How large is the menstruation of a narwhal and its frequency?

Narwhals have a relatively low reproductive rate, with females typically experiencing menstruation for about 2 to 3 days during their estrous cycle, which occurs once a year. This cycle generally aligns with the breeding season, taking place in late winter to early spring. The specifics of their menstruation are not well-documented, but like other marine mammals, it is expected to be less pronounced due to adaptations to their aquatic environment.