Archaeology suggests that human ownership of dogs as pets may date back to at least 12,000 years ago. The hobby of collecting stamps featuring animals is not quite that ancient.
Countries throughout the world have featured companion animals on stamps since the early 20th Century. Most popular have been working and companion animals such as horses, dogs, cats, fish, and birds.
US Postal issues include a number of issues dedicated to humane animal treatment and pet adoption. Recent issues include commemorate stamp tributes to military working dogs and dogs assisting individuals with disabilities.
While many countries have issued stamps similar to the United States' tributes to working animals, a number of countries have issued whimsical and comic stamps featuring popular pets. Notably, Croatia has recently issued very colorful and humorous issues dedicated for young stamp collectors.
For a serious stamp collector including a focus on pets can provide insights into an animal's role in a country's economic and social life. Adding worldwide issues featuring your favorite pet can also add warmth and humor to your personal collection. Take a quick look at County Stamp's home page search using words such as "pets", "animals", or your favorite pet and you'll find some great new companions to add to your collection.