Whales coordinate deep dives to evade predators

FEBRUARY 6, 2020

by Nature Publishing Group

Groups of beaked whales reduce predation risk through extreme diving synchronization, according to a study in Scientific Reports. This behaviour has not been observed in other deep diving whales and the underlying reasons have remained unclear.

Natacha Aguilar de Soto, Mark Johnson and Peter Madsen and colleagues analysed data on 26 beaked whales carrying sensors that tracked the depths they swam to, the steepness of their dives, and the sounds they made.

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Sea snakes make record-setting deep dives

Date:  April 2, 2019

Source:  University of Adelaide

Sea snakes, best known from shallow tropical waters, have been recorded swimming at 250 metres in the deep-sea 'twilight zone', smashing the previous diving record of 133 metres held by sea snakes.

Footage of a sea snake swimming at 245 metres deep, and another sea snake at 239 metres has been provided to University of Adelaide researchers by INPEX Australia, an exploration and production company operating in the Browse Basin off the Kimberley coast of Australia. Both snakes appeared to belong to the same species.

Sea snakes are found in tropical waters of the Indian and Pacific Oceans and are typically associated with shallow water habitats like coral reefs and river estuaries.

"Sea snakes were thought to only dive between a maximum of 50 to 100 metres because they need to regularly swim to the sea surface to breathe air, so we were very surprised to find them so deep," says Dr Jenna Crowe-Riddell, lead author of the study and recent PhD graduate at the University of Adelaide's School of Biological Sciences.

Read on

Why do sharks dive?

January 7, 2019 by ​michelle Wheeler, Particle

Is it to regulate their body temperature? Conserve energy? Find food?

Tiger sharks at Ningaloo Reef are thought to search the seafloor for prey as they dive down and scan for silhouettes as they swim up to the surface.

But could there be other reasons why the sharks continuously move up and down through the water column?

That's what UWA student Sammy Andrzejaczek is hoping to find out for her Ph.D. research.

Sammy captured 24 tiger sharks at Ningaloo Reef and attached tracking devices to them for up to 48 hours.

Best described as Fitbits for sharks, the devices recorded activity rates and other data 20 times a second.

"I can even look at each individual tail beat," Sammy says.

"It helps us understand why they move the way they do, how environmental change might impact their movements and how removal of prey species from the water column may affect their movement."

Caught On Camera

The tags also contained video cameras, so Sammy could see the habitats the sharks moved through and the animals they encountered.

She watched how the sharks reacted to prey and how the prey reacted to the sharks.

Spoiler alert: Tiger sharks can be pretty lazy—Sammy says something as simple as a turtle noticing a shark and turning away could cause the shark not to bother hunting the turtle down.

"It's all the interactions that are happening on a daily basis that we don't actually usually see," Sammy says.

"Because if you put a human in the water, it's not a natural system any more."

"We get the daily life of a tiger shark without having to distract it from its normal routine."

Read more at: 

The freediving champions of the dolphin world

July 17, 2018, Frontiers

For the first time, researchers have explored the physiological adaptations that enable different populations of the same species of dolphin to vary in diving ability by almost 1000m. The research, published in two complementary studies in Frontiers in Physiology, compared the lung mechanics and metabolic rates of bottlenose dolphin populations known for their different hunting depths. Using theoretical estimates of gas management, the results support a new hypothesis that lung architecture and the management of blood flow allow the dolphins to access oxygen in the lungs while preventing uptake of nitrogen, thereby avoiding decompression sickness.

Bottlenose dolphin populations are often found close to land in shallow coastal environments, making short, shallow dives of less than 10m for their prey. However, some populations—such as the Bermudian population in this study—frequently dive to depths of up to 400m, and as deep as 1000m on occasion, spending up to 13 minutes underwater in search of food on a single breath.

"How can a single species have such extremely different life styles?" This question motivated Dr. Andreas Fahlman of the Fundación Oceanográfic in Valencia, Spain, who led both studies with his international team. "We wanted to measure what kind of differences are responsible for these huge variations. This allows us to determine how far the physiology can change within a single species and understand the threat that stressors may have on these deep diving dolphins."

Anyone who has previously scuba-dived will know about decompression sickness, commonly known as 'the bends'. This painful and potentially life-threatening condition is caused from surfacing too quickly at the end of a dive. The rapid expansion of nitrogen bubbles—which form in the bloodstream and tissues during the dive—are not given enough time to diffuse from the body naturally during the ascent.

Dolphins run the same risks when diving to great depths. The team measured the physiology of the lungs and energy consumption of several bottlenose dolphins known to make deep dives to understand how these problems are avoided.

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Scientists eavesdrop on little-known beaked whales to learn how deeply they dive

Date: October 11, 2017

Source: NOAA Northeast Fisheries Science Center

Summary:

Scientists have reported the first dive depths for Gervais' and True's beaked whales, two of the least known beaked whale species known as mesoplodonts. The study is also the first to use a towed linear hydrophone array to document dive depths for beaked whales, and researchers say it's a promising method to obtain dive depths for other beaked whale species.

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Baby seals that practice in pools make better divers

Date: July 1, 2015

Source: Society for Experimental Biology

Summary: Being able to dive is what matters most for seal pups, but how do they learn to do it? Grey seal pups that can play in pools may have better diving skills once they make the move to the sea, and this could increase their chance of survival. Researchers have found that spending time in pools of water helps seal pups hold their breath for longer.

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First Documented Report of Swimming and Diving in Apes

Aug. 14, 2013 — Two researchers have provided the first video-based observation of swimming and diving apes. Instead of the usual dog-paddle stroke used by most terrestrial mammals, these animals use a kind of breaststroke. The swimming strokes peculiar to humans and apes might be the result of an earlier adaptation to an arboreal life.

For many years, zoos have used water moats to confine chimpanzees, gorillas or orangutans. When apes ventured into deep water, they often drowned. Some argued that this indicated a definitive difference between humans and apes: people enjoy the water and are able to learn to swim, while apes prefer to stay on dry land.

But it turns out that this distinction is not absolute. Renato Bender, who is working on a PhD in human evolution at the School of Anatomical Sciences at Wits University, and Nicole Bender, who works as an evolutionary physician and epidemiologist at the Institute of Social and Preventive Medicine at the University of Bern, have studied a chimpanzee and an orangutan in the US. These primates were raised and cared for by humans and have learned to swim and to dive.

'We were extremely surprised when the chimp Cooper dived repeatedly into a swimming pool in Missouri and seemed to feel very comfortable,' said Renato Bender.

To prevent the chimp from drowning, the researchers stretched two ropes over the deepest part of the pool. Cooper became immediately interested in the ropes and, after a few minutes, he started diving into the two-meter-deep water to pick up objects on the bottom of the pool. 'It was very surprising behavior for an animal that is thought to be very afraid of water,' said Renato Bender. Some weeks later, Cooper began to swim on the surface of the water.

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Cormorant's deep underwater dive filmed

A South American seabird's high-speed deep dive to the ocean floor has been filmed by researchers.

A camera was fitted to an imperial cormorant's back before it dived 150ft underwater off Argentina's Patagonia Coast in 40 seconds.

The footage shows how in just over a minute it finds and catches a fish, before returning to the surface.

A Wildlife Conservation Society (WCS) team is studying the birds to help spot priority feeding areas.

The team led by Dr Flavio Quintana and including conservationists from the National Research Council of Argentina, was able to witness the birds' feeding techniques firsthand for the first time by capturing the underwater behaviour on camera.

Read on and watch video:  http://www.bbc.co.uk/nature/19077825

Diving Seabirds: Working Hard and Living Long

ScienceDaily (July 2, 2012) — Scientists have found that diving birds reach their 30s and then die quickly and suddenly, showing few signs of aging prior to death.

Their findings, which will be presented at the Society for Experimental Biology meeting in Salzburg on 2nd July could help us understand the aging process, providing critical insights for our aging population.

The guillemots -- which look similar to penguins but can fly -- have the highest flight costs of any bird and expend substantial energy for diving. Their high metabolisms and frequent dives should produce oxidative stress, causing the birds to deteriorate as they age. But, the researchers discovered that the birds stay fit and active as they grow older, maintaining their flying, diving, and foraging abilities.

Kyle Elliott, a PhD student at the University of Manitoba and the study's lead author, said, "Most of what we know about aging is from studies of short-lived round worms, fruit flies, mice, and chickens, but long-lived animals age differently. We need data from long-lived animals, and one good example is long-lived seabirds."

Continued: http://www.sciencedaily.com/releases/2012/07/120702134744.htm

How penguins 'time' a deep dive

Emperor penguins "time" their dives by the number of flaps they can manage with their wings.

This is according to a new study published in the Journal of Experimental Biology.

It aimed to show how the birds reached the "decision" that it was time to stop feeding and return to the surface to breathe.

Tracking the birds revealed that they flapped their wings, on average, 237 times on each dive.

The study was led by Dr Kozue Shiomi, from the University of Tokyo, Japan.

Dr Shiomi and his team think that the penguins' decision to end their foraging dive and return to the surface is constrained by how much power their muscles can produce after every pre-dive breath. This "flying" motion propels the birds forwards, allowing them to swim quickly through the water, gulping fish.

Using data collected from diving penguins on previous field trips, the team analysed the patterns of more than 15,000 penguin dives.

They studied 10 free-ranging birds and three birds that were foraging through a hole in the ice.

Read more here ...