File photo: the Humpback whale pushes Nan Hauser around in the water, her from shark.) (Nan Hauser / Suitable)
(Nan Hauser / Suitable)
Whales are giant beasts, but why not even bigger, supersize whales swimming around?
The answer has to do with food, according to a new study, which found that it is actually impossible for a sea-bound creature to eat enough food to support a body bigger than a whale.
“At a certain point, you just can’t eat enough food, no matter how much there is to support the largest sizes,” study lead research Will Gearty, a doctoral student in geological sciences at the University of Stanford, told the Science. [Whale Album: Giants of the Deep]
Gearty and his colleagues were looking at how the body size changed as land mammals evolved into water creatures. This was not just to whales and dolphins, which are related to hippos and other hoofed animals, but also seals and sea lions, which are family of the dogs, and manatees, which are of the same origin with the elephants, the researchers said.
So why are the marine mammals in general are larger than their earthly family? Previously, many scientists suspect that the water relieved marine animals from some of the pressure of gravity, “and that makes it difficult to walk when you are large,” Gearty said. In addition, a large body size “limited how far you can roam and how much food you can eat,” he said. “Once you’re in the water, the idea goes, you should be able to get as big as you want, without limitations.”
But in contrast to these ideas, the researchers found that mammal growth is actually more constricted in the water than on land. In fact, mammals have a larger range of sizes than mammals in the ocean, the researchers found.
Once land mammals in the water, they often grow to much larger animals, the researchers found. This is probably because the surrounding water is colder than the mammals’ body temperature.
“If you’re very small, you lose heat back into the water so fast, there is no way to eat enough food to keep,” study co-investigator Jonathan Payne, a professor in geological sciences at the University of Stanford, said in a statement.
To keep warm and also have enough energy to hunt and reproduce, species need to grow to large sizes “, so they can produce more energy in their body,” Gearty said. That’s because small animals have more surface area than the volume and the heat lost through the surface. But if an animal is bigger, which means more volume is the volume-to-surface ratio is smaller, so it’s still toastier. In other words, bigger animals are usually warmer than smaller animals.
But these mammals may not be entirely supersize themselves, because as they get larger, their metabolism increases, and it is challenging to eat the food that is needed to support such a huge body, although the baleen whales are the exception.
“That is, unless you can think of a different way to eat, such as baleen whales, where you swallow whole schools of krill at a time,” Gearty said. “This hyper-efficient feeding seems to allow you to have more than this maximum limit and achieve even larger sizes outside of our model.”
How they did it
The researchers made the find by looking at the body mass of more than 3,800 live and nearly 3,000 fossil mammals. Their analysis showed that after the land, the animals adapt to the water, they undergo huge growth spurts, usually grow until they are about 1,000 kg. (500 kg). [Photos: Tracking Humpback Whales]
However, the big advantage is just one point because of the aforementioned food barrier. In addition, not all animals in a 1,000-lb. mass, which is good, because then they are all there in the same niche, Gearty said.
“Instead, they are spread across the range of possible sizes, with sperm whales along with sizes where they need to eat a lot, but no need to worry about many predators, and the small seals will evolve to in the smallest sizes where they don’t need to eat as much, but are potentially more vulnerable to predators,” Gearty said.
Strange, otters are an exception to the model because they do not get huge as soon as they evolved into a semi-aquatic lifestyle. Maybe otters stayed small because they are still half a life on the land, Gearty said.
The study is published online today (26 March) in the journal Proceedings of the National Academy of Sciences.
Original article on Live Science.