Responses to a Model Predator of New Zealand’s Endangered Takahe and Its Closest Relative, the Pukeko

Abstract

New Zealand's avifauna, characterized by several species of endemic flightless birds, has evolved in isolation from terrestrial mammalian predators. Consequently, there has been no selection pressure to develop defense mechanisms against terrestrial predators. When Polynesians (AD 1000-1200) and Europeans (AD 1850) arrived, much of New Zealand's naive avifauna became easy prey to predators introduced by these settlers (Diamond & Veitch 1981; Holdaway 1989). Vulnerability may have been exhibited by unusual tameness (lack of defensive behavior) or by nesting, roosting, and perching in areas exposed to introduced predators (Bell 1991). The Takahe (Porphyrio manteUO is a large, flightless gallinule endemic to New Zealand. It was thought extinct until its rediscovery in Fiordland in 1948 and is still among the most highly endangered bird species in the world. The Takahe population consists of approximately 120 adult birds in Fiordland's isolated alpine habitat and 30 others that have been established on four, small, predator-free islands (Crouchley 1994). Subfossil evidence indicates that Takahe were once found throughout New Zealand, apparently most abundant along forest margins and streams in lowland regions (Beauchamp & Worthy 1988). Bunin and Jamieson (1995) review the reasons behind the Takahe's decline, which began with the arrival of humans 800-1000 years ago. The main predatory threat to Takahe in their current environment is the stoat (Mustela erminea), first introduced with early European settlers toward the end of the nineteenth century (King 1990). There is a correlation between years of high stoat numbers in Fiordland