How seals dive, new research

This 2017 video is called Meet the Harbour Seal.

From PLOS:

Wearable device reveals how seals prepare for diving

June 18, 2019

A wearable non-invasive device based on near-infrared spectroscopy (NIRS) can be used to investigate blood volume and oxygenation patterns in freely diving marine mammals, according to a study publishing June 18 in the open-access journal PLOS Biology by J. Chris McKnight of the University of St. Andrews, and colleagues. The results provide new insights into how voluntarily diving seals distribute blood and manage the oxygen supply to their brains and blubber, yielding important information about the basic physiological patterns associated with diving.

In response to submersion in water, mammals show a suite of cardiovascular responses such as reduced heart rate and constriction of peripheral blood vessels. But investigating dive-by-dive blood distribution and oxygenation in marine mammals has up to now been limited by a lack of non-invasive technology that can be used in freely diving animals.

The authors hypothesized that NIRS could address this gap in knowledge by providing high-resolution relative measures of oxygenated and deoxygenated hemoglobin within specific tissues, which can in turn be used to estimate changes in blood volume. In the new study, McKnight and colleagues adapted NIRS technology for use on freely diving harbor seals to investigate blood volume and oxygenation patterns specifically in the brain and blubber, using a device that they dub the PortaSeal.

The authors used the PortaSeal to obtain detailed continuous NIRS data from four seals swimming freely in a quasi-natural foraging habitat. The device is superglued to the animals’ fur; either on their heads to measure cerebral blood, or on the shoulder to monitor peripheral circulation; it is then easily removed, and the data downloaded.

Intriguingly, the results showed that seals routinely constrict their peripheral blood vessels, accompanied by increased cerebral blood volume, approximately 15 seconds before submersion. These anticipatory adjustments suggest that blood redistribution in seals is under some degree of cognitive control and is not just a reflex response to submersion. Seals also routinely increase cerebral oxygenation at a consistent time during each dive, despite a lack of access to air.

The authors propose that the ability to track blood volume and oxygenation in different tissues using NIRS will enable a more accurate understanding of physiological plasticity in diving animals in what is an increasingly disturbed and exploited environment.

“Discovering that seals, which are physiologically fascinating animals, can seemingly actively exert control over their circulatory systems is really exciting,” Said Dr McKnight. “It gives a new perspective on the capacity to control the body’s fundamental physiological responses. Getting this insight with non-invasive wearable technology from the bio-medical field offers many exciting future research avenues. We can start to study organs, like the brain, of seals in the open ocean performing exceptional feats like diving to 2000m for 2hrs with heart rates as low as 2bpm, and yet somehow avoid brain trauma.”


Alaska lake seals unique, new research

This 2018 video is called Hidden Seals Of Siberia [Fresh Water Seal Documentary] | Wild Things.

From the University of Washington in the USA:

Chemical records in teeth confirm elusive Alaska lake seals are one of a kind

May 1, 2019

Summary: Lifelong chemical records stored in the canine teeth of an elusive group of seals show that the seals remain in freshwater their entire lives and are likely a distinct population from their relatives in the ocean. Their home territory, Iliamna Lake, is in the heart of the proposed Pebble Mine project.

Hundreds of harbor seals live in Iliamna Lake, the largest body of freshwater in Alaska and one of the most productive systems for sockeye salmon in the Bristol Bay region.

These lake seals are a robust yet highly unusual and cryptic posse. Although how the seals first colonized the lake remains a mystery, it is thought that sometime in the distant past, a handful of harbor seals likely migrated from the ocean more than 50 miles (80 kilometers) upriver to the lake, where they eventually grew to a consistent group of about 400. These animals are important for Alaska Native subsistence hunting, and hold a top spot in the lake’s diverse food web.

Scientists now know these “colonizing” seals must have found the lake suitable enough to stay and raise their offspring. Generations later, the lake-bound seals appear to be a genetically distinct population from their ocean-dwelling cousins — even though they are still managed as part of the larger Eastern Pacific harbor seal population.

But if the lake seals are distinct and show signs of local adaptation to their unique ecological setting, this would mean that their conservation — especially in the face of the rapidly changing climate of western Alaska and proposed industrial developments — should differ from that of nearby marine populations.

Lifelong chemical records stored in their sequentially growing canine teeth show that the Iliamna Lake seals remain in freshwater their entire lives, relying on food sources produced in the lake to survive. In contrast, their relatives in the ocean are opportunistic feeders, moving around to the mouths of different rivers to find the most abundant food sources, which includes a diverse array of marine food items in addition to the adult salmon returning to Bristol Bay’s nine major watersheds. These findings are described in a paper published online in March in Conservation Biology.

“We clearly show these seals are in the lake year-round, throughout their entire lives,” said lead author Sean Brennan, a postdoctoral researcher at the University of Washington’s School of Aquatic and Fishery Sciences. “This gives us critical baseline information that can weigh in on how we understand their ecology, and we can use that information to do a better job developing a conservation strategy.”

This new study comes at a time when federal agencies are considering whether to permit mining activities in Bristol Bay, a region teeming with wildlife, including Alaska sockeye salmon. Iliamna Lake, and the seals and other animals that live there, is located in the heart of the proposed Pebble Mine project.

The U.S. Army Corps of Engineers this spring released a draft environmental impact statement that analyzes the project’s proposal, presents alternative plans and gives the public a chance to comment. Ultimately, the document will help decide whether the controversial mine is approved.

Because of their current conservation status, the Iliamna Lake harbor seals aren’t assessed as a distinct and ecologically significant population in the project’s draft environmental impact analysis. If the seals are determined to be a distinct population, that has important implications for how the Iliamna Lake system is managed, the study’s authors said. The lake and its resident fishes would then be considered critical habitat for seals.

Separately, federal regulators have considered whether the lake seals should be named a distinct population, but scientists have been unable to agree on whether the seals are both distinct, and ecologically and evolutionarily significant, mainly because little is known about their ecology — including whether adult lake seals potentially migrate to the ocean to feed each year.

Brennan was a doctoral student at the University of Alaska Fairbanks when he heard about early efforts to evaluate whether the lake seals were a distinct population. Chemical tracing methods he was using to track the life patterns of salmon could also work for the seals, he realized.

“The light just went off in my head,” Brennan said. “What I was doing for salmon was directly applicable to this population of seals.”

Brennan and collaborators at the UW, University of Utah and University of Alaska Anchorage looked at the chemical signatures present in the teeth of lake seals during each year of their life to better understand where they moved and what they ate. Specifically, the scientists drilled into the growth lines of the seals’ canine teeth, then measured the ratio of heavy and light isotopes of carbon, oxygen, and strontium present in each growth layer.

Because of the young bedrock geology of the Kvichak (QUEE-jak) River watershed, which encompasses Iliamna Lake, strontium isotope levels in the ocean are consistently much higher than in the lake. Unlike other elements, strontium signatures in mammal teeth directly reflect what animals assimilate from their environment, in particular, what they eat. Therefore, by looking at the strontium isotope ratios over the course of a seal’s life, the researchers saw that the ratios were consistent with lake signatures — meaning these seals only live in Lake Iliamna, depend principally on fish produced within the lake, and do not migrate to the ocean.

They also determined that young seals eat very little adult sockeye salmon. But later in life, the seals shift to supplement their diets with the seasonally abundant sockeye salmon that return each summer to the lake.

The researchers say this method could be used to better understand the life patterns of other elusive mammals around the world, such as river dolphins in the Amazon or the Mekong Basin. Broadly, marine mammals in coastal regions are among the most endangered animals on Earth, Brennan said.

“In terms of the broader picture of aquatic mammal conservation across the globe, I think we show that strontium isotopes can be really powerful because they collapse a lot of uncertainty. This method is completely underutilized across the world,” Brennan said.

Elephant seals benefit from United States government shutdown

This 29 January 2019 video from California in the USA says about itself:

Government Shutdown Brings Elephant Seals To Point Reyes Beach

Elephant seals used the opportunity of an empty Drake’s Beach on Point Reyes National Seashore – due to the government shutdown – to gather for mating and bearing pups. Wilson Walker reports.

Donald Trump’s shutdown blackmail to try to build his wall was a disaster for many workers; and for national parks and their wildlife. At least, one good consequence, for the elephant seals.

SECOND SHUTDOWN LOOMS AS TALKS BREAK DOWN Talks between congressional Republicans and Democrats aimed at averting another government shutdown have broken down without an agreement. Last month’s federal funding deal runs out on Friday. Acting White House chief of staff Mick Mulvaney said over the weekend another partial government shutdown “absolutely cannot” be ruled out.  [Reuters]

Climate change, not seals, endanger Baltic Sea fish

This January 2018 video says about itself:

Nord Stream 2 is supporting a program of telemetry studies of the Baltic ringed seal in the Gulf of Finland launched in summer 2017. Telemetry studies using GPS tags deployed on seals allow to collect necessary information on seal behaviour and movement patterns. Expanding scientific knowledge is vital for developing an effective strategy to preserve the population of this protected species. This documentary film explains the methodology and fieldwork conducted by an expert group in 2017.

From Stockholm University in Sweden:

Increasing seal population will not harm largest fish stocks in the Baltic

December 10, 2018

Seals feeding on fish does not decrease fish stocks of Baltic cod, herring and sprat the most — climate change, nutrient load and fisheries do, shows a new study from Stockholm University.

It has long been debated whether the seal predation of fish play a major role in the fish decline in the Baltic Sea compared to human fishing. The debate escalated worldwide since conservation efforts to protect seals and fish-eating birds resulted in increased number of them.

A new study taking into account human pressures on the environment, shows that the seals are not the main problem on commercial fish stocks in the open water of the Baltic Sea.

“We currently have 30,000 grey seals in the Baltic Proper, but we can even have more than 100,000 seals and it will still not affect the amount of cod negatively as much as climate change, nutrient load and fisheries. The Baltic is very sensitive to human impact”, says David Costalago, a former postdoctoral researcher at Department of Ecology, Environment and Plant Sciences, Stockholm University.

The cod population size for example, decreased more by environmental change and by human fishing, than the seals eating the fish. How much fish the seals eat is also affected by the climate and nutrient load.

The scientists made projections by computer simulations that stretch until the year 2098. The scenarios with the highest temperature and nutrient load of the Baltic are damaging to cod but not for herring and sprat. It could lead to a worsened effect of hypoxia and as a result less fish. Higher nutrient load together with higher temperatures could also lead to higher toxic cyanobacterial blooms of low food quality — making fish smaller and slender.

“We need to start to focus on the main problem that the Baltic is facing for its fish populations — which is for example climate change and eutrophication. We need to find ways to both secure the revenues of the fishers and guarantee the conservation of the fish stock and good status of the grey seal population”, says Monika Winder, professor at Department of Ecology, Environment and Plant Sciences, Stockholm University.

The study focused on fish living in the open waters. Therefore, nothing could be said about how seals affect salmon, eel, pike or whitefish that live closer to the coast.

“We want our insights to affect management and conservation that considers the whole ecosystem and multiple pressures, not only the direct biological interaction between fisheries and seal. Often debates about the impact of seals arise from poor understanding of the complexity of predator-prey interactions”, says Monika Winder.

Eleven seal species nearly exterminated

This 2017 video is called Cute baby seals doing funny things compilation.

From Bielefeld University in Germany:

Eleven seal species narrowly escaped extinction

November 16, 2018

Their fur was used as a raw material for coats; their fat was used for oil lamps and cosmetics: right up to the end of the nineteenth century, millions of seals were being hunted and killed every year worldwide. The consequences of this episode of commercial hunting for today’s seal populations is the subject of a study published today (16.11.2018) in Nature Communications. Population geneticists at Bielefeld University and the British Antarctic Survey have found that eleven seal species only narrowly escaped extinction. The scientists managed to include nearly all of the species alive today in their research. The study nevertheless reveals that most species survived the heyday of seal hunting in sufficient numbers to retain most of their genetic diversity.

‘Hunting, epidemics, and climate change all have the potential to reduce the number of individuals in a population to the point where genetic diversity is lost’, says Professor Dr Joseph Hoffman, head of the Molecular Behavioural Ecology research group at Bielefeld University and sub-project manager in the Transregio Collaborative Research Centre NC³ that is studying animals and their individual niches. ‘These extreme population reductions are known as bottlenecks and can affect a species’ potential to survive’.

‘When a species lacks genetic diversity, it has a lower chance of adapting to changing environmental conditions or protecting itself against parasites or pathogens. You can compare the gene pool with a toolbox: the fewer tools you have, the less well-equipped you are for different situations,’ says Hoffman.

The researchers analysed which seal species passed through bottlenecks due to overhunting. They carried out this research in cooperation with colleagues in ten different countries. ‘This enabled us to collect genetic data on thousands of seals from 30 different species’, says Martin Stoffel, the lead author of the study and a doctoral student in Joseph Hoffman’s research group. As there are 33 different seal species alive today, this makes the study the most comprehensive work on the genetic diversity of seals. For example, it even used data from a study of the Antarctic fur seal that lives on Bird Island (South Georgia) in the Sub Antarctic. This research on fur seals is part of the work at the Transregio Collaborative Research Centre NC³.

In their analyses, the researchers used computers to simulate how much genetic diversity would be expected in each seal species if that species were hunted to the brink of extinction around a hundred years ago. They compared these computations with the genetic data from animals living today.

The result: seal hunting around a century ago led to the near extinction of almost one-third of the species studied. ‘Most species have recovered and are still genetically quite diverse despite strong population declines’ says Martin Stoffel.

‘However, there are four exceptions: the northern elephant seal, the Mediterranean monk seal, the Hawaiian monk seal, and the Saimaa ringed seal,’ says Stoffel. ‘The genetic material of individual animals within these species is very similar. These four species only have up to 20 per cent of the genetic diversity of those species that have been hardly or not hunted at all. In the northern elephant seal, for example, only few dozen individuals survived hunting to rebuild the current population of over 200,000 animals.’ Stoffel is an expert on the northern elephant seal. To study them for his dissertation, he went on an expedition to the Islas San Benito, an uninhabited group of islands off the Mexican Pacific coast.

Which factors explain why certain species suffered more from being hunted than others? The study confirms that ‘species that bear their young on land declined much more strongly as a result of excessive hunting than species that give birth on ice,’ says Stoffel. ‘This is probably because those giving birth on ice tend to live in remote Arctic and Antarctic areas where they were out of reach of hunters.’ Population bottlenecks can also be found in those species where a single male defends a harem of several dozen females during the breeding season. ‘This is the case with the northern elephant seal and the southern elephant seal just as much as the Antarctic fur seal’, says Stoffel. ‘Their mating systems result in dense aggregations of breeding animals, making them easier for hunters to kill.’

Whereas at the end of the nineteenth century, millions of seals were still being killed by hunters, the German animal protection society (Tierschutzbund) reports that nowadays, 750,000 seals are killed each year for commercial purposes. Most of these seals are now being hunted in Canada, Greenland, and Namibia.

Scientists have already observed and predicted that high ringed seal pup mortality rates are linked to poor environmental conditions like early ice breakup and low snow. Researchers have now gone a step further by coupling these hypotheses with forecasts of future spring snow and ice conditions, developing a mathematical model, and following it to some stark conclusions for populations off the Amundsen Gulf and Prince Albert Sound in Canada: here.