Most tennis balls held in the mouth - dog

According to Official Guinness Records,

The world record for the most tennis balls held in the mouth by
a dog at one time is five. Augie, a golden retriever owned by
the Miller family in Dallas, Texas, USA, successfully gathered and
held all five regulation-sized tennis balls on 6 July 2003.

For a complete list of 2003 records, please visit 2003 Guinness Records in United States.

Other United States records that might interest you:

• Most drink cans collected (8 hours)
• Largest collection of thermometers
• Farthest distance skipping on a rolling globe
• Fastest time to row the length of the Mississippi River by a team
• Largest biscuit / cookie