Why scientists need your help to spot blue whales off Australia’s east coast

Vanessa Pirotta, Macquarie UniversityBlue whales, the largest animals to ever live, are surprisingly elusive.

They’re bigger than the biggest dinosaur ever was, capable of growing over 30 metres long and can weigh over 100 tonnes — almost as long as a 737 plane and as heavy as 40 elephants. They also have one of the loudest voices, and can talk to each other hundreds of kilometres across the sea.

Why, then, are they so difficult to find in some parts off Australia?

My new research paper recorded only six verified sightings of the pygmy blue whale off Sydney in the last 18 years. Two of these occurred just last year. This blue whale subspecies is known to mostly occur along Australia’s west coast.

Rare sightings like these are important because pygmy blue whales are a “data deficient” animal. Every opportunity we have to learn about them is crucial to help us better protect them.

Blue whales down under

Don’t let its name fool you, the pygmy blue whale can still grow shockingly large, up to 24 metres in length. It’s one of two blue whale subspecies that occur in Australian waters – the other being the Antarctic blue whale, the biggest whale of them all at around 33 metres long.

A blue whale lunging for krill.

Unfortunately, historical whaling hunted blue whales to near extinction in the Southern Ocean. The Antarctic blue whale was depleted to only a few hundred individuals and, while they’re slowly bouncing back, they’re still listed as critically endangered by the International Union for the Conservation of Nature (IUCN).

In contrast, we know little about pre- and post-whaling numbers for pygmy blue whales. Their listing as a data deficient species by the IUCN means we don’t have a full understanding of their population status.

Blue whales can grow to around 30 metres, almost the same length as a 737 plane.
Vanessa Pirotta, Author provided

One reason may be because blue whales are logistically challenging to study. For example, blue whales don’t just hang around in one area all the time. They’re capable of swimming thousands of kilometres for food and to breed.

They can also hold their breath for up to 90 minutes underwater, which can make them hard to spot unless they’re near the surface. To see them, people need to be in the right place at the right time.

This may require scientists to be on dedicated research vessels or in a plane to spot them, which can be expensive and weather-dependent.

This also makes learning about them much harder compared to other, more accessible species, such as coastal bottlenose dolphins.

To learn more about pygmy blue whales in Australia, marine scientists have developed a variety of techniques, including listening to whales talking, taking skin samples and satellite tagging.

While this work is useful, it has focused mainly in areas where pygmy blue whales are known to occur, such as southern and western Australian waters.

Pygmy blue whales are known to feed in the Perth Canyon, Western Australia, and between the Great Australian Bight and Bass Strait during summer. They most likely breed in the Indian and western Pacific Oceans during winter.

But we don’t know much about pygmy blue whale presence in other parts of Australian waters, such as the east coast.

Two bottle nose dolphins — Bottlenose dolphins are more commonly seen.
Shutterstock

How can we conserve a species we know very little about?

Well, it can be tricky. The more information we know, the better we’re placed to assess their conservation needs. But focusing our efforts on species we know nothing about may require a conservative approach until we learn more.

Some would argue it’s better to protect a species we know needs our conservation dollar before spending precious resources on something uncertain.

Fortunately, Australia has some of the world’s best protection policies for marine mammals, including whales. This means a precautionary approach is already in place to protect these creatures.

Since blue whales are listed as a threatened species, they’re protected under Australia’s primary environment law, the Environmental Protection and Biodiversity Conservation (EPBC) Act.

And on an international level, Australia is a signatory to the International Whaling Commission (the global body for whale conservation) and the Convention on International Trade of Endangered Species (which ensures wildlife trade doesn’t threaten endangered species).

Two blue whales near a boat — Citizen science sightings help contribute to our understanding of blue whale distributions in Australian waters.
Shutterstock

To help uphold this international and national protection, scientists must continue to learn more about data-deficient animals like the pygmy blue whale to help safeguard against known and future threats.

This includes collisions with ships, overfishing, entanglement with fishing gear, increased human activity in the ocean, and climate change, which may affect when and where whales occur.

We need extra eyes

There are more than 14,600 animal species listed as data deficient by the IUCN.

Some, like the pygmy blue whale, are poorly studied. One reason is because they’re cryptic or boat shy, such as the Australian snubfin dolphin.

Or, they might be tricky to see, such as the false killer whale, whose sightings remain irregular in Australian coastal waters. Opportunities to learn more about them occur when they become stranded.

A false killer whale pokes its head out of the water — False killer whales are another data-deficient marine animal.
Shutterstock

So while citizen science sightings of pygmy blue whales may be rare off the Australian east coast, they do help contribute to our understanding of their distribution in Australian waters.

The two sightings of pygmy blue whales off Maroubra, Sydney, last year were within two months of each other. This was thanks to drones (flown under state rules).

This prompted my research review of blue whale sightings off Sydney, which found citizen scientists made similar sightings in 2002 – the first official sighting from land off Sydney — and between 2012-14.

We don’t know exactly what type of pygmy blue whales these are (three distinct groups are recognised: the Indo-Australian, New Zealand and Madagascar groups). However, whale calls detected along Australia’s east coast in previous years suggest they’re most likely New Zealand pygmy blue whales, and they could have been heading to breeding waters north of Tonga.

So, the next time you are by the sea, keep a look out and tell a scientist via social media if you see something interesting. You just never know when the world’s biggest, or shiest, animal may turn up out of the blue.

Vanessa Pirotta, Wildlife scientist, Macquarie University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Humpback whales have been spotted ‘bubble-net feeding’ for the first time in Australia (and we have it on camera)

Vanessa Pirotta, Macquarie UniversityIf you gaze at the ocean this winter, you might just be lucky enough to spot a whale migrating along Australia’s coastline. This is the start of whale season, when the gentle giants breed in the warm northern waters off Australia after feeding in Antarctica.

This north-south migration happens every year, but the whales can still surprise us. Thanks to a citizen scientist and his drone, humpback whales were seen feeding in a mass super group and “bubble-net feeding” off the New South Wales coast last year.

As my new research paper confirms, this a big deal for two reasons: it’s only the second time a super group of humpbacks has been observed in the southern hemisphere (a first for Australia) and the first time bubble-net feeding has been seen in Australia.

So what is bubble-net feeding, and why are these observations so important?

Blowing bubbles, catching krill

Bubble-net feeding is when whales deliberately blow bubbles from their noses to encircle their food — krill and fish — like a net, concentrating their prey into a tight ball. Then, the whale or group of whales swim together from beneath, rise to the surface opening their mouths, and gulp up their prey.

It remains a mystery as to why the whales feed in this way and how they learned to do it.

Drone footage of a super group of humpback whales, some of which are bubble-net feeding. Video: Brett Dixon.

2020 was a year full of unprecedented events, and the humpback whales certainly didn’t disappoint.

Humpback whales in this eastern Australian population are usually observed lunge feeding on their side, or feeding below the surface. Bubble-net feeding, on the other hand, is mostly documented in some Northern Hemisphere populations.

But we know there are individual whales in the eastern Australian humpback population who bubble-net feed in Antarctic waters. This means the unique behaviour in Australian waters may have evolved independently, or through cultural transmission (learning new behaviours from different whales).

The drone footage and observations made in September from whale-watching boats was the first to document bubble-net feeding. To add to the excitement, citizen scientists also documented bubble-net feeding behaviour further south of Tasmania a month later.

Drone footage captures humpback whales feeding in large numbers off the New South Wales coast.
Brett Dixon

Using stills from the September drone footage, an estimated 33 humpback whales can be seen feeding at the same time. Unfortunately, it’s not known exactly what the whales were feeding on.

Until then, humpback whale congregations this large had never been observed in Australian waters.

In fact, the only other time a mass humpback feeding event has been seen in the Southern Hemisphere was off South Africa in 2011 (this now occurs regularly there). This was the first time the term “super group” was used to describe a group of 20 or more whales feeding this way.

Humpback whale rising up in the middle of a visible bubble-net to engulf its prey.
Jessica Millar/Sapphire Coastal Adventures

But why were they feeding in ‘breeding waters’ anyway?

The majority of the east Australian humpback whale population spends the summer months feeding in Antarctic waters. They then head north to warm breeding waters in the Great Barrier Reef during winter (June-August) to mate and give birth.

They forego feeding for love — humpbacks can go for months without eating, relying instead on energy reserves in order to reproduce. Animals that do this are called capital breeders.

From August to November, humpbacks migrate southward back to Antarctica. Along the way, they sometimes take a “pit-stop” on parts of Australia’s east coast to feed.

It was originally thought this population never fed along the migratory route. However, we know they do now to possibly supplement their energy intake as they migrate.

Humpback whales migrate along the east coast of Australia annually for warmer breeding waters in the Great Barrier Reef.
Dr Vanessa Pirotta

So why are these observations important?

Whales play important an important role in the ecosystem of the ocean because they feed in one area and poo in another.

This action — known as the “whale pump” — moves nutrients around the ocean. Their poo feeds tiny organisms, such as plankton, which are eaten by krill, and then eaten by whales.

Seeing these super group feedings highlights changes in our marine environment we might not have otherwise been aware of.

Bubble net feeding in Antarctica.

One possible explanation for this behaviour could be favourable environmental conditions. A combination of ideal water temperatures and nutrients may have resulted in an abundance of food, which saw large numbers of humpback whales feeding in the same area.

Or perhaps it has something to do with the recovery of the east coast humpback whale population, which has been increasing in numbers since whaling ended in the 1960s.

Humpback whales engulfing their prey after bubble-net feeding cooperatively off the New South Wales coast.
Wayne Reynolds/Sapphire Coastal Adventures

Regardless, it’s important to understand how changes in the marine environment influence the extent humpback whales depend on feeding opportunities along their migratory route.

This will help to predict how whale populations respond to future changes in the ocean. This includes climate change, which will warm ocean temperatures and alter when and where the prey of humpback whales are found. As a result, humpback whales will also move to different locations.

One thing, at least, is abundantly clear: more eyes on land and sea through citizen science will provide a valuable opportunity to document such exciting future events. So keep your eyes peeled for whales this season, and be sure to tell a scientist if you see something unexpected.

Vanessa Pirotta, Wildlife scientist, Macquarie University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Humpback whales may have bounced back from near-extinction, but it’s too soon to declare them safe

Olaf Meynecke, Griffith UniversityThe resurgence in humpback whale populations over the past five decades is hailed as one of the great success stories of global conservation. And right now, the federal Department of Agriculture, Water and the Environment is considering removing the species from Australia’s threatened list.

But humpback whales face new and emerging threats, including climate change. Surveying whales is notoriously hard, and the government has not announced monitoring plans to ensure humpback populations remain strong after delisting. We need a plan to keep them safe.

Australia’s whale season is about to begin. Each year between May and November, the mammals migrate north along Australia’s coastline from their feeding grounds in Antarctica to warmer waters. There, they breed before returning south.

So now’s a good time to take a closer look at the status of this iconic, charismatic species.

A pod of humpback whales lunge feeding. — The resurgence of humpback whales is one of conservation’s greatest success stories.
Shutterstock

A host of threats

Humpback whales live in every ocean in the world, and have one of the longest migrations of any mammal.

Humpback whale numbers dwindled as a result of commercial whaling, which in Australia began in the late 18th Century. Whaling and the export of whale products was Australia’s first primary industry. Between 1949 and 1962 Australia’s whalers killed about 8,300 humpback whales off the east coast, until only a few hundred were left.

The International Whaling Commission banned humpback whaling in the Southern Hemisphere in 1963. By then, humpback populations had fallen to about 5% of pre-whaling numbers. In the years since, some whaling continued, but has now largely ceased.

Today humpback whales face new threats. These include:

underwater noise which interferes with whale communication
pollution
vehicle collisions
getting caught in fishing gear
over-harvesting prey such as krill
marine debris
habitat degradation
climate change.

In particular, the effects of climate change – such as warming waters, shifting currents and ocean acidification – may affect the availability of prey that humpback whales need to survive.

Combined, these worsening threats could disrupt humpback whales’ recent resurgence. Indeed, under one scenario, scientists predict the increase Australia’s humpback numbers could stall — or worse, start declining – in the next five to ten years.

A humpback whale calf caught in a fishing net.
SeaPix, Author provided

The humpback whales’ plight

According to the federal government’s delisting assessment, humpback whales’ strong recovery suggests current threats are not a risk to the population. But this assessment has shortcomings.

It states humpback whales on Australia’s east and west coast have reached, or are exceeding, the original population size – increasing by 10-11% a year over the past decade or longer.

But this information is based on models using data collected prior 2010 for Australia’s west coast, and prior to 2015 for the east coast. This data isn’t readily available to the public and does not include recent population trends.

The predicted population growth from these models doesn’t account for current and future impacts from major threats, including climate change. This is despite recent research and observations suggesting changes in the humpback population.

For example, 2019 research showed potential shifts in calving locations, with newborn humpback whales now frequently spotted outside Australian tropical waters. This — along with the early arrival of migrating humpback whales in Australia in the past years — may be a first sign of changes in breeding and migration habits.

It’s also important to compare humpback whale populations in Australia with those elsewhere, such as in the North Pacific. There, calving rates are declining, and whale abundance and distribution is showing marked shifts. The risk of entanglements with fishing gear is also rising.

A whale tail with a fishing line caught in it — Whales can get caught in fishing gear.
Todd Burrows, Author provided

The problem with counting whales

The pre-whaling population size of humpback whales on the east and west coast of Australia is thought to be between 40,000 and 60,000. But information is limited and the actual number may have been much higher

Today, the estimated numbers from population models are similar: roughly 28,000 on the east cost and up to 30,000 on the west coast. But counting humpback whales accurately is very difficult. For example, on the east coast of Australia humpback whales frequently move between populations and during a census may not be attributed to their original population.

What’s more, conditions prior to whaling are not comparable with today’s conditions. Krill is a major food source for whales, and widespread whaling in the Southern Hemisphere caused krill numbers to increase. Research from 2019 suggests humpback whales’ fast recovery after whaling ceased may have been due to widely available krill.

But krill numbers have declined or their availability has shortened in recent years due to threats such as climate change and industrial fishing.

Aerial view of humpback under icy water . — Every year humpback whales migrate from Antarctica where they feed, to breed in Australia.
Shutterstock

Proceed with caution

Humpback whales off Australia’s coast will continue to have some protection under the Environment Protection and Biodiversity Conservation Act, even if they’re taken off the threatened species list.

Generally, all marine mammals are protected in Australian waters. But getting delisted means fewer resources devoted to their protection.

Forecasting the complex interactions of today’s threats, in order to predict tomorrow’s humpback whale populations, is challenging. A cautionary approach should therefore be taken.

In 2016, the US delisted some humpback whale populations. But before doing so, it established a ten-year monitoring plan to track population changes, threats and species abundance.

If Australia proceeds with the delisting, it should follow the US’ lead. Humpback whales should remain listed for another five years so a monitoring plan can be developed. Federal and state governments must invest resources into this process, and react swiftly if changes are detected.

A number of whale researchers and organisations concerned about the humpback whale delisting, including the author, prepared a detailed response to the proposal here.

Olaf Meynecke, Research Fellow in Marine Science, Griffith University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Humpback Whales

These are the plastic items that most kill whales, dolphins, turtles and seabirds

Lauren Roman, CSIRO; Britta Denise Hardesty, CSIRO; Chris Wilcox, CSIRO, and Qamar Schuyler, CSIRO

How do we save whales and other marine animals from plastic in the ocean? Our new review shows reducing plastic pollution can prevent the deaths of beloved marine species. Over 700 marine species, including half of the world’s cetaceans (such as whales and dolphins), all of its sea turtles and a third of its seabirds, are known to ingest plastic.

When animals eat plastic, it can block their digestive system, causing a long, slow death from starvation. Sharp pieces of plastic can also pierce the gut wall, causing infection and sometimes death. As little as one piece of ingested plastic can kill an animal.

About eight million tonnes of plastic enters the ocean each year, so solving the problem may seem overwhelming. How do we reduce harm to whales and other marine animals from that much plastic?

Like a hospital overwhelmed with patients, we triage. By identifying the items that are deadly to the most vulnerable species, we can apply solutions that target these most deadly items.

Some plastics are deadlier than others

In 2016, experts identified four main items they considered to be most deadly to wildlife: fishing debris, plastic bags, balloons and plastic utensils.

We tested these expert predictions by assessing data from 76 published research papers incorporating 1,328 marine animals (132 cetaceans, 20 seals and sea lions, 515 sea turtles and 658 seabirds) from 80 species.

We examined which items caused the greatest number of deaths in each group, and also the “lethality” of each item (how many deaths per interaction). We found the experts got it right for three of four items.

Plastic bag floats in the ocean. — Film plastics cause the most deaths in cetaceans and sea turtles.
Shutterstock

Flexible plastics, such as plastic sheets, bags and packaging, can cause gut blockage and were responsible for the greatest number of deaths over all animal groups. These film plastics caused the most deaths in cetaceans and sea turtles. Fishing debris, such as nets, lines and tackle, caused fatalities in larger animals, particularly seals and sea lions.

Turtles and whales that eat debris can have difficulty swimming, which may increase the risk of being struck by ships or boats. In contrast, seals and sea lions don’t eat much plastic, but can die from eating fishing debris.

Balloons, ropes and rubber, meanwhile, were deadly for smaller fauna. And hard plastics caused the most deaths among seabirds. Rubber, fishing debris, metal and latex (including balloons) were the most lethal for birds, with the highest chance of causing death per recorded ingestion.

What’s the solution?

The most cost-efficient way to reduce marine megafauna deaths from plastic ingestion is to target the most lethal items and prioritise their reduction in the environment.

Targeting big plastic items is also smart, as they can break down into smaller pieces. Small debris fragments such as microplastics and fibres are a lower management priority, as they cause significantly fewer deaths to megafauna and are more difficult to manage.

Image of dead bird and gloved hand containing small plastics. — Plastic found in the stomach of a fairy prion.
Photo supplied by Lauren Roman

Flexible film-like plastics, including plastic bags and packaging, rank among the ten most common items in marine debris surveys globally. Plastic bag bans and fees for bags have already been shown to reduce bags littered into the environment. Improving local disposal and engineering solutions to enable recycling and improve the life span of plastics may also help reduce littering.

Lost fishing gear is particularly lethal. Fisheries have high gear loss rates: 5.7% of all nets and 29% of all lines are lost annually in commercial fisheries. The introduction of minimum standards of loss-resistant or higher quality gear can reduce loss.

Other steps can help, too, including

incentivising gear repairs and port disposal of damaged nets
penalising or prohibiting high-risk fishing activities where snags or gear loss are likely
and enforcing penalties associated with dumping.

Outreach and education to recreational fishers to highlight the harmful effects of fishing gear could also have benefit.

Balloons, latex and rubber are rare in the marine environment, but are disproportionately lethal, particularly to sea turtles and seabirds. Preventing intentional balloon releases and accidental release during events and celebrations would require legislation and a shift in public will.

The combination of policy change with behaviour change campaigns are known to be the most effective at reducing coastal litter across Australia.

Reducing film-like plastics, fishing debris and latex/balloons entering the environment would likely have the best outcome in directly reducing mortality of marine megafauna.

Lauren Roman, Postdoctoral Researcher, Oceans and Atmosphere, CSIRO; Britta Denise Hardesty, Principal Research Scientist, Oceans and Atmosphere Flagship, CSIRO; Chris Wilcox, Senior Principal Research Scientist, CSIRO, and Qamar Schuyler, Research Scientist, Oceans and Atmospheres, CSIRO

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Pacific killer whales are dying — new research shows why

A female killer whale leaps from the water in Puget Sound near Seattle.
(AP Photo/Elaine Thompson)

Stephen Raverty, University of British Columbia and Joseph K. Gaydos, University of California, Davis

Killer whales are icons of the northeastern Pacific Ocean. They are intimately associated with the region’s natural history and First Nations communities. They are apex predators, with females living as long as 100 years old, and recognized a sentinels of ecosystem health — and some populations are currently threatened with extinction.

There are three major types of killer whales in the region: the “resident” populations that feed mainly on salmon, the “transients” that prey on other marine mammals like seals and sea lions, and the “offshores” that transit along the continental shelf, eating fish and sharks.

In the 1990s, an abrupt decline in the fish-eating southern resident population dropped to 75 whales from 98, prompting both Canada and the United States to list them as endangered.

A dead killer whale lies on her side in shallow water. — Emaciated female killer whale from Hawaii.
(NOAA/NMFS/PIRO), CC BY

Since then, southern resident killer whales, whose range extends from the waters off the southeast Alaska and the coast of British Columbia to California, have not recovered — only 74 remain today. Because killer whale strandings are rare, scientists have been uncertain about the causes of killer whale mortality and how additional deaths might be prevented in the future.

As a pathologist and wildlife veterinarian, and with the help of countless biologists and veterinarians, we have carried out in-depth investigations into why killer whales in this region strand and died. If we don’t know what is causing killer whale deaths, we are not able to prevent the ones that are human-caused.

We can do better

Human activities have been implicated in the decline and lack of recovery of the southern resident killer whale population, including ship noise and strikes, contaminants, reduced prey abundance and past capture of these animals for aquariums.

Only three per cent and 20 per cent of the northern and southern resident killer whales, respectively, that died between 1925 and 2011 were even found and available for a post-mortem exam. And in most cases, only cursory or incomplete post-mortem exams can be done, generating a limited amount of information.

To figure out why these killer whales are dying — and what it means for the health of individual animals and the population as a whole — we reviewed the post-mortem records of 53 animals that became stranded in the eastern Pacific Ocean and Hawaii between 2004 and 2013. We identified the cause of death in 22 animals, and gained important insight from nine other animals where the cause of death could not be determined.

Human-caused injuries were found in nearly every age group of whales, including adults, sub-adults and calves. Some had ingested fishing hooks, but evidence of blunt-force trauma, consistent with ship and propeller strikes, was more common.

A dead killer whale lies on a beach — The 18-year-old male southern resident killer whale, J34, stranded near Sechelt, B.C., on Dec. 21, 2016. Post-mortem examination suggested he died from trauma consistent with vessel strike.
(Paul Cottrell/Fisheries and Oceans Canada), Author provided

This is the first study to document the lesions and forensic evidence of lethal trauma from ship and propeller strikes.

In recent years governments have focused on limiting vessel noise and disturbance. This study reinforces the need for this, showing that in addition to noise and disturbance, vessel strikes are an important cause of death in killer whales.

Direct human impact

We also developed a body condition index to evaluate the animals’ nutritional health — were they eating enough salmon, for example — to see what role food might play in the sickness and death of stranded animals. Observations of free-ranging killer whales from boats and by unmanned aerial drones have documented sub-optimal body condition or generalized emaciation in many southern resident killer whales.

In this study, we found that longer and therefore older animals tend to have thicker blubber. Our study also found that those animals that died from blunt-force trauma had a better body condition — they were in good health before death. Those that died from infections or nutritional causes were more likely to be in worse body condition.

This new body condition index can help scientists better understand the health of killer whales, and gives us a tool to evaluate their health regardless of their age, reproductive status and health condition.

Our team, working with numerous collaborators including the National Marine Mammal Foundation, is building a health database of the killer whales living in the northeastern Pacific Ocean so that their health can be tracked over time. This centralized database will let stranding response programs, regional and national government agencies and First Nations communities collaborate with field biologists, research scientists and veterinarians.

Ultimately, the information about the health of these killer whales must be conveyed to the public and policy-makers to ensure that the appropriate legislation is enacted to reverse the downward trend in the health and survival of these killer whales. We should now be able to assess future efforts and gain a better understanding of the impact of ongoing human activities, such as fishing, boating and shipping.

Stephen Raverty, Adjunct professor, Veterinary Pathology, University of British Columbia and Joseph K. Gaydos, Wildlife Veterinarian and Science Director, The SeaDoc Society, University of California, Davis

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Humpback whales have been spotted in a Kakadu river. So in a fight with a crocodile, who would win?

Vanessa Pirotta, Macquarie University

In recent months, three humpback whales were spotted in the East Alligator River in the Northern Territory’s Kakadu National Park. Contrary to its name, the river is full of not alligators but crocodiles. And its shallow waters are no place for a whale the size of a bus.

It was the first time humpback whales had been recorded in the river, and the story made international headlines. In recent days, one whale was spotted near the mouth of the river and scientists are watching it closely.

The whales’ strange detour threw up many questions. How did they end up in the river? What would they eat? Would they get stuck on the muddy river bank?

And of course, there was one big question I was repeatedly asked: in an encounter between a crocodile and a humpback whale, which animal would win?

A crocodile partially submerged in a river — The whales swam into a crocodile-infested river.
Dean Lewins/AAP

Scientists double-take

The humpback whales were first spotted in September this year by marine ecologist Jason Fowler and fellow scientists, during a fishing trip. Fowler told the ABC:

I noticed a big spout, a big blow on the horizon and I thought that’s a big dolphin … We were madly arguing with each other about what we were actually seeing. After four hours of raging debate we agreed we were looking at humpback whales in a river.

The whales had swum about 20 kilometres upstream. Fowler photographed the humpback whales’ dorsal fins as evidence, and reported the unusual sighting to authorities and scientists.

Thankfully, two whales returned to sea on their own, leaving just one in need of help. There was concern it might become stranded in the shallow, murky tidal waters. If this happened, it might be attacked by crocodiles – more on this in a minute.

Experts considered a variety of tactics to encourage the whale back out to sea. These included physical barriers such as nets or boats, and playing the sounds of killer whales – known predators of humpback whales.

But none of these these options was needed. After 17 days, the last whale swam back to sea on its own.

The whale that spent two weeks in the river has recently returned and been spotted swimming around the mouth of the river. It appears to have lost weight – most likely the result of migration. It is now being monitored nearby in Van Diemen Gulf.

Questions are now being raised about the health of the animal, and why it has not headed south for Antarctic feedings waters.

A humpback whale that spent two weeks in the East Alligator River has recently been spotted nearby.
Dr Carol Palmer

So why were whales in the river?

The whales are part of Australia’s west coast humpback whale population, which each year travels from cold feeding waters off Antarctica to warm waters in the Kimberley to breed.

There are various theories as to why they swam into the East Alligator River. Humpback whales are extremely curious, and may have entered the river to explore the area.

Alternatively, they may have made a navigation error – also the possible reason behind September’s mass stranding of pilot whales in Tasmania.

And the big question – what about the crocs?

Long-term, a humpback whale’s chances of surviving in the East Alligator River are slim. The lower salinity level may cause them skin problems, and they may become stranded in the shallow waters – unable to move off the muddy bank. Here the animal might die from overheating, or its organs may be crushed by the weight of its body. Or, of course, the whale may be attacked by crocodiles.

In this case, my bet would be on the whale – if it was in relatively good condition and could swim well. Humpback whales are incredible powerful creatures. One flick of their large tail would often be enough to send a crocodile away.

If a croc bit a whale, their teeth would likely penetrate the whale’s skin and thick blubber. But it would take a lot more to do serious harm. Whale skin has been shown to heal after traumatic events, including the case of a humpback whale cut by a boat propeller in Sydney 20 years ago. Dubbed Bladerunner, it survived but still bears deep scars.

Humpback whales are very large and powerful. One flick of their tail could send a crocodile away.
Dr Vanessa Pirotta

What next?

The whale sighting continues to fascinate experts. Scientists are hoping to take poo samples from the whale in Van Diemen Gulf, and could also collect whale snot to learn more about its health. However, the best case scenario would be to see the whale swim willingly to offshore waters.

This unusual tale will no doubt go down in Australian whale history. If nothing else, it reminds us of the vulnerability – and resilience – of these marine giants.

The author would like to thank Northern Territory Government whale expert Dr Carol Palmer for her assistance with this article.

Vanessa Pirotta, Wildlife scientist, Macquarie University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Photos from the field: these magnificent whales are adapting to warming water, but how much can they take?

Olaf Meynecke, Griffith University

Environmental scientists see flora, fauna and phenomena the rest of us rarely do. In this new series, we’ve invited them to share their unique photos from the field.

The start of November marks the end of the whale season in the Southern Hemisphere. As summer approaches, whales that were breeding along the east and west coasts of Australia, Africa and South America will now swim further south to feed around Antarctica.

This annual cycle of whales coming and going has taken place for at least 10,000 years. But rising ocean temperatures from climate change are challenging this process, and my colleagues and I have already seen signs that humpback whales are changing their feeding, migration and breeding patterns to adapt.

As krill stocks decline and ocean circulation is set to change more drastically, climate change remains an unprecedented threat to whales. The challenge now is to forecast what will happen next to better protect them.

Losing krill is the biggest threat

I’m part of an international team of researchers trying to learn what the next 100 years might look like for humpback whales in the Southern Hemisphere, and how they’ll adapt to changing ocean conditions.

Whales depend on recurring environmental conditions and oceanographic features, such as temperature, circulation, changing seasons and biogeochemical (nutrient) cycles. In particular, these features influence the availability of krill in the Southern Ocean, their biggest food source.

Whales are particularly sensitive to this because they need enormous amounts of food to develop sufficient fat reserves to migrate, give birth and nurse a calf, as they don’t eat during this time.

In fact, models predict declines in krill from climate change could lead to local extinctions of whales by 2100. This includes Pacific populations of blue, fin and southern right whales, as well as fin and humpback whales in the Atlantic and Indian oceans.

Still, when it comes to their migration and breeding cycles, recent studies have shown humpback whales can adapt with changes in ocean temperature and circulation at a remarkable level.

Whales can adapt to warming water, but at what cost?

In a long term study from the Northern Hemisphere, scientists found the arrival of humpback whales in some feeding grounds shifted by one day per year over a 27-year period in response to small fluctuations in ocean temperatures.

This led to a one-month shift in arrival time, but a big concern is whether they can continue to time their arrival with their prey in the future when the water gets warmer still.

Likewise, in breeding grounds near Hawaii, the number of mother and calf humpback whale sightings dropped by more than 75% between 2013 and 2018. This coincided with persistent warming in the Alaskan feeding grounds these whales had migrated from.

Collecting humpback whale exhale (“whale snot”)

But humpback whales shifting their distribution and behaviour can cause unexpected human encounters, and cause new challenges that weren’t an issue previously.

Research from earlier this year found humpback whales switched to fish as their main prey when the sea surface temperature in the California current system increased in a heatwave. This has been leading to record numbers of entanglements with gear from coastal fisheries.

And between 2013 and 2016, we documented hundreds of newborn humpback whales in subtropical and temperate shallow bays on the east coast of Australia, 1,000 kilometres further south from their traditional breeding areas off the Great Barrier Reef.

However, since these aren’t designated calving areas, the newborns aren’t well protected from getting tangled in shark nets or colliding with jet skis or cruise ships.

Protecting whales

The Whales and Climate Program is the largest project of its kind, combining hundreds of thousands of humpback whale sightings and advanced modelling techniques. Our aim is to advance whale conservation in response to climate change, and learn how it threatens their recovery after decades of over-exploitation by the whaling industry.

Each whale season between June and October, I sail out to the open ocean. This means I have unique opportunities to see and engage with whales, especially during the breeding season. The following photos show some of our breathtaking encounters, and can remind us of our marine ecosystem’s fragile beauty.

A humpback whale fin — Olaf Meynecke, Author provided

Breaching humpback whale in front of buildings — Olaf Meynecke, Author provided

During one of our boat-based surveys on the Gold Coast, we encountered this acrobatic humpback whale calf, shown in the photos above. We counted 254 breaches in two hours, making it the record holder of most breaches in our 10 years of observation.

To check on whales’ health, we collect and study the air they exhale through their blow hole (“whale snot”), and measure their size at different times of the year. The photo above shows me tagging a whale with CATs suction cup tags, to collect data on short term changes in their movement patterns.

Close up of a humpback whale's mouth — Olaf Meynecke, Author provided

In regions where the whales adapt to ocean changes and, as such, move closer to shore for feeding and shift their breeding grounds, there’s a higher risk of entanglements and other human encounters. This is particularly concerning when they travel outside protected areas.

A newborn humpback whale resting on its mum's head — Olaf Meynecke, Author provided

Look closely and you can see a newborn humpback, just one to three days old, resting on its mother’s head.

In the first days of life, baby humpback whales sink easily and aren’t able to stay on the water surface for long. They need their mothers’ support to stay on the surface to breathe.

Once they’ve gained enough fat from the mothers milk they become positively buoyant (meaning they can float), making it easier for them to breathe.

Photo of a whale underwater — Olaf Meynecke, Author provided

A final note — during one of our land-based whale surveys this year, a keen whale watcher approached us, and we helped him find the whales with our binoculars. I will never forget the joy in his face when he spotted them.

It’s a joy I hope many future generations can experience. To ensure this, we need to understand how we can best protect whales in a changing climate.

Olaf Meynecke, Research Fellow in Marine Science, Griffith University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Genome and satellite technology reveal recovery rates and impacts of climate change on southern right whales

University of Auckland tohorā research team, Department of Conservation permit DJI

Emma Carroll

After close to a decade of globe-spanning effort, the genome of the southern right whale has been released this week, giving us deeper insights into the histories and recovery of whale populations across the southern hemisphere.

Up to 150,000 southern right whales were killed between 1790 and 1980. This whaling drove the global population from perhaps 100,000 to as few as 500 whales in 1920. A century on, we estimate there are 12,000 southern right whales globally. It’s a remarkable conservation success story, but one facing new challenges.

A southern right whale calf breaches in the subantarctic Auckland Islands.
University of Auckland tohorā research team, Author provided

The genome represents a record of the different impacts a species has faced. With statistical models we can use genomic information to reconstruct historical population trajectories and patterns of how species interacted and diverged.

We can then link that information with historical habitat and climate patterns. This look back into the past provides insights into how species might respond to future changes. Work on penguins and polar bears has already shown this.

But we also have a new and surprising short-term perspective on the population of whales breeding in the subantarctic Auckland Islands group — Maungahuka, 450km south of New Zealand.

Spying on whales via satellite

Known as tohorā in New Zealand, southern right whales once wintered in the bays and inlets of the North and South Islands of Aotearoa, where they gave birth and socialised. Today, the main nursery ground for this population is Port Ross, in the subantarctic Auckland Islands.

Adult whales socialise at both the Auckland and Campbell Islands during the austral winter. Together these subantarctic islands are internationally recognised as an important marine mammal area.

In August 2020, I led a University of Auckland and Cawthron Institute expedition to the Auckland Islands. We collected small skin samples for genetic and chemical analysis and placed satellite tags on six tohorā. These tags allowed us to follow their migrations to offshore feeding grounds.

It matters where tohorā feed and how their populations recover from whaling because the species is recognised as a sentinel for climate change throughout the Southern Hemisphere. They are what we describe as “capital” breeders — they fast during the breeding season in wintering grounds like the Auckland Islands, living off fat reserves gained in offshore feeding grounds.

Females need a lot in the “bank” because their calves need a lot of energy. At 4-5m at birth, these calves can grow up to a metre a month. This investment costs the mother 25% of her size over the first few months of her calf’s life. It’s no surprise that calf growth depends on the mother being in good condition.

Females can only breed again once they’ve regained their fat capital. Studies in the South Atlantic show wintering grounds in Brazil and Argentina produce more calves when prey is more abundant, or environmental conditions suggest it should be.

The first step in understanding the relationship between recovery and prey in New Zealand is to identify where and on what tohorā feed. The potential feeding areas for our New Zealand population could cover roughly a third of the Southern Ocean. That’s why we turn to technologies like satellite tags to help us understand where the whales are going and how they get there.

Where tohorā go

So far, all tracked whales have migrated west; away from the historical whaling grounds to the east near the Chatham Islands. As they left the Auckland Islands, two whales visited other oceanic islands — skirting around Macquarie Island and visiting Campbell Island.

It also seems one whale (Bill or Wiremu, identified as male using genetic analysis of his skin sample) may have reached his feeding grounds, likely at the subtropical convergence. The clue is in the pattern of his tracks: rather than the continuous straight line of a whale migrating, it shows the doughnuts of a whale that has found a prey patch.

Migratory track of southern right whale Bill/Wiremu, where the convoluted track could indicate foraging behaviour.

The subtropical convergence is an area of the ocean where temperature and salinity can change rapidly, and this can aggregate whale prey. Two whales we tracked offshore from the Auckland Islands in 2009 visited the subtropical convergence, but hundreds of kilometres to the east of Bill’s current location.

As Bill and his compatriots migrate, we’ve begun analysing data that will tell us about the recovery of tohorā in the past decade. The most recent population size estimate we have is from 2009, when there were about 2,000 whales.

I am using genomic markers to learn about the kin relationships and, in doing so, the population’s size and growth rate. Think of it like this. Everybody has two parents and if you have a small population, say a small town, you are more likely to find those parents than if you have a big population, say a city.

This nifty statistical trick is known as the “close kin” approach to estimating population size. It relies on detailed understanding of the kin relationships of the whales — something we have only really been able to do recently using new genomic sequencing technology.

Global effort to understand climate change impacts

Globally, southern right whales in South Africa and Argentina have bred less often over the past decade, leading to a lower population growth rate in Argentina.

Concern over this slowdown in recovery has prompted researchers from around the world to work together to understand the relationship between climate change, foraging ecology and recovery of southern right whales as part of the International Whaling Commission Southern Ocean Research Partnership.

The genome helps by giving us that long view of how the whales responded to climate fluctuations in the past, while satellite tracking gives us the short view of how they are responding on a day-to-day basis. Both will help us understand the future of these amazing creatures.

Emma Carroll, Rutherford Discovery Fellow

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Environment, Wildlife and Wilderness – Articles and News

Category Archives for Whales

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Photos from the field: these magnificent whales are adapting to warming water, but how much can they take?

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Where tohorā go

Global effort to understand climate change impacts

Sperm Whales

Blue whales down under

How can we conserve a species we know very little about?

We need extra eyes

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Blowing bubbles, catching krill

But why were they feeding in ‘breeding waters’ anyway?

So why are these observations important?

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Like this:

A host of threats

The humpback whales’ plight

The problem with counting whales

Proceed with caution

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Some plastics are deadlier than others

What’s the solution?

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We can do better

Direct human impact

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Scientists double-take

So why were whales in the river?

And the big question – what about the crocs?

What next?

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Losing krill is the biggest threat

Whales can adapt to warming water, but at what cost?

Protecting whales

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Spying on whales via satellite

Where tohorā go

Global effort to understand climate change impacts

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