Beach Hangout

We nipped out to the beach after dinner on Saturday. We had a nice walk on our lovely, lonely bit of coastline.

But the beach was busy with youth hanging out (up to no good, probably). Some were alone, and some were in groups, strutting their stuff.

But these youth weren’t your usual crowd of city kids, they were juvenile spotted shags, Strictocarbo punctatus punctatus, also known as spotted cormorants, parekareka, and kawau tikitiki.

Shags were once heavily persecuted as pests. Fisherman believed they destroyed the fisheries, snapping up all the commercial fish and decimating their numbers. Research has shown, however, that their impact on fisheries is minimal. On the other hand, there is some evidence that, in our area at least, shag populations are hurt by commercial fishing. Spotted shag populations on the Banks Peninsula rose from 9,787 pairs in 1960 to 22,123 pairs in 1996 following a reduction in commercial fishing around the peninsula. Illegal shooting can also cause local population declines.

The spotted shag is a marine species, never venturing far from the sea and feeding in deep water up to 16 km from shore. They’re gregarious, breeding and roosting in colonies with up to 2000 birds. The groups of juveniles on our beach were small—a few dozen birds at most. These birds were probably born on cliffs around the Banks Paninsula, and when mature, they’ll head back to those cliffs to lay eggs and rear their young.

So they really were just hanging out on the beach, just like teenagers from Christchurch hang out on the beach on weekends, away from the adults, goofing off and getting takeaways.

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.

Sticky Feet! The Eucalyptus Tortoise Beetle

Hanging up the laundry this morning, I found this lovely beetle making its way along the washing line. It’s a eucalyptus tortoise beetle (Paropsis charybdis). I see them occasionally, but with only one eucalyptus tree in the yard, they’re not common.

I’m quite fond of tortoise beetles. This one isn’t much to look at, but many species are sparkling gold, and my first glimpse of them, as a kid, was a truly magical experience that I’ve never forgotten. What tortoise beetles have in common is their domed tortoise-like shape.

Their shape, combined with some pretty awesome feet is what keeps them safe.

Tortoise beetles have wide pads on their feet (this one obligingly sat on a clear surface and showed its feet under the microscope). The pads are covered densely in short hairs, like the bristles of a toothbrush. Each hair is moistened by oil, which helps it stick to the waxy surfaces of leaves in the same way two wet drinking glasses stick together if they’re nested. The oil bonds to both surfaces and acts as glue. When disturbed, the tortoise beetle presses its feet against the surface, employing as many as 60,000 sticky bristles (about 10 times more than other beetles have) to keep it attached. These sticky feet, combined with the dome-like shape make it difficult for predators to dislodge the beetle.

Entomologist Tom Eisner performed a series of elegant experiments with the palmetto tortoise beetle, attaching weights to the beetles to see how much force they could withstand before being pulled off a leaf. He found they could hold up to 240 times their body mass. Those are some seriously sticky feet!

So if their feet are so sticky, how do they walk? Eisner showed, by looking at palmetto beetle footprints on glass, that when they walk, they don’t let all the bristles on their feet touch the surface. Their full adhesive power is only deployed for defence.

I don’t think anyone has tested eucalyptus tortoise beetle grip strength, but it’s definitely impressive. I popped this one into a narrow jar, and it never hit the bottom—it reached out with one leg, like some movie superhero, and grabbed the smooth wall of the jar, arresting its fall. Then, when I tried to get it out of the jar, it stuck like glue to the side. I had to slide a stiff piece of paper under its feet, prying them up one by one. It was obliging for the photo shoot, but when I tried to let it go, it stuck itself to the paper. It took a few determined nudges, but eventually I got it to the edge of the paper and it dropped off.

The eucalyptus tortoise beetle is not native to New Zealand, and is considered a pest in the forest industry here. Still, I have to admire the beetles’ sheer tenacity, and am willing to share my eucalyptus tree with them for the opportunity to see those sticky feet in action.

Fabulous Flatworms

Australian flatworm

One of the common animals in my yard and garden is the flatworm. Strictly speaking, “the” flatworm here in New Zealand is actually multiple species—possibly up to a hundred—but they have been poorly studied, so it’s unclear just how many species there are.

Flatworms are some of the most impressive predators in the garden, able to consume prey up to 55 times their own size. That’s the equivalent of your house cat taking down a female elk. They eat snails, slugs, and earthworms, digesting them externally before sucking them up with one or more mouths located midway along their bodies.

I love to find flatworms around the yard. They come in striking colours, and some have lovely brown stripes—the orange Australian flatworm (Australoplana sanguinea) is most common in my garden, followed by the relatively nondescript brown New Zealand flatworm (Arthurdendyus triangulatus). Like the slugs they eat, they prefer damp places, and they protect themselves with a layer of mucous. Flatworm mucus is stickier than slug mucous, and they use it to attach themselves to their prey during feeding.

New Zealand is full of non-native invasive organisms, but New Zealand flatworms are one of the few organisms that have turned the tables and become pests overseas. They are easily transported in potted plants, and have successfully invaded Ireland and Scotland. Though there was widespread panic at first about their potential to threaten the local ecology, they appear to have caused little damage to earthworm populations in the UK. Like most cold-blooded animals, their appetites are small. Far from being a devouring hoard, each flatworm can manage, on average, just one earthworm per week. And if they don’t manage to find an earthworm every week, it’s not a problem—they can go a year without eating.

Backyard Biodiversity

Craterium minutum

I know it’s been a good weekend when I arrive in my office Monday morning to find my microscope in the middle of the desk, and dirt and bits of plant material strewn about.

It means I’ve been outdoors, seeing cool stuff, identifying plants, insects, or other organisms.

Once you start looking at and identifying what lives around you, the variety is astounding. A glance at the citizen science website iNaturalist shows a pile-up of dozens of observations at our address—and those are only the species we’ve bothered to upload.  I’ve identified 58 species of weeds in the vegetable garden alone. We have half a dozen slime moulds, dozens of fungi and lichens, who knows how many insects and other invertebrates. Then, of course, there are the birds, rats, mice, stoats and other vertebrates. I’ve never bothered to make lists of anything beyond the weeds.

So here in the dark depths of winter, I’ve decided to start a comprehensive list of the biodiversity on our little acre and a half. It will take time. It will require my microscope and many Monday mornings brushing dirt off my desk. But wouldn’t it be cool to know exactly how many other species we share this patch with?

And though many of the species I’ll put on my list are ones I’ve noted many times before, I’m sure some will be new and surprising, like the beautiful slime mould, Craterium minutum my daughter found last week.

Because, the truth is, we needn’t travel far to find natural wonders. We merely need to look closely and have a sense of wonder.

Currant Clearwing

Mating currant clearwings. Photo: Plantsurfer, public domain

They’re the most beautiful pests in the garden. Currant clearwings are moths, but they would like you to think they’re wasps, with their clear, narrow wings and yellow stripes. The deception deters predators who don’t want to tangle with a dinner that stings.

Adults emerge in early summer. They lay their eggs on the growing tips of currants and gooseberries. The caterpillars hatch out and burrow into the stems, killing them.

We’ve had the occasional currant clearwing in the past. Mostly, I let them go, because there were few of them, and I do like the way they look.

But this year there are many, many more than usual. I’m squishing all that I see. They leave gold dust on my hands when I do.

Hopefully, my efforts will be effective, and we’ll go back to just a few currant clearwings next year, so I don’t have to kill so many of these beauties.

Pheasants: Honorary Natives

We’ve had a lot of pheasants around the house this spring. The common pheasant (Phasianus colchicus), also known as the ring-necked pheasant. Is a curious bird…or rather, our relationship to it is curious.

The common pheasant is native to Asia, but has a long history in Europe. It was probably introduced by the Romans, and the first printed mention of the bird in Britain was in 1059.

Who knows what ecological impacts the pheasant had in Britain? I doubt anyone paid attention at the time. By the time people began to worry about conservation, in the early 1800s, it was the pheasant they worried about, as its numbers declined with land-use changes and the introduction of firearms for hunting.

The pheasant was first introduced to North America in the 1770s, and has naturalised in many areas. As in Europe, it has become a popular game animal and is the focus of conservation efforts, in spite of its non-native status.

Many years ago, I applied for a job with a ‘conservation’ organisation in Minnesota. Though I was ultimately offered the job, I turned it down, because its sole focus was on the maintenance of pheasant populations for sport hunting. I struggled to view that as conservation in a place where pheasant habitat was incompatible with habitat for threatened native animals, and where maintaining a pheasant population required captive breeding, because winters are simply too harsh for it to survive, even with appropriate habitat.

Even in Hawaii and New Zealand, where introduced species are almost universally considered pests, the pheasant is fussed over and cared for as a native—bred in captivity and released to keep its numbers up for the benefit of sport hunting.

A search for information on the ecological impact of pheasants is curious. Many sources presuming to address the ecology of pheasants deal only with the threats to pheasants themselves, not pheasants’ impact on the native ecology around them. It is as if even researchers have turned a blind eye to the fact pheasants are non-native over most of their current range. In truth, their impact is undoubtably small compared with non-native predators like stoats, cats, and rats. They tend to prefer disturbed, agricultural habitats (though they have been recorded as competing with native prairie birds in North America) and feed primarily on cultivated foods, weeds, and insects.

Yes, they feed primarily on crops. They’re crop pests. They particularly like grains and small fruit crops, and can cause significant losses in grape vineyards and in small holdings.

So, why do we embrace the pheasant so unreservedly? Let’s face it, most of us don’t eat pheasant, so we get no benefit from the bird. But it seems its long historical association with people and the agricultural landscape have made it almost a domesticated species. And, as we put up with the chickens occasionally wreaking havoc in the garden, so we put up with the pheasants, too.