It's no secret the U.S. Postal Service is wrestling with financial problems. But those aren't the only hazards they face. The number of mail carriers on the receiving end of a dog bite is on the rise, too.

USPS released the numbers for 2016 Thursday and they show there were 6,755 dog attacks against postal employees last year. That's a couple hundred more than 2015, when the total was way up from the previous year.

The Postal Service listed the cities with the most dog attacks against mail carriers. In Minneapolis there were 43. That was the 10th most in the country and was up from 30 the year before. St. Paul's total of 26 was an increase of two. Los Angeles led the way with 80 attacks.

Why?

The nationwide figure is at its highest level in 30 years, the Associated Press reports, and they suggest it's a product of online shopping leading to more package deliveries.

As for why some dogs want to take a bite out of the mail carrier, one dog trainer says there could be several reasons but basically it's a territorial thing. After all, that mail carrier walks onto the dog's territory – and then does it again the very next day, even if they've been warned through barking and growling.

The Postal Service put together a video with tips on how dog owners can cut down on canine-to-carrier special deliveries. Putting your dog in another room before opening the door to sign for a package is a good idea.

4.5 million total dog bites per year

While more mail carriers are getting attacked, they are still a small percentage of the dog bite victims in country. The Centers for Disease Control says kids are the most frequent victims of the 4.5 million bites per year.

With National Dog Bite Prevention Week starting on Sunday, the American Veterinary Medical Association offers some safety tips.

Experts recommend holding still if you're threatened by an unfamiliar dog and say you should not try to run away. If you are knocked down by a dog, curl up into a ball with your head tucked in and your hands over your ears and neck.