New Approaches Toward a Better Understanding of the Decline of Takahe (Porphyrio mantelli) in New Zealand

Abstract

Island populations of endemic birds are known to be particularly susceptible to extinction. This paper focuses on factors behind past and present declines of the highly endangered Takahe (Porphyrio mantelli), a flightless rail endemic to New Zealand. Subfossil evidence indicates that Takahe were once found throughout this island nation, being most abundant along forest margins and streams in lowland regions. Their numbers have declined dramatically since human colonization about 800–1000 years ago, probably due to a combination of habitat destruction and hunting by early Polynesian settlers. Today, the wild Takahe population consists of about 100 adult birds in an isolated alpine habitat and approximately 30 individuals recently released on several small offshore islands. Despite protection and intensive management, including removal of an introduced competitor (red deer, Cervus elaphus), the alpine population has continued to decline. In contrast, the Takahe’s nearest relative, the Pukeko (Porphyrio porphyrio) has expanded its range across New Zealand despite heavy hunting pressure since its colonization from Australia less than 1000 years ago. We suggest that, unlike Pukeko, Takahe lack appropriate behavioral responses to cope with mammalian predators such as stoats (Mustela erminea), which have been introduced relatively recently by European colonists. A study comparing predator defense behavior between these two closely related species is currently underway.