The research provides some of the strongest evidence to date for the idea of evasive mimicry, a strategy in which animals protect themselves from predators by matching the colors or patterns of agile relatives. First proposed more than 60 years ago, the hypothesis has been a challenge to test.

But in an experimental setting, researchers found that wild birds learned and remembered the wing patterns of artificial butterflies that evaded their attacks, as well as those that had a foul flavor, equally spurning both in follow-up tests and often ignoring lookalikes with similar color patterns. Unexpectedly, the birds learned to avoid evasive butterflies faster than distasteful ones.

The results suggest that being hard to catch may deter predators at least as effectively as chemical defenses.

“There’s a common idea that being distasteful is one of the best kinds of defense to have, but at least in this experiment, that didn’t prove to be the case,” said study co-author Keith Willmott, curator and director of the Florida Museum of Natural History’s McGuire Center for Lepidoptera and Biodiversity.

Most research on warning coloration has focused on species with chemical defenses and those that mimic them. Monarch butterflies, for example, sport bright wing patterns of black lines on a field of orange, indicating they contain bad-tasting toxins. A predator that eats one will likely avoid both monarchs and the similar-looking viceroy butterfly in the future.

But a growing number of studies suggest a flashy exterior can mean something entirely different: that an animal is quick. Predators learn to associate these kinds of patterns with a futile chase that leaves them hungry, and species that evolve imitations of these “racing stripes” can capitalize on a defensive strategy while reinforcing the visual message.

“When many species share the same color pattern, they’re better able to educate predators to avoid them,” Willmott said. “The more species that share it, the better.”

During his Ph.D. studies, Willmott worked on the classification of a group of fast-flying tropical butterflies known as Adelpha. At first, he found them nearly impossible to identify. It seemed the genus either contained only a few species with slight variations in wing pattern or dozens of species that looked virtually the same. The latter turned out to be the case, with more than 90 species making up the group. Like some researchers before him, Willmott began to wonder whether evasive mimicry could explain why so many species of Adelpha looked alike.

“It was always mysterious to me,” he said. “Species whose upper wings looked incredibly similar were distantly related, and we started to see cases where even subspecies of multiple species suddenly developed very unique color patterns. Really, the only way you can explain that is through mimicry.”

While other researchers suggested some Adelpha must have hidden chemical defenses, the explanation didn’t quite satisfy Willmott. Toxic butterflies are usually slow fliers with long wings and a propensity for playing dead when caught. Adelpha butterflies, however, don’t display these traits, having instead a short, stout thorax and smaller, triangular wings — characteristics that enable fast, erratic flight and sharp turns.

But he wasn’t sure how to test this hypothesis until a conversation with fellow researchers at a 2018 conference in India: Johanna Mappes was an expert at developing predator-prey experiments with wild birds; Pável Matos-Maraví was interested in the evasive behavior of skipper butterflies; and Marianne Elias and her Ph.D. student Erika Páez were eager to study what drove the evolution of wing color patterns in the genus Adelpha, including the possible effects of predators.

Simulating how evasive mimicry might play out in the wild appealed to the group. The ability of prey to escape predators’ attacks has been “virtually unstudied,” said Elias, a research group leader at the Institute of Systematics, Evolution, Biodiversity at the National Museum of Natural History in France.

Previous work had shown birds can identify the visual cues of evasive prey. Together, the team designed an experiment to test whether potential examples of evasive mimicry in Adelpha could be the result of natural selection.

At a special facility in Finland, the researchers collaborated with Janne Valkonen of the University of Jyväskylä to capture wild blue tits, birds that would never have encountered tropical Adelpha butterflies, and train them to catch a paper butterfly with an almond treat attached to its underside. Then, the birds were presented with a plain brown paper butterfly as a control and a paper butterfly with one of three common Adelpha wing patterns: a vertical white band on black forewings, a vertical orange band on black forewings or a combination of orange-striped forewings with white-striped hindwings.

The paper Adelpha butterfly either concealed an almond soaked in a bitter substance — a proxy for chemical defense — or evaded the bird’s attack by gliding away on a rail. The birds learned to connect a particular wing pattern with the negative experience of distastefulness or escape, eventually avoiding this butterfly and striking the control instead. In a final test, they were given four butterflies at the same time: the plain brown butterfly and all three Adelpha butterflies, including one with the pattern they had seen before.

They strongly avoided the butterfly they had learned to associate with the bitter almond or fast flight and often avoided butterflies that shared a similar color or pattern.

Birds were 1.6 times more likely to attack the distasteful butterfly than evasive ones, perhaps because they had varying levels of tolerance for the bad-tasting almond, said Páez, who co-led the study with Valkonen. After all, even a bitter morsel of food is better than nothing.

“Bad-tasting prey could provide a nutritive meal whereas missing prey completely cannot,” she said.

While birds tend to avoid colorful prey by default, the study provides evidence of learned behavior, Willmott said.

“This potentially explains many cases of apparent mimicry that lacked evidence of chemical defense.”

Matos-Maraví of the Biology Centre, Czech Academy of Sciences, and Mappes of the University of Jyväskylä and the University of Helsinki also co-authored the study.

Avoidance of wind turbines can decrease collision mortality for birds, but can also make it more difficult and time-consuming for migrating flocks to find safe and suitable rest and refueling locations. The study’s insights into migratory behavior could improve future siting decisions as wind energy infrastructure continues to expand.

“In the past, federal agencies had thought of impacts related to wind energy primarily associated with collision risks,” said Aaron Pearse, the paper’s first author and a research wildlife biologist for the U.S. Geological Survey’s Northern Prairie Wildlife Research Center in Jamestown, N.D. “I think this research changes that paradigm to a greater focus on potential impacts to important migration habitats.”

The study tracked whooping cranes migrating across the Great Plains, a region that encompasses a mosaic of croplands, grasslands and wetlands. The region has seen a rapid proliferation of wind energy infrastructure in recent years: in 2010, there were 2,215 wind towers within the whooping crane migration corridor that the study focused on; by 2016, when the study ended, there were 7,622 wind towers within the same area.

Pearse and his colleagues found that whooping cranes migrating across the study area in 2010 and 2016 were 20 times more likely to select “rest stop” locations at least 5 km away from wind turbines than those closer to turbines.

The authors estimated that 5% of high-quality stopover habitat in the study area was affected by presence of wind towers. Siting wind infrastructure outside of whooping cranes’ migration corridor would reduce the risk of further habitat loss not only for whooping cranes, but also for millions of other birds that use the same land for breeding, migration, and wintering habitat.

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“Rice is the primary crop in India, China, and other countries in Southeast Asia. Rice consumption is also growing in the U.S. and elsewhere in the world,” says Prasanta Kalita, professor in the Department of Agricultural and Biological Engineering at U of I and lead author on the study.

“If you look at where they traditionally grow rice, it is countries that have plenty of water, or at least they used to. They have tropical weather with heavy rainfall they depend on for rice production. Overall, about 4,000 liters of water go into production and processing per kilogram of rice,” he states.

Climate change is likely to affect future water availability, and rice farmers must implement new management practices to sustain production and increase yield, Kalita says.

The United Nations’ Food and Agriculture Organization (FAO) estimates the world population will grow by two billion people by 2050, and food demand will increase by 60%.

“We will need multiple efforts to meet that demand,” Kalita states. “And with two billion more people, we will also need more water for crop production, drinking water, and industrial use.”

Kalita and his colleagues conducted the study at the Borlaug Institute for South Asia’s research farm in Bihar, India. Farmers in the region grow rice during the monsoon season, when heavy rainfall sustains the crop.

The researchers collected data on rice yield and climate conditions, then used computer simulations to model future scenarios based on four global climate models. The purpose of the study was to estimate rice yield and water demand by 2050, and evaluate how farmers can adapt to the effects of climate change.

“As the weather changes, it affects temperature, rainfall, and carbon dioxide concentration. These are essential ingredients for crop growth, especially for rice. It’s a complicated system, and effects are difficult to evaluate and manage,” Kalita states.

“Our modeling results show the crop growth stage is shrinking. The time for total maturity from the day you plant to the day you harvest is getting shorter. The crops are maturing faster, and as a result, you don’t get the full potential of the yield.”

If farmers maintain current practices, rice yield will decrease substantially by 2050, the study shows. But various management strategies can mitigate the effects of climate change, and the researchers provide a series of recommendations.

Traditional rice farming involves flooding the fields with water. Rice transplants need about six inches of standing water. If fields aren’t level, it requires even more water to cover the crops, Kalita says. However, if farmers use direct-seeded rice instead of transplants, they can increase production while using significantly less water.

Another practice involves soil conservation technology. “The soil surface continuously loses water because of temperature, humidity, and wind. If you keep crop residue on the ground, it reduces the evaporation and preserves water. Furthermore, when the crop residue decomposes, it will help increase soil quality,” Kalita explains.

The researchers also suggest implementing strategies to prevent post-harvest crop losses. FAO estimates about 30% of crops are lost or wasted after harvest, so efforts to reduce those losses can further increase crop availability and food security.

Overall, the best approach to achieve a 60% increase in rice production while minimizing additional irrigation needs is a combination of conservation strategies and a 30% reduction in post-harvest loss, the researchers conclude.

But a more recent discovery by a research team — that includes two University of Wyoming faculty members — reveals the oldest documented site of an indiscriminate mass killing 6,200 years ago in what is now Potocani, Croatia.

“The DNA, combined with the archaeological and skeletal evidence — especially that indicating systematic violence, perhaps even execution-style — demonstrates an indiscriminate massacre and haphazard burial of 41 individuals from an early pastoralist community in what is now eastern Croatia,” says James Ahern, a UW professor in the Department of Anthropology and associate vice provost for graduate education.

Ahern was a nonsenior co-author of a paper, titled, “Genome-Wide Analysis of Nearly All the Victims of a 6,200-Year-Old Massacre,” that was published March 10 in PLOS ONE. The journal accepts research in over 200 subject areas across science, engineering, medicine, and the related social sciences and humanities.

Mario Novak, a research associate with the Institute for Anthropological Research in Zagreb, Croatia, was the paper’s lead author. Ivor Jankovic, a UW adjunct professor of anthropology and assistant director of the Institute for Anthropological Research, also was a nonsenior co-author of the study.

Other researchers who contributed to the paper were from the Universitat Pompeu Fabra in Barcelona, Spain; Harvard University; Archaeological Museum in Zagreb, Croatia; University of Zagreb; University of Vienna; Broad Institute of Harvard and Massachusetts Institute of Technology; and the Howard Hughes Medical Institute at Harvard Medical School.

In 2007, the Croatian site underwent a “rescue” excavation that occurred when the burial was uncovered during the construction of a garage on private land, Ahern says. Archaeologists, led by Jacqueline Balen of the Archaeological Museum in Zagreb, working nearby on a cultural resource impact assessment related to the construction of a motorway, were called in to investigate.

In 2012, Ahern and Jankovic, then a research scientist at the Institute for Anthropological Research, were invited by the archaeologists in charge of Potocani discoveries to analyze the skeletal remains. The skeletal remains needed to be cleaned and inventoried, and basic analysis — such as estimation of age and sex, recording of preserved elements, and basic documentation of pathologies and trauma — was conducted by Jankovic, Ahern and Zrinka Premuzic, a Ph.D. student at the University of Zagreb.

“This is the oldest known case of indiscriminate, mass killing that we know of,” Ahern says. “In some ways, it goes against the conventional wisdom about early agriculturalists — the Neolithic and Eneolithic — who have long been thought to have lived in small villages or herding groups.

“The DNA evidence indicates just a few close relatives in such a large sample, meaning that, not only was the violence seemingly indiscriminate, it involved a subset of a much larger local population.”

Prior research shows that some early farmers lived in large settlements, such as at Catalhoyuk in Western Asia; and some later Eneolithic peoples, such as those who lived at the Vucedol site in the Balkans. However, Potocani is approximately 1,000 years older than the latter settlement.

The genetic analysis revealed that 70 percent of the analyzed skeletons did not have close kin among the deceased. Additionally, there was no sex bias, as the number of males and females found at the site were almost equal in number. This indicates the massacre was not the outcome of inter-male fighting one would expect in battles, nor was the result of a reprisal event targeting individuals of a specific sex.

Cranial injuries were found on 13 of the 41 individuals massacred at the site, according to the study.

“Although we do not have evidence on the cause of death for the other individuals, their deaths were almost certainly violent,” Ahern says. “Multiple radiocarbon dates, as well as the sedimentology of the burial, all indicate a single burial event.

“Furthermore, a majority of violent deaths do not leave clear evidence of trauma in the preserved skeletal remains,” he continues. “Individuals could have been strangled, bludgeoned, cut or stabbed in soft-tissue areas or in manners that did not damage underlying bones.”

The study also considered the potential role of climate change in the mass burial event. When climate changes, resources such as water, vegetation — including feed for cattle and other livestock — and game animals become less predictable. Furthermore, hazards, such as unpredictable extreme weather, become more common.

“These factors tend to disrupt human lifeways, and groups sometimes try to take over others’ territories and resources,” Ahern explains. “Increases in population size cause groups to overextend their local resources and require expansion into other areas. Both climate change and population increase tend to cause social disruption and violent acts, such as what happened at Potocani, that become more common as groups come into conflict with each other.”

Data in the study reveal how organized violence in this period could be indiscriminate, just as indiscriminate killings have been an important feature of life in historic and modern times. The history, development and causes of human violence are crucial to our ability to understand and reduce violence in our own society, Ahern says.

“Perhaps, because of the long history of human violence and warfare and its contemporary relevance, the public is engaged by the sort of narrative about the deep human past that we’ve been able to recreate through our scientific research,” Ahern says. “Furthermore, DNA, heredity and human ancestry are issues that touch everyone’s lives. Our research also highlights UW’s global engagement and research enterprise.”

The Scythian people, who lived across the Pontic steppe around 700-200 BCE, are often portrayed as a culture of nomadic warriors. But this idea is challenged by archaeological evidence that indicates a more complex and varied culture at this place and time. In this study, researchers employed isotopic analyses to investigate patterns of diet and mobility in Scythian populations.

The authors measured isotopes of carbon, nitrogen, oxygen, and strontium in human teeth and bones from several Scythian-era burial sites in Ukraine. Isotopes that reflect diet, indicate that in some places there was a varied diet including numerous domesticated crops, while isotopes that reflect geologic surroundings indicate that most people did not travel long distances during their lifetimes.

These results support the growing understanding that Scythian populations were not a homogenous culture, but a more diverse group which, in some places, lived more sedentary lives with a dependence on agriculture. The authors suggest that future studies should expand this work to compare multiple generations of people over more varied geographical locations. This work will help archaeologists move toward a more complete idea of what it meant to be Scythian.

The authors add: “Our multi-isotopic study challenges romantic notions of wide-ranging Scythian nomads. We show that while some individuals from classic Scythian contexts traveled long distances, the majority remained local to their settlements, farming millet and raising livestock in mixed economic systems.”

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