Feeds:
Posts
Comments

Posts Tagged ‘Hawaii’

Since it’s going to be a cold day tomorrow, and since I’m already feeling a little nostalgic for Hawai`i, I dug through my pictures to find these images of moths! I have no idea what kind they are. They could be invasives for all I know. Aren’t they pretty though?

I wish I knew how to identify moths.

I wish I knew how to identify moths.

I could totally see this being a Hyposmocoma, but who knows?

I could totally see this being a Hyposmocoma, but who knows?

 

Advertisements

Read Full Post »

Hyposmocoma is not the only unusual group of moth caterpillars I failed to observe in Hawai`i. Oh no precious, they are not.

Everyone knows what an inchworm looks like. Inchworms are the caterpillars of a family of moths called, appropriately, geometer moths. They tend to be well-camouflaged, resembling twigs. They eat plants, like most caterpillars, and some are serious agricultural pests.

A handful of Hawaiian species of the genus Eupithecia decided to break with tradition and become carnivores. They take advantage of their camouflage to fool unsuspecting insects into stepping on them. Then they suddenly reach back, grab the interloper with their talon-shaped legs, and eat it.

What’s especially cool is that they are not visual hunters. One species, in fact, hunts in the dark. Instead, they respond to touch: sensitive hairs on their backs tell them when prey is within striking distance. An insect walking on the caterpillar’s head or the front two thirds of its body will be unharmed.

It has been suggested, but not tested, that carnivorous Eupithecia‘s prey capture technique evolved from the “strike response” seen in some herbivorous caterpillars. The behaviour is best studied in the tobacco hornworm (Manduca sexta), the larva of a large sphinx moth. When something brushes against it, it reaches back and sometimes rasps its mouthparts against its skin. This behaviour could serve to startle birds that attempt to eat a hornworm, or to remove parasitoid wasps that would lay their eggs on it (and whose larvae would then eat the caterpillar alive).

By this point you should be dying of curiosity. You want to see these caterpillars in action, don’t you? Well fortunately, the BBC has delivered this nightmarish footage. And io9’s got your animated gif needs covered. Wicked, eh?

I’m going to end this post on a somber note, though. Carnivory by Hawaiian Eupithecia was discovered in the 1970s. The discoverer, Steven Montgomery, described a later foray to the site where he first found a caterpillar chewing on a fly. His report struck a chord with me, calling to mind my own impressions of the Hawaiian rainforest—and this paper is from 1983.

I recently returned to the volcanic cone on the Big Island where I first learned that Hawaii’s caterpillars were insect killers. After 10 years, I was keen to see if the endangered lobelia-like plants still found sanctuary in the steep cinder cone, because a carelessly set fire had destroyed the only other clump of these stately wonders. As I climbed the steep slope, I was stung on the head by a yellowjacket, a recently arrived pest that apparently stole into the Islands with cargo from the mainland. Rounding the top, I searched in vain for the lobelias. With them, half of the native forest plants had disappeared, and signs of rooting by pigs were frequent. Suddenly, a large European boar charged from under the koa tree and fled. I found no caterpillars that day, and heard few native birds. For this place, a conservation opportunity has passed, but on behalf of other Hawaiian forests, it teaches us what is at stake.

These species are not listed as endangered, but their habitat is dwindling; like many endemic Hawaiian species, their days may be numbered.

References
Montgomery, Steven L. (1983). Carnivorous caterpillars: the behavior, biogeography and conservation of Eupithecia (Lepidoptera: Geometridae) in the Hawaiian Islands GeoJournal, 7 (6), 549-556 DOI: 10.1007/BF00218529
van Griethuijsen LI, Banks KM, & Trimmer BA (2013). Spatial accuracy of a rapid defense behavior in caterpillars. Journal of Experimental Biology, 216 (Pt 3), 379-387 PMID: 23325858

Read Full Post »

Let me begin by admitting that when I worked in Hawai`i, I didn’t pay much attention to the tiny moths that I sometimes scared out of the moss. So this is a post about what I missed.

Hawai`i, being remote and geologically active, is famous for its endemic, explosive evolutionary radiations: a single founding population, finding itself far from both its natural food sources and its natural predators, diversifies into a flock of functionally diverse new species in a relatively short time. The honeycreepers, descended from a finchlike bird, are well-known for this; the Hawaiian picture-wing Drosophila flies are another oft-cited example.

There may be more species in the endemic Hawaiian moth genus Hyposmocoma than in the Hawaiian section of Drosophila, and I personally think these moths are way cooler. Consider the many decidedly non-mothlike things these guys do:

  • The caterpillars make cases for themselves out of silk and bits of vegetation, pebbles, and other detritus. Silk-spinning is not unusual for a moth (viz. silkworms), but it’s usually reserved for building a coccoon to protect a pupa. Hyposmocoma caterpillars carry their silk homes on their backs much like a caddisfly larva. This fascinates me because caddisflies are the sister group to butterflies and moths. Is Hyposmocoma case-making an example of reversion to an ancestral state?
  • The cases come in a wide variety of shapes—researchers studying them classify them into such categories as purse-, bugle-, cone-, and burrito-shaped. (Some of them look like oyster shells to me.) You can see some examples of these cases and of the adult moths here. Both moths and cases are quite pretty, but I expect they would be highly cryptic in their natural habitats.
  • Four known species in the genus eat snails; they are the only lepidopterans to do so. I’ll let the researchers who discovered this behaviour describe it:

When [the caterpillars] encounter a resting snail of the native genus Tornatellides, they immediately begin to spin silk webbing attaching the snail shell to the leaf on which it rests, apparently to prevent the snail from sealing itself against the leaf or dropping to the ground once the larva attacks the soft tissue of the living snail. The larva then wedges its case next to or inside the snail shell and stretches much of its body out of its silk case, pursuing the retreating snail to the end of the shell from which there is no escape.

  • Several species have amphibious caterpillars—that is, they can develop successfully either completely submerged in water or on dry land. While many insects, including caddisflies, dragonflies, and stoneflies, have aquatic young that become terrestrial adults, their young are obligately aquatic—they can’t develop out of water. The amphibious Hyposmocoma species are thus unique among insects. This ability has evolved several times independently within the genus. When underwater, the larvae can anchor themselves to the substrate with silk, preventing them from being swept away by strong currents. Scientists suggest that this amphibious lifestyle may be an adaptation to frequent floods in the rainforests in which these species live. Additionally, the limited diversity of insects with aquatic young in Hawai`i compared to such habitats on the mainland may have opened up a niche for these moths to occupy.

So let this be a lesson to me and to all of us who are focused on charismatic macrofauna that we should pay attention to invertebrates once in a while. You never know what they’re up to.

References

 
Rubinoff D, & Haines WP (2005). Web-spinning caterpillar stalks snails. Science (New York, N.Y.), 309 (5734) PMID: 16040699

Rubinoff D, & Schmitz P (2010). Multiple aquatic invasions by an endemic, terrestrial Hawaiian moth radiation. Proceedings of the National Academy of Sciences of the United States of America, 107 (13), 5903-6 PMID: 20308549

Read Full Post »

I am indebted to my hiking buddy “A” for doing all the botanizing necessary for me to write this post. And for hiking with me!

Normally, at the end of a stint in the field, I try to get back home as fast as I possibly can, rushing through the 8 mile hike then, er, adhering strictly to the speed limit in our state vehicle as we drive down the road from Koke’e State Park. But there’s another way home from the field, a little-used trail that runs from our camp all the way back to civilization. My boss hinted that trying it once would be mandatory, so a few weeks ago, armed with a GPS route and instructions to “turn left after the redwood grove”, my hiking buddy/fellow field tech A and I trekked downhill about 18 miles (29 km) from our field site in the Alaka’i Wilderness Preserve to the coastal town of Waimea.

After a week of mostly sunny weather—unusual for a site only a few miles from Mt. Wai’ale’ale, allegedly the wettest place on earth—the heavens finally opened the night before our hike. I remember lying awake fretting that the trail would become a series of mudpits connected by slip-‘n’-slides, and that the streams might be uncrossable the next day. But in the morning, another tech reassured us (sort of) by insisting that we’d miss this weather about a third of the way into the hike, when we hit dry forest.

So off we went—early, as we’d been warned the hike could take up to twelve hours, and laden with litres of water that seemed redundant at the time. What at first appeared to be a lull in the rain soon became a genuine cessation—or was that because we were leaving the rainforest already? After only three miles the understory already appeared more open, and more and more nonnative plants were showing up. And we began to hear fewer and fewer native birds. In fact, it wasn’t long before we saw our first rooster—chickens run wild on Kaua’i—and soon after that, our first mynah. A suggested marking waypoints on our GPSs for these unfortunate firsts, but I found that too depressing.

We reached the redwood grove we’d been warned about—there are a few such groves scattered around the edges of the native rainforest on Kaua’i, and the towering trees with almost no undergrowth look stark and mystical—and had no problem finding the left turn, which led us down a series of switchbacks into more mixed forest.

The switchbacks led to a river valley, our first stream crossing. The stream was, as I had worried, swollen with rain and would clearly overtop our hiking boots, so we crossed barefoot, though our socks were soaked already from the muddy trail. We took a break across the stream by an old cabin, and the newly-shining sun combined with the dripping grass convinced me to take off my heavy rain gear, too.

The next section of trail was a mix of rain-damp grasses and brambles, alternately cutting and soothing my legs as I passed. Once, ahead of us, a deer crossed the path, then froze and stared at us. We stared back until it marched away. The mixed forest gave way to a monoculture of strawberry guava, a plant with tasty fruits that has become a major invasive pest in Hawaiian native forests. This stand was truly eerie: every trunk looked the same—of the same size and with smooth, brown bark lacking the moss that covers everything in the Alaka’i—and not a bird could be heard, native or otherwise.

Our first sign of civilization was a pile of horse dung—still pretty far into the forest. I was surprised a horse could actually be taken there; not only is the terrain steep but the path itself is extremely narrow. The next sign of civilization was, I kid you not, a pink mansion with a massive lawn in the middle of the jungle. Presumably, this was located outside of the state park and on private land. A and I debated about whether we could see a road along the ridge leading to this strange building; we ultimately decided that we couldn’t see any ingress to this place by road and that the owners probably helicoptered in.

Waimea Canyon from its east slope

We left the guava grove and hiked through a forest compose of increasingly stunted and dry-looking plants. Ghostly pale ohia snags stuck up above the lower vegetation and the trail change from slippery to hard-packed and dry, with gouges indicating that the upslope forest watered this drier habitat. On a barren knoll we stopped for lunch and our first clear view of Waimea Canyon with its distinctive red soil (exposed, so I’m told, by grazing goats, which have caused serious erosion problems). Around us grew spiky-leaved lobelias and greenswords and stunted ohia trees—the dominant tree of the wet forest also thrives, in a different growth form, on the drier side of the island.

Our lunch, and the rest of the hike, was constantly interrupted by helicopters. They carry tourists over the canyon and the Alaka’i plateau, where they can see spectacular waterfalls and forested ridges. I certainly would jump at the chance myself, if I had the money and didn’t want to hike, but a copter flew by us almost once a minute for most of the afternoon, a constant reminder that we were nowhere near as remote as we felt out there.

A greensword and some ohias, with Waimea Canyon in the background.

The trail continued downhill as the forest gave way to chapparal. There was no shade, but it was fortuitously overcast, making the hike warm but not unpleasant. On a sunny day it would’ve been miserable. Having been soaked through in the forest, I began to dry off, and soon reached an equilibrium where the sweat seeping into my clothes perfectly balanced the evaporating rainwater.

The trail was also obviously well-worn. Horse and donkey hoofprints—we now saw dry dung in abundance—had worn a path as deep as a foot into the clay. In some places, charred branches littered the ground, as if a small wildfire had been contained. We encountered water catchments and little shelters (filled, sadly, with more garbage than we could carry out), probably intended for state workers but mostly used by hunters. Good conservationists, we checked any standing water for mosquito larvae, but found none—mosquito season, apparently, isn’t til the fall.

While the red clay makes Waimea Canyon iconic, we found a few places where it came in an array of colours—reds, oranges, yellows, even purples and blues. Erosion by wind or rain had sculpted it into ridges and moguls. Where harder, black volcanic rocks were scattered, the clay had eroded out from under them, leaving them on little pedestal. But for the shrubs, it looked like Mars or the moon.

This was easily the most beautiful part of the hike, but also one of the hardest. It was exposed and hot, and began to turn uphill. We approached Pu’u Ki, a conical hill in the middle of the canyon—fortunately the trail would lead us around it. A pointed out wiliwili (Erythrina sandwicensis), a  Hawaiian endemic with orange bark and strange orange flowers. Unfortunately they weren’t flowering at this time of year.

The multicoloured clay soils above Waimea Canyon

After Pu’u Ki, we descended into another river valley. Black bluffs loomed above our heads, and—finally—some shady trees grew along the riparian corridor. The path wound through tall grasses, crossing and recrossing the stream via stepping stones. Soon, this river joined up with the Waimea River—my GPS calls it Waimea Ditch. We were now on the last few miles of the Waimea Canyon Trail—actually a dirt road at this point. A noticed that all the trees here were curved in the same direction, as if regular, massive flooding had sculpted them. Piles of logs and other debris did, indeed, seem to indicate that the river was sometimes higher—several metres higher—but it was hard to imagine it. Surely the houses along the lower reaches of the river would have been swept away?

We had to ford the Waimea River twice, at shallow gravelly points where 4WD vehicles can cross. At the first of these, there’s also a long, rickety Indiana Jones-style suspension bridge which I skipped across. Bizarrely, though, there was no proper path on the other side, just a rock face with some agave, so I skipped right back. Crossing on the “road”, I made a stupid mistake: stepped on a wet rock (never step on wet rocks; it’s lesson #1 in the Alaka’i), slipped, and fell on my back. This was such a stupid thing to do, and the cold water felt so good, that I just lay there and laughed until A helped me up.

Across the river, a dog appeared down the trail, then another, and another, and finally a man on horseback and a fourth dog. A genuine paniolo? The first human we’d seen since that morning cheerfully told us that we were only two miles from the end.

At the next river crossing, I gave up trying not to overtop my boots—my socks had been wet for the whole hike anyways—and instead welcomed the refreshing water rushing in. I think A managed to keep his feet dry at both crossings. And here we were at the end of the trail—or the beginning of the road, for here were houses and families swimming in the river, and soon the mango-lined, chicken-infested streets of Waimea. Conversation ceased; subdued by the shock of civilization—even the most laid-back town in the United States—we walked with suddenly-aching feet and staring eyes.

Read Full Post »

Here’s a new 30-minute video about the problems facing Hawai’i’s birds and the many efforts to protect them. In addition to forest birds, it also covers the sea- and shorebirds of the all the islands, and has some really nice footage. And while it’s a bit more optimistic about Hawaiian bird conservation than I am, it really doesn’t shy away from the political crap that obstructs many conservation efforts.

Read Full Post »

This is the final post in my series about the native forest birds of Kaua’i, Hawai’i. Previous entries introduced the ‘Akikiki, ‘Akeke’e, Kaua’i ‘Elepaio, ‘Anianiau, Kaua’i ‘Amakihi, ‘Apapane, ‘I’iwi, and Puaiohi.

Nine native forest birds on Kaua’i are extinct or likely so. Four of these species are known only from subfossils (remains that aren’t quite old enough to be fossils); it’s not clear whether they went extinct before or after Polynesians first arrived in Hawai’i. The other five, described below, disappeared in the twentieth century, and four of them have been lost in my own lifetime.

Kaua’i ‘Akialoa (Akialoa stejnegeri): Rare even when it was discovered by Europeans in the late 1700s, this yellow-green honeycreeper had a thin, downcurved beak almost as long as its body. It was last seen in 1965, two years before it was listed as an endangered species.

Kaua’i ‘O’o  or ‘O’o’a’a (Moho braccatus): This beautiful, black, yellow-legged honeyeater was last detected in the late eighties. Like several other of the birds listed in this post, Hurricane Iniki in 1991 may have been the killing blow that wiped out a population already devasted by mosquito-borned diseases, hunting, competition with introduced birds, and habitat loss.

Kama’o or Large Kaua’i Thrush (Myadestes myadestinus): The Puaiohi’s larger and more common cousin also disappeared around the time of Hurricane Iniki. Only a century before, it was the most common bird on the island.

‘O’u (Psittirostra psittacea): Not formally listed as extinct, but again no confirmed sightings in more than 20 years. This bird—confusingly not related to the ‘O’o—was found on most of the windward Hawaiian islands. It was green with a yellow head (in males) and a thick, hooked beak like a parrot’s.

Nukupu’u (Hemignathus lucidus): This spectacular yellow honeycreeper with a thin, downcurved beak a little shorter than that of the ‘Akialoa persisted on Kaua’i and Maui until the late nineties, although later sightings may have been misidentified ‘Amakihi.

Generally, a species is declared extinct when it hasn’t been detected for 50 years or more, and there have been a few false alarms in which Hawaiian bird species were provisionally declared extinct and then rediscovered. So perhaps there’s hope that a few individuals are out there, beyond the next ridge or up the next inaccesible sidestream. But even if there are, will that be enough? Or will inbreeding gradually weaken the gene pool, or climate change bring disease-bearing mosquitoes to these last outposts, or the next big hurricane simply blow them away?

Read Full Post »

Here’s the penultimate installment in my series on Kaua’i’s native forest birds. (Yep, there’s that few of them.) A table of contents will be included in the forthcoming final post when I’m back from the field in another week or so.

The Puaiohi or Small Kaua’i Thrush (Myadestes palmeri) is actually one of the larger of Kaua’i native forest birds. (In case you’re wondering, the Large Kaua’i Thrush is extinct.) It’s a secretive dweller of the narrow, steep-sided jungle streams that thread their way through the central mountains, where it feeds mainly on fruit, like the Hawaiian raspberry or akala.

‘Akala looks like a giant raspberry, and tastes a little bit less sweet.

Not a honeycreeper like most of the forest birds I’ve written about but a relative of the American Robin and European blackbird, the Puaiohi is rotund and comparatively long-tailed. Its dull grey plumage—scalloped with black in younger birds—makes it difficult to see, but its hoarse, croaking call rings out above the babble of flowing streams. Its song, in contrast, is sweet and melodious, as you’d expect from a thrush. It also nests in embankments over streams, rarely in trees as the honeycreepers do. This habitat requirement makes studying these birds challenging, as much of their habitat is extremely inaccessible to humans. This may be a blessing, though, because that also means it’s somewhat inaccessible to pigs—but it’s no obstacle to rats or mosquitoes, the largest threats to Hawaiian avifauna.

Puaiohi habitat – well, one of the easier-to-reach parts of it.

The Puaiohi was the first of Kaua’i’s endemic forest birds to be federally listed as endangered. A captive breeding and release program has supplemented the wild population for several years now. Here’s a short video depicting scientists monitoring recently released captive-bred birds (“at a camp we can’t show you for its protection”).

While Puaiohi do live rather close to the trails in Koke’e State Park, they’re difficult to see unless you walk along the stream itself. (Don’t do this. Stay on the trails.) If you keep your ears open, though, you might hear one—and it might even be one of the captive-raised birds learning to live in the wild.

Further Information:

Kaua’i Forest Bird Recovery Project

Audubon WatchList

Hawai’i Comprehensive Wildlife Conservation Strategy factsheet

ARKive

Fish & Wildlife Service

BirdLife International

Read Full Post »

Older Posts »