Reports of polar bears in the Arctic eating each other are coming in at a higher rate, according to a scientist with the Russian Academy of Sciences, Russia's top scientific body. Among the factors responsible for the change include increased human activity and diminished hunting grounds, he said.

While cannibalism among polar bears has been understood to happen on rare occasions in the past, Ilya Mordvintsev, a senior researcher with the Severtsov Institute of Ecology and Evolution, said there has been an "increase in the number of cases," according to Russian news agency Interfax. He made the remarks at a conference in St. Petersburg.

Mordvintsev believes there's two possible causes for the reported rise. One is insufficient nutrition, which might cause large males to attack females and their cubs. The other is a rise in people in the Arctic, which means a larger proportion of cases may be getting reported.

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"Now the signals are coming not only from scientists, but also from the growing contingent of employees of oil and gas companies, the Ministry of Defense," he said. "We note that cannibalism of the polar bear is increasing."

Mordvintsev stressed human activity in the Arctic has "seriously" impacted the lives of polar bears. He mentioned development in the Gulf of Ob and the passage from there to the Barents Sea, which has become a more popular route for ships carrying liquefied natural gas. The Gulf of Ob is known to be a hunting ground for the animals — but now it has broken ice all-year round, Mordvintsev said, making it difficult for the animals to hunt seals.

In December, dozens of polar bears moved into the outskirts of a village in Russia's far north, forcing residents to take extra precautions as the hungry animals scrounged for food. Environmentalists said the warming climate could be to blame, as there's not enough coastal ice for the bears to move out over the sea where they would normally be hunting.