying in your garden? We have for more than a decade, with some monarchs eclosing in November and December.
- Author: Kathy Keatley Garvey
He points out that he is a Lepidopterist but "not a monarch specialist."
Shapiro's 10 monitoring sites stretch from the Sacramento River Delta through the Sacramento Valley and Sierra Nevada mountains to the high desert of the Western Great Basin. The largest and oldest database in North America, it was recently cited by British conservation biologist Chris Thomas in a worldwide study of insect biomass.
Shapiro records his research on his website at http://butterfly.ucdavis.edu/.
At the Bohart Museum open house, his topics included the research that he co-authored, "Understanding a Migratory Species in a Changing World: Climatic Effects and Demographic Declines in the Western Monarch Revealed by Four Decades of Intensive Monitoring" (Anne Espeset et al), published in Oecologica in 2017. Professor Matthew Forister of the University of Nevada, one of his former graduate students, is among the co-authors.
The abstract: "Migratory animals pose unique challenges for conservation biologists, and we have much to learn about how migratory species respond to drivers of global change. Research has cast doubt on the stability of the eastern monarch butterfly (Danaus plexippus) population in North America, but the western monarchs have not been as intensively examined. Using a Bayesian hierarchical model, sightings of western monarchs over approximately 40 years were investigated using summer flight records from ten sites along an elevational transect in Northern California. Multiple weather variables were examined, including local and regional temperature and precipitation. Population trends from the ten focal sites and a subset of western overwintering sites were compared to summer and overwintering data from the eastern migration. Records showed western overwintering grounds and western breeding grounds had negative trends over time, with declines concentrated early in the breeding season, which were potentially more severe than in the eastern population. Temporal variation in the western monarch also appears to be largely independent of (uncorrelated with) the dynamics in the east. For our focal sites, warmer temperatures had positive effects during winter and spring, and precipitation had a positive effect during spring. These climatic associations add to our understanding of biotic-abiotic interactions in a migratory butterfly, but shifting climatic conditions do not explain the overall, long-term, negative population trajectory observed in our data."
Handout. "When I was asked to participate in this event, it got me thinking…" Shapiro began in his monarch comments handout.
"My group did an analysis of the Monarch vis-à-vis climate in a 2017 paper (Espeset et al.,, DOI: 10.1007/s00442-01607600-1) None of my group is a Monarch specialist, and that includes me. Since 1999 I have done counts of all butterfly species at 4 Valley sites (Suisun, West Sacramento, North Sacramento and Rancho Cordova) using standard “Pollard walk” methods, slightly modified. As a result we have a quantitative picture of Monarchs in breeding season... Such data are very rare. Population estimates of Monarchs are typically based on the overwintering (non-breeding) aggregations and we know from published material that what breeding-season data exist routinely diverge from the overwintering data. That is, trends in population size as measured by overwinter animals are not routinely reflected in the summer numbers. There can be a variety of explanations for this. To me the most likely is that as a very mobile species, the Monarch may breed in different places in different years, so that a monitoring program like mine, based on a limited number of fixed, Intensively-monitored sites, is unlikely to capture this stochasticity in where Monarchs breed. I am attaching the overwintering estimates from the Xerces Society. Direct quantitative comparisons are inappropriate, but you can judge how well the local trends match them just by eyeball (until we develop a convincing statistical approach to the problem!)
"My assignment for today forced me back to the original data for my Valley sites. The actual data are reproduced on the attached sheets. It is immediately evident that:
- There is very high variability in Monarch numbers among years at all sites, but
- There are short-term trends that may be associated with climatic fluctuations, in particular drought, and
- Among my sites, Suisun has had the highest counts, partly but not entirely reflecting coastward migration from farther inland early in the season, but these high numbers have effectively disappeared—perhaps reflecting a systematic change in migratory trajectories, and
- Rancho Cordova has very consistently had the lowest counts, with little year-to-year variation compared to other sites..
"My interest is now piqued and I am going to go with this. From 1972 to 1998 at all sites, and from 1972 to date at our 5 mountain sites, monitoring was on a presence/absence basis only because there are too many species to Pollard-count simultaneously. But the seasonal distribution of the Monarch is still easily extracted. We know Monarch breeding seasonality has changed over the 50-year time span of this study. We also have devised and published methods to use presence-absence data (“day-positives”) as a crude proxy for population trends. This is perhaps a good moment to revisit the Espeset et al. paper and try to get into the specific components of Monarch trends. Suggestions are welcome!" (amshapiro@ucdavis.edu)
Shapiro, who joined the UC Davis faculty in 1971, continues his research. The author of the book, Field Guide to Butterflies of the San Francisco Bay Area and Sacramento Valley Regions, he has studied more than 160 species of butterflies in his transect.