Great white sharks scared of killer whales


This video says about itself:

This Is The Biggest Great White Shark Ever Caught On Camera

Great white sharks are… big. Obviously. But a few years ago, divers met up with Deep Blue, probably the biggest great white shark ever caught on camera. So what do we know about the massive great white?

From the Monterey Bay Aquarium in the USA:

White sharks flee feeding areas when orcas present

Electronic tag data reveals white sharks do not return until following season; elephant seals benefit

April 16, 2019

Summary: New research challenges the notion that great white sharks are the most formidable predators in the ocean. The research team documented encounters between white sharks and orcas at Southeast Farallon Island off California. In every case examined by the researchers, white sharks fled the island when orcas arrived and didn’t return there until the following season. Elephant seal colonies in the Farallones also indirectly benefited from the interactions.

New research from Monterey Bay Aquarium and partner institutions published today in Nature Scientific Reports challenges the notion that great white sharks are the most formidable predators in the ocean. The study “Killer Whales Redistribute White Shark Foraging Pressure On Seals” shows how the great white hunter becomes the hunted, and the elephant seal, the common prey of sharks and orcas, emerges as the winner.

“When confronted by orcas, white sharks will immediately vacate their preferred hunting ground and will not return for up to a year, even though the orcas are only passing through,” said Dr. Salvador Jorgensen, senior research scientist at Monterey Bay Aquarium and lead author of the study.

The research team — which included Jorgensen and Monterey Bay Aquarium scientist Scot Anderson, and research partners from Stanford University, Point Blue Conservation Science and Montana State University — documented four encounters between the top predators at Southeast Farallon Island in the Greater Farallones National Marine Sanctuary, off San Francisco, California. The scientists analyzed the interactions using data from 165 white sharks tagged between 2006 and 2013, and compiled 27 years of seal, orca and shark surveys at the Farallones.

“The research in this paper combines two really robust data sources,” said Jim Tietz, co-author of the study and Farallon Program Biologist at Point Blue Conservation Science. “By supplementing the Aquarium’s new shark tagging data with Point Blue’s long-term monitoring of wildlife at the Farallon Islands National Wildlife Refuge, we were able to conclusively show how white sharks clear out of the area when the orcas show up.”

In every case examined by the researchers, white sharks fled the island when orcas arrived and didn’t return there until the following season.

Elephant seal colonies in the Farallones also indirectly benefited from the interactions. The data revealed four to seven times fewer predation events on elephant seals in the years white sharks left.

“On average we document around 40 elephant seal predation events by white sharks at Southeast Farallon Island each season,” Anderson said. “After orcas show up, we don’t see a single shark and there are no more kills.”

Each fall between September and December white sharks gather at the Farallones to hunt for young elephant seals, typically spending more than a month circling Southeast Farallon Island. Transient orcas also feed on elephant seals, but only show up occasionally at the island.

To determine when orcas and sharks co-occurred in the area, researchers compared data from the electronic shark tags with field observations of orca sightings. This made it possible to demonstrate the outcome on the rare instances when the predators encountered each other.

Electronic tags showed all white sharks began vacating the area within minutes following brief visits from orcas. Sometimes the orcas were only present for less than an hour. The tags then found the white sharks either crowded together at other elephant seal colonies farther along the coast or headed offshore.

“These are huge white sharks. Some are over 18 feet long (5.5 meters), and they usually rule the roost here,” Anderson said. “We’ve been observing some of these sharks for the past 15 to 20 years — and a few of them even longer than that.”

The study’s findings highlight the importance of interactions between top predators, which aren’t well-documented in the ocean.

“We don’t typically think about how fear and risk aversion might play a role in shaping where large predators hunt and how that influences ocean ecosystems,” Jorgensen said. “It turns out these risk effects are very strong even for large predators like white sharks — strong enough to redirect their hunting activity to less preferred but safer areas.”

The researchers drew no conclusions about whether orcas are targeting white sharks as prey or are bullying the competition for the calorie-rich elephant seals.

“I think this demonstrates how food chains are not always linear,” Jorgensen said. “So-called lateral interactions between top predators are fairly well known on land but are much harder to document in the ocean. And because this one happens so infrequently, it may take us a while longer to fully understand the dynamics.”

Advertisements

Ancient four-legged whale discovery in Peru


This 4 April 2019 video says about itself:

Four-legged whale ancestors reached South America in an otter-like swimming style

A four-legged whale from Peru indicates that early whales crossed the South Atlantic before 42.6 million years ago and may have propelled like otters: with a robust tail and webbed fingers on their long feet.

Production: Stéphane Van Israël, Royal Belgian Institute of Natural Sciences

From ScienceDaily:

Ancient, four-legged whale with otter-like features found along the coast of Peru

April 4, 2019

Cetaceans, the group including whales and dolphins, originated in south Asia more than 50 million years ago from a small, four-legged, hoofed ancestor. Now, researchers reporting the discovery of an ancient four-legged whale — found in 42.6-million-year-old marine sediments along the coast of Peru — have new insight into whales’ evolution and their dispersal to other parts of the world. The findings are reported in the journal Current Biology on April 4.

The presence of small hooves at the tip of the whale’s fingers and toes and its hip and limbs morphology all suggest that this whale could walk on land, according to the researchers. On the other hand, they say, anatomical features of the tail and feet, including long, likely webbed appendages, similar to an otter, indicate that it was a good swimmer too.

“This is the first indisputable record of a quadrupedal whale skeleton for the whole Pacific Ocean, probably the oldest for the Americas, and the most complete outside India and Pakistan”, says Olivier Lambert of the Royal Belgian Institute of Natural Sciences.

Some years ago, study co-author Mario Urbina of Museo de Historia Natural-UNMSM, Peru, discovered a promising area for digging fossils in the coastal desert of southern Peru, named Playa Media Luna. In 2011, an international team, including members from Peru, France, Italy, the Netherlands, and Belgium, organized a field expedition, during which they excavated the remains of an ancient whale they’ve since named Peregocetus pacificus. It means “the traveling whale that reached the Pacific.”

“When digging around the outcropping bones, we quickly realized that this was the skeleton of a quadrupedal whale, with both forelimbs and hind limbs,” Lambert says.

With the help of microfossils, the sediment layers where the skeleton was positioned were precisely dated to the middle Eocene, 42.6 million years ago. Anatomical details of the skeleton allowed them to infer that the animal was capable of maneuvering its large body (up to 4 meters long, tail included), both on land and in the water. For instance, features of the caudal vertebrae (in the tail) are reminiscent of those of beavers and otters, suggesting a significant contribution of the tail during swimming.

The geological age of the new four-limbed whale and its presence along the western coast of South America strongly support the hypothesis that early cetaceans reached the New World across the South Atlantic, from the western coast of Africa to South America, the researchers report. The whales would have been assisted in their travel by westward surface currents and by the fact that, at the time, the distance between the two continents was half what it is today. The researchers suggest that, only after having reached South America, the amphibious whales migrated northward, finally reaching North America.

The international team continues to study the remains of other whales and dolphins from Peru. “We will keep searching in localities with layers as ancient, and even more ancient, than the ones of Playa Media Luna, so older amphibious cetaceans may be discovered in the future,” Lambert says.

Sperm whale hunts squid, video


This video says about itself:

Rare Footage of a Sperm Whale Hunting a Squid

For decades, scientists and filmmakers have been trying to capture footage of the world’s largest active predator hunting 3,000 feet below the surface, deep in the dark depths of the ocean. Witness a sperm whale echolocate its prey with intense clicking and then successfully hunt down what is believed to be a squid.

New killer whale species discovery?


This 12 March 2019 video says about itself:

Mysterious Orcas Confirmed Alive in New Video | National Geographic

A team of NOAA scientists have, for the first time, found and studied the fabled Type D killer whale alive in the wild. They were first documented in 1955 when more than a dozen unidentified animals were found beached on the coast of New Zealand.

Compared with other types of orcas, these killer whales have a more rounded head, a narrower and more pointed dorsal fin, and a small white eyepatch. The orcas were seen off the tip of southern Chile in January 2019. Type D killer whales live in the subantarctic, home to some of the world’s stormiest waters. This inhospitable environment, and the fact that they aren’t usually found near shore, makes them nearly impossible to study. The scientists expect lab results to show that the Type D killer whale is a new species, and the largest undescribed animal left on the planet.

How blue whales migrate


This 2009 video is called BBC Planet Earth (Blue whale).

After migration of bats, small mammals, the migration of the biggest of all mammals.

From Oregon State University in the USA:

Migrating blue whales rely on memory more than environmental cues to find prey

February 26, 2019

Blue whales reach their massive size by relying on their exceptional memories to find historically productive feeding sites rather than responding in real time to emerging prey patches, a new study concludes.

Researchers examining records of both whale migration and oceanic conditions in the California Current Ecosystem found that blue whales almost perfectly match the timing of their migration to the historical average timing of krill production, rather than matching the waves of krill availability in any given year.

The findings suggest that blue whales locate prey by relying on memory to return to stable, high-quality foraging sites, which historically have served them well but could make it difficult for the whales to adapt if novel ecosystem changes emerge as a result of climate change.

Results of the study are being published next week in Proceedings of the National Academy of Sciences.

The concept of tracking the timing of food availability along migration routes is not unusual for land animals, but it has been more difficult to identify in marine creatures, according to Briana Abrahms, a research ecologist with the NOAA Southwest Fisheries Science Center in Monterey, Calif., and lead author on the study.

“We know that many species that migrate on land, from caribou in the Arctic to wildebeests in the Serengeti, enhance their survival by carefully adjusting the pace and timing of their migrations to find food as it becomes seasonally available along the way, rather than just migrating to get from point A to point B,” Abrahms said.

Blue whales seem to embrace that same strategy, which is enhanced by their memory, she noted. “These long-lived, highly intelligent animals are making movement decisions based on their expectations of where and when food will be available during their migrations.”

“This novel study is particularly noteworthy in that if focuses on the phenology, or timing of migration in a large marine predator,” said Sue Moore, an affiliate professor at the University of Washington Center for Ecosystem Sentinels, who was not involved in the study.

The study also raises the question of what will happen to the population if changing climate conditions cause food availability to deviate strongly from the whales’ expectations.

The interdisciplinary research team used 10 years of tagging data from the Marine Mammal Institute at Oregon State University to determine daily blue whale movements of 60 individual whales in the California Current Ecosystem, and then compared that with satellite-based measurements of ocean productivity.

“We think that blue whales have evolved to use historical migration routes and timing that put them in proximity to the most predictably high production feeding areas and then make minor adjustments based on local conditions,” said Daniel Palacios, a principal investigator with Oregon State’s Marine Mammal Institute and a co-author on the study.

“There are various time scales of events that could change the timing of phytoplankton blooms — and thus the availability of the whales’ preferred prey, krill,” he noted, “including La Nina and El Nino events and the Pacific Decadal Oscillation. But the whales’ strategy of relying on memory and historic timing at least gets them into ‘the Goldilocks zone.'”

Blue whales can grow to the length of a basketball court, weigh as much as 25 large elephants, and their mouths can hold 100 people, though their diet is primarily krill — tiny shrimp-like creatures less than two inches in length. The blue whale is thought to be the largest creature to ever inhabit the Earth, yet little was known about their range or where they went to breed until Oregon State’s Bruce Mate led a series of tracking studies featured in the popular 2009 National Geographic documentary, “Kingdom of the Blue Whale.”

“There is still a lot we don’t know about blue whales, but it is apparent that they have strong fidelity to certain sites along the West Coast of the United States, which they use year after year,” said Mate, who directs OSU’s Marine Mammal Institute.

An estimated 2,500 of the world’s 10,000 blue whales spend time in the waters off the West Coast of the Americas and are known as the eastern North Pacific population. The huge whales can travel from the Gulf of Alaska all the way down to an area near the equator known as the Costa Rica Dome. The majority of the population spends the summer and fall in the waters off the U.S. West Coast, with the tagged whales most heavily using areas off Santa Barbara and San Francisco, California, which puts them in routine peril from ship strikes.

“We still have a lot to learn about how large animals navigate in the ocean, how they find good habitat and how they are affected by human activities and environmental changes,” said NOAA’s Abrahms.

Understanding how blue whales make movement decisions give scientists insight into how they may, or may not, be able to cope with changing ocean conditions in the future, she added.

Cuvier’s beaked whales, world’s deepest diving mammals


This June 2017 video says about itself:

Sea Shepherd Captures NEVER SEEN BEFORE drone footage of the rare Cuvier’s Beaked Whales (Ziphius cavirostris) while conducting research on Mexico’s Guadalupe Island.

From Duke University in the USA:

Beaked whales‘ incredible diving abilities confirmed

Cuvier’s beaked whales go a mile deep, hold breath for an hour

February 6, 2019

A new Duke University-led study provides the first detailed record of the diving behavior of Cuvier’s beaked whales in U.S. Atlantic waters.

Cuvier’s beaked whales are the world’s deepest-diving mammal, but studies of their behavior are constrained by the animals’ offshore location and limited time spent at the surface.

The new data, recorded from 5,926 dives of tagged whales off Cape Hatteras, N.C., showcases the remarkable diving abilities of these animals and provides new clues to how they make a living at the extremes of depth and cold.

“Their deep dives average about 1,400 meters, lasting about an hour, while they are feeding near the sea floor. They typically only spend about two minutes at the surface between dives,” said Jeanne Shearer, a doctoral student in ecology at Duke University’s Nicholas School of the Environment. “It’s amazing that they can dive to such depths, withstand the pressure, and be down there that long, with such brief recovery times.”

Past studies have documented the diving behavior of Cuvier’s beaked whales in Pacific waters, Italy, and the Bahamas, but this is the first one focused in the U.S. Atlantic. Scientists estimate about 6,500 Cuvier’s beaked whales live in the northwest Atlantic. Populations in different areas exhibit some differences in diving behavior, highlighting the need for data from around the world.

To conduct the study, scientists attached LIMPET satellite-linked tags to 11 Cuvier’s beaked whales that live and dive most of the year in waters a two-hour boat ride from Cape Hatteras. One tag failed, but the other 10 recorded 3,242 hours of behavioral data from 5,926 individual dives — both deep and shallow — between 2014 and 2016.

Aside from the extremely deep dives that these whales are able to make, the data showed that they dive nearly continually, with deep dives followed by 3-4 shallow dives that extend to around 300 meters. How they continuously dive to these depths without long recovery periods is still a mystery to scientists.

“Cuvier’s beaked whales are only half the size of the sperm whale,” Shearer said. “Their dives push the limits of mammalian physiology, but we still don’t know how they’re able to behave this way.”

She and her colleagues published their peer-reviewed findings Feb. 6 in the journal Royal Society Open Science.

Aside from adding to our knowledge of the species’ remarkable diving capability, the findings provide a baseline for controlled experiments, now underway at Duke, to study their reactions to low levels of sonar.

“It’s important to understand their typical diving behavior in order to interpret the results of behavioral response studies,” said Shearer, who conducts her research at the Duke University Marine Laboratory in Beaufort, N.C.

“These animals are fascinating and there is so much we still don’t know about their behavior and physiology,” Shearer said. “They are the world’s deepest mammalian divers, but we don’t yet understand how they dive to such extremes.”