The answer is:
Animal names related to the BEATLES.
Walruses, birds, ponies, tigers, elephants, cats, monkeys, bulldogs, bees, raccoons, cats, octopuses, pigs, bullfrogs, blue jays, Eagles, worms, fish, horses, homing birds, blackbirds, kittens, hogs, crabs, penguins, doves, sheep, sheepdogs, glow worms, butterflies, canaries, puppies, lizards, lambs.
Animal names occuring in songs by the Beatles:
I am the walrus. Free as a Bird. And Your Bird Can Sing. Dig a Pony.
Bungalow Bill went out tiger hunting with his elephant and gun.
Three Cool Cats. Everybody's Got Something To Hide Except Me And My Monkey.
Hey Bulldog. Bees. Rocky Raccoon. Octopus's Garden. Piggies.
Hey Bulldog (Bullfrog, doing it again). Blue jay way. Etc. etc. etc.
Rooster, songbirds, cat, dog, horse, sheep, lion, elephant, cow, hen, crickets, blackbirds, either ducks, swans, or geese.
Animal sounds occuring in songs by the Beatles.
Good Morning Good Morning (starts with rooster crow, birds, a cat,
a dog, a cow, a horse, a sheep, a lion, an elephant, and a
group of bloodhounds).
Sun King (cricket sounds).
Rams, horses, alligators, frog, bison, blue birds, blackbird, cock, seagull, cow, snake, honeybee, inchworm, dragonfly, moose, goose, koala bears, magpies.
Paul McCartney: Album "ram"; songs "All You Horse Riders",
"Alligator", "Rupert and the Frog Song", "Bison", "Bluebird",
"Blackbird", "Great Cock and Seagull Race", "Cow", "What It Is",
"The inchworm", "Little Lamb Dragonfly", "Morse Moose & The Grey Goose",
"Ode To A Koala Bear", "Two Magpies".
Struszia mccartneyi (trilobite) named after him.
Category 3: Chicken, fish, monkey. Struszia (trilobite)
George Harrison: Song "Tandoori Chicken", "Fish on the Sand",
"Tweeter & The Monkey Man".
Struszia harrisoni named after him.
Category 4: Mouse, blackbird, monkey, reindeer. Avalanchurus (trilobite)
Ringo Starr: Songs "Scouse The Mouse", "Bye Bye Blackbird",
"Monkey See - Monkey Do", "Rudolph the Red-Nosed Reindeer".
Avalanchurus starri named after him.
Category 5: Turkey, hound dog. Bumba (tarantula)
John Lennon: Songs "Cold turkey" and "Hound dog".
Tarantula "Bumba lennoni" named after him.