Utahn Don Peay, founder of the group Sportsmen for Fish and Wildlife, said his group has asked its 15,000 members to contact their representatives in Congress and register their displeasure with the arrangement.

A series of four Humane Society stamps are available from Zazzle.com, a Web site where anyone can create a customized stamp. They are not endorsed by the postal service. Twenty percent of the net proceeds - about $2 from every book of 20 - goes to the Humane Society.

"We're opposed to the Humane Society getting any kind of dividend from any kind of public resource like that," Peay said. "Sportsmen across the country don't want them getting any part of any public revenue stream."

Wayne Pacelle, president of the Humane Society of the United States, said the organization has raised about $30,000 from the stamp sales, nearly all of it going to the society's disaster rescue programs for animals.

Pacelle said the stamps are offered by a private company, without any support from the U.S. Postal Service. "If these hunters don't want to buy the stamps, they don't have to."

"Frankly, I find it appalling that this small band of extremist hunters would want to deny support for our disaster-relief services," Pacelle said. "We help people and their pets when hurricanes or forest fires or any other natural disaster strikes and almost every American, including hunters I presume, would support that."

During Hurricane Katrina, for example, the Humane Society helped rescue more than 10,000 animals, Pacelle said.

But it is more controversial political issues that the Humane Society is involved in that puts the group at odds with the sportsmen. They have opposed an effort to open dove hunting in Michigan, for example, and are party to a lawsuit that would protect bears in Florida from hunts.

In Utah, the Humane Society was a party to a lawsuit challenging a sportsmen-backed constitutional amendment that erects obstacles to ballot measures restricting hunting.

A federal appeals court upheld the Utah constitutional provision last year.

"If they'd stick to their mission of taking care of dogs and cats they wouldn't have the opposition," Peay said.

The Humane Society stamps bear pictures of caged puppies and advocate preventing puppy mills; show a baby seal and call for a stop to seal hunts; show a chicken and encourage protection for farm animals, and depict a dog being carried out of floodwaters and urge support for animal disaster rescues.

The U.S. Postal Service began in 2004 to allow companies like Zazzle.com and Stamps.com to offer personalized, non-commercial postage stamps.

This year, Congress changed a prohibition against advertising on stamps that had stood since 1872, allowing things like corporate logos to be printed on stamps.

An alert earlier this summer warned hunters and fishermen that "Every penny earned through such fundraisers is another penny that will be used to bring an end to hunting, fishing and trapping in the United States."

It encouraged sportsmen to contact their members of Congress and urge them to "put an end to this exploitation of the U.S. Mail to benefit an inflammatory organization such as the HSUS."

"We object that they've found a way to exploit the Postal Service and to use their non-hunting, non-animal-use rhetoric on postal stamps," said Dale Miles, spokesman for the U.S. Sportsmen's Alliance.