Forest fauna restoration
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A biodiversity collapse
There is no historical record of what vertebrate and invertebrate species were present in the sanctuary valley before it was cleared. Assuming the original vegetation was a dense multi-tiered lowland podocarp/broadleaf forest, then it is likely that most forest vertebrates of the southern North Island would have been present. A list of species known to have been present south of the Manawatu River before human settlement forms the basis for our Restoration Plan.
An amazing diversity of animal life probably flourished in the Wellington area in pre-human times. The pre-European forest would have contained bats and birds such as bellbird, bush wren, fantail, falcon, grey warbler, Haasts' eagle, huia, kaka, kakapo, kakariki, kereru, kiwi, kokako, laughing owl, moa, piopio, robin, saddleback, hihi, tomtit, tui, weka, and whitehead. There are many stories of the deafening birdsong in the bush around Wellington last century.
Stoat with bird
Overall the indigenous fauna of the valley was in a seriously depleted state before the restoration work was begun in 1999, with only about 21% of the previous vertebrate fauna present. Some species are now extinct but it is possible that analogue species might be introduced to replace these.
The valley of the birds
Now that the sanctuary is free of significant predators such as rats, mustelids and cats, the remnant populations of native birds in sanctuary valley (such as tui) have shown a rapid increase and are spreading beyond the sanctuary borders. To date 15 species of native fauna have been reintroduced (see wildlife releases). Other species will be introduced over time.
Some species with strong homing instincts may be successfully established in a new area by introducing captive-bred juveniles (e.g. kaka). Other species are so rare in the wild that captive breeding is the only way to source sufficient numbers for release (e.g. brown teal).
Supplementary feeding of birds, such as kaka, hihi and bellbird is important to encourage birds to stay in the Sanctuary and thereby ensure that a breeding population is established. Supplementary feeders are also useful in that they help staff and visitors see the birds and monitor activities.
Restoring the dawn chorus
The sanctuary developed a 10 year Restoration Strategy in 2000 with a three stage release programme for birds.
Stage 1: Robust species (relatively accessible birds that should be able to coexist with low numbers of predators, assuming there may be breaches of the fence): Re-introduction of this group began within months of the completion of the pest eradication programme in 2000. Included are: bellbird, kaka, kereru, kiwi, tomtit, weka and whitehead. Next on the list is red-crowned parakeet (kakariki).
Stage 2: Rare or vulnerable species (birds that may be difficult to obtain, may be more vulnerable to predation or may be difficult to establish): Some of these species have begun to be introduced, such as the saddleback and hihi. Others may be re-introduced at a later stage, including kokako, rifleman, takahe, and yellow-crowned parakeet. South Island takahe may be introduced to replace the now extinct North Island takahe.
Stage 3: Endangered and analogue species (birds that are endangered in status or rare species that may be introduced as analogues for species that are now extinct): Included are: kakapo and snipe. These are unlikely to be considered in the near future due to the available habitat.
In regard to other fauna:
Reptiles
There are approximately 40 species of native gecko, divided between the mainly nocturnal brown geckos and the day-active green geckos (which can be seen in the display near the Round Lawn). Of these, five have been identified as appropriate for release into the sanctuary, but only the forest gecko is known to be present. New Zealand also has nearly 40 species of skink - several of which are endangered. Three of the five species identified as appropriate for the sanctuary have been found naturally occuring here. In 2006, the sanctuary reintroduced tuatara.
Bats
The two extant species of indigenous bat (the short-tailed and the long-tailed bat) have a threatened status so it may be some time before animals can be safely obtained for release into the sanctuary. Translocation techniques for bats still need to be developed so any transfers will need to be part of an approved research project.
Invertebrates
Invertebrates are animals without backbones. Very little is known of what invertebrates would have been found in pre-human times in the sanctuary but we have made some best guesses about large-bodied species that should be present. These include: the giant pill millipede, giant weta, giraffe weevil, speargrass weevil and large landsnails.
The question of which native invertebrates should be reintroduced to the sanctuary will be the focus of a research programme and will require a systematic survey of what species are already present.
The introduction of any invertebrates will require caution to ensure that potentially injurious exotic species are not accidentally introduced. Quarantine measures, such as using sterilised potting mix during the re-vegetation programme, have been used to limit the risk, and strict biosecurity measures are in place to prevent the accidental introduction of pests such as Argentine ants. Whenever possible, pest invertebrates such as Vespula wasps are controlled.
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