“Fish make hanging motionless in the water column look effortless, and scientists had long assumed that this meant it was a type of rest,” begins the article. However, a new study reveals that fish use nearly twice as much energy when hovering in place compared to resting.

The study, led by scientists at the University of California San Diego’s Scripps Institution of Oceanography, also details the biomechanics of fish hovering, which includes constant, subtle fin movements to prevent tipping, drifting or rolling. This more robust understanding of how fish actively maintain their position could inform the design of underwater robots or drones facing similar challenges.

The findings, published on July 7 in the Proceedings of the National Academy of Sciences, overturn the long-standing assumption in the scientific literature that maintaining a stationary position in water is virtually effortless for fish with swim bladders. The reason for this assumption was that nearly all bony fishes have gas-filled sacs called swim bladders that allow them to achieve neutral buoyancy — neither sinking nor rising to the surface. The presence of a swim bladder and the stillness of hovering fish caused the research community to assume hovering was a form of rest that was easy for fish to maintain.

Prior research from lead study author and Scripps marine biologist Valentina Di Santo found that the energy required for skates to swim at various speeds followed a distinct U-shaped curve, with slow and fast swimming requiring the most energy and intermediate speeds being the most energy-efficient. Based on these findings, Di Santo suspected there might be more to hovering than meets the eye.

To learn more, Di Santo and her co-authors conducted experiments with 13 species of fishes with swim bladders. The team placed each fish in a specialized tank and recorded their oxygen consumption during active hovering and motionless resting (when the fish supports its weight with the bottom of the tank). While the fish were hovering, the researchers filmed them with high-speed cameras to capture their fin movements, tracking how each fin moved and how frequently they beat.

The researchers also took a variety of measurements of each fish’s body size and shape. In particular, the scientists measured the physical separation between the fish’s center of mass, which is determined by weight distribution, and its center of buoyancy, which is related to the shape and location of its swim bladder. All these measurements provided a way to quantify how stable or unstable each fish was.

The study found that, contrary to previous assumptions, hovering burns roughly twice as much energy as resting. “Hovering is a bit like trying to balance on a bicycle that’s not moving,” said Di Santo.

Despite having swim bladders that make them nearly weightless, fish are inherently unstable because their center of mass and center of buoyancy don’t align perfectly. This separation creates a tendency to tip and roll, forcing fish to make continuous adjustments with their fins to maintain position. The study found that species with greater separation between their centers of mass and buoyancy used more energy when hovering. This suggests that counteracting instability is one of the factors driving the energy expended during hovering.

“What struck me was how superbly all these fishes maintain a stable posture, despite their intrinsic instability,” said Di Santo.

A fish’s shape and the position of its pectoral fins also influenced its hovering efficiency. Fish with pectoral fins farther back on their body were generally able to burn less energy while hovering, which Di Santo suggested may be due to improved leverage. Long, slender fish, such as the shell dweller cichlid (Lamprologus ocellatus) and the angelfish (Pterophyllum scalare), were found to be less efficient hoverers compared to more compact species like the guppy (Poecilia reticulata) and the zebrafish (Danio rerio).

The study’s findings have significant implications for the design of underwater robots. “By studying how fish achieve this balance, we can gain powerful design principles for building more efficient, responsive underwater technologies,” said Di Santo.

In particular, the findings could help improve the maneuverability of underwater robots, which could allow them to access and explore complex, hard-to-navigate environments like coral reefs or shipwrecks. According to Di Santo, underwater robots have historically been designed with compact shapes that make them stable. As in fish, shapes with more built-in stability are less maneuverable.

“If you want a robot that can maneuver through tight spaces, you might have to learn from these fishes to design in some instability and then add systems that can dynamically maintain stability when needed,” said Di Santo.

The study was co-authored by Xuewei Qi of Stockholm University, Fidji Berio of Scripps Oceanography, Angela Albi of Stockholm University, the Max Planck Institute of Animal Behavior, and the University of Konstanz, and Otar Akanyeti of Aberystwyth University in Wales. The research was supported by the Swedish Research Council, the European Commission, the Stockholm University Brain Imaging Centre and the Whitman Scientist Program at the Marine Biological Laboratory.

In a groundbreaking study published online on June 18 in iScience, researchers have found that female chimpanzees who were more socially integrated with other females before giving birth had a significantly higher chance of raising surviving offspring. This discovery sheds light on the crucial role of social connections among female chimps, particularly in the absence of close kin.

The study, led by Joseph Feldblum, assistant research professor of evolutionary anthropology at Duke University, analyzed three decades’ worth of behavioral data from 37 mothers and their 110 offspring. The researchers focused on association and grooming behavior – how often females spent time near each other or engaged in social grooming – in the year before birth.

The results showed that females who were more socially connected had a considerable better chance of raising their babies through to their first year, the period of highest infant mortality. In fact, a female with a sociality score twice the community average had a 95% chance her infant would survive the first year, while one who was halfway below average saw that chance drop to 75%. The effect persisted through age five, which is roughly the age of weaning.

Interestingly, the researchers found that having close female kin in the group – like a sister or mother – did not account for the survival benefit. Neither did having bonds with males, who could potentially offer protection. What mattered most was having social connections with other females, regardless of kinship.

“This tells us it’s not just about being born into a supportive family,” said Feldblum. “These are primarily social relationships with non-kin.”

The researchers propose several possibilities for the survival benefit, including:

* Social females receiving less harassment from other females
* More help defending food patches or protecting their young
* Offspring being less likely to be killed by another group member
* Social connections helping these females stay in better condition – maybe better fed and less stressed – through pregnancy, giving their offspring a better chance from the get-go.

Moreover, social females stayed social after their babies were born – a sign of stable relationships, not short-term alliances. “Our results don’t prove causation, but they point to the value of being surrounded by others who support you, or at least tolerate you,” said Feldblum.

This study has significant implications for understanding human evolution and cooperation. As Feldblum noted, “Human females who don’t have access to kin – for example because they moved to a new city or village – are still able to form strong bonds that can benefit them.” Studying these social dynamics in chimpanzees can help us understand how we evolved to be the social, cooperative species we are today.

The world’s oceans are home to an incredible array of marine life, from massive blue whales to tiny plankton. However, many of these ocean giants are facing significant threats, including overfishing, pollution, and climate change. A recent study has shed new light on the plight of these marine animals, using satellite tracking data to pinpoint where they need the most protection.

Led by Ana Sequeira of Australian National University and supported by the United Nations, the research project, called MegaMove, brought together nearly 400 scientists from over 50 countries. The team used biologging data collected from satellite tags to inform a new blueprint for ocean conservation.

“This is one of the largest marine tracking data sets ever assembled,” said Francesco Ferretti, a marine ecologist at Virginia Tech who contributed to the study. “It’s not just about drawing lines on a map. We need to understand animal behavior and overlap that with human activity to find the best solutions.”

The research revealed some startling insights into the migratory patterns of these ocean giants. For example, Virginia’s coastline is part of a major migratory corridor for marine species, including sharks, which play a critical role in maintaining healthy marine ecosystems.

“Sharks, for example, play a critical role in maintaining healthy marine ecosystems, which in turn support fisheries and recreation,” Ferretti said. “What happens to apex predators can ripple across the food web and impact local economies.”

Past collapses of shellfish fisheries in North Carolina and impacts on seagrasses meadows have shown how predator loss can shift entire ecosystems.

The MegaMove project aimed to inform the United Nations’ 30×30 target: a global goal to protect 30 percent of the world’s oceans by 2030. However, the findings show that even if all 30 percent of protected areas were perfectly placed, it wouldn’t be enough.

“Sixty percent of the tracked animals’ critical habitats would be still outside these zones,” Ferretti said. “In addition to protected areas, we need targeted mitigation, changing fishing practices, rerouting shipping lanes, and reducing pollution.”

The project highlights the importance of collaboration and global science in addressing these challenges. Virginia Tech’s participation reflects a broader push to contribute to international, data-driven science.

“This project shows where the field is heading,” Ferretti said. “We’re seeing a revolution in big data approaches in marine science. Students need to be trained not only in fieldwork but in data science to meet future challenges.”

The MegaMove project can also help inspire the next generation of researchers and showcase how Virginia Tech connects local talent to worldwide impact.