Ready for this? Harvesting honu again

Forget the bald eagle and

consider the Hawaiian
green sea turtle as a
conservation success.
The most prominent turtle
researcher in the Islands,
whose work has chronicled
the severely depleted
population since the days in the
1970s when it was uncommon to find turtles
in nearshore waters, now says the population may be
recovered sufficiently to consider hunting them again.
This will be heresy to a generation of Hawai'i residents
raised to revere the turtle, who have accepted it as a
personal symbol, who have tattooed its image on ankle and
breast.
But Hawaiian turtle meat was once served in Hawai'i
restaurants. Enough residents—this writer included—are
old enough to have seen turtles caught and slaughtered on
the beaches. And to know that green sea turtle fat is green
in color, ostensibly dyed by the limu they eat.
During the last century, they have been hauled out of the
waters around the main Hawaiian islands, they've been
hauled off their nesting beaches—where they had no chance
of escape—and their eggs have even been harvested, dug up
out of the sand.
Turtles have not been legally harvested in more than 30
years, but they're now common again. They're seen gliding
through nearshore waters, grazing on beds of weed, their
big dark shells humping up on the ocean's surface, their
beaked heads poking up for air.
And far more turtles than are in nearshore waters are
still young and in a phase of their lives in which they
live out on the open sea.
George Balazs has spent a career monitoring the recovery
and the various difficulties of the turtles, and he has
taken the massive step of writing a paper that considers
the once-unthinkable possibility of allowing harvesting of
turtles once more.
With Australia ecological monitoring expert Milani Chaloupka,
Balazs in the journal Ecological Modelling, has written
“Using Bayesian state-space modelling to assess the recovery
and harvest potential of the Hawaiian green sea turtle stock.”
They studied the results of commercial fishing take of
turtles from 1944 to 1973, when fishing was halted. And
they looked at how many turtles showed up to nest from 1973
to 2004 at the turtles' primary nesting ground,the sandbars
of French Frigate Shoals in the Northwestern Hawaiian Islands.
The 1944 start date is important, because it was in that
decade that turtle take converted from subsistence to
commercial.
Using statistical techniques, they worked out that the
turtle stock in 1974, when hunting was stopped, was about
20 percent of its level before hunting started. And after
30 years of protection, they figure it's now up to about
83 percent.
Although a successful one, it's a slow recovery, in part
because turtles are such long-lived and slow-to-mature
creatures.
“So, this once-seriously depleted green turtle stock is
well on the way to recovery and a limited harvest might
now be demographically feasible,” the authors write.
Balazs and Chaloupka do not suggest all-out hunting can
be resumed. They suggest public discussion of “sustainable
harvest potential” and a public debate on “the restoration
of indigenous hunting rights in the Archipelago.”
Most of the turtles found in the main Hawaiian Islands are
still too small for harvest. And there's an issue that was
not apparently a problem in the harvesting days: many suffer
from grotesque external and internal tumors called
fibropapilloma. The cause of this disease, which affects
turtles worldwide, is not yet known. Does it make sense to
harvest for human consumption a diseased stock?
The Balazs-Chaloupka paper doesn't discuss that. It just
says that from a pure numbers standpoint, with a low enough
harvest quota, the population could be sustained.
The ensuing conversations will undoubtedly be animated.

© 2007 Jan W. TenBruggencate

Lying in wait: "Sleeper" barnacles

The most vulnerable place in Hawai'i for the arrival of new invasive species may be our harbors and waterways.

While air passengers' luggage and carryons are inspected and crew check for brown tree snakes in cargo containers, the bottoms of ships arrive daily covered with wildlife.

“We really have no protection against hull fouling, and travel through the freshwater lake (Lake Gatun) in the middle of the Panama Canal isn't sufficient to kill most barnacles. They just close up and wait, and the wait isn't that long for getting through Panama,” wrote Michael Hadfield, Professor of Zoology at the University of Hawaii at Manoa.

And a some of those animals may be “sleeper species,” getting comfortable in the Hawaiian environment before they make the genetic shifts required to become real pests.

Hadfield and co-author John Zardus review the issue of marine alien invasions in a couple of recent papers:“Multiple origins and incursions of the Atlantic barnacle Chthamalus proteus in the Pacific,” in Molecular Ecology in 2005; and “A tale of three seas: consistency of natural history traits in a Caribean-Atlantic barnacle introduced to Hawaii,” in Biological Invasions in 2006, with additional co-authors Chela Zabin, Fabio Bettini Pitombo and Vanessa Fread.

Using mitochondrial DNA, they tested Chthamalus in Hawai'i and found evidence that Hawai'i specimens are related to Atlantic representatives from several different areas. It shows that there were multiple immigrants that are now interbreeding.

The researchers also tested representatives of the barnacle in other south Pacific and western Pacific harbors, and found similar results.

“We found compelling evidence that it has arrived multiple times in the Pacific from several areas in its native range,” they wrote.

One of the odd things they found is that a significant proportion come from the coast of Brazil well south of Panama. It suggests that a fair number of the imports came around Cape Horn rather than through the Panama Canal. That may be because Chthamalus isn't as tolerant of the fresh water bath in Lake Gatun, and that some of the potential barnacle immigrants from that route died.

Although it's an invader, thus far there haven't been significant impacts from it, the authors say. But Hadfield said it seems to have the potential of some other weedy species: They simply hold on for a while, over time make an adaptation to their new environment, and then become problem species.

“In the case of introduced animals, its clear that a lot of predatory species have quickly undergone prey and even habitat shifts in new locales. Witness the predatory snail, Euglandina rosea, that came from relatively low, moist habitats in the U.S. Southeast where it ate a variety of other snails from soil litter or low trees. In Hawaii, it not only eats a variety of new prey (including all of our native tree snails), but also has ascended the mountains and ravines to live in habitats the likes of which don't occur in North and South Carolina, Georgia and Florida,” he said.

“Some people call these invaders 'sleeper species,' meaning that their introduction appears to be benign, until they finally 'adapt' and take off to become a major problem,” Hadfield said.

© 2007 Jan W. TenBruggencate

What coqui eats: Does frog lunch bug you?

The coqui frog must be having a big impact on something it feeds on, because there seem to be a lot of them.

Beloved in Puerto Rico but driving people nuts in Hawai'i with its piercing nighttime calls, the coqui tree frog has invaded a number of habitats, and not a few back yards, in the Islands.

It has been vilified as a potential predator of native insects, although some folks suggest it might actually be a benefit, because it could reduce populations of invasive pest insects.

Which is it?

Maybe a problem for natives, but it doesn't seem to be much help with pest species, writes Utah State researcher Karen H. Beard in the May 2007 issue of Copeia, the quarterly journal of the American Society of Ichthyologists and Herpetologists. Beard studies the invasion of coqui frogs through their impacts on the environment, Her paper is entitled, “Diet of the invasive frog, Eleutherodactylus coqui, in Hawaii.”

To determine what impact the coqui might be having on insects, Beard went out to 11 sites on Maui and Hawai'i and collected hundreds of frogs, as well as collecting bugs and other creepy-crawlies from the same areas.

In comparing frog stomach contents with what she'd found in the environment, she concluded that the frogs are mostly feeding among the leaf litter.

They are also opportunistic, meaning their food sources change based on what's available.

But generally, they seem to do a pretty good job on ants, which aren't native to Hawai'i and which make up 30 percent of their food. Next most common are types of amphipods, relatives of shrimps and crabs, sometimes called landhoppers, which may or may not be native. The endangered Kaua'i cave amphipod, which lives in cracks and lava tube caves in the Koloa region of Kaua'i is in this group, so there are native animals in this group.

Beard's review found a higher proportion of the ants and amphipods in the frogs than in the environment, suggesting that the frogs key in on these species.

But they'll also eat mites, beetles, flies and other little critters

If anyone was hoping the frogs would be going after really annoying pests, like mosquitoes and termites, no such luck. Beard found no mosquitoes at all, and while termites were present, they represented less than one percent of the frogs' prey.

Beard concluded that endemic species—ones found in Hawai'i and nowhere else on the planet—may be at risk from the coqui, and that more research should be done in areas where endemic populations are high.

“It is these locations where E. coqui may have the greatest impact,” she wrote.

To learn more about the frogs, see www.hear.org/AlienSpeciesInHawaii/species/frogs/.

© 2007 Jan W. TenBruggencate

Nitrogen-fixing plants: Self-feeding as a bad thing

One of the important traits of some invasive plants is the ability to make their own fertilizer.

The firetree, Myrica faya, can do it. And as Peter Vitousek and Lawrence Walker, then both of Stanford University, reported in the journal Ecological Monographs back in 1989 (“Biological Invasion by Myrica Faya in Hawai'i: Plant Demoraphy, Nitrogen Fixation, Ecosystem Effects”), it quickly became a problem invader.

The firetree has the additional feature of producing a lot of fruit that birds like—so it has a built-in fast-spreading mechanism.

They found that the leaf litter of the firetree essentially fertilizes the ground.

“We concluded that biological invasion by Myrica faya alters ecosystem-level properties in this young volcanic area; at least in this case, the demography and physiology of one species controls characteristics of a whole ecosystem,” they wrote.

The problem, of course, is that one of the survival mechanisms of some native Hawaiian plants is the ability to survive in poor soils where other plant's can't. If aliens show up and begin scattering fertilizer in these habitats, they create further openings for a mass of other plants that otherwise couldn't compete with the natives.

The invasive two-spotted leafhopper, which attacks native and alien species alike but significantly damages firetree, may have reduced the plant's aggressiveness, although Vitousek in an email said that's more the case in dry areas than wet.

"Unfortunately, it looks green and vigorous across much of its range, despite the leafhopper, Vitousek wrote.

But there's another nitrogen-fixing invader following right on the fire tree's heels.

This time, it's the stately albizia, Falcataria moluccana, which has been fast-invading the back country on several islands in recent years. (It has also been known as Albizia falcata, Albizia falcataria, and Paraserianthes falcataria.)

“Invasion by N2-fixing tree alters function and structure in wet lowland forests of Hawai'i,” was printed in the October 2005 issue of “Ecological Applications,” R. Flint Hughes and Julie Denslow, of the U.S. Forest Service's Institute for Pacific Islands Forestry in Hilo, studied the trees in Kilauea lava flows 48 years old, 213 years old and 300 years old.

Like the firetree, the albizia fertilizes the ground around it. It spreads quickly due to seeds readily blown by the wind.

Among their findings was that native plants like 'ohi'a declined in the presence of the invaders, and other alien species, like strawberry guava increased in population.

“Results provide a clear example of how invasive tree species, by modifying the function and structure of the ecosystems that they invade, can facilitate invasion by additional nonnative species and eliminate dominant native species,” Hughes and Denslow wrote.

They added: “Invasive species pose major threats to the integrity and functioning of ecosystems. When such species alter ecosystem processes, they have the potential to change the environmental context in which other species survive and reproduce and may also facilitate the invasion of additional species.”

The nitrogen-fixing abilities of the albizia has been put to use in Hawai'i. Forester Bill Cowern on Kaua'i interplants albizia with valued hardwood species to reduce or eliminate the need to fertilize them. He has been experimenting with uses for the soft, fibrous wood of the species.

© 2007 Jan W. TenBruggencate

Feral feline status: Cat's ill, cats kill

Feral cats have been spreading in the wild in Hawai'i, and new research indicates that all's not well with the environment, nor with the cats themselves.

The felines, some of which are just a generation or two out of domesticity, and others dating their heritage back to early European sailing ships, not only eat imported birds, like meijiro, cardinals, shama thrush and others, but they also attack native birds, often in the most remote terrain.

Wildlife scientists Steven Hess, Daniel Goltz, Raymond Danner, Kevin Brinck, Paul Banko, Heidi Hansen and others, working from the U.S. Geological Survey's Pacific Island Ecosystems Research Center at Kilauea, conducted a series of capture and test experiments on feral cats on Mauna Kea.

They've also been looking into cat issues in other ways. One is cameras set at bird nests.

Cats are opportunist feeders. A chick in a nest? They'll kill it, even if sometimes they don't eat it, Banko said. He estimated 10 percent of Mauna Kea's endangered palila chicks are taken each year by cats.

They also attack the Hawaiian state bird, the nene, sometimes eating mother geese as they sit on nests on the ground.

They will creep into seabird burrows, and take adults and chicks, which have no way out once the cats are in the entrance to the burrow.

A lot of the cats carry disease. Many have the cat form of HIV, feline immunodeficiency virus. Some also have the cat form of leukemia, feline leukemia virus.

And, as in most populations of cats, there is toxoplasmosis, a protozoan disease that doesn't make otherwise healthy cats ill, but can infect other animals. The last wild individuals of the critically endangered Hawaiian crow were pulled out of the wild into captivity when it was found that some were dying and others were ill from toxoplasmosis.

Cats pass toxoplasmosis through their feces, which grazing animals can inadvertently take up while feeding, and creatures like rats and pigs can get by feeding directly on cat scat. The disease can be passed to humans through the incompletely cooked meat of infected animals, or by directly contacting and ingesting infected cat droppings—for example by wiping your mouth after gardening in soil where a cat's done its business.

In humans, it's generally only a problem for the fetuses of women pregnant when they are infected, and in people with compromised immune systems. Toxoplasmosis can be treated if it's detected.

© 2007 Jan W. TenBruggencate