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As drones have become more popular over the last few years, so has footage of creatures such as hawks, kangaroos and alligators attacking airborne cameras.

Such close encounters of the animal kind might make for great YouTube material, but is it bad for the creatures? And what can be done to protect wildlife from drone operators who fly too close?

It's not a problem that is going away anytime soon. About 700,000 drones could sell in the United States in 2015, the Consumer Electronics Association estimates. With the Federal Aviation Administration working to release basic regulations by next year, protecting wildlife might not be regulators' top priority.

"Right now they're focusing on how to protect people and airplanes," Ryan Calo, drone expert and law professor at the University of Washington, told NBC News. "They haven't even thought about privacy much, let alone animals."

Drones and animals don't always mix

Last spring, volunteers at Zion National Park in Utah watched as a drone harassed a herd of bighorn sheep.

The incident troubled the National Park Service, which subsequently made flying a drone in Zion punishable with up to six months in jail and/or a $5,000 fine. Later, the NPS banned drones from all national parks.

"Animals can be injured when attempting to escape or avoid drone activity," Cassie Waters, a biologist at the park, said in a statement. "Drones can also change the natural behavior of wildlife and lead to unnecessary energy expenditures."

Mark Ditmer wanted to know just how stressed out animals get when confronted by drones. The University of Minnesota researcher outfitted black bears with GPS trackers and devices to track their heart rates.

Ditmer and his team flew drones near the tracked bears 18 times. Only twice did the bears react in ways visible to outside observers. But every single encounter resulted in elevated heart rates.

"I didn't expect to see such strong responses," Ditmer, who released his study in August, told NBC News. For some reason, the buzz of the drones caused more stress than the sounds generated by a car or tractor. And it wasn't like Ditmer was dive-bombing the bears — he kept each drone at least 65 meters away from the animal and around 25 to 30 meters in the air.

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None of the animals were injured during the study, but that doesn't mean drones aren't bad news for bears.

"Having a single encounter might not be detrimental," Ditmer said. "But if a bear was constantly harassed, it could cause health problems."

Of course, an out-of-control drone could physically injure an animal just like they have hurt human beings.

Keeping wildlife safe

The FAA "does not have rules that specifically address unmanned aircraft and wildlife protection," a spokesperson for the agency told NBC News.

While the National Park Service's ban is far-reaching, it isn't solely concerned with protecting animals. It's also about addressing "noise and nuisance complaints from park visitors" and "visitor safety concerns."

Most of the laws out there specifically restricting the use of drones near animals are drawn up by state and local governments. Many of them are bans on hunting with drones.

Others are meantto protect hunters from members of organizations such as PETA, like a Michigan law passed in March that makes it illegal to use a drone to "affect animal or fish behavior in order to hinder or prevent the lawful taking of an animal or a fish."

But what about using a drone to simply fly near an animal?

Calo doesn't think it's fair to single out drone operators -- harassment is harassment, he says, and people bother wildlife in other ways.

"You can't harass animals by throwing sticks at them, you can't do it by shooting pellet guns at them, and you can't do it by flying a drone into them," Calo said.

But if lawmakers did make it illegal to fly too close to wildlife, courts would probably have to distinguish between two types of incidents: accidental encounters and reckless behavior.

The YouTube video "Hawk vs. Drone!" looks like an example of the former.

In the video, which has more than 4.9 million views, a drone flies above Cambridge, Massachusetts, when a hawk appears in the distance, swoops in with talons raised, and knocks the machine to the ground. Christopher Schmidt, the drone operator, wrote that it looked like the hawk escaped unscathed and that he was donating all funds generated by the footage to the Massachusetts Audubon Society.

Other videos, however, show drone operators who appear to intentionally approach animals in the wild. Those people would be more likely to get hit by a fine or jail time if an anti-drone law was passed, according to Calo. In that scenario, putting evidence of your aerial exploits on YouTube probably wouldn't be a great idea.

Right now, it doesn't seem like drone operators have anything to worry about. The FAA already missed its deadline from Congress for creating national drone regulations. Even if the agency meets its rough new deadline of "next spring," it hasn't given any indication that those rules will include bans on harassing animals.

Related: Patrick Stewart Backs Drones That Collect Whale Snot

There is still a lot of research that has to be done on the effects of drones on different species, Ditmer said. He also pointed out that unmanned aerial vehicles can help scientists learn about and protect wildlife.

But a public awareness campaign around the potential harm to animals couldn't hurt, he said. The same goes for laws that might annoy drone operators.

"As a conservation biologist, I would err on the side of being too restrictive," Ditmer told NBC News. "At least in areas where we treasure wildlife viewing, it's probably not a bad idea to ban them or at least restrict them to certain areas and times."