Posted on Category:Animal Care

Climate Change Causes California Male Sea Lions to Gain Weight

A recent study published in Current Biology revealed that the male sea lions that live in California are actually getting bigger, not smaller, due to climate change. They also showed an increase in average height with sustained population growth, resulting in increased competition for food and resources.

In the study, published on April 27, the researchers found that the mating selection process was an important driver for males to strengthen their neck and jaw muscles, which were used for action during the breeding season, thus strengthening them even more.

Another factor contributing to their Mass is that sea lions are now responding to climate-related food shortages by diversifying their diet and feeding further from the coast.

Since the adoption of the Law on the Protection of Marine Mammals in 1972, the number of breeding females has tripled, which could be considered a positive sign that such protection laws are working.

“Reducing the size is not the universal answer to the increase in the population of marine predators,” said co-author and Paleoecologist Ana Valenzuela-Toro from The University of California at Santa Cruz and the Smithsonian Institution in a press release on the subject.

“The California sea lions have been very resistant over the decades that we have sampled and have been able to overcome the increasing competition thanks to the availability of prey. They are like the raccoons of the sea: they can consume almost anything and compensate if something is not found.”

The researchers examined museum specimens of mature California sea lions of both gender, collected from 1962 to 2008. To estimate the differences in body size, they compared the total size of more than 300 skulls, taking into account other associated characteristics, such as the size of the muscle attachment points, to determine the changes in neck flexibility and bite force.

To find out where the creatures ate and what they ate on, the scientists took tiny samples of bones from the animals’ skulls to measure their stable composition of carbon and nitrogen isotopes.

“Carbon provides information about habitat use – whether they search along the coast or offshore — and Nitrogen provides information about trophic levels of their prey, for example when they eat smaller or larger fish,” Valenzuela-Toro added.

Ultimately, their results suggested that male sea lions had increased in size overall. Women, on the other hand, remained stable in size. The idea is that the difference is probably due to the fact that height is more important for a man in terms of mating.

“A male can reproduce with many females, and the males in the breeding colony action with each other to establish their territory,” Valenzuela-Toro explained. “Larger males are more competitive in body actions and can go without food for longer, which allows them to stay longer and defend their territory.”

This advantage is the difference between Harems full of cows and Observation from the sideline.

Unfortunately, many other species, such as polar bears, are decreasing in size and number, as climate change is causing a certain number on the planet. So how long will the sea lions avoid the proverbial bullet?

“As climate change progresses, the prey availability of sardines and anchovies will decrease even more, and eventually we will have more permanent El Niño-type warming conditions that will reduce the size and cause a pole shift of these and other pelagic fish,” continued Valenzuela-Toro. “This will be a really hostile environment for the California sea lions, and eventually we expect that the size of their population will stop growing and actually decrease.”

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