We're going to go out on a limb here and say that we her at Shmoop would like to see Watership Down from the perspective of the female rabbits. What's their experience really like? Because the does don't get a lot of time in the spotlight here to show us what they would do as main characters. And we think that's a bummer.
But that does mean these does probably serve some sort of symbolic purpose. Sure, they may not be fascinating characters, but the male rabbits of Watership Down sure are obsessed with getting some ladies.
Of course what they symbolize depends on where they are. In Sandleford, does are connected to the idea of home, as when the wandering rabbits fondly remember the home dug "by countless great-grandmothers and their mates" (12.65). Yes, that sentence does mention "mates," but notice that it's "great-grandmothers" who get all the attention here. For once, the does get top billing—when it's connected to the idea of home (and the work that goes into making a home).
In Efrafa, the does are symbolic of how unnatural the warren is under Woundwort's control. Hyzenthlay neatly sums this up for Holly: the does "can't produce litters, because of the overcrowding, but no one is ever allowed to leave" (27.34). So we pretty much know all we need to know about Efrafa through how the does live. It's a tightly controlled place where the natural cycle of things is messed up by the tyrannical rule of Woundwort.
And for Hazel's rabbits, does mean children and the continuation of the warren. As Hazel explains, without does "this warren's as good as finished, in spite of all we've done" (23.102). The warren won't die out immediately without mating (though it might feel that way), but it will in a few years. That's precisely the amount of time that Hazel gives the warren: "no does means no kittens and in a few years no warren" (23.106). So for Hazel's rabbits, does symbolize the future and the continuation of the warren, which is kind of the whole reason they got outta Dodge (Sandleford) in the first place.