Sub-Alpine Idyll

We recently went on a lovely hike up Peak Hill, overlooking Lake Coleridge. The start of the track crosses paddocks, but once on the reserve land, the vegetation changes to a beautiful sub-alpine spread of daisies, Spaniard, matagouri, and tussocks. The daisies, in particular, were spectacular—so many were in bloom that the whole hillside looked frosted. The Spaniard was blooming, too, spiky flower heads rising above the daisies like something from a Dr. Seuss book. Native bees, mānuka beetles, and syrphid flies were all taking advantage of the abundance of nectar and pollen. The air hummed with insects.

You could be forgiven for thinking it was a beautiful, peaceful place. And it was, for us. But among the insects buzzing around were predators—pompillid wasps hunting for spider prey, robber flies snatching unwary insects out of the air, and birds snapping up bugs to feed to their young.

And then there were the plants themselves. At least one hapless beetle impaled itself on a Spaniard leaf. 

It may be pretty, but it’s a rough world out there when you’re insect-sized.

Alpine Delights

The family spent a delightful hour on the Dobson Nature Walk in Arthur’s Pass National Park on Wednesday. The track is an easy one, and hiking it quickly takes about 20 minutes. But it’s not a walk you want to do quickly, especially in summer. It winds through alpine and sub-alpine vegetation, including some beautiful tarns, and in summer, so many plants are blooming, it’s hard to take five steps without finding another lovely orchid, daisy, or hebe in bloom.

For me, the best part of the walk is the abundance of sundews in the tarns. As an entomologist, I’m naturally drawn to carnivorous plants like sundews. Sundews catch insects on the sticky hairs you can see glistening in this photo. The hairs are sensitive to both touch and taste, and when they sense a struggling insect, they fold inward to further entangle their prey. Enzymes exuded by the hairs then digest the insect, and the leaf takes up the nutrients in order to grow in the nutrient-poor alpine wetlands. 

These sundews were just beginning to flower—many plants had flower buds, but none had yet opened. The flowers sit above the leaves—an important adaptation, since the plant needs to be pollinated by the very insects it eats.

The alpine summer is short, so when these plants are done flowering, the leaves will slowly shrink into a structure called a hibernaculum that sits near the soil surface and protects the plant through the winter.

Catlin’s River Walk—a little bit of magic

My family and I were in the Catlins last week, in the southeast corner of the South Island. It’s a wild and remote area, home to more penguins and fur seals than humans. No urban adventures here—it’s a place for outdoor recreation.

One of the things we did was to hike part of the Catlins River Track (we didn’t have time to do the full track). It was unlike any other place I’ve been in New Zealand.

In fact, it reminded me most of eastern Pennsylvania, in spite of the fact that it shares not a single common species of plant or animal.

The track follows the Catlins River, a beautiful waterway that cuts through layers of limestone in one little cascade after another. Swing bridges cross the river several times, providing great aerial views of the water (and a little excitement for those who don’t like heights). The forest is old-growth beech which provides habitat for myriad native birds, carefully protected by intensive predator control. 

In addition to the beech, we were delighted to see two species of orchid on the forest floor, red-flowered mistletoes in the treetops, several species of slime mould, some lovely mushrooms, and a beautiful native harvestman. The birdlife was noisy and varied, but we weren’t lucky enough to see any endangered mohua. And, amazingly, there wasn’t a single sandfly! 

The whole effect was one of an enchanted forest. We were certainly enchanted.

The track is relatively flat—easy hiking for kids or those who can’t face the usual Kiwi hiking track going straight up a mountain, and because there’s no “goal” to reach, you can simply walk as far as you’d like, and then return. The entire length is 12 km one-way, with a return loop option through forestry land away from the river. 

I highly recommend this track. I’ll certainly be going back when I have enough time to do the whole thing.

A Weakness for Weevils

I was excited to find a new weevil on our property the other day. At least until I identified it.

Meet Otiorhynchus sulcatus—the black vine beetle—pest on a wide range of garden plants, including grapes, black currants and strawberries (all common in my garden).

I admit, I have a weakness for weevils—no matter how much of a pest they are, I think they’re cute. And this one is no exception. She’s lovely, in spite of her diet. And I’m certain she’s a ‘she’, because no males of this species have ever been found. The black vine beetle reproduces parthenogenetically, producing viable eggs without the need for fertilisation by males. 

This ability is the result of a bacterial symbiont in the genus Wolbachia. When researchers in California eliminated Wolbachia in black vine beetles (by giving the beetles antibiotics), the beetles’ unfertilised eggs were no longer viable. It’s a clever little ploy by the bacterium to ensure its own reproduction—only infected insects can reproduce, and they can do so without the trouble of finding a mate (I wrote more about this fascinating relationship in Putting the Science in Fiction and on Dan Koboldt’s Science in Fiction blog).

Another cool feature of the black vine beetle is that it is flightless. It’s not uncommon to find flightless insects and birds here in New Zealand, but it’s a little unusual to see it in invasive pests like the black vine beetle. Native to Europe, the black vine beetle is now distributed all around the world. Pretty impressive travelling for a 6 mm-long flightless insect.

Apparently black vine beetles can cause significant damage to plants. The larvae eat roots in the soil and do the most damage, particularly in potted plants, where root growth is limited. I’ve decided not to worry about them at the moment. I’ve got more damaging pests to worry about, and to be honest, I wouldn’t mind seeing them again. They are awfully cute.

Awesome Alpine Plants

Whipcord hebe flowering in the snow

My daughter and I went for a hike on Saturday after being cooped up in the house all day Friday by a rip-roaring southerly storm. The storm lashed us with rain and hail, but in the mountains, it brought snow. Saturday morning, the beech forest at Cragieburn Forest Park was a winter wonderland.

Climbing up out of the forest into the alpine areas, the intensity of the storm was clear—thigh-deep drifts filled the path in some places, while other areas had been blown clear down to the scree. Every tussock had a long train of sculpted snow on its leeward side, so you could almost feel the howling wind and the sting of blowing snow, in spite of it being a clear calm day.

Nestled among the rocks, we found this lovely whipcord hebe, flowering in spite of its slowly melting blanket of snow. And there were other plants peeking out of the snow, clinging to the scree.

Alpine plants are some of the toughest organisms around. They have to cope with intense sun, wide temperature fluctuations, drought, wind, and ice and snow. They have evolved a variety of adaptations in order to combat these dangers.

Short, cushion-shaped growth: A tight ball of branches and leaves resists damage and drying from fierce wind. The pinnacle of this growth form has to be plants in the genus Raoulia. Known as ‘vegetable sheep’, they form hard, tight masses of tightly packed leaves (akin to the texture of a head of cauliflower). Inside the mound, dead plant material builds up around the branches and acts like a sponge, soaking up rain when it’s available. Adventitious roots on the plant’s branches tap into this reservoir of water when the weather is dry.

Long roots: Unstable rocks and shifting scree make it difficult for alpine plants to stay put, and water is often far below the surface. To cope, they have long roots that anchor them deep into the rock. Some are also able to regrow from their roots if the top of the plant is snapped of by rockfall.

Drought-resistant leaves: Many alpine plants have leaves that are fuzzy on the underside, where the stomates (the breathing holes) are located. The hairs trap a layer of calm air against the leaf surface, slowing down water loss from the stomata. Other plants have narrow, vertically-oriented leaves that minimise exposure to the intense alpine sunshine, reducing evaporation.

Sunscreen: A waxy coating on many alpine plant leaves protects against intense sunlight and high temperatures.

Antifreeze: Ice crystals forming inside a living cell break the cell walls and kill it, so organisms living in cold environments have to somehow avoid freezing. Alpine plants protect themselves from freezing by manufacturing antifreeze from proteins in their tissues. The antifreeze prevents ice crystals from forming in the plant’s cells.

Energy conservation: The growing season in alpine areas is short, and nutrients are scarce. Many alpine plants respond by not reproducing every year. Instead of producing low-quality seeds that may not survive, they hoard resources until they have accumulated enough to reproduce successfully.

All these adaptations give most alpine plants a similar look—low, mounded, small-leaved and tough. But one plant in particular stands out as oddly showy and out of place.

Mount Cook buttercup (Ranunculus lyallii)

The Mount Cook buttercup (aka Mount Cook lily), is an unusual alpine plant, in that it has big leaves and large, showy flowers. But even so, it is well-adapted to the alpine environment. Most plants have stomates on the underside of their leaves, because the underside is generally shaded and cooler, leading to less water loss. But in the alpine environment, sun-warmed rocks radiate heat, making the underside of the leaves warmer than the upper side on sunny days. The Mount Cook buttercup and its relatives have evolved stomates on the upper side of the leaves, in addition to the ones on the underside. The stomates on the top open when the underside of the leaf grows too warm.

Kaitorete Spit: An Overlooked Gem

Earlier this week, my daughter and I hiked onto the Banks Peninsula from Birdlings Flat. The walk afforded us gorgeous views of Kaitorete Spit.

Kaitorete Spit is only about 6000 years old, but is an important natural and cultural resource. Te Waihora / Lake Ellesmere, formed by the spit, is home to or visited by 166 species of birds and 43 species of fish which support commercial fisheries, recreational fishing and hunting, and traditional food gathering. In spite of its harsh, exposed environment, Kaitorete Spit is home to a remarkable number of threatened plants and animals, including pīngao (a native sand sedge prized for weaving), a flightless moth, and the katipo spider. A variety of lizards also flourish on the spit. The lake and spit have been important sources of food and fibre for Māori since they arrived in the area. Fragments of the oldest known Māori cloak were uncovered on the spit, dating to around 1500 AD, and many other signs of early Maori use of the spit have also been found there.

In pre-European times, Māori used the spit as a convenient highway as they travelled up and down the island. Unfortunately, the shifting gravel of the spit and the regular opening of the lake to the sea mean the spit isn’t passable in anything but the most capable of four-wheel drive vehicles. Today, travellers make the long trek all around the lake, so our home near the pointy end of the spit is a 40-minute drive from Birdlings Flat, just 25 km away on the fat end of the spit. But I’m happy to leave the spit to foot traffic—it helps protect the unique plants and animals that live there.

On a windy, wet day, Kaitorete Spit is a miserable, exposed place to be, but visit it on a warm sunny day, and you’ll see why it is an overlooked gem.

Spring Babies

It’s that time of year again! The preying mantis egg case I collected in the autumn is hatching.

Because these mantids were in the warm office for half the winter, they’re early. Mantids in the egg cases outdoors haven’t yet emerged. So they need a little extra care. As the babies emerge, I transfer them to a large tank where they’ll be warm and well-fed for a few weeks while the weather improves. Eventually, I will release most, keeping only a few for use in educational programmes.

I never tire of this annual event. I love watching the newborn mantids stretch their legs and catch their first meal. And I’m always amazed that so many insects can emerge from such a small egg case. The current one, just 15 mm long, has disgorged 35 mantids so far, and only half the case has hatched. The mantids don’t all hatch at once—hatching seems to progress from one end of the egg case to the other over the course of a few days. In the wild, I suspect most of the later hatchlings are eaten by the early ones—it’s a mantid-eat-mantid world out there. It happens in my tanks, too, though I try to minimise cannibalism by spreading them out as much as possible and giving them plenty of hiding spots. I used to raise each individual in its own peanut butter jar, but that gets to be pretty time and space-consuming when there can be 70 mantids in each egg case.

Everyone’s heard the sensational ‘fact’ that female preying mantids eat the males after mating. It does happen, sometimes, in some species, but not as often as you might think. Mantids are creatures of instinct, and one of their most powerful instincts is to capture prey. In fact, this urge is so strong that, even when their digestive system is completely full, and they can’t actually eat anything else, they will continue to capture prey.

So it’s no surprise that a female mantid might snack on her mate, especially since she’s bigger than he is. In species where the females are significantly larger than the males, there’s a higher incidence of cannibalism after mating. Among New Zealand mantids, cannibalism at mating is rare—females are only slightly larger than males, and so the males have a good chance of fighting off the females. I’ve seen this in action in captivity—one of my females had a go at her mate, but he was every bit as feisty as she, and their tussle ended with both alive and unharmed.

My little babies won’t have to worry about mating cannibalism for a while yet, but there are plenty of other dangers out there—other predators, parasites, pathogenic fungi, freezing weather, and careless gardeners all take their toll. Of the maybe 70 mantids that will hatch from my egg case, only one or two are likely to survive to adulthood.

I’ll give my babies the best start I can, and then they’ll be on their own. Watching them now, catching gnats like pros, I think they’re well-equipped.