On our third full day in the park we pile into the sheep shearing shed complete with a lingering aromatic reminder of its relatively recent use, in order to learn more about Tawh’s (pronounced “Tawf”) ecology. Our master of ceremonies is Maurice “Mo” Puckett, the Auckland Council’s head ranger at Tawharanui who has been part of Tawh’s legacy for 20 years. He started life at the reserve as a single man but now lives on property with his wife where they have also brought up their two kids – a 14 and 16 year old.
Mo launches into an explanation of the park’s ecology while keeping a burlap sack mysteriously on hand. He reveals to us that New Zealand is literally an island nation for the birds – there are no native mammals save a specie or two of bat. He begins telling us that there are, however, plenty of mammals around that have been introduced by other means. As he tells us about each, he unceremoniously pulls out and drops frozen examples from trapping efforts at Tawh.
Both the Maoris who first came to New Zealand’s shores and the Europeans who followed years later brought over certain creatures to help them meet their needs. Rabbits, one of the earlier introduced mammals, were a prime example of an animal that could provide meat, pelts, and sport for those who liked to hunt. However as rabbits tend to do, they multiplied rather quickly. In areas where farming had already depleted vegetation, the holes that rabbits dig for their burrows further de-stabilized the landscape. Paired with rainfall, the afflicted hillsides would erode away or deposit sediment into local waterways, stressing fragile aquatic ecosystems. In addition to fencing and poisoning efforts, ferrets, weasels, and stoats were released in an attempted form of biocontrol. However all three introduced their own havoc on New Zealand’s native flora and fauna, with stoats being the most insidious. Stoats are efficient hunters, “little killing machines” as Mo stressed, and have an inordinate impact on birds. Mo also relayed that stoats are originally adapted to colder climes and tend to bury their prey. But since New Zealand experiences warmer temperature at times, the stoat’s spoils sometimes rot before they ever retrieve their cache. Additionally, female stoat kits may become impregnated before they even open their eyes. The embryos they carry will go into stasis until they are able to give birth sometime later.
Other pests in the country include possums (the variety originally native to Australia, not the Opossum Americans are used to) who have a greater variety of New Zealand trees to eat relative to the limited variety they enjoy back home. Their fur is soft and has great insulating properties, so is often mixed with merino wool products in New Zealand. Hedgehogs which can often rid gardens of unwanted slugs and other nuisances have themselves become overabundant and a threat to native insects, lizards, and the eggs and chicks of certain birds with ground-nesting behavior. Feral cats or even people’s pets may have impacts on wildlife. Rats may be the most damaging of all as they devastate vegetation and seed banks that support the habitat for bird species.
Staff have armed Tawharanui with a whole suit of ways to combat these pests. One of the most important components is the pest-proof fence lining most of the park’s boundaries. It is constructed with a mesh size small enough to keep anything unwanted, down to the smallest mouse, from getting through. All access points in the fence are designed with two-door entryways where only a single door may be open at a time. The top of the fence is sloped so animals can’t easily climb over and nearby branches are kept trimmed to further discourage stealth breaches of the perimeter. Different varieties of traps are baited and set, and rangers will check them regularly. And while the fence does not extend over the full reaches of the beach that lines the coastlines of the park, it does have an interesting feature. The ends of the fence curl inward in a spiral. Many animals have a tendency to follow the length of the fence and will find themselves corralled into the coiled terminus and into more awaiting traps.
One tool Mo showed us which I found delightfully elegant and fascinating was what they referred to as “talls” (and more formally sold under the name “the black trakka”). These basically consist of baited tubes with floors lined with inked cards. Animals wander through the tubes, inking their feet and leaving tracks on a blank portion of the cards. The cards can then be later retrieved and examined as a sort of record of what small mammals might be roaming park grounds.
Tawh is certainly not only susceptible to threats of the mammal or even faunal kind. In later posts I will describe some of the additional challenges, including invasive varieties of plants, that park staff must vigilantly respond to.
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It’s interesting how these introduced species have a far broader impact than you would expect. Take the rabbits, destabilizing the soil and influencing aquatic systems but also geomorphology. The same goes for the possums as the remove a ton of leaves decreasing the carbon sink potential of forests, probably altering roughness length as well as the albedo of the forest (important biophysical factors).
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