3 types of bears and old sharks


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The Conversation

We found grizzly, black and polar bears together for the first time

November 20, 2018

Author: Douglas Clark, Centennial Chair in Human Dimensions of Environment & Sustainability, University of Saskatchewan

Disclosure statement: Douglas Clark receives funding from The Social Sciences and Humanities Research Council of Canada. This research has also been financially supported by Parks Canada, the University of Saskatchewan, and the Churchill Northern Studies Centre’s Northern Research Fund.

Partners: University of Saskatchewan provides funding as a founding partner of The Conversation CA.

North America’s three bear species — black bears, grizzly bears and polar bears — don’t typically live in the same place. But in Wapusk National Park, on the west coast of Hudson Bay in northern Manitoba, we caught all three bears on camera — for the first time.

My colleagues and I began studying the bears in Wapusk in 2011, after more polar bears than expected began visiting new field camps in the park. We used remote cameras — a widespread, economical and non-invasive tool for studying wildlife — to find out why and when the polar bears were visiting these camps.

The cameras picked up more than 366 visits by polar bears to the camps in five years. They also detected other bears.

A bevy of bears

Wapusk is best known for its polar bears. They come ashore in the summer and autumn when the sea ice in Hudson Bay melts. Some stay for the winter to den in the permafrost where they give birth. What we see on the cameras reflects that pattern.

But Wapusk also lies along the northern edge of the boreal forest, where black bears are well established. We saw them too, but we were surprised that their visits to our most southerly cameras, on the Owl River, were almost as numerous as those by polar bears.

What was new to us were the grizzlies. It wasn’t just one or two transient bears, but several, and we suspect at least one of them may be denning there.

Barren-ground grizzly bears have been expanding their range across the Arctic in recent decades. In Wapusk, they’ve been increasingly frequent since the 1990s, and have even shown up in the nearby town of Churchill.

Ecosystem convergence

There’s much our observations don’t tell us, but they are significant for conservation efforts and, more fundamentally, for understanding what to do with these new ecological insights.

Three dynamic ecosystems — forest, tundra and ocean — converge at Wapusk, and all are changing quickly as the Arctic warms.

What we’ve seen in Wapusk is consistent with how researchers expect northern carnivore populations to respond to climate change. The waking life of all bear species is governed by their need to accumulate fat stores for the next hibernation, so this overlap is most likely a response to changes in the availability of bear foods. Which foods, however, we don’t yet know.

We also don’t know how these species interact with each other, but we predict that grizzlies will benefit most since they dominate both other species elsewhere.

Grizzly bears have displaced and eaten black bears and polar bears in other places, and polar-grizzly hybrids have been documented in the Northwest Territories. It’s clear that the potential for hybridization exists in western Hudson Bay too.

Polar bears and grizzly bears face conservation challenges in many parts of Canada. Learning more about they way they interact with each other — and their surroundings — would probably tell us more about why they are now inhabiting the same place.

Controversial change

But how might we use this information?

When environmental changes occur in national parks, they often become controversial. People often assume the conditions present when the park was established, or the status quo, are “baselines” that must be protected, even though they may just be snapshots in ecological time.

Change has become increasingly central in ecological theory, and its implications have produced heated debate within the conservation community.

This matters for the grizzly because its expansion into the Arctic has been portrayed as a threat to polar bears. Some argue such a threat should be removed.

In 1998, when I worked in Wapusk, I was told by a manager to get rid of the first grizzly we saw. (I didn’t.)

Such actions might not be wise since the long and complex evolutionary relationship between grizzlies and polar bears suggests their populations have, at times, benefited from the other.

Instead of looking at this new range overlap as a risk to any of the bears, my colleagues and I think it should be viewed as an ecological response to environmental change that needs to be better understood.

What’s at stake?

While locals may not be surprised by this scientific observation of the three bears, it is a novel situation that we can learn from — and one that matters beyond northern Manitoba.

Climate change will continue to move species around and create new combinations of them. It’s no easy task for wildlife or park managers to determine which environmental changes are desirable and which aren’t.

Wapusk, however, is a co-managed park that aims to integrate scientific and traditional knowledge with human values. It is equipped for addressing these hard questions. And the question of how to navigate increasing environmental variability more effectively — while recognizing the stakes local people have in these conservation decisions — is the biggest challenge environmental managers face today.

This particular story of the three bears isn’t over, and we don’t know how it will end. Consequently, we need to bring a heavy dose of humility to answering the scientific and societal questions the three bears have handed us.

The Conversation

Caught on camera: Ancient Greenland sharks

February 27, 2018

Authors

Brynn Devine

Ph.D. candidate, Memorial University of Newfoundland

Jonathan A. D. Fisher

Research scientist, Memorial University of Newfoundland

Disclosure statement

Brynn Devine receives funding from the Research and Development Corporation of Newfoundland & Labrador.

Jonathan Fisher receives funding from the Natural Sciences and Engineering Research Council of Canada and the Ocean Frontier Institute (OFI; www.oceanfrontierinstitute.com). The OFI was established within the Canada First Research Excellence Fund. The Centre for Fisheries Ecosystems Research receives funding from the Government of Newfoundland and Labrador.

Partners: Memorial University of Newfoundland provides funding as a founding partner of The Conversation CA.

The Greenland shark is one of the world’s largest marine species, reaching lengths over six metres. And yet these fish, which prefer the deep, cold waters of the Arctic and North Atlantic oceans, have largely eluded scientific study.

Their evasiveness highlights how little we know about Arctic marine ecosystems — and how much we can learn by developing and employing new technologies.

For scientists like us, the observation and monitoring of marine species can be challenging under the best of circumstances. But sampling at extreme depths and in seasonally ice-covered waters is especially difficult.

However, we recently captured some of the first underwater video footage of Greenland sharks in the Canadian Arctic. The recordings gave us valuable insight into their abundance, size and behaviour, as well as their distribution in the Canadian Arctic.

These findings are the first step towards closing a major knowledge gap on the population status of the Greenland shark.

And we did it without taking any sharks from the water.

Sleeper sharks revealed

Until now, most of what we knew about Greenland sharks came from the historical records of commercial landings. They were fished in the North Atlantic for their oily livers until 1960. A limited harvest still occurs in Greenland, and the species is sometimes encountered as bycatch in fisheries that occur within its geographical range.

But in areas of the North Atlantic and Arctic where commercial fishing has not historically occurred — such as the waters of the Canadian Arctic Archipelago — their full geographic range has remained unknown.

Due to their sluggish and seemingly lethargic behaviour, the Greenland shark is part of the family of “sleeper sharks.” Despite being remarkably slow swimmers and effectively blind, thanks to eye parasites, the Greenland shark is one of the Arctic’s top predators.

Although they feed mostly on a diverse buffet of bottom-dwelling fishes, there is some evidence that they can capture live seals. Just how they catch these fast-swimming marine mammals, remains a mystery to researchers.

Greenland sharks are by far the largest fish in the Arctic. They rival the Great white shark in length, if not its fear factor.

Scientists have also puzzled over their life span and growth rates. They appear to grow extremely slowly — less than one centimetre per year — and are believed to not reach maturity until females are 4.5 metres long and males are three metres long.

They also have remarkable lifespans. Scientists recently used radiocarbon dating techniques on the eye lens of a Greenland shark, and found they can live for more than 272 years, making the species the longest living vertebrate on the planet.

While these are impressive traits, their age and large size leave Greenland sharks more vulnerable to stressors such as overfishing or habitat loss than other fishes.

Candid camera

Scientists know little about Greenland sharks living in the unfished waters of the eastern Canadian Arctic. To help collect information on sharks residing in this region, we baited cameras with squid and dropped them into the deep waters of Nunavut.

After two summer field seasons, we had more than 250 hours of high-resolution video recorded from 31 locations.

Greenland sharks arrived at 80 per cent of our deployments. We used the video to distinguish one individual from the next based on their unique skin markings, a method researchers also use to identify for whale sharks and great white sharks. Altogether, we identified 142 individual sharks.

The videos also gave us additional information about the sharks, including their length and swimming speeds. In some locations, the sharks were relatively small — less than 1.5 metres long — in others, they were over three metres long, but nearly all of them were likely still too young to reproduce.

Researchers are increasingly using video to survey marine wildlife. Baited-camera surveys eliminate the adverse effects of scientific longline surveys, where fish are caught on hooks. Even though the sharks are later released, many suffer from the stress of capture or can become entangled in the fishing gear, which can lead to death.

New information for a changing Arctic

We did most of this work within the region of Tallurutiup Imanga (Lancaster Sound), which could become Canada’s largest marine protected area.

This area is known as a vital feeding and nursery ground for many Arctic species of both ecological and Inuit cultural significance, including whales, seabirds, polar bears, seals and walruses. Our video data now shows that this area might of be important to Greenland sharks too, at least in summer months.

In addition, given the significance of top predators in controlling the dynamics of high latitude marine ecosystems, the role of Greenland sharks may represent an important link in Arctic food webs.

At a time when oceans are rapidly warming, Arctic sea-ice cover is shrinking and there is increasing interest in Arctic fisheries and conservation, it’s important that we understand the domains of these large, ancient creatures.

The Conversation

A 400-year-old shark is the latest animal discovery to reveal the secrets of long life

August 11, 2016

Author: Paul Butler, Research Lecturer, School of Ocean Sciences, Bangor University

Disclosure statement: Paul Butler receives funding from the EU.

Partners: Bangor University provides funding as a member of The Conversation UK.

For the local Pangnirtung Inuit, the Greenland shark is an animal that does not die easily.

Dad used to say to me that sharks’ flesh has a hard time dying. The shark can be rotten, even sticky rotten, and when you touch the skin or the meat it still moves. You know, it is still alive but it is rotten.

This might sound rather gruesome, but it turns out that this reputation has an element of truth to it. With an estimated lifespan of 400 years, the Greenland shark has just been reported to be the longest-lived vertebrate on the planet. This is only the latest of a series of recent findings that push the boundaries of animal longevity, and it raises the perennial question of what factors enable some animals to achieve what we might call extreme longevity – lifespans that can be measured in centuries.

The key to becoming a long-lived species is for individuals to regularly die of old age (and not from disease or being eaten) in the first place. Experiencing age-related degeneration allows a species to evolve resistance to it. So an effective defence mechanism against predators, such as a thick external shell, must be in place first. Once this “safe space” has been achieved, living longer becomes a way to produce more offspring in the most efficient way, especially when the food supply is intermittent.

Here are five of the longest-living animals ever recorded.

1. Greenland shark

As well as being a top predator itself, the Greenland shark has developed a defence against predators in the form of highly poisonous flesh. Not being hunted in its early years allows the shark to pursue a more relaxed reproductive strategy. Females don’t reach reproductive maturity until an estimated age of 150 years.

At the high latitudes where the shark lives, the limited amount of light during the winter means fewer plants and algae for other creatures to feed on, which can affect the amount of nutrients right up the food chain. So the ability to withstand the poor years and reproduce during the good years is key to the shark’s’ survival, and a long lifetime is a great way to maximise the number of good years. Bottom of the sea, top of the pile.

2. The ocean quahog

The clam species Arctica islandica holds the record for the longest-lived animal known to science. We can measure its exact age by counting the annual bands in its shell, and this is how we identified a specimen (now popularly known as “Ming”) collected from Iceland that had lived for 507 years.

In common with many species of mollusc, A. islandica grows more slowly and lives longer with increasing latitude. North of Iceland, they regularly live more than 300 years, while further south in European and North American waters (where nutrients are less limited) their age limit is about 250 years. As with the Greenland shark, this is a useful reproductive strategy in nutrient-poor waters when there is no threat from predators.

3. Bowhead whale

A bowhead whale collected during a whaling expedition off Alaska in 2007 was found to have the head of a late 19th-century harpoon embedded in its neck blubber. Its age was estimated by radiocarbon dating to be 211 years, making this the longest-lived mammal so far identified. Unlike other whales, the bowhead lives entirely in cold Arctic and subarctic waters. Once again, this suggests a strategy that uses longevity to compensate for low nutrients in the winter.

Analysis of bowhead whale DNA suggests that the lack of natural predators has enabled the whale to evolve natural mechanisms to resist age-related decline. For example, cancer, while occasionally present, is extremely rare.

4. Giant tortoise

The only terrestrial animal known to live beyond 200 years, the giant tortoise, is now confined to a few islands in the Indian and Pacific Oceans. An individual Aldabra giant tortoise died in a Kolkata zoo in 2006 at an estimated age of 255 years. The oldest giant tortoise living now, a Seychelles tortoise called Jonathan is reportedly 184 years old.

The giant tortoise employs a “belt and braces” approach to predators, and maintains its thick shell even while living on isolated predator-free islands. Without the fear of predators, the animal can –- like the Greenland shark and A. islandica – slow its metabolic activity right down, helping it to survive periods of drought when food supply is limited.

5. Homo sapiens

Jeanne Calment, who died in 1997 at the age of 122, was the oldest person (and probably the oldest land mammal) ever to have lived whose age has been precisely verified. In fact, Homo sapiens is the only terrestrial mammal known to live for more than 100 years, and it is an interesting question whether this was the case even before the advent of organised agriculture.

One indicator of longevity in mammals seems to be brain size. This reflects an increased ability to adapt to a changing environment and, of course, is also an effective defence against predators. It seems that even early humans, if they could survive childhood, commonly lived to 70 or 80 years, significantly longer than the other great apes. The frequency with which modern humans live beyond 100 years may also be related to modern medical practice, or may simply reflect the sheer number of humans.

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