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Nature’s Corner Mid Summer to Early Autumn 2007

Artful fern ephemera

Fertile kiokio frond unfurling
Fertile kiokio frond unfurling

It looks like an Art Nouveau design, but this is a new frond belonging to a large ground fern, the kiokio (Blechnum novae-zelandiae). It was not fully unfurled when captured on camera at the Karori Wildlife Sanctuary on 4 February. A few hours later its elegant curls would be straightened out and it would hardly rate a second glance. All the Blechnum species have two kinds of frond – sterile and fertile. The sterile fronds are the usual green fronds we expect a fern to have, but if you turn one over there is no pattern of brown sori (clusters of spore capsules) on the underside. These fronds concentrate on manufacturing food for the plant by photosynthesis and have no reproductive role. That is the speciality of the fertile fronds. Those of the kiokio look as if they have been crafted from coarse string when they first emerge and are often a brownish colour. Later their leaflets resemble very narrow strips of green leather. The undersides are crowded with brown sori. Dust-like spores will be released for wind dispersal when the capsules are ripe. By then the fertile leaflets are shrivelled, string-like, and dark brown. If you touch them, you feel a dusting of spores on your fingers.

Who made those marks?

Flax looper moth caterpillars did this
Flax looper moth caterpillars did this

The leaves of the wharariki / coastal or mountain flax (Phormium cookianum) growing in the back border at Tui Terrace are speckled with pale streaks. The recently released wetapunga / giant weta want you all to know that they are not responsible for this graffiti. The damage had been done before they arrived. The real culprits were caterpillars of the flax looper moth (Orthoclydon praefectata) and the streaks are where they have been dining in secret. If you look closely you will see that they must have done all their eating while lying concealed on the underside of the leaf blade thus avoiding exposing themselves to the weather and the beady eyes of birds or predatory insects passing above. Each streak is really a little channel formed by the caterpillar as it strip-mined the leaf, consuming everything in its path except the tough translucent skin on the upper surface.

A night beetle sees the light

Tupanapana / Click beetle
Tupanapana / Click beetle
© Allison Buchan

The seed heads of matau a Maui / hook grass (Uncinia uncinata) look like brown pipe-cleaners but an unexpected bulge at the end of one caught my eye and caused me to stop for a closer look. There was a beetle, apparently sound asleep. It was aligned with the seed head but its wider body was the giveaway. An ill-advised attempt at a flash-lit photograph disturbed its repose, causing it to stand up and turn to look for the source of the shock. ‘What the blazes was that?’ it might have been thinking. It didn’t react when I took this second photo (without a flash). After a few more seconds it apparently concluded it was not in danger, realigned itself with the seed head again and presumably returned to sleep. It was still there when I passed the same spot about an hour later.

Comparing my picture with the illustrations in Andrew Crowe’s Which New Zealand insect?, I concluded that I had met a tupanapana / click beetle, probably the acute-winged click beetle (Metablax acutipennis). The larval stage is a grub that tunnels under bark and in dead wood. The nocturnal adult beetle breeds in late spring and summer. Tupanapana / click beetle strategy for escaping predators is to make a loud click and hurtle out of the way. It achieves propulsion by popping a special peg joint from its socket and that action is the source of the click sound. If the beetle falls or is flipped upside down, it uses the same mechanism to right itself. It often has to repeat the manoeuvre several times in succession before achieving a successful outcome, hence the Maori name meaning repeated twitches, jerks or spasms.

Discarded skeletons

Exoskeleton of a cicada nymph
Exoskeleton of a cicada nymph

On fine days in late summer and early autumn the air vibrates with the serenades of male kihikihi / cicadas as they compete to attract females for mating. Their adult lives only last one or two months from the time that they emerge from the ground as wingless nymphs, climb up something and moult to emerge in their final winged form. What they leave behind we call a nymph ‘skin’ but really it is their external skeleton (exoskeleton). Being invertebrates they are without a bone in their body and depend on outside support rather like wearing an all-enveloping corset. Usually they climb up a tree or other vegetation to make that final moult, but some have been using our pegs that mark planting sites. They leave behind hollow replicas of their former selves, having squeezed out through a split in the back.

Rata Milestone

First northern rata flowers at Round Lawn
First northern rata flowers
at the Round Lawn
Photo by Ken Drayton

Here is the young northern rata (Metrosideros robusta) at the Round Lawn fulfilling its promise of Christmas flowers. Buds started to open in the week prior to Christmas Day and this picture was taken on 31 December when it still had some unopened bud clusters. Flowering continued into early January but was over by mid-month. This is the first of the northern rata that have been planted in the Karori Wildlife Sanctuary to flower and we look forward to many more passing this milestone in future years. Don’t expect too much from this one next Christmas though. Pohutukawa and rata typically follow a boom and bust cycle with a good flowering season being followed by one or more poor ones. The rest period allows the tree to recover from its big expenditure of food and energy and build up its reserves again. It may also keep populations of seed-destroying pests in check.

Northern rata flowers in detail
Northern rata flowers in detail
Photo by Ken Drayton

Rata flowers closely resemble those of pohutukawa (Metrosideros excelsa), but with fewer flowers per cluster. The red stamens, tipped with anthers shedding yellow pollen, surround shallow cups where nectar accumulates. Insects, geckos, birds (and short-tailed bats, although we have none of the latter in residence yet) get dusted with pollen when taking the nectar. Red is a colour known to attract birds, and nectar-eating birds are particularly desirable pollinators because they range quite widely, making repeated visits to many flowering trees in a day. That increases a flower’s chances of being cross-pollinated with pollen brought from another tree. Such genetic mixing should give the tree healthier more adaptable offspring.

The big old rata that can be seen on the western scarp from Tui Terrace also came to the party and gave us some Christmas flowers. As for the pohutukawa, often called the New Zealand Christmas tree, it put on an outstanding display of festive red all around Wellington this December and January. Towards the end of February I noticed a few akakura / scarlet rata vine flowers starting to show. This is Metrosideros fulgens. We will find out in autumn and winter if it can match its cousins in the flowering stakes. Maybe red-flowered Metrosideros are on a roll.

What the eel is happening?

Longfin eel
Longfin eel

The tuna / eel in the photo looks to be in grave peril but its situation was not as dire as you might think. It was rescued from Roto Kawau, the lower lake, after getting caught up in the electric fishing carried out over several days in late February as lake management specialists from Waikato University investigated the high density population of an exotic pest fish, the European red-finned perch. It is hoped that the research will ultimately lead to strategies for the control or elimination of the perch and the recurring algal bloom problem in which they are implicated. There are an estimated 20,000 to 30,000 perch in the 2.5 hectare lake and the native fish species we want to restore to the Sanctuary’s freshwater ecosystem don’t stand a chance with that level of competition. This longfin eel (Anguilla dieffenbachii) was the only native fished from the lake on the day I was present. It was put in a tub of water to recover and remained in temporary confinement until the electric fishing was completed. Then it was released back into the lake.

Longfin eels are unique to New Zealand. They are long-lived. The one photographed was estimated to be 10 years old. A larger specimen recovered from the lake on a subsequent day was estimated to be 20 years old. Eventually they migrate to an ocean breeding-ground in the southwest Pacific where they spawn and die. The average age of females when they migrate to sea is 33 years but some remain in their freshwater habitats much longer and can reach ages of 50 to 60. There is a large specimen living in Te Mahanga stream that may fall into that age group. How to accommodate an aquatic species that needs to migrate to complete its life cycle while at the same time protecting the Sanctuary behind a pest-excluding barrier is a brainteaser. Hopefully there will be a solution.

He or she, which is this tree?

Mahoe flowers en masse
Mahoe flowers en masse

Quite a number of New Zealand trees and shrubs are dioecious species in which male and female flowers are on separate plants. The flowers are small - even tiny - so it’s not something that is obvious. However people do sometimes wonder why a certain tree flowers profusely every year but never has fruit while another tree of the same species growing in close proximity does produce fruit. You can solve the mystery by comparing their flowers. Male flowers are designed to produce pollen and female flowers are designed to be fertilized by pollen and develop fruit. Two common dioecious species in the Karori Wildlife Sanctuary are mahoe and mapau. When these are flowering, use a magnifying glass to take a close look at the individual flowers. Ask yourself, is this flower equipped to produce pollen or fruit?

Male mahoe flowers
Male mahoe flowers

Mahoe / Whiteywood (Melicytus ramiflorus). This bloomed abundantly through much of summer, its tiny (3-4 mm across) flowers seen as a pale yellowish mass covering branchlets. On a male tree, flowers open to reveal an inner circle of plump yellow anthers containing a store of pollen. Soon the anthers develop splits and become shrivelled as the pollen escapes to stick to tiny insects that come to consume the minute amounts of nectar on offer.

Female mahoe flowers
Female mahoe flowers

Female flowers are smaller than the male flowers and have quite a different structure. The most prominent feature is the rounded green ovary in the centre of each one. It looks like a potential berry and so it is, but it needs to be fertilized by male pollen before it can develop. To collect the pollen from insects that land to take nectar, each ovary is topped by a white, lobed stigma. The two flowers seen in profile (on the large version of the photo) on the lower side of the branchlet show the structure most clearly. At the far right is a new fruit that has grown from a flower fertilized earlier in the season. In February some fruits will already be changing colour to violet-blue or dark purple as they ripen and this will continue in March.

Female mapau flowers
Female mapau flowers

Mapau / Matipou / Red matipo (Myrsine australis). Flowering started in January, has continued though February and usually extends well into March. The flowers appear whitish to cream, are around 2 mm across, and grow in clusters on twigs between the leaves. To distinguish the sexes, look for the parts essential to their different functions. These female flowers were photographed in mid February on a young tree beside Lake Road, across from posts 71-72 of the Research Area fence. At the centre of each flower, there is a pinkish ovary topped by a white, fringed stigma. This is easiest to see when the flowers are in profile. Lower down the stem are ripe black fruits. Mapau fruits take a year or more to ripen, so these are the produce of last summer’s flowers.

Male mapau flowers after dispersing pollen
Male mapau flowers after
dispersing pollen

Male mapau flowers, on the other hand, have four (occasionally five) prominent anthers to carry out their pollen-producing function. If the flowers are fresh, the anthers will be projecting stiffly from the flower when viewed in profile. As they lose their pollen and deflate, they loll in different directions. When the petals curl back out of sight or wither, the anthers can be mistaken for petals. These were photographed at Round Lawn where there are both male and female trees.

What's that on the track?

Fallen male mahoe flowers
Fallen male mahoe flowers

In late February many male mahoe were carpeting the ground with tiny discarded flowers like these. Female mahoe create less litter because their fertilized flowers develop into fruit. They discard bits that are no longer needed, like the petals, but need to retain the flower stalks to be fruit stalks and the central ovaries that become the fruit.

Fruit to Go

Kanono fruit ripening
Kanono fruit ripening

Kanono (Coprosma grandifolia). Small fruits (7-9 mm) have been ripening to orange on female trees since January but in greater quantities through February. Having small fruit means many different birds are available as seed dispersal agents. As kanono fruiting declines in autumn, the ripening fruit of the related karamu (Coprosma robusta) increasingly takes its place on the bird menu. Both these trees are quite common along Lake Road and the other tracks. Kanono has larger, broader, mottled leaves. The males of both species are naturally fruitless but are probably developing flower buds in preparation for the next round of pollination.

Ripe titoki fruit
Ripe titoki fruit

Titoki (Alectryon excelsus). The fruits combine fleshy red arils with shiny black seeds to create an eye-catching display. They take about a year to ripen and, until ready, have been kept hidden in furry brown capsules. Although titoki are fruiting in the Sanctuary they are not in places where they can be easily seen from a track. However, in Waiapu Road, just south of the boom-gate used to close the Sanctuary’s car park, there are two overhanging the footpath with ripe fruit on view in February and early March.

Other colourful fruits likely to be noticed in late summer and early autumn include karaka, karewao / supplejack, kawakawa, porokaiwhiri / pigeonwood, and maire tawake.

Quite a handful!

Cook Strait giant weta
A Cook Strait giant weta
meets the people

Wetapunga o Raukawa Moana / Cook Strait giant weta (Deinacrida rugosa). These are the first invertebrates to be restored to the Karori Wildlife Sanctuary ecosystem. Many Sanctuary members were present on 11 February to witness their release and take the opportunity for a really close look at these impressive and seldom seen nocturnal insects. Big they may be, but they are ‘gentle giants’ and those who handled them felt only footsteps. They are primarily vegetarian and might have a role in dispersing small seeds. Unlike the more familiar putangatanga / tree weta, the males do not have a combative culture requiring big jaws for fighting and defence. Nor have we erected any Weta Hotels for the newcomers. They don’t spend the day sleeping in tree holes with their mates. They are solitary nomads that wander about and take temporary shelter wherever they are when dawn approaches. Such careless camping out makes them an easy meal for mammalian predators like rats and led to their extinction in mainland New Zealand. They survived only on rat-free islands in Cook Strait. After Matiu / Somes Island in Wellington Harbour was cleared of pest mammals a population was established there and that has been the source of the 100 released in the Sanctuary.

Female Cook Strait weta showing ovipositor
The rear spike on a female is
her egg-laying tube (ovipositor)

Wetapunga is a contraction of ‘weta a Punga’ meaning Punga’s weta. In Maori creation stories, Punga was the ancestor of creatures that were considered ugly, scary and potentially dangerous. Tribes differed about the identity of Punga’s descendants, but invertebrates, reptiles and sharks were among the candidates. Giant weta, with their stout bodies, looked like the kingpins of the weta world and were therefore thought to be particularly close to Punga.

Face to face with a wetapunga
Face to face with a wetapunga
Photo by Tom Lynch

If you were small enough to come face to face with a wetapunga, this is what it would be like. Those spindly side-limbs that end in blobs are called palps and are used to taste food before eating. The things attached to its head are not electrodes but the animal’s natural antennae, used to feel, smell, and sense vibrations. Wetapunga have a reputation as ‘living fossils’, but some of them have the latest technology. As you can see on the large version of the photo, this one carries its backtop (like a laptop, only specially adapted for creatures without laps) everywhere it goes. Yeah, right! Really it is a tiny radio transmitter. To learn more about the behaviour of giant weta and monitor their dispersal within the Sanctuary, 20 have been fitted with these transmitters to enable researchers to track them with telemetry gear and detect their locations. I wonder if we have any long distance champions among them?

Kaka Gazette

Our North Island kaka (Nestor meridionalis septentrionalis) population continues to grow. Eight pairs bred this season, including a newly formed pair with no previous parenting experience. Two of the experienced pairs had previously bred with other partners but deaths and a divorce had necessitated a reshuffle. The divorced couple were brother and sister so we are glad they have come to their senses! Inbreeding can have unhealthy consequences in later generations.

Kaka chicks, around 20 days old
Kaka chicks, around 20 days old
Photo by Matt Robertson

This picture of down covered chicks was taken early in the season when fledging was still a long way off. At this stage they are totally confined to the nest and fully dependent on their parents for nourishment. You can see that the chick on the right must be the older of the two as it is just starting to grow feathers on its head. It takes about two months before they are fully feathered and can venture out for their first attempt at flight.

There are now 23 fledglings out and about. The last three departed their nest in mid February. They all have a black band on one leg and two coloured bands on the other. You may see them begging food from their parents at times, although they are also learning how to find their own. They will probably hang about with their parents for most of the autumn.

More Nature's Corner...

This edition of Nature's Corner was written by Karori Wildlife Sanctuary volunteer Allison Buchan on 23, 26-27 February and 2 March. Statistical information relating to the kaka breeding season is drawn from a report by Sanctuary conservation scientist Raewyn Empson. Unless otherwise indicated, photographs are taken by Allison Buchan and are © Karori Wildlife Sanctuary. Clicking on photos will take you to a larger version.

Published 10 March 2007.

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