Wolves in Yellowstone, USA, new study


This video is called [2017] – National Geographic Documentary Wild – Wild Yellowstone She Wolf HD.

From S.J. & Jessie E. Quinney College of Natural Resources, Utah State University in the USA:

Wolf reintroduction: Yellowstone’s ‘landscape of fear’ not so scary after all

June 22, 2018

After wolves were reintroduced to Yellowstone National Park in the mid-1990s, some scientists thought the large predator reestablished a ‘landscape of fear’ that caused elk,

North American elk should not be confused with still larger moose (Alces alces) to which the name “elk” applies in British English and in reference to populations in Eurasia.

the wolf‘s main prey, to avoid risky places where wolves killed them. This fueled the emerging idea that predators affect prey populations and ecosystems not only by eating prey animals, but by scaring them too. But according to findings from Utah State University ecologists Michel Kohl and Dan MacNulty, Yellowstone’s ‘landscape of fear’ is not as scary as first thought.

“Contrary to popular belief, the wolf is not a round-the-clock threat to elk; it mostly hunts at dawn and dusk, and this allows elk to safely access risky places during nightly lulls in wolf activity”, says Kohl, who completed a doctoral degree at USU in 2018 and is lead author of the paper. “Despite their Hollywood portrayal as nighttime prowlers, wolves tend to hunker down at night because their vision is not optimized for nocturnal hunting.” With colleagues Daniel Stahler, Douglas Smith, and P.J. White of the U.S. National Park Service, Matthew Metz of University of Montana, James Forester of University of Minnesota, Matthew Kauffman of University of Wyoming, and Nathan Varley of University of Alberta, Kohl and MacNulty report their findings in an Early View online article of Ecological Monographs. The article will appear in a future print edition of the Ecological Society of America publication. The team’s research is supported, in part, by the National Science Foundation.

The researchers revisited data from 27 GPS radio-collared elk that had been collected in the early years after the reintroduction, 2001-2004, but never fully analyzed. These collars recorded the location of each elk every 4-6 hours. This was the first time GPS technology had been used to track Yellowstone elk, and no one imagined that elk might sync their habitat use to the wolf’s 24-hour schedule. Little was known about this schedule until researchers first equipped wolves with GPS collars in 2004.

“In the days before GPS, when we tracked wolves by sight and with VHF radio-telemetry, we knew they hunted mainly in the morning and evening, but we didn’t know much about what they did at night” says MacNulty, a veteran Yellowstone wolf researcher and associate professor in USU’s Department of Wildland Resources and the USU Ecology Center. “GPS data showed that wolves were about as inactive in the middle of the night as they were in the middle of the day.”

Kohl used the GPS data to quantify the 24-hour schedule of wolves, and he compared how elk use of risky places — sites where wolves killed elk — differed between periods of high and low wolf activity. “Elk avoided the riskiest places when wolves were most active, but they had no problem using these same places when wolves were least active,” says Kohl. “An elk’s perception of a place as dangerous or safe, its landscape of fear, was highly dynamic with ‘peaks’ and ‘valleys’ that alternated across the 24-hr cycle in response to the ups and downs of wolf activity.”

The ability of elk to regularly use risky places during wolf downtimes has implications for understanding the impact of wolves on elk and the ecosystem at large. “Our results can explain why many other studies found no clear-cut effect of wolf predation risk on elk stress levels, body condition, pregnancy, or herbivory”, says MacNulty. “If our results reflect typical elk behavior, then actual killing rather than fear probably drives most, if not all, of the effect of wolves on elk and any cascading effect on the plants that elk eat such as aspen and willow.”

This conclusion runs counter to popular views about the ecological importance of fear in Yellowstone and elsewhere. “Although our study is the first to show how a prey animal uses predator downtime to flatten its landscape of fear, I suspect other examples will emerge as more researchers examine the intersection between prey habitat use and predator activity rhythms”, says Kohl.

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Snowshoe hares’ camouflage, new study


This 2015 video is called Epic Hunting Chase of the Canadian Lynx and Snowshoe Hare in HD.

From The University of Montana in the USA:

How snowshoe hares evolved to stay seasonally camouflaged

June 21, 2018

Many animals have evolved fur or feather colors to blend in with the environment and hide from predators. But how do animals stay camouflaged when their environment changes with each new season? Researchers at the University of Montana recently discovered that hybridization played an important role in snowshoe hares’ ability to match their environment.

An international scientific team led by UM Associate Professor Jeffrey Good and graduate student Matthew Jones set out to discover how snowshoe hares have evolved to molt to a white coat in areas with prolonged winter snow cover while populations from mild coastal environments of the Pacific Northwest retain brown fur year-round.

“Like other seasonal traits, the autumn molt in snowshoe hares is triggered by changes in day length”m Good said. “But the color of their winter coat is determined by genetic variation that has been shaped by evolution to match the local presence or absence of snow.”

In a new article published in the journal Science, Good’s team discovered that the development of brown or white winter coats in snowshoe hares is controlled by genetic variation at a single pigmentation gene that is activated during the autumn molt.

“This result is exciting because it shows that critical adaptive shifts in seasonal camouflage can evolve through changes in the regulation of a single gene,” Jones said.

The genetic discovery came with a surprising twist.

“When we looked at the same gene in other closely related species”, Jones said, “we found that the brown version of the gene in snowshoe hares was recently acquired from interbreeding with black-tail jackrabbits, another North American species that remains brown in the winter.”

Hybridization between species has played a key role in the development of many domestic plants and animals, and recent research suggests that it is also surprisingly common in nature. In snowshoe hares, hybridization with black-tailed jackrabbits provided critical coat color variation needed to adapt to coastal areas where winter snow is ephemeral or absent. But what does this mean for snowshoe hares going forward?

“Brown winter coats are currently rare across the range of snowshoe hares”, Good said. “If snow cover continues to decrease due to climate change, brown winter coats may become more common in the future and play a critical role in the resilience of this species. These discoveries are helping us understand how organisms adapt to rapidly changing environments.”

UM Professor Scott Mills is a co-author on the paper. For this research, UM partnered with the Universidade do Porto and CIBIO-InBIO in Portugal, North Carolina State University, Arizona State University, Ecole Polytechnique Fédérale de Lausanne in Switzerland and University of Cambridge in the United Kingdom.

Zebrafish see well, new study


This 2017 video is called Eyes of Zebra fish may help unveil cure for human blindness, say scientists.

From the University of Sussex in England:

Zebrafish‘s near 360 degree UV-vision knocks stripes off Google Street View

June 21, 2018

Summary: A zebrafish view of the world has been forensically analyzed by researchers to reveal that how they see their surroundings changes hugely depending on what direction they are looking.

Tiny freshwater fish have a view of the world that blows Google Street View out of the water — using different parts of their eyes to deliver optimum uses of colour, black-and-white and ultraviolet.

A zebrafish view of the world has been forensically analysed by researchers at the University of Sussex to reveal that how they see their surroundings changes hugely depending on what direction they are looking.

The study of the colour vision system of zebrafish larvae, published today in Current Biology, reveals they use their near 360 degree view of their world to detect threatening silhouettes above them in black-and-white but can seek out the almost transparent single-cell organisms they feed on by detecting the scattering of light in UV.

Dr Tom Baden, a senior lecturer in neuroscience at the University of Sussex who led the research, said: “By measuring the activity of thousands of neurons in the live animal while presenting visual stimuli, we established that different parts of their retinas, looking at different parts of the visual world, do different things. This multi-faceted view makes perfect sense for zebrafish as that’s how colour is distributed in their natural habitat. In their natural visual world, most colour information is on the ground and the horizon but above them the objects of most interest are dark silhouettes, so colour vision here is rather pointless.”

The study is the first in-depth physiological description of any vertebrate’s retinal setup for colour vision that uses “4 input colours” which includes a large proportion of non-mammal species such as most birds, reptiles, amphibians and fish. By comparison humans only use three and mice, dogs and horses only two.

The researchers say little is understood on how colour vision based on four or more spectral inputs works at a neuronal level but their paper, should help pave the way for further discoveries in this field. The team custom-built a hyperspectral scanner that allowed them to capture the full spectrum of light in the zebrafish natural world at each pixel including for UV vision.

The study found that zebrafish, who during larval and juvenile life stages live mostly in shallow, low current pockets on the sides of streams and rice paddies, only seem to use their colour vision repertoire for looking down and along the horizon, use colour-blind circuits for looking straight up and extremely sensitive ultraviolet vision for looking forward and upwards.

The zebrafish has made a supreme evolutionary effort to develop this superior vision, with about half of all its neurons inside the eyes making up nearly a quarter of their total body volume and requiring substantial metabolic investment. Similar ratios on a human being would mean eyes around the size of a large grapefruit which would require an optic nerve the width of an arm.

Dr Baden said: “Clearly, animals like zebrafish use specialised strategies to better navigate their natural environment by adjusting their eyes to look out for different things in different parts of their visual field. In contrast, technology has not really caught up with these types of ideas. For example, most standard camera systems still “blindly” use the same type of light detection and compression across an entire image even if half the image shows bright blue sky and the other half the overgrown and shadowed ground.”

New Sri Lankan spiders get Enid Blyton names


This video says about itself:

Science Bulletins: Seeking Spiders—Biodiversity on a Different Scale

4 October 2012

Recognizing the tiny species of any ecosystem is hugely important for defining its overall diversity. But miniscule forms of life are often invisible to conservation efforts because they have yet to be described in detail. Dr. Norman Platnick of the American Museum of Natural History is leading an important initiative to discover biodiversity on a smaller scale. Having devoted decades to the study of spiders, Dr. Platnick now leads a team of 45 investigators from 10 countries in the largest-ever research project on spiders, identifying members of the goblin spider family. This group of spiders is widely distributed but largely unknown, primarily due to their small size—at 1.2-3mm, they measure one-half to one-third the length of the average spider. This video follows Dr. Platnick’s team into the Ecuadorian jungle as they collect and identify scores of unrecognized goblin spiders, showing how little we know about the full breadth of global biodiversity.

From ScienceDaily:

Six new species of goblin spiders named after famous goblins and brownies

June 21, 2018

Summary: A remarkably high diversity of goblin spiders is reported from the Sri Lankan forests. Nine new species are described in a recent paper, where six are named after goblins and brownies from Enid Blyton‘s children’s books. There are now 45 goblin spider species belonging to 13 genera known to inhabit the island country.

Fictional characters originally ‘described’ by famous English children’s writer Enid Blyton have given their names to six new species of minute goblin spiders discovered in the diminishing forests of Sri Lanka.

The goblins Bom, Snooky and Tumpy and the brownies Chippy, Snippy and Tiggy made their way from the pages of: “The Goblins Looking-Glass” (1947), “Billy’s Little Boats” (1971) and “The Firework Goblins” (1971) to the scientific literature in a quest to shed light on the remarkable biodiversity of the island country of Sri Lanka, Indian Ocean.

As a result of their own adventure, which included sifting through the leaf litter of the local forests, scientists Prof. Suresh P. Benjamin and Ms. Sasanka Ranasinghe of the National Institute of Fundamental Studies, Sri Lanka, described a total of nine goblin spider species in six genera as new to science. Two of these genera are reported for the very first time from outside Australia.

Their paper is published in the open access journal Evolutionary Systematics.

With a total of 45 species in 13 genera, the goblin spider fauna in Sri Lanka — a country taking up merely 65,610 km2 — is already remarkably abundant. Moreover, apart from their diversity, these spiders amaze with their extreme endemism. While some of the six-eyed goblins can only be found at a few sites, other species can be seen nowhere outside a single forest patch.

“Being short-range endemics with very restricted distributions, these species may prove to be very important when it comes to monitoring the effects of climate change and other threats for the forest habitats in Sri Lanka”, explain the researchers.

In European folklore, goblins and brownies are known as closely related small and often mischievous fairy-like creatures, which live in human homes and even do chores while the family is asleep, since they avoid being seen. In exchange, they expect from their ‘hosts’ to leave food for them.

Similarly, at size of a few millimetres, goblin spiders are extremely tough to notice on the forest floors they call home. Further, taking into consideration the anthropogenic factors affecting their habitat, the arachnids also turn out to be heavily dependent on humans.

Dinosaur tongues, new research


This 2017 video is called How to Sculpt a Dinosaur Part 2 – Eyes, Teeth, Tongue & Skin Texture – PREVIEW.

From the University of Texas at Austin in the USA:

T. Rex couldn’t stick out its tongue

June 20, 2018

Dinosaurs are often depicted as fierce creatures, baring their teeth, with tongues wildly stretching from their mouths like giant, deranged lizards. But new research reveals a major problem with this classic image: Dinosaurs couldn’t stick out their tongues like lizards. Instead, their tongues were probably rooted to the bottoms of their mouths in a manner akin to alligators.

Researchers from The University of Texas at Austin and the Chinese Academy of Sciences made the discovery by comparing the hyoid bones — the bones that support and ground the tongue — of modern birds and crocodiles with those of their extinct dinosaur relatives. In addition to challenging depictions of dino tongues, the research proposes a connection on the origin of flight and an increase in tongue diversity and mobility.

The research was published June 20 in the journal PLOS ONE.

“Tongues are often overlooked. But, they offer key insights into the lifestyles of extinct animals,” said lead author Zhiheng Li, an associate professor at the Key Laboratory of Vertebrate Evolution and Human Origins of the Chinese Academy of Sciences.He conducted the work while earning his Ph.D. at the UT Jackson School of Geosciences.

The researchers made their discovery by comparing the hyoid bones of extinct dinosaurs, pterosaurs and alligators to the hyoid bones and muscles of modern birds and alligator specimens. Hyoid bones act as anchors for the tongue in most animals, but in birds these bones can extend to the tip. Because extinct dinosaurs are related to crocodiles, pterosaurs and modern birds, comparing anatomy across these groups can help scientists understand the similarities and differences in tongue anatomy and how traits evolved through time and across different lineages.

The comparison process involved taking high-resolution images of hyoid muscles and bones from 15 modern specimens, including three alligators and 13 bird species as diverse as ostriches and ducks, at the Jackson School’s High-Resolution X-Ray Computed Tomography Facility (UTCT). The fossil specimens, most from northeastern China, were scrutinized for preservation of the delicate tongue bones and included small bird-like dinosaurs, as well as pterosaurs and a Tyrannosaurus rex.

The results indicate that hyoid bones of most dinosaurs were like those of alligators and crocodiles — short, simple and connected to a tongue that was not very mobile. Co-author and Jackson School Professor Julia Clarke said that these findings mean that dramatic reconstructions that show dinosaurs with tongues stretching out from between their jaws are wrong.

“They’ve been reconstructed the wrong way for a long time”, Clarke said. “In most extinct dinosaurs their tongue bones are very short. And in crocodilians with similarly short hyoid bones, the tongue is totally fixed to the floor of the mouth.”

Clarke is no stranger to overturning dinosaur conventions. Her 2016 study on dinosaur vocalizations found evidence that large dinosaurs might make booming or cooing sounds, similar to the sounds made by crocodiles and ostriches.

In contrast to the short hyoid bones of crocodiles, the researchers found that pterosaurs, bird-like dinosaurs, and living birds have a great diversity in hyoid bone shapes. They think the range of shapes could be related to flight ability, or in the case of flightless birds such as ostriches and emus, evolved from an ancestor that could fly. The researchers propose that taking to the skies could have led to new ways of feeding that could be tied to diversity and mobility in tongues.

“Birds, in general, elaborate their tongue structure in remarkable ways”, Clarke said. “They are shocking.”

That elaboration could be related to the loss of dexterity that accompanied the transformation of hands into wings, Li said.

“If you can’t use a hand to manipulate prey, the tongue may become much more important to manipulate food”, Li said. “That is one of the hypotheses that we put forward.”

The scientists note one exception linking tongue diversity to flight. Ornithischian dinosaurs — a group that includes Triceratops, ankylosaurs and other plant-eating dinosaurs that chewed their food — had hyoid bones that were highly complex and more mobile, though they were structurally different from those of flying dinosaurs and pterosaurs.

Further research on other anatomical changes that occurred with shifts in tongue function could help improve our knowledge of the evolution of birds, Clarke said, giving an example of how changes in the tongues of living birds are associated with changes in the position of the opening of the windpipe. These changes could in turn affect how birds breathe and vocalize.

However, the researchers note that the fossil record as yet can’t pin down when these changes to the windpipe occurred.

“There is more work to be done,” Li said.

The study was funded by the Chinese Academy of Sciences, The University of Texas at Austin, the Smithsonian Institution and the Gordon and Betty Moore Foundation.

How primates got fingernails, new research


This 2016 video says about itself:

Nails evolved from claws roughly 50 million years ago. Why did this happen and what purpose do nails serve?

Oldest evidence of nails in modern primates: “From hot pink to traditional French and Lady Gaga‘s sophisticated designs, manicured nails have become the grammar of fashion. Scientists have now recovered and analyzed the oldest fossil evidence of fingernails in modern primates, confirming the idea nails developed with small body size and disproving previous theories nails evolved with an increase in primate body size.” Read more here.

“Which came first, the nail or the claw? The answer is unclear, but researchers have discovered a clue: an early primate that had a toe bone with features of both a grooming claw and a nail. A fossil of the 47-million-year-old primate, Notharctus tenebrosus, had a lemur-like grooming claw on its second digit, but it was flattened, a bit like a nail, according to a new study in the journal PLoS One.” Read more here.

Evidence for a Grooming Claw in a North American Adapiform Primate: Implications for Anthropoid Origins: “Among fossil primates, the Eocene adapiforms have been suggested as the closest relatives of living anthropoids (monkeys, apes, and humans). Central to this argument is the form of the second pedal digit. Extant strepsirrhines and tarsiers possess a grooming claw on this digit, while most anthropoids have a nail. While controversial, the possible presence of a nail in certain European adapiforms has been considered evidence for anthropoid affinities.” Read more here.

From the University of Florida in the USA:

Fossils show ancient primates had grooming claws as well as nails

Why don’t we have them? Maybe because we have each other

June 20, 2018

Humans and other primates are outliers among mammals for having nails instead of claws. But how, when and why we transitioned from claws to nails has been an evolutionary head-scratcher.

Now, new fossil evidence shows that ancient primates — including one of the oldest known, Teilhardina brandti — had specialized grooming claws as well as nails. The findings overturn the prevailing assumption that the earliest primates had nails on all their digits and suggest the transition from claws to nails was more complex than previously thought.

“We had just assumed nails all evolved once from a common ancestor, and in fact, it’s much more complicated than that,” said Jonathan Bloch, study co-author and Florida Museum of Natural History curator of vertebrate paleontology at the University of Florida.

The findings are scheduled to be published today in the Journal of Human Evolution.

Grooming in mammals is not just about looking good. Thick body hair is a haven for ticks, lice and other parasites — possible health threats, as well as nuisances. Having a specialized claw for removing pests would be an evolutionary advantage, said Doug Boyer, an associate professor in the department of evolutionary anthropology at Duke University and the study’s lead author.

It’s one that has been retained in many primates. Lemurs, lorises, galagoes and tarsiers have nails on most of their digits and grooming claws on their second — and in tarsiers, second and third — toes.

So, why did the ancestors of monkeys, apes and humans lose their grooming claws? One possible answer: because we have each other.

“The loss of grooming claws is probably a reflection of more complex social networks and increased social grooming”, Boyer said. “You’re less reliant on yourself.”

This could explain why more solitary monkey species, such as titi and owl monkeys, have re-evolved a grooming claw, he said.

Researchers had thought grooming claws likely developed independently several times along the lines that gave rise to living primates. But these fossils suggest grooming claws were hallmark features of the earliest primates, dating back at least 56 million years.

They also come from five different genera of ancient primates that belonged to the omomyoids, the ancestors of monkeys, apes, humans and tarsiers — not the branch of primates that gave rise to lemurs, lorises and galagoes.

In 2013, Boyer was at the University of California Museum of Paleontology, sifting through sediment collected in Wyoming several decades earlier, when he found several curious primate fossils. They were distal phalanges, the bones at the tips of fingers and toes, from omomyoids. The shape of these bones reveals whether they support a claw or nail. Bones topped with a claw mimic its narrow, tapered structure while bones undergirding a nail are flat and wide. The distal phalanges that Boyer discovered looked like they belonged to animals with grooming claws.

“Prior to this study, no one knew whether omomyoids had grooming claws”, Boyer said. “Most recent papers came down on the side of nails.”

Meanwhile, Bloch, picking through collections recently recovered from Bighorn Basin, Wyoming, came across what looked like a “strange, narrow nail” bone. But when he compared it to modern primates, “it looked just like a tarsier grooming claw.” Smaller than a grain of rice, it matched the proportions of Teilhardina brandti, a mouse-sized, tree-dwelling primate.

Bloch and Boyer had co-authored a 2011 study describing the first fossil evidence of nails in Teilhardina. At the time, they believed the primate had nails on all its digits. Now, fossils were making them reevaluate their assumptions, not only about Teilhardina, but other omomyoids.

On the off-chance that they could add one more ancient primate to the growing list of claw-bearers, the pair drove out to Omomys Quarry, Wyoming, once inhabited by another genus of omomyoid, Omomys.

“We spent a day combing that site, never expecting to find something as tiny and delicate as a grooming claw,” Boyer said.

The team picked one right off the surface. They had found grooming claws at three independent sites from omomyoids spanning about 10 million years in the fossil record.

“That was the last nail in the coffin”, Boyer said.

Why did primates develop nails at all? The question is a contentious one, but Bloch and Boyer think the transition away from claws could have mirrored changes in primate movement. As we ramped up climbing, leaping and grasping, nails might have proven more practical than claws, which could snag or get in the way.

Grooming claws might seem insignificant, but they can provide crucial insights into ancient primates, many of which are known only from fossil teeth, Bloch said. These tiny claws offer clues about how our earliest ancestors moved through their environment, whether they were social or solitary and what their daily behavior was like.

“We see a bit of ourselves in the hands and feet of living primates”, Bloch said. “How they got this way is a profoundly important part of our evolutionary story.”

Beluga whales’ hearing, new research


This 2017 video is called Things You Should Know About Beluga Whales.

From Woods Hole Oceanographic Institution in the USA:

Beluga whales have sensitive hearing, little age-related loss

June 20, 2018

Scientists published the first hearing tests on a wild population of healthy marine mammals. The tests on beluga whales in Bristol Bay, Alaska, revealed that the whales have sensitive hearing abilities and the number of animals that experienced extensive hearing losses was far less than what scientists had anticipated.

The latter findings contrasted with expectations from previous studies of humans and bottlenose dolphins, which showed more hearing loss as they aged, says Aran Mooney, a biologist at Woods Hole Oceanographic Institution (WHOI) and lead author of two new studies on beluga whales. “But unlike the wild beluga population, the dolphins that were studied lived in a very noisy environment, as most humans do.”

At a time when noise in the ocean is increasing from human activities, such as oil and gas exploration and ship traffic, understanding the natural hearing abilities of whales and other endangered marine mammals is crucial to assessing potential noise impacts on animals and to management efforts to mitigate sound-induced hearing loss.

In the two related studies, WHOI researchers and their colleagues measured the hearing sensitivity of 26 wild belugas and then compared the audiograms to acoustic measurements made within their summer habitat in Bristol Bay to study how natural soundscapes-all sounds within their environment-may influence hearing sensitivity. The soundscape also reveals sound clues that the belugas may use to navigate. The first study was published May 8, 2018, in the Journal of Experimental Biology. Results from the soundscape study were published June 20, 2018, in the Journal of Ecoacoustics. “In the first paper, we characterized the beluga population’s hearing ability, which had not been done before in a healthy, wild population”, says Mooney. “And in the second paper, we put that into context to see how they might use acoustic differences in their habitat and how their hearing is influenced by the natural ambient noise in their environment.”

How do you test a beluga whale‘s hearing? Researchers applied the same screening method that doctors use to test the hearing of newborn babies who can’t yet vocally respond to whether or not they hear sounds: automated auditory brainstem response.

A suction cup sensor is gently placed on the whales’ head, just behind the blowhole, and another is placed on the back for reference. A series of quiet tones are played, and the sensors help measure the brain’s response to the sounds from the surface of the skin.

“It’s fairly straightforward,” Mooney says. “We just had to make a portable system that we could bring out into an extreme environment in order to perform the hearing tests.”

The test itself goes quickly, taking only about five minutes to measure each frequency. The most challenging part, says Mooney, is catching the participants.

For that, the researchers relied on the expertise of Alaskan Natives who hunt belugas. From small aluminum boats, the team would approach an individual adult whale-no calves were included in the study-in shallow waters of the bay. Taking care not to stress or injure the whale, they would catch it in a soft net. Marine mammal handlers, including teams from Georgia Aquarium, Shedd Aquarium, and Mystic Aquarium, would then get in the water to help secure the animal’s tail with a rope before moving it to a belly band (like a small stretcher) in the water next to a soft inflatable boat where the hearing tests took place.

“The belugas stayed relatively relaxed during the tests, seemingly employing a resting behavior that they may use to avoid killer whales“, Mooney explains. “When a killer whale is hunting them, belugas will often move to very shallow water and quietly stay there until they can safely return to deeper waters.”

In addition to the auditory testing, the researchers also performed a physical exam to assess the overall health, sex, and estimated age of each animal and obtained skin, breath, and blood samples to collect information on the whales’ hormone levels, microbiome bacteria, and other health-related data. The assessments were part of a beluga population health assessment program coordinated by the NOAA Fisheries Alaska Fisheries Science Center, the Alaska Department of Fish and Game, and Alaska SeaLife Center. Satellite transmitters were attached to some of the whales before release to study the whales’ movements.

The hearing tests revealed little hearing loss in the seemingly older members of the population, which could be because the estuary where the belugas reside is fairly quiet compared to more urban areas.

“Because there haven’t been any other studies of the hearing of wild marine mammals, we compared the results to previous studies of captive dolphins in San Diego and in Russia”, Mooney says. “The dolphins showed clear hearing loss as they aged, but the San Diego group lives in a very noisy environment, as most humans do.”

Mooney and colleagues also compared the wild belugas tests to those of belugas living in human care facilities. Both groups heard similarly well, and the authors suggest that it is likely due to the quiet environments in which they live.

“Sensitive hearing within a quiet soundscape could allow belugas to detect predators, navigate, and communicate with their young via low-amplitude signals,” Mooney explains. “This hearing sensitivity could be compromised in a noisier environment. It also suggests management concerns for animals that inhabit noisy areas, where they may already be showing greater proportions of hearing loss.”

The two studies are important to efforts to evaluate the effects of underwater noise on endangered Cook Inlet beluga whales, whose numbers have dwindled to an estimated 328. The species lives in habitats close to Anchorage, AK, and is exposed to noise from shipping, pile driving, construction, and explosive noise from nearby military bases.