Squirrel

Squirrels were a species of animal found on Earth.

Species
Amongst the known breeds of squirrel were black squirrels, (AUDIO: Mother Russia) red squirrels and grey squirrels. Grey squirrels, which were more aggressive, replaced red squirrels in their natural habitat. (COMIC: Revolutions of Terror)

On Earth
In November 1605, the First Doctor and Robert Cecil accidentally startled a red squirrel while searching the Privy Garden of the Palace of Westminster. (PROSE: The Plotters)

In the 20th century, Slake made some squirrels vampiric and used them to "guard" the Orpheum Theatre, the lair of Slake's vampire clan. When the Eighth Doctor and Sam entered the theatre, they were viciously attacked by the vampire squirrels. (PROSE: Vampire Science)

Squirrels lived in the forests of the Catskill Mountains. In the early 21st century, they were mostly gone when the Butler Institute got rid of the trees to build a project site, although Brodie saw one after a failed attempt to smash a security camera. They seemed to be returning after the site's destruction. (PROSE: Cat's Cradle: Warhead)

In 2006, a group of squirrels tormented Fester Cat in the garden on Paul and Jeremy's home. (PROSE: The Story of Fester Cat) When Fester was writing The Story of Fester Cat, a book about his life, he wrote a short story. In this story, Fester (and Bessie) encountered the group of squirrels, and Fester asked one of their members, Derek, if he knew where Gleep was. (PROSE: Fester and the Christmas Mouse)

Elsewhere
When the Demon Magician threw up a huge wall around the TARDIS, the First Doctor used his "magic box" to super-size a squirrel. The Doctor, John and Gillian crossed the wall on the giant squirrel's back. (COMIC: A Christmas Story)

Larles, a Grigori, had a lifelong phobia of squirrels, which she found embarrassing and concealed from her life partner Kwol. When Larles became trapped with Chris Cwej and Kady Williams inside a ship whose rooms were based on their fears, guilt, nightmares and painful memories, they encountered multiple rooms full of ferocious, giant squirrels. As a result of the experience, Cwej himself also began to find squirrels unsettling, as evidenced when, after they tricked the alien intelligence manipulating them to its doom, destroying the ship, he saw a regular-sized scampering up a tree in the surrounding natural landscape and winced. (PROSE: Ring Theory)

Behind the scenes

 * In an interview with US chat show host Conan O'Brien in September 2015, Jenna Coleman revealed she had taken the clockwork squirrel prop from Before the Flood as a souvenir of her time on Doctor Who.