An abandoned elderly Shih Tzu was found tethered to a post outside the Calgary Humane Society after spending the night in the rain.

The animal was in such poor health it had to be euthanized.

The society is asking the public to help identify the person responsible for the animal's severe neglect.

Blood tests and a physical examination revealed the dog was suffering from end-stage renal failure and a large open sore on his rear end, said Brad Nichols, senior manager of animal cruelty investigations.

The animal showed signs of severe neglect, but not abuse, says Nichols. (Calgary Humane Society)

His hair was matted to such an extent that suggested months, if not years, of irresponsibility, Nichols said.

"Knowing that this dog was suffering the way that it was, to leave it out in the rain overnight is callous and cowardly," Nichols said.

Taking the dog to a 24-hour emergency clinic, or surrendering the animal during regular business hours, are just two options that "would've been more palatable," he added.

CCTV footage released

Indoor surveillance cameras captured a shadowy figure on the night of June 14, around 10 p.m., who brings the dog to the door, leaves it there and walks away.

The quality of the footage is too poor to properly identify the person, so the humane society is appealing to the public for help identifying either the dog or its owner.

Nichols said he can count on one hand the number of times someone has so "brazenly" abandoned a pet on the shelter's steps.

The humane society has "a big, red, criminal sign" posted on its main door, warning that abandonment is a criminal offense, he explained.

"There's really no excuse or no ignorance defence when you've got that education piece right in front of your face."

The society said it wants to find the owner to hold him or her responsible, and that he or she could face charges, such as allowing an animal to be in distress or abandoning the animal.