A trio of biologists at the University of Minnesota has found that when male crickets need to save energy, they narrow their mating filter, to focus more exclusively on females.

In their paper published in the Proceedings of the National Academy of Sciences, Jon Richardson, Isabelle Hoversten and Marlene Zuk describe experiments they conducted with sexual filters in Pacific field crickets on varied diets and what they learned from them.

Prior research has found that some biologists, including zoologists, have left out data related to same-sex sexual behavior (SSB) during their research efforts, making it more difficult to understand such behavior in non-human creatures. Still, the research has shown that SSB is quite common in the wild across a range of creatures.

Such behavior is under investigation because it tends to take up a lot of energy and may even put some creatures at risk, without an apparent evolutionary advantage. In this new study, the research team focused their efforts on the idea of mating filters—where a creature increases or decreases its area of interest regarding its sexual behavior.

They chose to study certain aspects of male sexual behavior in the Pacific field cricket—a creature that is known to attempt to mate with both males and females of its kind. Prior research has shown that interest by males can be measured by tracking the intensity, or lack thereof, of the crickets’ short-range courtship songs. Females have been found to be less receptive to males who fail to produce quality short-range tunes.

The experiment consisted of putting some of the males on a well-fed diet, and others on a restricted calorie diet. Members of each group were then given access to other crickets fed a normal diet to see if they would attempt to mate with them.

In watching and recording the behavior of the test males, the research team found that the hungry crickets were less likely than the well-fed crickets to attempt mating with other males—an example of narrowing their mating filter. They found no such change in attempts at mating with females. The researchers also found no change in the males that had been well-fed.

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Off the coast of Chile, in waters filled with krill and anchovy by the Humboldt Current system, live an elusive and little-known population of orcas. Thanks to citizen science and years of dedicated surveillance, a team of scientists led by Dr. Ana García Cegarra of the Universidad de Antofagasta is unveiling their secrets—starting with dinner.

García Cegarra’s team, who previously observed these orcas using fishing boats to help them capture sea lions, have now spotted them successfully hunting dusky dolphins for the first time and sharing the food among the pod. This new evidence about their eating habits may help experts understand how populations of orcas in the southern hemisphere are linked, promoting conservation efforts.

“Studying orcas in their natural environment is very challenging as they are marine top predators, traveling long distances and living offshore, which makes observation difficult,” said García Cegarra, lead author of the study in Frontiers in Marine Science. “But understanding their role in the marine environment is crucial for the conservation of this poorly-known species in the Humboldt Current.”

You are what you eat

Orcas are apex predators with an impressively varied diet—but not all orcas eat the same things. Populations can be assigned to different ecotypes based on their preferred foods, acoustics, and genetics, so understanding what the orcas of the Humboldt Current eat is a major step towards understanding where they fit in among the other orcas of the world.

Five different ecotypes are reported in the southern hemisphere: some, like Type A and Type B1 orcas, focus on marine mammals, while other types prefer fish. Understanding where the Humboldt Current animals fit in would help us understand the way these populations relate to each other more broadly and conserve them for the future.

García Cegarra and her colleagues used a combination of their own surveys and citizen science data collection from whale-watching trips and fishing vessels to monitor the population and track their hunting choices. Observers recorded the presence of orcas, group composition and location, and took pictures and videos which the scientists could cross-reference with catalogs of known individuals.

By combining this data with their own systematic surveys and drone footage, the scientists built up a map of orca presence in the area and tracked pods’ behavior and prey choices.

This allowed the researchers to capture evidence of the Menacho pod of orcas catching dusky dolphins—a species no orcas in this area have ever been reported successfully hunting. Dramatic images show the matriarch, Dakota, tossing a dusky dolphin into the air.

These sightings could indicate that these orcas may belong to the mammal-hunting Type A ecotype. Their prey, and their small pod sizes, would be consistent with this hypothesis, although their white eye patches are smaller than is typical of Type A orcas. They have also never been recorded in Patagonia with other Type A orcas.

“We wish we could obtain skin biopsy samples to analyze their genetic data, as there is no genetic information for orcas in this region of the south-east Pacific,” said García Cegarra. “However, they are very elusive and intelligent, which makes it difficult to approach them in the boat for biopsies.”

Sharing the spoils

The scientists’ observations of the dusky dolphin hunting also revealed that the Menacho pod were sharing their food. Food sharing is recorded among many populations of orcas, sometimes to help feed kin, and sometimes because the pod hunts cooperatively and everyone gets a share.

In this case, García Cegarra and her colleagues suggest that the Menacho pod were sharing food with kin, similar to Type A orcas who hunt sea lions by deliberately stranding: female orcas were seen sharing meat with group members, allowing closer relations to eat first.

García Cegarra emphasized that much more information and systematic study is necessary to fully understand and protect this secretive population of orcas.

“The fact that we have observed newborn calves is important, because it indicates that they are having offspring, but we don’t know their survival rate,” she said. “Thanks to citizen science, we can follow the presence of killer whales along thousands of kilometers of the coast of northern Chile—but most orca sightings are opportunistic.”

When thinking of animal camouflage, we typically imagine creatures remaining still, blending seamlessly into their surroundings. But remaining motionless isn’t always practical, and many animals are highly mobile, constantly moving through their environment to graze their food.

New research suggests that high-contrast patterns on animals’ bodies may serve a dual purpose: offering camouflage when stationary, then creating a ‘motion dazzle’ effect when moving, confusing potential predators into misjudging their location—and helping them avoid being eaten.

The study, by Dr. Louise Tosetto, Professor Nathan Hart and Dr. Laura Ryan from Macquarie University’s School of Natural Sciences and published in PeerJ, is the first to show that humbug damselfish—known for their striking black and white stripes—use motion dazzle as a defense strategy.

“Our findings also show that humbug damselfish adapt their behavior based on their environment,” says Dr. Tosetto.

“In their natural habitat, when they encounter backgrounds resembling their own striped patterns, like branching corals, they tend to move closer and reduce their movement. This likely helps them blend in and stay hidden from predators.

“However, when feeding outside the coral colony, where camouflage is less effective, they increase their movement and rely more on the confusing effects of their stripes, known as motion dazzle.”

Methodical study

Humbug damselfish are small, striped coral reef fish that often live in social groups protected by branching corals. While their stripes help camouflage them when still, these fish frequently move to feed, risking predator attacks.

The research team studied how different backgrounds might affect the fish’s ability to confuse predators using motion dazzle, by filming humbugs swimming in tanks against various striped backgrounds, then using computer models to simulate how predators like coral trout would see this movement.

They also used anatomical data from the retinas of humbug damselfish to help understand how clearly the fish might see different striped patterns in their environment.

The team found that when they were against backgrounds where predators would find it hard to see them clearly, humbugs tended to move closer to the background and increase their overall movement, so their own stripes would create confusing motion cues—anti-predator behavior.

But when the background had clear, wider stripes that predators could easily see, the fish gained two advantages. First, the edges of their bodies became less distinct, making them harder to spot. Second, the combination of their own stripes and the background stripes created confusing motion signals (motion dazzling), so predators couldn’t accurately judge the speed or direction of the humbug fish.

“This suggests that humbugs can see different backgrounds and might then change their behavior to improve their protection from predators,” Dr. Tosetto says.

Senior author Dr. Ryan says the findings show that these fish have complex anti-predator strategies.

“This is an essential baseline study that provides new insights into the motion dazzle phenomenon,” says Dr. Ryan.

“Future research should investigate how factors like the water’s light-filtering properties and interactions with other damselfish might affect motion dazzle. The humbug damselfish offers a perfect model to explore these important questions.”

This content was originally published on The Macquarie University Lighthouse.