Weasels are the trickiest kind of elil in the Watership Down series. They are notorious for being bloodthirsty killers, able to easily slip into a warren and clear out burrows without the rabbits knowing thanks to their long and slender bodies. They are known for their sinister nature, and are also known to be able to kill a full grown buck. Some weasels even speak broken Lapine.
In the Watership Down television series, weasels appear as minor antagonists.
- The Weasel who only appear in the two episodes, Home on the Down and The Vision, was the first danger the rabbits of Watership Down encountered when they first arrive on the Down. A weasel with similar design appeared in two flashbacks in other epsiodes, The Shadow of Efrafra and Prisoner of Efrafa, revealing it to be the weasel who killed Woundwort's mother, although this could possibly be a different weasel.
Other weasels are seen several times more often in the third season of the TV series than other predators; they are depicted as long-tailed weasels. They appeared in The Wanderer, The Dark Deal, and The Beginning of the End.
- In The Wanderer, a weasel attacks Vervain and Aspen by the pond, succeeding in killing Aspen. At the end of this episode, the weasel attacks Vervain again, but is attacked and driven off by General Woundwort, who saved Vervain at the last second.
- In The Dark Deal, another weasel is seen attacking Redstone Warren and threatened to invade the burrow, but it is attacked by General Woundwort and either killed or chased away.
- A weasel appears in The Beginning of the End, running down a log and disappearing out of sight while following the Darkhaven rabbits when they are treking the woods to Watership Down. It was mentioned that the elil in the surrounding area, including the weasel, are aware that the Darkhaven rabbits are going through the woods in the open, in which Woundwort is informed of by Vervain. That night, the weasel attacks Hannah, planning to kill her before making a meal out of the rabbits. He nearly kills the mouse, but he is tackled by two of the Darkhaven Owsla, who were then joined by two others to assist in fighting the weasel. The weasel manages to escape the scuffle when the bats began attacking the Darkhaven rabbits to provide Campion, Blackberry, and Spartina a means of escape. The weasel briefly takes cover in the same log Hannah was hiding in; he looks at her with a menacing snarl but he runs off to escape the confusing chaos.