The RSPCA is urging anyone considering getting a pet as a Christmas present this year to buy one from the shelter.

Manager Narelle Biddell said the shelter took in 162 surrendered and lost animals in November and December, an increase on last year's 134 in the same period, its busiest time of the year as families surrender their pets before going away.

The shelter has received 103 cats in November and December, compared with last year's figure of 99, and 54 dogs compared with 35 for the same time last year.

Five other animals including rabbits, guinea pigs and birds have been surrendered in the past two months, compared with three last holiday season.

Spokesperson Aimee McKay said the RSPCA was extremely concerned about the increase.

"We want to remind Port Lincoln residents that when you adopt an animal, it's for life, and you need to consider where you'll be in 20 years before you make that commitment," she said.

"Before they adopt a pet people need to consider what hardships they may encounter in the future, and if they can foresee any reason as to why they might need to surrender a pet, then don't get one."

However people finding they cannot manage their pets should bring them to the RSPCA instead of dumping them.

"Leaving your pet at home by itself or dumping it on the side of the road is illegal and incredibly dangerous for the animal, so if you do get to the unfortunate point where you can't look after your animal, surrendering the animal is preferable to the more cruel options."

Shelter animals are desexed, microchipped, vaccinated and tested, so if people are planning to buy someone a pet for Christmas, they are the best option.

"We test dogs with other dogs, with children, cats, and we test whether they are likely to escape over fences - everything.

"You won't get that extensive personality testing at a pet shop or even with a breeder.

"But we only want people adopting who have thoroughly prepared themselves for it, knowing it will be a long-term choice, and have their fences and gates secured and their home ready for a pet.

"They need to be ready for their lifestyle to change quite severely and it's a decision that should be researched and talked through with the family.

"If you do all that, the holiday period is a great time to adopt, because you can spend a lot of time with the pet and it has time to adopt to you and its new home."