A new study reveals which is the most powerful of all whales and dolphins.
Some animals just look strong. Male gorillas parade their ripped muscular bodies, while elephants are capable of great displays of power, such as tipping over trees.
But the strongest animals in the world live somewhere else – in the ocean.
Whales, being the largest animals alive, also have the largest muscles.
Now a new study has determined which is the strongest whale of all.
And crucially, it has revealed that despite being massively powerful,
whales are impotent when entangled by fishing gear, as they are just not strong enough to break free.
The study, published in the journal Marine Mammal Science, was conducted by a team of US-based researchers led by Logan Arthur of the University Of North Carolina in Wilmington.
The team investigated which is the strongest of all cetaceans, the group that includes whales and dolphins.
It has established that
blue whales are the strongest, in terms of the absolute amount of force they can generate. They are stronger than other large whales, including the massive sperm whale, the largest toothed cetacean, although they are not the strongest relative to their body size.
But despite their massive strength,
whales are not powerful enough to break free from fishing gear, the research reveals. Whales often become entangled in fishing lines or nets that have been set or discarded in the ocean. Yet even a blue whale would struggle to break a single strand of a fish net, the scientists have discovered.
“I am fascinated by the sheer size of cetaceans,” Mr Logan told BBC Earth.
“As mammals, cetaceans have the same body systems as we do, however they are massive animals that thrive in a completely different habitat than humans. I wanted to understand how they were able to do it.”
Prior to the study, scientists had only measured the amount of force and thrust that bottlenose dolphins can produce.
Blue whales are the strongest and it is due to their massive sizeDolphins and whales power themselves using large fluked tails that move up and down, with each movement generating a similar force that propels their bodies forward.
“This motion is primarily powered by two muscles groups called the epaxial muscles, which power the up stroke, and the hypaxial muscles, which power the down stroke,” says Mr Logan.
His team related the amount of force produced by the dolphin to a cross-section of its epaxial tail muscles.
That reveals a ratio of force per unit area of muscle, commonly referred to as “muscle stress”.
By measuring the cross-section of muscles in larger cetaceans, they could then use this ratio to scale up and estimate the force output from a bottlenose dolphin to a blue whale.
“Blue whales are the strongest and it is due to their massive size,” says Mr Logan.
The blue whale measured in the study had an estimated body mass of 70,800 kg. It produced a maximum force of 60 kN. Given that blue whales can reach twice this weight, others are likely to be even more powerful.
“Blue whales are capable of generating really large forces, the largest we calculated for any swimming cetacean.”
However the study also reveals that
smaller cetaceans are relatively stronger. “When compared to smaller cetaceans [blue whales] produce less force relative to their body size.”
So when body size is taken into account,
large whales are actually weaker than dolphins.
The strength of each species may relate to its lifestyle.
Blue whales have the most slender body shape. That generates less drag, allowing blue whales to cruise at high speed. So while they are the absolute strongest, they might require less power relative to their size to overcome drag than smaller, less slender species.
The sperm whale was, perhaps surprisingly, not that powerful compared to other large whales. It is not clear why. But sperm whales have much larger heads than other whales, perhaps leaving less of their body to be devoted to muscle.
Overall, though having greater absolute strength, large whales aren’t that strong relative to their size when compared to some land animals.
For example,
an elephant, the largest of the terrestrial mammals, cited by the study had a total body mass of 2,500 kg. It produced a force while running of 27 kN.
“
A young minke whale has a similar total body mass but is calculated to produce a force of only 6.4 kN,” says Mr Logan.
“A buffalo had a total body mass of 500 kg and produced a force of 12 kN. In comparison a small pilot whale is calculated to produce only 2.7kN of force.”
“The difference in force output between the terrestrial and marine mammals illustrates a fundamental difference in the kinds of selective pressures these animals are exposed to,” Mr Logan told BBC Earth.
Land animals need to use their skeleton and muscles to support their body mass against the force of gravity, for example, whereas marine mammals are supported by the buoyant force of water.
Despite their great size and power, whales may be helpless when confronted by floating fishing lines.
The researchers also examined the force required to break various lines used in commercial fishing. The breaking strength of each single line is often higher than the forces whales can produce.
“That would suggest they would have an issue breaking out of the line,” says Mr Logan.
Indeed, much of the time, it may be impossible.
www.bbc.com/earth/story/20150529-the-strongest-whale-in-the-worldFrom Carnivora.
