Curious Kids: What sea creature can attack and win over a blue whale?



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Blue whales are the largest creatures to have ever lived on Earth.
Shutterstock

Wally Franklin, Southern Cross University and Trish Franklin, Southern Cross University

This is an article from Curious Kids, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky! You might also like the podcast Imagine This, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.


What sea creature can attack and win over a blue whale? – Drake, age 7, Sydney.


Hi Drake. That is an interesting question.

As you probably know, blue whales are the largest creatures to have ever lived on Earth – bigger than any dinosaur. They can grow up to 30 metres in length and weigh over 150 tonnes. This is very, very BIG. To give you an idea of how big a blue whale is, it’s the size of a Boeing 737 plane! Because of their size, power and speed, adult blue whales have virtually no natural ocean predators.

The only sea creature known to attack blue whales is the orca whale (scientific name: Orcinus orca) also known as the “killer whale”. They have been known to work in groups to attack blue whales.

However, there are very few reports of orcas actually killing blue whales. We know that orca whales interact with them because many blue whales carry scars from the teeth of orcas. But blue whales probably see orcas as more of a pest than a predator.

Orcas have sharp teeth.
Shutterstock



Read more:
Curious Kids: Why do sea otters clap?


Blue whales can grow 30 metres in length and weigh over 150 tonnes.
Kurzon/Wikimedia Commons, CC BY-SA

The human threat

A much more serious problem for blue whales is humans. Humans have caused a lot of trouble for blue whales over the years.

One big problem is what we call “ship strikes”. This is when large ships collide with blue whales causing dreadful wounds and, in many cases, death.

Blue whales migrate freely across all the great oceans of the world to breed. They travel each year to the Antarctic in search of food. Global warming is a major future threat to their way of life. This is because rising sea temperatures and ocean acidification (which are caused by climate change) are likely to cause severe disruption to the production of their main food source, the very small crustacean we call “krill”.

Blue whales were the target of commercial whalers, mainly in Antarctica, between 1900 and the 1970s. During that time, over 330,000 blue whales were killed.

Fortunately – and only just in time – the International Whaling Commission banned commercial whaling in 1966. Blue whales are now a protected species and are recovering from the brink of extinction. People on whale watching trips at various locations around the world can see them, if they are lucky. The risk of whaling still exists in several countries, including Japan, Iceland and Norway. Many people in these countries are seeking to return to commercial whaling. Recently, whalers in Iceland killed a hybrid blue whale.

Blue whales can talk

One of the most interesting things about blue whales is that they use very low frequency sounds to communicate. Through this they can talk to each other over great distances. The low frequency sounds can pass through the earth, so it’s possible to record their songs and sounds from anywhere in the world.

In the 1960s, an American scientist called Chris Clark got permission to use the USA’s submarine listening system across the Atlantic Ocean to listen to blue whales. One day, he heard a blue whale calling from the far northeast Atlantic Ocean and realised another whale many thousands of miles away in the southwest Atlantic Ocean was answering it. Through their calls, he tracked them over the next few weeks moving towards each other. The two blue whales met and spent time together in the middle of the Atlantic. Then they separated and went on their way!

A pair of blue whales swims under the surface in Monterey Bay, California.
Shutterstock

It is important for all who are interested in the conservation and protection of these amazing creatures to remain vigilant and involved in making sure that they remain safe. Whales are part of the international heritage of all people of the Earth.




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Curious Kids: How do plastic bags harm our environment and sea life?


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Wally Franklin, Researcher and co-director of the The Oceania Project, Southern Cross University and Trish Franklin, Researcher and co-director of The Oceania Project , Southern Cross University

This article was originally published on The Conversation. Read the original article.

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Antarctica’s blue whales are split into three distinct populations


Catherine R. M. Attard, Flinders University; Luciana Möller, Flinders University, and Luciano Beheregaray, Flinders University

Antarctica’s critically endangered blue whales, the world’s largest animal, are made up of three populations, according to our new DNA analysis.

Although the groups occur together when feeding in Antarctic waters, they are genetically distinct. This suggests that the three groups breed in different locations – possibly even different oceans – when they head north in the winter.

If we can find out where they go, and what hazards they face on the way, we will be a step closer to helping them recover from their near-annihilation by whalers during the 20th century.

Hidden giants

It is a daunting task to understand the ecology of the Antarctic blue whale (Balaenoptera musculus intermedia). Even though they can weigh more than 160 tonnes – the heaviest ever known animal – and reach more than 30 metres in length, locating such a rare and highly mobile species in a vast and remote ocean can be like finding a needle in a haystack. And even having tracked them down, it can be hard to deduce anything about their population structure.

The largest animal in the world.
Paula Olson, courtesy of IWC

By comparing similarities and differences in the DNA of individuals, we can tell which individuals are part of the same population and estimate the number of populations. Individuals from the same breeding population are more genetically similar than those from different populations. But we need recently collected DNA samples to do this for current populations.

The standard way to get DNA from a blue whale is to take a biopsy by firing a dart that collects a small piece of skin and blubber, bounces off the whale and floats on the water for collection. It is akin to a pinprick for an animal as massive as a whale.

Long before we started working with blue whales in 2007, expeditions have been carried out under the auspices of the International Whaling Commission to research Antarctic whales. These expeditions involved collecting precious biopsy samples from blue whales and there is now a collection stretching back to 1990.

We were granted access to samples, totalling 142 whales, and used these to create the largest and therefore most powerful genetic data set so far created for Antarctic blue whales. As our research published in Nature’s Scientific Reports shows, we found that these whales fall into three genetically distinct groups.

Where are these populations?

Blue whales, like many other whales, migrate between their Antarctic summer feeding grounds and their winter breeding grounds at lower latitudes.

We know Antarctic blue whales feed in the Antarctic, which is where they were hunted during whaling in the 20th century and where the biopsy samples were collected.

We found that individuals from the three populations occur together throughout the Antarctic, although possibly in different proportions in different areas. This is probably because the blue whales need to rove long distances around Antarctica to find the massive amounts of krill that make up their sole food source.

https://c311ba9548948e593297-96809452408ef41d0e4fdd00d5a5d157.ssl.cf2.rackcdn.com/2016-08-03-distribution-of-whale-populations/whales.html

Distribution of samples from the three genetically distinct populations of Antarctic blue whales

We suspect that the three populations go their separate ways when they head north to breed – presumably heading into the three major Southern Hemisphere ocean basins: the South Pacific, South Atlantic and Indian Oceans.

The next step will be to confirm this by finding their breeding grounds. This would involve satellite-tagging whales in Antarctic waters and then watching where they go. More biopsy samples could then be taken at the breeding grounds to confirm which populations are which.

Knowledge for conservation

Understanding the number of populations and their distribution is vital for helping Antarctica’s blue whales recover from 20th-century whaling, which reduced their numbers from 239,000 to just 360 individuals. While they are now protected from whaling, they remain critically endangered.

Some populations may be more endangered than others and may face different human threats along their migration routes and at their breeding grounds. Failing to take conservation action at a population level could therefore lead to local extinctions at these locations.

One threat that differs in intensity between locations is noise pollution, such as from seismic surveys for oil and gas as well as shipping activity. These noises can be heard underwater hundreds of kilometres from their source. Whales communicate through sound, so noise pollution can hinder their communications or, in extreme cases, make areas uninhabitable.

Our latest findings, together with our previous work on hybridisation, connectivity and population history of blue whales, provides important pieces in the puzzle of this species. But we are still at the tip of the iceberg in our understanding of the world’s largest animal and in the pathway to their recovery from whaling.

The Conversation

Catherine R. M. Attard, Lecturer in Molecular Ecology, Flinders University; Luciana Möller, Associate Professor in Marine Biology, Flinders University, and Luciano Beheregaray, Professor in Biodiversity Genetics and ARC Future Fellow, Flinders University

This article was originally published on The Conversation. Read the original article.