One of the men alleged to have sneaked into the Calgary Zoo is taken into custody on Monday

Police say two men who allegedly sneaked into the Calgary Zoo and were injured by a tiger had been drinking and may have wanted to surprise a friend working there that night.

Trever James Wearmouth, 27, and Thomas Anthony Bryce-Hart, 27, have each been charged with one count of trespassing, police announced Friday.

The charge, under a provincial act, is not the same as the Criminal Code charge of trespass, which is only applicable to homes, police said. The provincial offence carries a fine of up to $2,000 for a first offence.

According to police and zoo officials, two men climbed a 2.4-metre-high barbed wire fence at about 1 a.m. on Monday to enter the zoo.

"We do know the two offenders had been drinking prior to this. What their state of mind was, before that, during that, we don't know. We do know that they were intent on perhaps surprising somebody at the zoo, but things got a little carried away," acting Staff Sgt. Rick Halford said.

One of the men scaled the outer perimeter safety fence around the tiger enclosure, which is just over a metre high. He didn't enter the tiger exhibit, but approached the inside fence where a two-year-old male Siberian tiger was roaming.

Vitali, one of three Siberian tigers at the Calgary Zoo, remains on exhibit. (Jeff McIntosh/Canadian Press)

The tiger, named Vitali, likely hooked the man with a claw and pulled his arm inside the fence, said a zoo veterinarian. The second man, who tried to help his friend, was also hurt.

The men knew a security guard who worked at the zoo and called her on a cellphone for help.

"Police confirm this acquaintance was not involved in any manner," police said in a news release issued Friday. "The acquaintance was not aware that the individuals were on the zoo grounds prior to receiving the phone call and was not a party to the offenders' actions."

Security personnel took the men to a zoo office where they were both given emergency first aid until medical services arrived. The seriously hurt man was then taken to Foothills hospital by ambulance. Police took the second man to hospital.

Halford wouldn't give any details on the men's medical condition, citing privacy legislation.