Where the pet owners go

5. Kroger $1-1.5 billion (est.)

As the largest supermarket chain in the U.S., drawing 14% of all American grocery shoppers, the Cincinnati-based retailer is reaching plenty of pet owners.

4. Amazon $2.0 billion (est.)

One Click Retail reports $2 billion in Amazon online sales of pet products in the U.S., including $700 million in pet food alone. Expect that number to rise with a full year of Whole Foods Markets under its belt this year and the introduction last month of Amazon’s private label Wag pet food brand.

3. Costco $2.3 billion (est.)

Kirkland Signature is Costco’s private-label brand, offering dog and cat food among other products. The warehouse club is the place for members to stock up on giant bags of chow for their pets.

2. Target $2.5 billion (est.)

Last year, Target expanded its private label line of pet products with a limited-time Oh Joy! Collection designed by Joy Cho. This year pet lovers can expect to see pet treats inspired by Mickey Mouse, celebrating his 90th birthday with Target all summer long.

1. Walmart $8.7 billion (est.)

The behemoth from Bentonville is top dog when it comes to pet products, even surpassing pet big-boxers PetSmart ($7.0 billion) and Petco ($3.7 billion). Its Ol’ Roy private label dog food is used by 5% of dog-owning households in the U.S.