Prehistoric Beaver

Family: Giant Beaver
  Large beast, unaligned
  Armor Class 15 (natural armor) Hit Points 52 (7d8 + 21) Speed 30 ft., swim 40 ft.
  STR DEX CON INT WIS CHA 20 (+5) 12 (+1) 17 (+3) 3 (-4) 11 (+0) 5 (-3) Skills Survival +2 Senses passive Perception 10 Languages – Challenge 3 (700 XP)
  Special Traits
  Hold Breath. The prehistoric beaver can hold its breath for up to 20 minutes. Siege Monster. The prehistoric beaver deals double damage to objects and structures. Actions
  Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 27 (4d10 + 5) piercing damage. About
  Although the tail is thinner than the average beaver, the prehistoric beaver is more than twice the size of its modern kin, with substantially larger canine teeth.
  The beaver of prehistoric times averages over 7 feet long and 3 feet at the shoulder. It is an herbivore, surviving off tree bark and cambium, the soft tissue that grows beneath tree bark, and builds long, low lodges across large rivers. A family of prehistoric beavers can be the cause of an entire village’s demise should they dam the river that passes near it.
  A significant difference between a common beaver and a prehistoric beaver is the length of their teeth; suited to stripping bark, the front incisors are over 5 inches in length, and the beavers use them to defend their lodges.