Billings, Montana - An aggressive otter attacked three women floating down a river in Montana, with one victim being rushed to the hospital by helicopter.

The group was drifting along Jefferson River in inflatable inner tubes on Wednesday evening when they spotted two of the animals.

"An otter approached and attacked them," Montana's Fish Wildlife and Parks (FWP) service said in a statement. "All three women were injured."

FWP said otter attacks are rare, but the semi-aquatic animals can become aggressive when protecting their young or if they believe their food source is under threat.

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The FWP advises people to keep their distance but, if attacked, to "fight back, get away and out of the water, and seek medical attention."

FWP official Morgan Jacobsen told a local NBC affiliate that the women had called 911 for help and that one victim had to be flown to the hospital because of the bites on her face and arms.

Last month on the West Coast, surfers in California were attacked by a five-year-old female sea otter that tried to steal their boards. A viral video on social media shows the otter climbing on a surfer's board as he tries to shake the animal off. The otter lunged at the surfer and started biting the board.

Authorities in Montana have posted signs warning visitors that otters are in the area. In their statement, the FWP said that the low water levels may bring humans in closer contact with wildlife. Currently, no other response is planned.

Otters, members of the weasel family, were historically sought for their pelts, with hunting and habitat loss threatening the population of both river and sea otters.