The number of Americans owning pets is at a record high, and more people are making provisions in their wills to provide for these animals after they're gone.

But to ensure your pet is cared for as you intend, it's important to set up a pet trust—an arrangement that 46 states permit.

While some—including noted financier Muriel Siebert, who died in August—have left tens of thousands of dollars for the care of a pet, attorneys who specialize in planning for the care of pets say most pet owners allocate only enough to cover necessities like food and veterinary care.

"Pet trusts aren't just for the wealthy," says Frances Carlisle, a trust and estates attorney in New York. For most pet owners, she adds, the goal "is to make sure a plan exists for the care of the animal."

As of 2012, 68% of U.S. households owned pets, up from 62% in 2010. Among cat owners, 9% had made financial provisions in their wills for their animals, up from 6% in 2010, according to the American Pet Products Association, which represents manufacturers of pet food and other products. From 2010 to 2012, the percentage of dog owners making such arrangements rose to 9% from 5%.