The 2007-2008 Mazdaspeed Team featured "Mutts"-themed vehicles promoting pet adoption and the work of the Humane Society of the United States. In 2009 McDonnell collaborated with author Eckhart Tolle to create "Guardians of Being", a philosophical book about nature and the present moment. In 2011, McDonnell's children's book "Me... Jane" was published. It is a story about naturalist Jane Goodall growing up and her awakening curiosity about the lives of animals around her. A sequence of "Mutts" strips led to Goodall's interest in working with McDonnell on the book. "Me... Jane" won a Caldecott Honor in 2012. The "Mutts" comic strip is currently appearing in more than 700 newspapers across 20 countries. McDonnell has been a vegetarian for over 20 years, and vegan since 2012. McDonnell is a member of the Board of Directors of the Humane Society of the United States, the Fund for Animals, and The Charles M. Schulz Museum. McDonnell and his wife Karen reside in New Jersey, with their dog Amelie, and their cat, Willie Lebowsky. Their Jack Russell Terrier, Earl, who was the inspiration and constant muse for the "Mutts" character of the same name, died in November 2007 after living with McDonnell for over 18 years.