The Mercian Regimental Mascot, a Swaledale Ram, is known as 'Private (or other rank) Derby' and is held on the official strength of the Regiment. As one of a very few official mascots in the British Army he has his own regimental number, issued by the Army Veterinary Corps and is funded by the Crown. His line manager is firstly the Ram Major and then The Regimental Adjutant.

On 27th March 1858, Major General Roberts and 600 men of the 95th Regiment, with two 9-pounder guns, arrived at Kohtah in central India, where the troops of Raj Ram Singh of Kohtah had mutinied and were besieged by him in Kohtah's citadel. Major General Roberts divided his assaulting forces in to three columns, the 3rd Column was to be commanded by Lt Col Raines, the Commanding Officer of the HM 95th (Derbyshire) Regiment of Foot.

On the morning of the 30th March, the three columns of infantry crossed the river outside Kohtah by boats and on rafts made from arrack barrels lashed together. The combined troops stormed the rebel held city capturing 50 guns and therefore putting the Raj Ram Singh of Kohtah back in power.

During the aftermath of the battle Private Sullivan, of the Number 1 Company, found a fine fighting ram tethered in a temple yard. On showing it to the Commanding Officer, Lt Col Raines decided to keep the animal as a mascot for the Regiment. The ram, named 'Private Derby' marched nearly 3,000 miles with the 95th Foot throughout Central India and was present at six actions during the remainder of the Indian Revolt. In recognition of his service Derby I received the Indian Mutiny Medal in 1862 at Poona. Sadly he was accidentally drowned when he jumped into a well in Hyderbad, India in 1863.

The Regiment adapted a new Ram to continue the tradition and he was named Derby II. Since that time there has followed a succession of fine rams, each of which has inherited the official title of 'Private Derby' followed by his successive number. Some have even managed to achieve the rank of Lance Corporal. Replacement Rams were initially presented to the Regiment in whichever part of the world they were serving at the time, but since 1912 the Duke of Devonshire has selected a Swaledale Ram from his Chatsworth flock and presented it to the Regiment.