Humpback whales off Chile


This 21 March 2020 video says about itself:

Humpback whales thrive off the tip of Chile

Humpback whales have found a safe haven on the tip of Chile. Bad weather means the region is relatively untouched by humans. Humpback whale populations have grown five-fold in Francisco Coloane Marine Park. Almost 20 years ago biologists only counted 40 individuals in the park. Now, they’ve counted 190.

Globally there are around 87 cetacean species, and conservation efforts to protect humpback whales have been among the most successful. Hunting humpback whales has been banned since the ‘60s.

Read more here.

Narwhal tusks and sexuality, new research


This 2018 video says about itself:

There’s a lot of mystery that surrounds narwhals. We here to set the record straight on these fascinating creatures.

From Arizona State University in the USA:

For narwhals, the ‘unicorn of the seas’, size matters for sexual selection

March 17, 2020

Showy peacock feathers, extravagant elk antlers and powerful crayfish claws are just a few examples of the ostentatious animal extremes used to compete for and attract mates, a process called sexual selection.

Now, thanks to Arizona State University researcher Zackary Graham and his colleagues, we can add the “unicorn of the seas, the narwhal, to the list.

“Broadly, I’m interested in sexual selection, which is responsible for creating some of the craziest traits in biology. As an evolutionary biologist, I try to understand why some animals have these bizarre traits, and why some don’t”, said Graham, a doctoral student at ASU’s School of Life Sciences.

“One way we try to understand these traits is by looking at the morphology, or the size and shape of them. I immediately became obsessed with trying to think of some interesting animals to study. I was Googling everything; maybe I can find a dinosaur in a museum. Eventually, I found the narwhal tusk.”

Graham is the lead author of a new study which demonstrates the best evidence to date that the narwhal tusk functions as a sexual trait, published online in the journal Biology Letters.

A tusk among us

Like walruses and elephants, male narwhals (Monodon monoceros) grow tusks; these are modified teeth. In narwhals, the left tooth erupts from their head, reaching more than 8-feet-long in some individuals. The tusk grows out in a spiral pattern, giving the appearance of a sea-dwelling unicorn.

Since narwhals spend most of their lives hidden under the Arctic ice, there has been much speculation on what exactly the tusk is used for: hunting, fighting or perhaps something more amorous in nature?

Graham mentions that there have been reports of head scarring, broken tusks and tusks impaled in the sides of males, who may have been on the receiving end of some aggression. Other scattered observations include a behavior of “tusking”, where two narwhals cross and rub their tusks together, suggests that the tusk is used for communication during intra- or intersexual interactions.

Graham has studied sexual selection in all sorts of species, including the crayfish he studies for his PhD dissertation. He realized, that to demonstrate that the tusk is sexually selected, he could use the relationship between tusk size with body size to understand this mysterious trait. To do so, his team collected morphology data on 245 adult male narwhals over the course of 35 years.

With colleagues Alexandre V. Palaoro of the LUTA do Departamento de Ecologia e Biologia Evolutiva, UNIFESP, Brazil, and Mads Peter Heide-Jørgensen and Eva Garde, from the Greenland Institute of Natural Resources, they created a large dataset from the carefully curated narwhal field data.

When comparing individuals of the same age, sexually selected traits often exhibit disproportional growth — that is, for a given body size, sexually selected traits are often larger than expected in the largest individuals. Importantly, they compared the growth (or scaling) of the tusk to the scaling relationship between body size and a trait that is unlikely to have sexual functions. To do so, they used the tail of the narwhals, called the fluke.

“We also predicted that if the narwhal tusk is sexually selected, we expect greater variation in tusk length compared to the variation in fluke width,” said Graham. This is because many sexual traits are highly sensitive to nutrient and body condition, such that only the biggest and strongest individuals can afford the energy to produce extremely large traits.

According to Graham, they found that male tusks can have over 4-fold variation in tusk length (the same body size males can have tusks ranging from 1.5-feet to 8.2-feet) long. However, the fluke hardly varies at all, ranging from 1.5-feet to 3-feet long within individuals of the same body size. They also found disproportional growth in the tusk compared to the fluke. Based on the disproportional growth and large variation in tusk length they found, they have provided the best evidence to date that narwhal tusks are indeed sexually selected.

“By combining our results on tusk scaling with known material properties of the tusk, we suggest that the narwhal tusk is a sexually selected signal that is used during the male-male tusking contests,” said Graham. “The information that the tusk communicates is simple: “I am bigger than you.””

And if only the highest quality males produce and adorn the largest tusks, then the tusk likely serves as an honest signal of quality to females or males.

Under the Ice

Graham hopes that future researchers will use aerial and aquatic drones to provide concrete evidence of the tusk function in nature and elucidate the tusks exact role as either an aggressive weapon, a sexual signal or both.

Perhaps one day, we can look forward to a “Big Love: Narwhals Under the Ice” nature documentary coming to an IMAX near you.

“Overall, our evidence supports the hypothesis that the tusk functions both as a sexually selected weapon and sexually selected signal during male-male contests,” said Graham. “However, further evaluations of the narwhal’s ecology are warranted.”

Why whales, dolphins swim so well


This 2015 video says about itself:

DOLPHINS & WHALES

Ute Margreff lives on Ireland’s Atlantic coast, Florian Graner in the Puget Sound in the Northwest of the USA. Both Germans share a deep passion for the sea and its creatures. About 10 years ago Ute Margreff got to know the female solitary dolphin Mara – it was the start of an unusual friendship. Florian Graner found its private paradise close to Seattle. Right in front of his doorstep he dives into a world inhabited by sea lions, giant octopus and orca whales. Both Ute and Florian fight for the protection of marine habitats, each one in a different and very unique way.

From Lehigh University in the USA:

Secrets to swimming efficiency of whales, dolphins

March 19, 2020

Summary: Recent work has examined the fluid mechanics of cetacean propulsion by numerically simulating their oscillating tail fins. A team developed a model that, for the first time, could quantitatively predict how the motions of the fin should be tailored to its shape in order to maximize its efficiency. The research could influence the design of next-gen underwater robots.

Someday, underwater robots may so closely mimic creatures like fish that they’ll fool not only the real animals themselves but humans as well. That ability could yield information ranging from the health of fish stocks to the location of foreign watercraft.

Such robots would need to be fast, efficient, highly maneuverable, and acoustically stealthy. In other words, they would have to be very much like bottlenose dolphins or killer whales.

“We’re interested in developing the next generation of underwater vehicles so we’re trying to understand how dolphins and whales swim as efficiently as they do,” says Keith W. Moored, an assistant professor of mechanical engineering and mechanics in Lehigh University’s P.C. Rossin College of Engineering and Applied Science. “We’re studying how these animals are designed and what’s beneficial about that design in terms of their swimming performance, or the fluid mechanics of how they swim.”

Moored is the principal investigator on a paper recently published in the Journal of the Royal Society Interface that examined the fluid mechanics of cetacean propulsion by numerically simulating their oscillating tail fins. For the first time, Moore and his team were able to develop a model that could quantitatively predict how the motions of the fin should be tailored to its shape to maximize its efficiency. The research was part of a larger project supported by the Office of Naval Research under its Multidisciplinary University Research Initiative program. The project, which received more than $7 million in funding (with $1 million going to Lehigh) over more than five years, also included the University of Virginia, West Chester University, Princeton University, and Harvard University.

The tail fins of cetaceans (whales and dolphins) come in a wide variety of shapes. The way these animals move their fins, or their kinematics, also varies. Some cetaceans may flap their fins at a greater amplitude, or pitch them at a steeper angle. Moored and his team wanted to better understand this interplay between the two variables to determine if tail fin shape was tailored to a specific set of kinematics.

Using the shape and kinematic data for five cetacean species (with common names of bottlenose dolphin, spotted dolphin, killer whale, false killer whale, and beluga whale), they ran simulations on each of the species to determine its propulsive efficiency. Then they swapped the data around, for example, running a simulation on the fin shape of a killer whale attached to the kinematics of a dolphin.

“We ran 25 of these swapped simulations, and we were really surprised,” says Moored. “The pseudo orca fin shape was always the best, meaning it was the most efficient. It didn’t matter what kinematics we gave it. And the beluga whale kinematics were always the best, regardless of which shape it was attached to. We didn’t expect that, so we started digging into it more and developed this relatively simplistic model of how efficiency scales with different kinematic and shape variables.”

The model worked well to capture the data that Moored and his team had already generated, so they extended their data set to examine any resulting trends. They found that their model not only predicted efficiency beyond their data set but also revealed that specific shapes were tailored to specific kinematics.

One interesting revelation, says Moored, was the fundamental interplay between circulatory forces and added mass forces that contribute to an animal’s movement. Circulatory forces are those that generate lift, like with aircraft.

“A tail that’s flapping up and down generates forces just like an aircraft, but it also generates added mass forces that have to do with how fast the fluid is being accelerated,” says Moored. “In the past, people didn’t think those added mass forces were that relevant in cetacean swimming. It’s not acknowledged at all in the previous literature. But we found that the accelerations of the fin are integral to predicting the trends of efficiency, and that was fascinating to us. It ultimately gives us a predictive model that’s accurate. Without it, we’d basically be saying that fin shape doesn’t change the efficiency, and that’s not true.”

Having a model that can predict performance based on shape and kinematics provides a basic design equation of sorts for building an underwater robot that performs like a cetacean. To date, these equations haven’t existed. And the potential for these machines is huge. Fast, efficient, and highly maneuverable fish-shaped robots could help researchers test hypotheses about how the animals swim, and better understand the behavior of fish schools. They could be used to detect submarines and other submersibles. They could also be used to monitor the impact of climate change on fish stock populations.

Moored and his team have already moved on and expanded their scaling model to account for a larger range of variables they then validated with experimental data. Ultimately, they want to build a far more predictive model. One that captures the effects of these variables, and can then predict performance for a range of applications.

“This fish swimming problem is a really exciting problem because it’s so complicated,” he says. “It’s fascinating to take this chaos of variables and see order in it, to see the structure in it, and to understand what’s fundamentally happening.”

Sharks and whales, video


This 3 March 2020 video says about itself:

A Deep Dive Into the Lives of Sharks and Whales

Join us for a deep dive into the world of sharks and orcas. In this reel, we meet people who study, swim with and photograph these fascinating mammals, from the warm waters of Bimini to the frigid Arctic Ocean.

Antarctic killer whales’ unique calls


This 19 February 2020 video says about itself:

Calls of Antarctic Type C killer whales in McMurdo Sound, Ross Sea.

Want to hear what Antarctic Type C killer whales sound like?🎶Here is a sneak peek to some vocalising orca in McMurdo Sound recorded by our research team in the 2012 and 2013 season.

Recorded in the Ross Sea, this study will help with management tools of the RossSea MPA. More details on their sounds can be read in our recently published paper in Royal Society Open Science journal. Free to download from here.

From Curtin University in Australia:

New research sheds light on the unique ‘call’ of Ross Sea killer whales

February 26, 2020

New Curtin University-led research has found that the smallest type of killer whale has 28 different complex calls, comprising a combination of burst-pulse sounds and whistles, which they use to communicate with family members about the changing landscape and habitat.

The research, published in Royal Society Open Science, analysed data collected in 2012 and 2013 to better understand the call repertoire of Ross Sea killer whales, also known as Type C, which are found in the McMurdo Sound in Antarctica.

Lead author PhD candidate Rebecca Wellard, from Curtin’s Centre for Marine Science and Technology (CMST), said the remoteness of the Ross Sea can make it difficult to monitor and record the movements of killer whales, but it is essential to better understand their behaviour and acoustic repertoire.

“In Antarctic waters, there are five different types of killer whales, with Type C being the smallest, growing up to 6.1 metres in comparison to Type A males who can grow up to almost 10 metres long,” Ms Wellard said.

“By using passive acoustic monitoring, our team was able to analyse recordings from nine separate encounters with approximately 392 Type C killer whales, including adults, sub-adults and calves.

“We were able to identify that the calls of the Type C killer whale are multi-component, meaning that many calls transition from burst-pulse sounds to whistles. We also found that 39 per cent of the call types started with a series of ‘broadband pulses’.”

Ms Wellard explained that the most common killer whale behaviours observed in the study were travelling and foraging under the ice and socialising at the surface, which could explain the increase in call rate.

“During the calls, often two of the sounds occurred at the same time, also known as biphonation. These types of calls could be used to locate where other members of the pod may be. Due to the shifting and changing habitat in McMurdo Sound, calves could also be using biophonic calls to communicate with family members about available breathing holes,” Ms Wellard said.

“Our findings provide an initial step towards comparing and distinguishing Type C killer whale acoustics with those of other killer whale populations in the Southern Hemisphere.”

The research was co-authored by researchers from the CMST, Project ORCA, National Marine Fisheries Service and Oregon State University.

Why whales migrate, new research


This 2015 video says about itself:

Which Animal Has The Longest Migration?

Did you know a gray whale swims 14,000 miles when it migrates? How far do other animals travel?

“A North Pacific gray whale has earned a spot in the record books after completing the longest migration of a mammal ever recorded.”

Read more here.

From NOAA Fisheries West Coast Region in the USA:

Why do whales migrate? They return to the tropics to shed their skin

First suggested for killer whales, skin molt may drive long-distance migration for all whales that forage in cold waters

February 21, 2020

Whales undertake some of the longest migrations on earth, often swimming many thousands of miles, over many months, to breed in the tropics. The question is why — is it to find food, or to give birth?

In a research paper in Marine Mammal Science, scientists propose that whales that forage in polar waters migrate to low latitudes to maintain healthy skin.

“I think people have not given skin molt due consideration when it comes to whales, but it is an important physiological need that could be met by migrating to warmer waters,” said Robert Pitman, lead author of the new paper and marine ecologist with Oregon State University’s Marine Mammal Institute. He was formerly with NOAA Fisheries’ Southwest Fisheries Science Center in La Jolla, California.

More than a century ago, whalers recognized that most whales that forage in high latitudes migrate to the tropics for calving. Scientists have never agreed on why. Because of their size, large whales should be able to successfully give birth in frigid polar waters. Due to reduced feeding opportunities in the tropics, most whales fast during their months-long migrations.

So why go to the trouble?

Warm Water Speeds Molting

All birds and mammals regularly shed their skin, fur, or feathers in a process known as molting. Pitman and his coauthors propose that whales foraging in the freezing waters of Antarctica conserve body heat by diverting blood flow away from their skin. That would reduce regeneration of skin cells and halt the normal sloughing of skin.

Migrating to warmer water would allow whales to revive their skin metabolism and molt in an environment that does not sap their body heat. The authors suggest that this drives their migrations.

The two lead authors on the study first proposed in 2011 that skin molt could drive the migration for certain Antarctic killer whales. With new data, they now propose the same for all Antarctic killer whales and possibly all whales that migrate to the tropics.

Coauthors on the paper include scientists from NOAA Fisheries; SeaLife Response, Rehabilitation, and Research; and the Italian National Institute for Environmental Protection and Research.

Over eight years, scientists deployed 62 satellite tags on killer whales. They found that all four types that feed in frigid Antarctic waters migrated as far as 11,000 kilometers (almost 7,000 miles) round trip. Most migrations were fast, non-stop, and largely straight north and back. One whale completed two such migrations in 5.5 months. Researchers also photographed newborn killer whale calves in Antarctica, indicating the whales don’t need to migrate to warmer waters to give birth.

They suggest that larger whales that migrate to the tropics to molt may have begun giving birth in those same warmer waters. “Instead of whales migrating to the tropics or subtropics for calving, whales could be traveling to warm waters for skin maintenance and perhaps find it adaptive to bear their calves while they are there,” the scientists wrote. The warm water could speed the growth of calves in an environment with far fewer killer whales, their main predator.

Much like humans, whales and dolphins normally shed outer skin cells continuously. Scientists observed that whales in frigid Antarctic waters are often discolored by a thick yellow film of microscopic diatoms. This indicated that they were not experiencing their normal, “self-cleaning” skin molt.

Early whalers referred to blue whales with a heavy coating of diatoms on their white bellies as “sulfur-bottoms”. They also assumed that whales without a diatom coating were likely recent arrivals from the tropics. When whales shed their skin, they also shed the diatoms.

Molting Jettisons Harmful Bacteria

Recent studies have found that high concentrations of diatoms on the skin of Antarctic killer whales may also accumulate potentially harmful bacteria.

“Basically, the feeding is so good in productive Antarctic waters that the relatively small, warm-blooded killer whale has evolved a remarkable migration behavior. This enables it to exploit these resources and still maintain healthy skin function,” said John Durban, coauthor of the research, formerly with the science center and now a senior scientist at SEA Inc.

In another example, beluga whales in the Arctic are known for gathering in summer in river estuaries. The water there is warmer, fresher, and shallower than their typical habitat. At first, scientists assumed that they gathered there to give birth and that the warmer temperatures boosted calf survival.

It turned out that belugas do not calve or feed in the estuaries but go there to molt. In an earlier study, an Inuit hunter pointed out that “Belugas go to the rivers for warmth. And like seals they moult their skins. They moult in the warm water.”

The annual (versus continuous) molt cycle of the beluga was long thought to be unique among cetaceans. But, if whales are migrating to the tropics to molt, annual molt “may prove to be the rule among all high-latitude cetaceans,” the authors wrote.

In terms of biomass, whales complete the largest annual migrations on earth. They transport millions of tons of animals thousands of miles, with significant impact on local ecosystems, the scientists say. They also call for further testing of their hypothesis by assessing skin growth of migratory and non-migratory whales, at high and low latitudes, throughout the year.

Sperm whales disturbed by earthquakes


This 2015 video from the USA says about itself:

At 598 meters (1,962 ft) below the Gulf of Mexico off the coast of Louisiana, ROV Hercules encountered a magnificent sperm whale. The whale circled Hercules several times and gave our cameras the chance to capture some incredible footage of this beautiful creature. Encounters between sperm whales and ROVs are incredibly rare.

From the University of Otago in New Zealand:

Earthquakes disrupt sperm whales’ ability to find food

February 20, 2020

Otago scientists studying sperm whales off the coast of Kaikōura discovered earthquakes affect their ability to find food for at least a year.

The University of Otago-led research is the first to examine the impact of a large earthquake on a population of marine mammals, and offers new insight into how top predators such as sperm whales react and adapt to a large-scale natural disturbance.

Changes in habitat use by a deep-diving predator in response to a coastal earthquake, has recently been published in Deep Sea Research Part I.

Earthquakes and aftershocks can affect sperm whales in several ways, the study explains.

The whales depend on sound for communication, detection of prey and navigation and are also highly sensitive to noise.

Earthquakes produce among the loudest underwater sounds which can induce injuries, hearing damage, displacement and behavioural modifications.

While earthquakes and other extreme natural events are rare occurrences, they can really shift the state of ecosystems by wiping out animals and plants, lead author and Marine Sciences Teaching Fellow Dr Marta Guerra says.

“Understanding how wild populations respond to earthquakes helps us figure out their level of resilience, and whether we need to adjust management of these populations while they are more vulnerable.”

The fatal 7.8 magnitude Kaikōura earthquake on November 14, 2016 produced strong ground shaking which triggered widespread underwater mudslides in the underwater canyon off the coastline.

This caused what’s known as ‘canyon flushing’, which in the case of the Kaikōura earthquake, involved high-energy currents flushing 850 tonnes of sediment from the underwater canyon into the ocean.

The Kaikōura canyon is an important year-round foraging ground for sperm whales, which have an important ecological role as top predators and are a key attraction for the local tourism industry — the main driver of the town’s economy.

Just why the canyon is important to sperm whales is “a piece of the puzzle we are still trying to nut out,” says Dr Guerra.

“But it’s likely related to the immense productivity of the canyon’s seabed, and a combination of how the currents interact with the steep topography of the submarine canyon.”

Scientists examined data collected on the behaviour of 54 sperm whales between January 2014 and January 2018 — a timeframe which allowed an opportunity to determine any significant changes in pre and post-earthquake whale foraging behaviour.

“We really didn’t know what to expect, as there is so little known about how marine animals react to earthquakes,” Dr Guerra says.

The researchers found clear changes in the whales’ behaviour in the year following the earthquake: most noticeably whales spent about 25 per cent more time at the surface — which potentially meant they needed to spend more effort searching for prey, either by diving deeper or for longer times

There are two main reasons the whales may have expanded their search effort, the study explains.

Firstly, benthic invertebrate communities which lived in the upper canyon may have been removed by the canyon flushing event, resulting in sparser prey and reduced foraging abilities.

Secondly, sediment deposition and erosion may have required sperm whales to ‘re-familiarise’ with a modified habitat, increasing the effort to navigate and locate prey whose location may have changed.

“The flushing of almost 40,000 tonnes of biomass from the canyon’s seabed probably meant that the animals that normally fed on the seabed had a short supply of food, possibly moving away,” Dr Guerra says.

“This would have indirectly affected the prey of sperm whales (deep-water fish and squid), becoming scarce and making it harder for the whales to find food.”

Scientists were particularly surprised by how clear the changes were, especially in terms of where the sperm whales were feeding.

“The head of the Kaikōura canyon, where we used to frequently find sperm whales foraging, was quiet as a desert,” Dr Guerra says.

Although earthquakes happen relatively frequently in areas where marine mammals live, this study was the first to document the impact on a population, thanks to a long-term monitoring programme which has been in place since 1990.

Globally, there have been punctual observations, such as a fin whale displaying an ‘escape response’ after an earthquake on the Gulf of California, or particularly low sightings of humpback whales coinciding with the months following an earthquake off Alaska, Dr Guerra says.

“Deep-sea systems are so out of sight that we rarely consider the consequences of them being disturbed, whether by natural of human impacts.

“I think our results emphasise how far-reaching the impacts to the sea bed can be, affecting even animals at the top of the food chain such as sperm whales.”

The study found the whales’ behavioural changes lasted about a year after the 2016 earthquake and returned to normal levels in the summer of 2017-18.

Dr Guerra believes this study also highlights the importance of long-term monitoring of marine wildlife and ecosystems, without which scientists wouldn’t be able to detect changes that occur after marine mammals are exposed to disturbance.

A better pregnancy test for whales. New measurements will help biologists understand a changing ocean: here.