This Snares endemic was not described to science until 1953. It is similar to the Fiordland Penguin (Eudyptes pachyrhynchus) which has a smaller bill lacking the bare skin frame of Snares Penguin. The two are not known to interbreed even though 20-30 Fiordland Penguins visit the Snares each breeding season. Snares Penguins disappear from their breeding islands May-August during which time their whereabouts remain unknown. Three km away, a small subpopulation of Snares Penguins on the Western chain islets breed 6 weeks later than the main population. They are thus reproductively isolated temporally and may represent an undescribed cryptic species.