 Females are presumed to select mates based on the shape of the teeth, because the different species are otherwise quite similar in appearance.The social structure is not well known, but sightings of single males accompanying multiple females suggest a polygynous mating system, which would considerably limit the number of males a female can choose.Beaked whales comprise at least 22 species of small whales in the family Ziphiidae, which is one of the least-known families of large mammals; several species have been described only in the last two decades.