Distribution of southern right whales on the Auckland Islands calving grounds

Southern right whales (Eubalaena australis) were virtually extirpated from New Zealand by commercial whaling, but are now recovering. Previous research at the Auckland Islands has suggested that Port Ross, a sheltered embayment at the northern end of the islands, is the primary calving ground for right whales in New Zealand. However, an abundance of potentially suitable calving areas exist outside Port Ross, raising the question of whether the growing population might be expanding its distribution to occupy new or former habitats. To address this we conducted the first systematic line-transect survey of potential right whale calving habitat at the Auckland Islands in winter 2011. High densities of southern right whales were sighted inside Port Ross, including all but one of the 21 mother-calfpairs recorded. The survey confirmed that Port Ross is the principal calving area for southern right whales in the Auckland Islands. This conclusion has implications for the estimation of demographic parameters of right whales in New Zealand, which have thus far relied on data gathered largely in Port Ross, and highlights the importance of protecting this habitat.