Cowslip's Warren was the warren that the Watership Down Hlessil encountered on their way. Although Cowslip seemed to have some authority, he said that there was to be no Chief Rabbit. The Warren of Snares is usually dubbed "Cowslip's Warren", because Cowslip was the first rabbit that the Sandleford escapes meet and remains a prominent character in the novel.
Hazel and his friends believe that this is the perfect place for them, since the tenants seemed so healthy and safe. They overlook some odd tendencies like refusing to answer questions, reciting poetry, and building mosaics on the warren walls and decide to settle in. After repeated warnings from Fiver that the warren is not safe, Bigwig gets caught in a snare. The runaways from Sandleford Warren soon discover that what they thought was a new home is actually a death trap. The Cowslip rabbits refuse to help and get angry at Fiver for asking for them to release Bigwig. Once Bigwig is free, it becomes apparent that men snare the warren territory, but keep the rabbits happy with good food and only a few kills at a time. The Cowslip rabbits feel that this is a good enough trade for the safety and food they are offered and soon become odd and domesticated rabbits. The Sandleford Hlessil decide to leave. Also, Strawberry, a member from Cowslip's Warren, decides to ditch the warren and joins Hazel's adventure because his mate, Nildro-Hain is killed in a snare.
This is not the last that is heard of Cowslip's warren, however. Holly, Bluebell, and Pimpernel, after surviving Sandleford's demise, came to find Hazel and Bigwig and ran into Cowslip's Warren on their journey. When Holly and the rest of the travelers woke up, besides Pimpernel, they saw big rabbits and when Holly asked them if they'd seen anyone by the name Hazel or Bigwig, and were attacked viciously. The Snare Rabbits succeed in supposedly killing Pimpernel, or at least being left behind (since poor Pimpernel did not awake in time to see the fighting), and injuring Holly, but not before Holly scratched Cowslip's eye.
In the film Watership Down, Cowslip's people all look similar. They all were orange, and they have smooth fur. Most are rather large, yet they aren't good fighters. The Warren doesn't seem to have an Owsla because they rely on the man to kill their elil and feed them. Whenever rabbit dies, the other rabbits are ordered to act as if that rabbit never existed.
Cowslip's Warren makes an appearance in the animated series, called the Warren of the Shining Wires. With Cowslip as its Chief Rabbit, the warren intentionally abandoned the tricks and cunning El-ahrairah bestowed upon them. The local farmer feeds the rabbits of the warren and protects them from predators so that he can trap rabbits who come and go in snares surrounding the Warren. This is very similar to the novel.
It appears in the series.
They also have the belief that when one of their friends or relatives die it means wellbeing for them as sated by themselves.