Last month, The Wildlife Society, a national association made up mostly of specialists in the area of wildlife research and management, held its annual convention at the Waikoloa resort, on the Big Island.
Over the four days of discussions and symposia connected with the meeting, some of the most respected names in Hawai`i biology took to the podium, providing a largely mainland audience with their perspectives on what it will take to conserve and restore Hawai`i’s unique fauna – birds, of course, but also monk seals and humpback whales, bats, snails, and other invertebrates.
During one of the two plenary sessions, William Aila, head of the Department of Land and Natural Resources, made a moving plea for the need to control game animals, taking note of Governor Abercrombie’s recent watershed initiative. “We have to control ungulates. Fencing and removal of ungulates, especially in watersheds, is a major part of our plan going forward,” Aila said. “We have made a conscious decision that in priority watersheds, we are going to double the amount of fencing and protection.”
Fencing, removal of introduced game species, and restoration of habitat for native wildlife was an undercurrent in nearly all of the talks by Hawai`i presenters. In a few cases, their reports on recent research broke new ground. For the most part, they simply tried to carry the message of Hawai`i’s dire straits to an audience generally unaware of its problems. And they did so often with an eloquence and strength not usually found in dry academic discussions.
We present highlights here:
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Lowland Bird Populations May Be Developing Malaria Tolerance
Avian malaria, one of the scourges of Hawaiian forest birds, is a major reason why they are found so rarely in lowland forests. For years, it was generally thought that birds could only survive above the so-called “mosquito line” – elevations above which mosquitoes, which carry the disease, do not thrive.
But a few years ago, in connection with a major survey of biological complexity in the islands, Carter Atkinson and colleagues with the U. S. Geological Survey, Pacific Island Ecosystems Research Center were finding more Hawai`i `amakihi (Hemignathus virens virens) at low elevations than at high sites. “We were amazed,” Atkinson told a crowded meeting room at the annual conference of The Wildlife Society, held last month at Waikoloa.
“We were capturing `amakihi at rates five times higher than the capture rates at high-elevation sites,” he said. “Also, they had extremely high prevalences of malaria,” reaching a rate of up to 90 percent at one site.
He compared that to the mid-1990s, when no `amakihi were detected at any of the 90 stations surveyed in the Puna district of the Big Island. A decade later, 75 `amakihi were found at 37 of the stations – “a significant increase in the numbers,” he noted. “Since then, we have evidence this population is expanding toward Hilo. There’s been some change in the birds’ ability to deal with malaria infections.”
But the good news does not end with `amakihi. Researchers are finding that another one of the more common forest birds, the `apapane (Himatone sanguinea), is present at lower elevations on O`ahu and Moloka`i, where it also shows a high prevalence of malarial infection. In the Big Island districts of Puna and South Kona, the prevalence of malaria among `apapane can run as high as 100 percent among low-elevation populations of the bird.
“On Kaua`i, the prevalence of malaria is as high as 40 percent” among `amakihi.
“`Elepaio [Chasiempis sandwichensis] may also be showing similar disease patterns,” Atkinson said, “with a high prevalence of infections.”
“It’s good news about the more common species,” he said, but for rarer species, “it’s more problematic.”
“A lot of what we’re seeing may depend on genetic diversity,” he added. “But do these fewer birds still have sufficient genetic diversity?”
To confirm the `amakihi’s tolerance to malaria, Atkinson and colleagues exposed uninfected birds from both high- and low-elevation sites to malaria. “There was a dramatic difference,” he said. “We lost two low-elevation birds, but over half of the high-elevation birds died.” Other differences emerged as well. The high-elevation birds exposed to malaria suffered more from depressed appetite than did those from low elevations, which consumed as much food as birds in the healthy control population. Also, he said, the physiological effects of disease were much less severe in the low-elevation group.
“The results support the idea that low-elevation birds have some physiological tolerance to malaria,” he said, related to an increased ability to survive the disease.
“Disease tolerance may have appeared in lower Puna,” he continued, “because of abundant low-elevation habitat and high selective pressure by the parasite. There were also large, connected source populations across an elevational gradient, plus there is very high genetic diversity in `amakihi.”
Geneticists, he said, found the low-elevation birds were genetically distinct from their high-elevation counterparts. “But,” he went on to say, “when compared to museum specimens collected 100 years ago – there’s only one way you can interpret this – those birds were always there in low numbers at these sites; they simply expanded from relic populations.” Or, as Atkinson and his colleague Dennis LaPointe, also with USGS, wrote in a 2009 article in The Journal of Avian Medicine and Surgery, “the recent resurgence of these birds originated from pockets of surviving individuals with some natural disease resistance, rather than recolonization of the lowlands by high-elevation birds.”
As to why the lower-elevation populations may have developed this resistance while those in the higher elevations did not, Atkinson and his colleagues put forward an explanation in their 2009 article: “With transmission occurring year-round at lower elevations, and low-elevation populations not being continually diluted by emigrating, highly susceptible juvenile birds from high elevations, it might be predicted that disease resistance would first appear here. This suggests that disease resistance may subsequently spread over the next few decades, with eventual recovery of mid-elevation populations of the more resistant species.”
And while that is good news for `amakihi, it may not be for those less common birds. “There is concern that threatened and endangered species may not have sufficient genetic variability to adapt to these diseases,” they write.
The question now for resource managers is whether it may be possible to undertake actions that will enhance the birds’ disease tolerance.
Above all else, Atkinson said, “we have to preserve existing diversity, then manage habitats to maximize demographic variables, especially at lower elevations.” In their article, Atkinson and LaPointe stress the importance of managing mid-level habitats to reduce mosquito breeding areas. “Feral pigs and other ungulates can create larval habitat … and their removal through fencing and control programs may significantly reduce mosquito habitat, particularly on Kilauea and Mauna Loa Volcanoes … where volcanic soils are porous and streams and natural bodies of water are rare.”
In addition, they write, “there will likely be an important place for vaccines and chemotherapy for management of avian pox and malaria during translocation or release of captive birds or management of small populations of critically endangered forest birds,” although such treatments are not now available.
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The ‘Worst Vector’ and Its Partner
Dennis LaPointe, an ecologist with the U.S. Geological Survey in Hawai`i, has been studying mosquitoes and avian malaria for years, and in his view, Culex quinquefasciatus,
the first mosquito to hit Hawai`i’s shores, is “the worst vector of [avian] malaria in the world.”
But if the mosquito were here without pigs, chances are good that the overall health of Hawai`i’s forest birds would be much improved. To cause the damage that avian malaria and avian pox have wrought, the mosquitos needed water.
“Water is key to the vector,” LaPointe said, “polluted, organic-rich water.” But on Mauna Loa, standing water is in short supply, what with the porous volcanic substrate and no streams or other bodies of water to speak of.
Enter the pig. Not the small Polynesian pig, which Hawaiians brought with them when they colonized the islands and which, according to accounts of early visitors, rarely weighed more than 50 or 60 pounds. No, it required the much larger European pig, introduced in 1785 by Captain Cook and in multiple subsequent visits by any number of ship captains. As Quentin Tomich writes in his Mammals in Hawai`i, “The old Polynesian type of Sus scrofa has been absorbed or replaced by stocks of European origin.” The result is that “the feral Hawaiian pig of today is typically like the Eurasian wild boar.”
“Pigs love the rainforest,” LaPointe noted in his presentation to The Wildlife Society. “They’re particularly fond of tree ferns, whose starchy core is a favorite food of pigs.” The pigs knock down the ferns and root out hollows to reach the core, in the process creating cavities. Rain collects in the cavities, where mosquito larvae can mature.
What LaPointe and his colleagues set out to determine, in the early 2000s, was whether, absent the pigs, mosquitoes would find sufficient larval habitat to allow the malarial cycle to continue. Hunters defending their sport claim pigs alone aren’t responsible for the standing water.
“So we looked at the disease across a broad landscape of windward [eastern] Mauna Loa,” he said. They set up study sites in wet, closed-canopy `ohi`a forests, where both pigs and tree ferns typically occur.
“We found a direct relationship between the relative abundance of pigs and the abundance of tree fern cavities,” he said. Where pigs are controlled, he continued, “there were no tree fern cavities… Tree fern cavities are not the result of natural decay or rodent feeding.”
In addition, his team began monitoring mosquito populations by trapping. “The highest capture rates,” he said, were found at Cooper Center, in Volcano Village. There, he said, “pig-created tree fern cavities are the dominant available larval mosquito habitat.”
Until the pigs are gone or, at least, their numbers are significantly reduced, Hawai`i forest birds will continue to be at risk for disease. According to LaPointe, “you have to depress current pig abundance by at least 80 percent” before the birds are released from the impact of disease.
There could be one other factor at work, however. LaPointe noted that in 2002, the mosquito Aedes japonicus arrived on Hawai`i island and is now in all the same areas as Culex. Ae. Japonicus “cannot vector avian malaria,” LaPointe said. “We don’t know if it’s driving the abundance of Culex down, but it would sure be nice to hope so.”
Everything has its downside, though. While an increase in Aedes japonicus might knock back Culex quinquefasciatus, Ae. Japonicus is itself a possible vector of avipoxvirus, Japanese encephalitis, and West Nile virus, which can cause disease in both humans and birds.
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`Elepaio Moving Up in the World
Eric VanderWerf has been studying the O`ahu `elepaio for years and has watched its numbers decline dramatically in recent years. Since 1970, he told members of The Wildlife Society, it has seen a 75 percent decline in its range, which is now highly fragmented. Its overall population has declined as well, and is now thought to number no more than around 1,500 birds.
One of the greatest threats to the `elepaio is the black rat, which can take the birds from their nests at all life stages: eggs, juveniles, and incubating females. For this reason, he said, rat control is a primary tool in protecting `elepaio populations from further decline. With control, the population growth rate is positive at 1.1 (with 1 equal to a stable population). Without it, the growth rate is below 1.
But, he continued, “only a fraction of the remaining populations are being managed” with efforts to control the rats.
One of the reasons why `elepaio are so vulnerable, VanderWerf explained, was the fact that their nests tend to be low to the ground.
“But nowadays, their nests seem to be higher,” he said. He compiled data on recent nest heights, “and sure enough,” he said, “the average nest height is rising.” From an average of eight meters in 1996 it has soared to about 12 meters in more recent years. “`Elepaio are choosing larger trees,” he said.
There were two possible mechanisms to explain the change, he said: individual birds are learning that a higher nest is better and are adjusting nest height accordingly; or nest height is evolving through natural selection.
VanderWerf tested the first hypothesis by looking at the nest height of individual birds and found nothing to suggest that the birds were actually learning that higher nests were better.
He then looked at the success rates of lower nests and found that those lower than three meters “always failed or were abandoned,” he said.
Over time, the proportion of lower nests (below three meters) was decreasing, while nest success increased.
The most likely conclusion, VanderWerf said, is that nest height among `elepaio is evolving through natural selection.
How high will it go?
Most nests below three meters, VanderWerf noted, are being eliminated – suggesting that this is about as high as rats go. “The average height probably will not get much higher than it is right now,” he said.
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Forests as Fodder
Sheila Conant’s sadness and indignation were palpable. In an overview of the dire situation that Hawai`i’s native plants and animals are facing, Conant, an expert in the subject of endangered birds, talked about her personal experience: “I’ve seen living members of seven bird species now extinct,” she noted. “And I’m not yet 100 years old!” The line drew a laugh from the audience, but there was not much other humor in her talk to The Wildlife Society.
The examples of adaptive radiation found in Hawai`i “are unsurpassed,” she said – and are found in all manner of creatures and plants. “The silversword alliance – there are more than 30 different species. Spectacular plants,” she told the crowd.
“Hawaiian tree snails – just 14 of 40 Achatinella survive. They’re going down rapidly because of introduced predators and other reasons.”
She then gave the example of Hawai`i’s hyposmocoma moths: “They’re not as spectacular as our Drosophila [picture-wing flies], but there are over 350 species known, with more being found all the time.” They are also one of the few moths that are “scuba divers,” going underwater to pursue prey. “Only half a percent of all Lepidoptera have an aquatic stage,” she said.
After a recital of the flora and fauna that help make Hawai`i so special, Conant went on to discuss the reasons for their decline, citing habitat loss due to human activities, invasive predators as well as disease, ecosystem transformation by ungulates, and introduced plants that, while mild-mannered in their home range, quickly become invasive weeds in Hawai`i’s hospitable climate.
Of predators, she said, “feral cats are probably the worst thing we’ve got. They’re very difficult to control, and it’s politically a very sensitive issue. They’re doing a great deal of damage to petrels on this [Hawai`i] island and on Lana`i. I don’t even think about mongoose anymore because I see so many feral
cats. We need to address the issue in a suitable way.”
The brown tree snake, which has caused the extinction of many native birds on Guam, is another potential predator that keeps Conant up at night: “If we get this, it is just a matter of time before we lose all our small birds.”
Conant then addressed the subject of feral ungulates. “Our ecosystems are being transformed by feral ungulates and alien game species.”
“Hawai`i,” she continued, “is feeding its native forests to escaped barnyard animals” – pigs, sheep, and goats – “and axis deer… Protected by bag limits and hunting seasons, they are managed to provide recreational and limited subsistence hunting for less than one percent of the state’s population.”
Such practices “profoundly compromise Hawai`i’s watersheds – our only source of drinking water and irrigation for our crops, and the last remaining habitat for countless species of unique plants and animals.”
“We know what to do,” she concluded. “Let’s go out there and do it.”
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‘Funding Bias’ Hurts Hawai`i Birds
A frequently heard complaint from many members of Hawai`i’s conservation community is that the state, which has such a high percentage of endangered species in the United States, receives such a small share of federal funding for endangered species management and recovery. George Wallace, a vice president of the American Bird Conservancy, elaborated on some of the reasons for the vast abyss between needs and resources.
Hawai`i, Wallace pointed out, has 31 extant species of endangered birds – roughly 70 percent of all endangered bird species in the United States. Yet the average expenditure per species from 2002 to 2006 was 16 percent of what was spent on endangered bird species on the U.S. mainland. (If the enormously expensive captive propagation program for the `alala is not included, the per-species average expenditures drop down to 10 percent of the mainland per-species expenditures.)
“Why is there such a funding bias?” Wallace asked.
There’s the problem of Hawai`i’s remoteness from the mainland and the lack of awareness of the plight of its birds – both here in Hawai`i as well as elsewhere, he noted.
Wallace also cited the lack of “conflict species,” where high stakes bring public attention to the endangered animals – such as the spotted owl in the Pacific Northwest. These species, he said, get funding precisely because they generate conflict and much publicity. “It ties the Fish and Wildlife Service up in knots,” he said, “and draws a lot of funding and resources” to these species.
Another factor is the limited tax base in Hawai`i. Its relatively small population means that federal funding allocation formulas based on census counts put the state at a distinct disadvantage, Wallace noted.
Also there is the fact that Hawai`i shares borders with no other state, Wallace pointed out. Elsewhere, multiple states might cooperate to address common problems. In Hawai`i, that just doesn’t work.
“The pattern is, the highest-funded species tend to be charismatic conflict species, from large states and large ranges,” Wallace said. “Underfunded species tend to be island species, or from small states with small ranges.”
The upshot , he said, is “a few taxa receive most of the funding.”
Wallace then presented some estimates on what recovery of Hawaiian birds might cost over the next 10 years. Fencing, eradication of ungulates, and weed control needed for forest-bird recovery will require an initial expenditure of $578 million, with upkeep costs of $32 million a year. Add in waterbirds and seabirds, and the total investment costs rises to between almost $800 million and $1 billion.
“We need to set our sights on this,” he said. “There’s too much at stake not to. We have to keep reinforcing the message that we’ve already invested a tremendous amount and we need to protect those investments.”
While the amount may have prompted some in the audience to gasp, Wallace pointed out that the amount is reasonable, even modest, in light of expenditures for similar recovery efforts undertaken elsewhere. In Chesapeake Bay, for example, federal recovery funds alone came to more than $1 billion over the span of a decade, he said. In the Great Lakes region, $5 billion was spent over 10 years, while in the Florida Everglades, $3.9 billion was spent over 30 years.
“Hawai`i’s birds need a national priority restoration initiative, and we need it now,” he concluded.
Volume 22, Number 6 — December 2011