- Author: Kathy Keatley Garvey
The Republicans tout their elephants. The Democrats, their donkeys. But UC Davis ecologists believe that their “bears” will successfully predict which political animal will win the U.S. presidential election, as they've done for the past three decades.
Bears? That would be the woolly bear caterpillars, the immature form of the Ranchman's Tiger Moth, Platyprepia virginalis.
Professor Richard “Rick” Karban of the UC Davis Department of Entomology and Nematology and his graduate students study the woolly bear caterpillars that dine primarily on lupine along the cliffs of Bodega Bay. Sometimes the population booms; other times, it's a bust. When the population thrives, a Democrat heads to the White House. When the population dives, the Republicans take over.
The UC Davis scientists, known for their expertise in plant-insect interactions, are now drawing national headlines for their presidential predictions.
“The pollsters and talking heads seem unable to size up this election cycle,” said Karban. “Paul the Octopus had a pretty good run predicting soccer matches in 2012 so perhaps the woolly bears have earned as much credibility at forecasting this presidential election.”
The scientists first announced their findings in a poster displayed at the 2014 Ecology Society of America meeting. On April 25, they expanded on the concept, complete with intricate charts plotted in red and blue, in Lopresti's Natural Musings blog, “The Woolly Bear Presidential Election Outlook 2016,” co-written by scientists in the Karban lab.
Washington Post reporter Karin Bruilliard picked it up and ran with it on April 26 in a piece titled, “These Fuzzy Little Caterpillars Are Better at Predicting Elections Than Most Pundits.”
“Each March, Karban censuses the same patches of lupine that he has for over 30 years,” LoPresti explained in Natural Musings. “The study asks a vexing question: Why are there are so many caterpillars in some years and so few in others? Many insects, including pests cycle like this, therefore it is of keen interest to many. Dozens of papers later, Karban, his students, and his collaborators have answered a great many questions, including how caterpillars deal with parasites, whether population cycles are influenced by rain, whether caterpillars enjoy eating plant hairs, and how caterpillars avoid their predators.”
“A superficial examination suggests that 2016 will be a Republican year – woolly bear abundance is not particularly high,” LoPresti noted. “However, looking a little closer, it may not be. The number of woolly bears per lupine bush in 2016 (0.53) is higher than the average Republican year by 152% and is 36% above the highest Republican year ever recorded (1988). However, it is only 27% of an average Democratic year and still only 36% of the lowest Democratic year (2008). This result is without presidential precedent in the last 30 years.”
So, which party, aka political animal, will occupy the White House come Jan. 1, 2017?
“We suspect that the Republicans have the edge,” the UC Davis scientists surmised. “However, a valid hypothesis would be a third-party winner, such as a right-leaning independent (a logical placeholder in between Democrats and Republicans). Perhaps Donald Trump will take particular interest in our data. Alternately, a contested Republican convention could produce a fractured party and the old Republican woolly bear average would not accurately represent the mean caterpillar abundances seen by this new party.”
Responding to the April 25 blog, someone noticed the resemblance of the hair of a presidential candidate to the hair of the woolly bear caterpillar.
The UC Davis scientists study the caterpillars at the Bodega Marine Reserve above the Bodega Marine Laboratory. The reserve, which surrounds the Bodega Marine Laboratory, is a unit of the University of California Natural Reserve System and is administered by UC Davis.
“Platyprepia virginalis caterpillars are dietary generalists and feed on multiple host species within a single day,” Karban says.
In research, Diet Mixing Enhances the Performance of a Generalist Caterpillar, Platyprepia virginalis, published in February 2010 in the journal Ecological Entomology, “We found that relative growth rates and rates of survival were higher when they fed on mixed diets compared to lupine only,” Karban said. These results were consistent with hypotheses that mixed diets provided balanced nutrition, diluted toxins, and/or allowed recovery from parasitoids, although our data did not allow us to separate these non-exclusive explanations.”
The caterpillar's taste for plants containing alkaloids may help it survive parasitoids, Karban said.
- Author: Kathy Keatley Garvey
Now UC Davis researchers have found that some plants excrete a stickylike glue to entrap sand so predators won't eat them.
Graduate student Eric LoPresti and his major professor, ecologist Rick Karban, professor in the UC Davis Department of Entomology and Nematology, found that two plants, sand verbena Abronia latifolia and the honeyscented pincushion plant Navarretia mellita appear to deliberately make themselves unappealing with a coat of “sand armor.”
Sand entrapment on plant surfaces is called psammophory or sand armor, they said in newly published research in the journal Ecology.
Thus, herbivores like rabbits and bison, avoid eating them. “Sand and soil are nonnutritive and difficult for herbivores to process, as well as visually identical to the background,” they wrote in their abstract.
LoPresti and Karban set out to investigate whether the sand-coating serves as a camouflage or a shield from predators or both.
“We experimentally investigated whether this sand coating physically protected the plant from herbivores or increased crypsis (or the ability of an animal to avoid observation or detection),” they said. “We tested the former hypothesis by removing entrapped sand from stems, petioles, and leaves of the sand verbena Abronia latifolia and by supplementing natural sand levels in the honeyscented pincushion plant Navarretia mellita. Consistent with a physical defensive function, leaves with sand present or supplemented suffered less chewing herbivory than those with sand removed or left as is.”
They tested the “possible crypsis effect” by coating some sand verbena stems with green sand, matching the stem color, as well as others with brown sand to match the background color. “Both suffered less chewing herbivory than controls with no sand and herbivory did not significantly differ between the colors, suggesting crypsis was not the driving resistance mechanism.”
Since their paper's online publication, the work has been featured in Newsweek, Discover and on CBC Radio.