page_title: Pouteria costata
section_title: Threats
hierarchical_section_title: Pouteria costata / Threats
caption_attribution_description: Composite image showing how the fruit of Pouteria costata, Tawāpou or Bastard Ironwood, varies in shape (even on the same tree) and changes colour as it ripens. It is one of the foods of the New Zealand pigeon or Kererū. Auckland, New Zealand
context_page_description: Pouteria costata is a small coastal tree native to the northern North Island and to Norfolk Island. In New Zealand, its common name is tawapou; on Norfolk Island it is called bastard ironwood. The name costata is from the Latin costatus, a reference to the prominently raised primary nerves of the leaves. Pouteria is a genus of approximately 300 species in the tropics of America, Asia, Australia and the Pacific. A Pouteria species found in other Pacific Islands is sometimes erroneously included in P. costata.
context_section_description: The fruit and seeds of P. costata are very palatable to rats. Research in New Zealand has shown that the eating of the fruit and the destruction of the seeds by kiore (Pacific rats) has substantially reduced the population of the tree and significantly altered the composition of coastal forest of the northern North Island. Kiore were introduced by Māori sometime in the last 1,000 years and became widespread on the three main islands, and reached many of the offshore islands. Tawapou seedlings and saplings are now rare on the mainland and on off-shore islands where kiore are present, and abundant on islands where they are absent. Where kiore are present, it is rare to find tawapou seeds that have not had their kernels removed. Kiore eat the flesh from freshly fallen tawapou fruit but tend to take the seeds to 'husking stations' where they remove the kernels. As many as 1,400 discarded husks have been found at a single site.  The number of juvenile trees increases markedly on islands from which kiore have been removed. "The apparent thoroughness with which kiore find and eat the kernels before the seed germinates shows that kiore can substantially reduce seedling numbers… Numbers of tawapou, and the proportion of tawapou trees in forest vegetation, will increase after rat eradication on any island that still retains tawapou trees" (Campbell et al., 1999:280). Norfolk Island also has various species of rats, which no doubt contributes to the endangered status of P. costata there.
caption: The fruit take on a variety of colours as they ripen
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