BEIJING — A plague of rats has gobbled up vast swathes of grasslands in north China, sparking a mass extermination drive amid concerns for herders, state media said Thursday.

The proliferation has left holes across 65,000 kilometres (25,000 square miles) of Inner Mongolia, making it difficult for herders to ride their horses, whose hooves can get caught, the official People's Daily newspaper said.

Authorities have launched a massive extermination drive, with more than 1,000 tonnes of poison dumped over the affected grasslands, an area the size of Sri Lanka, in an effort to control the number of rats.

The population explosion has been caused by a rise in temperature since the start of May, as well as overgrazing, which suits the rodents' natural habitat as they prefer to live in shorter grasses, the report said.

The number of predators, such as foxes, eagles and snakes, has also dropped sharply in the grasslands, due in part to pollution, particularly the large-scale use of pesticides, it added.

Grasslands in Inner Mongolia have long been at risk of desertification due to excessive farming, overgrazing and drought.

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