Beasts are nonhumanoid creatures that are a natural part of the fantasy ecology. Some of them have magical powers, but most are unintelligent and lack any society or language. Beasts include all varieties of ordinary animals, dinosaurs, and giant versions of animals.
Here is a list of all of the special traits for monsters with the Beast type in the Dungeons & Dragons 5e Monster Manual:
Amphibious. The [listed creature] can breathe air and water.
Monsters: crab, frog, giant crab, giant frog, giant toad
Beast of Burden. The [listed creature] is considered to be a [size] animal for the purpose of determining its carrying capacity.
Monsters: mule
Blood Frenzy. The [listed creature] has attack on melee attack rolls against any creature that doesn’t have all its hit points.
Monsters: giant shark, hunter shark, quipper, swarm of quippers
Charge. If the [listed creature] moves at least 20 feet straight toward a target and then hits it with a [attack action] on the same turn, the target takes an extra [damage and damage type]. If the target is a creature, it must succeed on a DC [X] Strength saving throw or be knocked prone.
Monster: boar, elk, giant elk, giant goat, giant sea horse, goat, rhinoceros
Echolocation. The [listed creature] can’t use its blindsight while its deafened.
Monsters: bat, large bat, killer whale, swarm of bats
Flyby. The [listed creature] doesn’t provoke an opportunity attack when it flies out of an enemy’s reach.
Monsters: pteranodon, flying snake, giant owl, owl
Hold Breath. The [listed creature] can hold its breath for [time].
Monsters: pleisiosaurus, giant crocodile, killer whale
Hold Breath (underwater creatures). While out of water, the [listed creature] can hold its breath for [time].
Monsters: octopus
Illumination. The [listed creature] sheds bright light in a [distance] and dim light for an additional [distance].
Monster: giant fire beetle
Keen Hearing. The [listed creature] has advantage on Wisdom (Perception) checks that rely on hearing.
Monsters: bat, giant bat, killer whale, swarm of bats
Keen Hearing and Sight. The [listed creature] has advantage on Wisdom (Perception) checks that rely on hearing or sight.
Monsters: giant owl, owl
Keen Hearing and Smell. The [listed creature] has advantage on Wisdom (Perception) checks that rely on hearing or smell.
Monsters: dire wolf, giant weasel, jackal, mastiff, weasel, winter wolf, wolf
Keen Sight. The [listed creature] has advantage on Wisdom (Perception) checks that rely on smell.
Monsters: blood hawk, eagle, giant eagle, hawk
Keen Sight and Smell. The [listed creature] has advantage on Wisdom (Perception) checks that rely on sight or smell.
Monsters: giant vulture, vulture
Keen Smell. The [listed creature] has advantage on Wisdom (Perception) checks that rely on smell.
Monsters: badger, black bear, brown bear, cat, cave bear, giant badger, giant rat, lion, panther, polar bear, rat, saber-toothed tiger, swarm of rats, tiger
Mimicry. The [listed creature] can mimic simple sounds it has heard, such as a person whispering, a baby crying, or an animal chattering. A creature that hears the sounds can tell they are imitations with a successful DC [X] Wisdom (Insight) check.
Monsters: raven
Pack Tactics. The [listed creature] has advantage on an attack roll against a creature if at least one of the [listed creature]’s allies is within 5 feet of the creature and the ally isn’t incapacitated.
Monsters: baboon, blood hawk, dire wolf, giant rat, giant vulture, hyena, jackal, lion, reef shark, vulture, wolf
Pounce. If the [listed creature] moves at least [X] feet straight toward a creature and then hits it with a claw attack on the same turn, that target must succeed on a DC [Y] Strength saving throw or be knocked prone. If the target is prone, the [listed creature] can make one bite attack against it as a bonus action.
Monsters: allosaurus, lion, panther, saber-toothed tiger, tiger
Rampage. When the [listed creature] reduces a creature to 0 hit points with a melee attack on its turn, the [listed creature] can take a bonus action to move up to half its speed and make a bite attack.
Monsters: giant hyena
Relentless. If the [listed creature] takes an extra [damage] or less that would reduce it to 0 hit points, it is reduced to 1 hit point instead.
Monsters: boar (recharges after a Short or Long Rest)
Running Leap. With a [distance] running start, the [listed animal] can long jump up to [distance].
Monsters: lion
Spider Climb. The [listed creature] can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.
Monsters: giant lizard, giant spider, giant wolf spider, spider, swarm of spiders
Standing Leap. The [listed creature]’s jump is up to [distance] and its high jump i sup to [distance], with or without a running start.
Monsters: frog, giant frog, giant toad
Sure-footed. The [listed creature] has advantage on Strength and Dexterity saving throws made against effects that would knock it prone.
Monsters: giant goat, goat, mule
Swarm. The swarm can occupy another creature’s space and vice versa, and the swarm can move through any opening large enough for a [reference creature]. The swarn can’t regain hit points or gain temporary hit points.
Monsters: swarm of bats, swarm of beetles, swarm of centipedes, swarm of insects, swarm of poisonous snakes, swarm of quippers, swarm of rats, swarm of ravens, swarm of spiders, swarm of wasps
Trampling Charge. If the [listed creature] moves at least 20 feet straight toward a creature and then hits it with a gore attack on the same turn, that target must succeed on a DC [X] Strength saving throw or be knocked prone. If the target is prone, the [listed creature] can make one [attack type] against it as a bonus action.
Monsters: elephant, triceratops, mammoth, warhorse
Underwater Camouflage. The [listed creature] has advantage on Dexterity (Stealth) checks made while underwater.
Monsters: giant octopus, octopus
Water Breathing. The [listed creature] can breathe only underwater.
Monsters: giant octopus, giant sea horse, giant shark, hunter shark, octopus, quipper, reef shark, sea horse, swarm of quippers
Web Sense. While in contact with a web, the [listed creature] knows the exact location of any other creature in contact with the same web.
Monsters: giant spider, giant wolf spider, spider, swarm of spiders
Web Walker. The [listed creature] ignores movement restrictions caused by webbing.
Monsters: giant spider, giant wolf spider, spider, swarm of spiders