By Justin Grant

New York - On past Halloween holidays, nine-year-old Rosie has worn a tutu and dressed up as a bumblebee, joining millions of American children trick-or-treating over the holiday.

This year, as age catches up with her, the English bulldog will just be wearing a T-shirt to match her "dad", Justin Rudd.

"Traditionally, she's a ballerina and she wears a tutu and pearls," said 37-year-old Rudd, who lives in Long Beach, California, and shepherds Rosie around in a carpeted "chariot" tied to his bicycle.

Rudd, who said he typically spends around $50 on Rosie's Halloween costume, is one of a growing number of "pet parents" willing to dig deep into their pockets to buy their furry pals creative Halloween costumes and tasty holiday treats.

According to the National Retail Federation (NRF), American consumers are expected to spend $4.96-billion on Halloween-related merchandise this year, up from $3.96-billion a year ago.

With a growing portion of that money being spent on pets, the NRF said it hopes to track pet-related Halloween spending as an individual category starting next year.

"It all falls in line with the humanisation of the pet," said PetSmart spokesperson Michelle Friedman.

"Pets are sleeping in bed with their 'pet parents' and riding along with them to do errands around town. They're just like kids. They're participating in holidays," Friedman added.

From catnip-filled pumpkins to edible rawhide Halloween cards, more than 3.5 million Americans are expected to buy some type of Halloween product for their pets this year, according to a survey by the American Pet Products Manufacturers Association.

Phoenix-based PetSmart, the largest US retailer of pet food and supplies, is rolling out 12 costumes for dogs this year, including Superman, Darth Vader and a Devil Dog Hood.

The company is also carrying six styles of "cat hats" for feline lovers who'd like to get the often temperamental creatures into the spirit of the Halloween holiday.

"Some cats have no problem wearing it and are perfectly comfortable," Friedman said. "Others wear it for a little bit, take a picture and are done."

Rival retailer Petco Animal Supplies is also stocking pet costumes. Its pumpkin and pirate costumes for dogs are two of its top-selling items, according to the company's website.

"Every year (pet costumes) get more and more popular," said Shari Maxwell, co-owner of online store Annie's Costumes.

The online shop offers more than 100 different pet costumes so that cats and dogs can dress up as everything from superheroes to firemen, brides and even French chamber maids - frilly aprons, skimpy skirts and all.

Last year the company sold more than 8 000 pet costumes. This year, it expects to sell at least 11 000.

The most popular choice for both children and pets this Halloween is expected to be pirate costumes due to the success of the Hollywood blockbuster Pirates Of The Caribbean: Dead Man's Chest.

Last year, the Yoda Dog took the top spot at Annie's Costumes online store as Star Wars fans sought to dress their dogs as the wisest Jedi.

The growing popularity in pet Halloween costumes is giving new meaning to the tradition of trick-or-treating.

Contests for pets dressed in Halloween costumes are springing up across America this year and most are offering the winning animals goody bags filled with their favourite treats.

At the Haute Dog Howl'oween Parade in Long Beach, the dog voted to have the best costume wins a yearly supply of dog food, said Rudd, who spearheads the event.

The parade attracts nearly 600 dogs in costumes ranging from cowboys and firefighters, to pumpkins and devils.

"An octopus was pretty cool," said Rudd, laughing.

"There's always chicken dogs in the parade for some reason."