|Ecosystem||Hawksbill Turtle||Life Begins||Nene Goose|
|Petrel||Wild Pigs||Wild Rabbits|
A few million years ago: A spore from a fern somewhere in southeast Asia is released into the wind and carried by a rising current 8 miles high into the jet stream, where it is bourn eastward. Eventually, it drifts down and settles on a barren lava field in the middle of the Pacific Ocean. This is one of the ways life came to the Hawai'ian Islands.
Insects, seeds and spiders also reached the islands by riding on the air currents, but there were other ways. Migrating or storm driven birds carried seeds either in their digestive tracts or stuck to their feathers. Pacific Ocean currents transported salt-resistant seeds and rafted insects, plants, and snails on floating debris. Amphibians, reptiles, freshwater fish, and most mammals were unable to cross the vast expanse of ocean - only the monk seal and hoary bat succeeded. Of the millions of organisms that embarked on this chance voyage, very few made it here, and of those that did, few survived.
Over a span of about 70 million years, plants and animals colonized Hawai'i at the rate of roughly one every 70,000 years. These species changed gradually with time - they evolved into new forms that were better adapted to island life. In the absence of predators and competitors found in their former homelands, their survival no longer depended on elaborate defense mechanisms. Those qualities that once protected them proved unnecessary and were eventually lost. Contradictory terms describe these new life forms; nettleless nettles, mintless mints, stinkless stink bugs, and flightless birds.
Over 90 percent of Hawai'i's native flora and fauna is endemic - found nowhere else on earth. The island's 100 endemic land birds evolved from as few as 20 original ancestors; a thousand kinds of flowering plants evolved from 272 colonizers; over 1,000 mollusks evolved from at least 22 immigrants; and about 10,000 insects and spider species evolved from 350 to 400 precursors. The astounding diversity of life that flourished on these isolated, once barren islands bear witness to the force of evolution and the tenacity of life.
Hawai'i is not a place where large native animals abound. You may occasionally see humpback whales break the ocean surface, or a group of porpoises arcing gracefully in and out of the water. `Io (Hawai'ian hawks) and pueo (short-eared owls) sometimes hover overhead, and `ope`ape`a (Hawai'ian bats) flutter across bays and roadways at dusk. But the Island's most noticeable large native animal is the nene or Hawai'ian goose. Honored as the State Bird, the endangered nene symbolizes the precarious existence of Hawai`i's native birdlife.
At least nine species of geese evolved in the Islands, probably from ancestors much like the Canada goose. Eight of these species were flightless and probably grazed on the plants of the ancient Hawai'ian landscape. Extinction of these flightless geese resulted from hunting by Polynesians and land use changes in Hawai`i's lowlands.
This remaining goose is also a herbivore. Though it is a strong and frequent flyer, its short wings, long legs and reduced webbing between its toes indicate that it often walks and seldom swims.
Perhaps 25,000 nene existed in Hawai`i when Captain Cook arrived in 1778. By the mid 1940's only 50 birds remained. Populations were drastically reduced by introduced predators such as mongooses, cats and dogs; by foraging animals such as cattle, goats and pigs; by hunters; by introduced plants which compete with native food and cover plants; and by loss of lowland habitat.
In the 1970's, Hawai`i Volcanoes National Park began a captive nene breeding and reintroduction program. But, several factors hinder population increases. Mongooses and feral cats kill adults and goslings. Automobiles hit and kill nene along roadways. Nene that are attracted to the grassy fairways of golf courses suffer injury or death by errant golf balls. In upland habitats, nutrition is usually not adequate for gosling growth requirements.
Nene will probably always need help to survive. Currently, Park staff use a variety of techniques to improve nene breeding success controlling predators in nesting habitat, mowing pastures, closing sensitive brooding areas to the public, and maintaining predator-resistant enclosures in which free-flying birds can rest, feed, or nest. The park continues to search for improved and more efficient ways to encourage population growth.
Park biologists mark both wild and captive-reared Nene with leg bands to facilitate identification and tracking of individual birds. Usually, this is done when birds are young and cannot yet fly. From banding and subsequent monitoring, we have learned much about Nene family and flock life. If this population persists in the coming years, they will doubtless learn more about the behavior, biology, and ecology of this unique, terrestrial goose.
The Nene breeds during the wet season, generally October through April in the mid-elevation habitat it currently occupies. The exact timing of breeding appears dependent upon local food supplies (Banko 1988). Wild pairs in and adjacent to HVNP usually nest on sparsely vegetated lava flows or cinderfall areas where native vegetation predominates. The nest, typically concealed and sheltered by shrubs and small trees, is a saucer-like depression on the ground lined with down. One egg is laid every one to two days, and incubation lasts 30 days (Banko 1988). While the female incubates, the male usually positions himself on a nearby vantage point affording a view of the surrounding area. Several times daily, the female leaves the nest to feed nearby if food is available; or she and her mate may fly to pasture areas to feed (Banko 1988, Black et al. 1994).
Following hatching, the goslings remain in the nest with the female for approximately one day (Banko 1988). The family then leaves the nest site and walks to a traditional brooding location, in some cases several miles distant. Currently-utilized brooding grounds are characterized by the presence of alien pasture or lawn grasses, all currently managed to some extent. In most locations, the birds probably also use nearby native shrubs. Families remain on the brooding grounds until the goslings die or fledge. Although the observed patterns are somewhat erratic, adults generally undergo molt near the time their goslings are fully feathered or after their breeding attempt fails (Banko 1988, D. Hu pers. obs.). Adults become very secretive while flightless. Telemetry suggests that they move to nearby areas (HVNP unpubl. data) that afford better cover or have lower densities of introduced mammalian predators.
In the summer, Nene congregate in traditional flocking areas. For the Park's population, these include an adjacent golf course, an adjacent cattle ranch, and a cinderfall area whose main attraction appears to be mamaki, a native, berry-bearing shrub. Two of these locations are also brooding grounds. During this time, surviving families remain together, although the strict spatial segregation between pairs (maintained during the breeding season) relaxes. By late summer, distinct pairing reemerges. Numbers of geese move to some of the brooding grounds in late summer or early fall, once these generally dry summer grasslands begin to green up following rains (D. Hu pers. obs.), perhaps to allow pre-breeding adults to accumulate sufficient body reserves prior to nesting.
Early observers state that the species historically nested in the lowlands and then migrated to the uplands with their fledged young (Munro 1960). Although today we see little altitudinal movement of the type described, in recent years several pairs have nested outside the Park's four known, traditional nesting areas (HVNP unpubl. data, D. Hu, pers. obs.). In two instances where broods survived for at least several months post-hatch, the families foraged widely in an area surrounding the nest site (or the presumed nest site). Although alien grasses grow in both locations, in neither case was there access to actively or passively managed alien grasslands aside from a small area of roadside grasses that appeared to be used infrequently. Since none of the early observers recorded defined, traditional Nene brooding grounds of the type we see today within and adjacent to HVNP, these cases may be reminiscent of pre-western contact nesting habits. In most other locations in the state, wild (free-flying) nesting Nene currently use more heavily altered habitats for nesting and brooding.
Age at first breeding:
In the Park, most males begin breeding at age 2; females begin at age 3.
Nene are herbivorous, eating a wide variety of native and non-native plants. On many food plants, they eat the leaves. They also eat berries, especially during the breeding season. They are very adept and selective foragers, carefully plucking chosen grass blades or berries with their bills.
Called Honu 'Ea or 'Ea by the Hawai'ians, the hawksbill (Eretmochelys imbricata), is an endangered sea turtle that lives in the waters of the islands. They are known to nest on nine beaches on Hawai`i, on one beach on Maui and at an unknown number of locations on Moloka`i. Three of the beaches on Hawai`i are protected along the remote coast here in the park at Halape, Apua Point, and Keauhou.
Loss of nesting habitat, predation and poaching (their shells make attractive jewelry, illegally sold worldwide as tortoiseshell) have reduced turtle populations to critically low levels.
Late May signals the nesting season, which extends to December. A female waits until night to crawl ashore in search of a suitable site on the beach near vegetation. She uses her strong flippers to dig a flask-shaped cavity. After she deposits an average of 178 eggs she covers the nest with sand. Exhausted, she returns to the sea, leaving the eggs to incubate during the next two months.
Working as a team, the tiny hatchlings scrape the sand off the roof of the cavity and pack it on the floor. In doing so, they raise their nest toward the surface of the beach. When they are about an inch from the surface, they test the sand. If it is cool, an indication of darkness, they emerge from the nest as a group and scramble to the water. Any artificial light source may attract the hatchlings and cause them to head away from the water, get stranded and die.
A female hawksbill will nest three to six times per season, every 16 to 24 days. And she lays an average of 178 eggs each time. The eggs require about 60 days to hatch, and the hatchlings often must be helped to the water. After laying her eggs, the female is ready to return to her natural element, the ocean. After nesting several times during the season, the female is not likely to nest again for two or three years.
Protect endangered hawksbill turtles by observing the following regulations:
At one time such numbers of Hawai'ian Dark-rumped petrels, or `ua`u, returned at twilight to their island nests that the incoming birds were said to have "darkened the skies." Now, only a few thousand of these shy seabirds struggle to survive on the fringes of their former nesting range. Confined primarily to the frigid extremes of Hawai'i Volcanoes and Haleakala National Parks' subalpine, this endangered species requires a helping hand to prevent its critical nesting place from becoming a final resting place.
The `ua`u is a dark gray bird with a white face and underparts. Its narrow three-foot wingspan and short wedge-shaped tail enable high flight interspersed with downward glides, steeply banked arcs, darts and zigzags. Roaming vast expanses of the Pacific Ocean, the typically solitary petrel spends most of its nearly thirty years at sea where it alternately feeds on squid, fish, and crustaceans and slumbers on rolling waves.
Just as the sea is its food pantry, the islands are its mating ground and nursery. Every February, `ua`u are bound to return to Hawai`i to breed and raise their young. After dark, the petrels fly miles inland to nesting colonies where they excavate burrows, or enlarge existing lava tubes and earthcracks, in the parks' steep and rocky terrain. Adults pair for life and return each year to the same nest site to clean out or elongate their burrow, collect grass, twigs or other nearby nesting materials, and mate. In March, adults desert the colony and return to sea to bulk up before egg laying.
By late April or May, successful breeders lay one fertile white egg in their earthen hollow, and both parents share in its incubation. After hatching, whenever its parents return to the nest chamber, the chick incessantly cheeps and nibbles at the adult's bill to stimulate regurgitation of stomach oil and semidigested seafood. By the time the chick is ninety days old it is nearly double the weight of its parent. About two to three weeks before fledging, the chick ventures forth under cover of darkness to explore the outside world. During these forays, it stretches and rapidly beats its wings, and sometimes climbs up on a rock that might one night serve as its takeoff platform.
All fuzz and fat, the nestling is at this point quite defenseless and, to some both past and present, most delectable. Henshaw, in Birds of the Hawai'ian Islands (1902), wrote that "the nestlings of the `ua`u were considered a great delicacy and were tabooed for the exclusive use of the chiefs. Natives were dispatched each season to gather the young birds which they did by inserting into the burrows a long stick and twisting it into the down of the young which were then pulled easily to the surface." In Birds of Hawai'i (1944), Munro noted that "the natives used the old birds as well as the young for food, netting them as they flew to the mountains in the evening."
The ravaging of `ua`u nesting colonies initiated by the Polynesians accelerated after Europeans and others introduced dogs, black and Norway rats, Small Indian mongooses and house cats. The petrel's 60-day incubation period followed by a 120-day nestling period makes easy prey of both parents and chick. Additionally, the strong fishy odor of the bird and its food is a sure lure.
Wily predators drag eggs and chicks from burrows, ambush birds at tunnel entrances, and leave behind telltale signs of deadly deeds. Dogs mutilate carcasses, scattering feathers and limbs over a wide area. Rats leave eggshell pieces unevenly chewed, and eat and drink the contents. Mongooses chew a small hole in the side of the egg and lick up the insides. Cats crunch the back of the bird's skull and often leave both wings attached to a slightly chewed carcass stripped of most flesh, called a "bridle" carcass.
Because wild house cats are large, far-ranging night hunters, they pose perhaps the greatest threat to Hawai'i Volcanoes' remnant `ua`u population. In 1995, a cat trapped in a petrel nesting area had petrel feathers in its gut. In 1990, researchers found the carcasses of ten Dark-rumped petrels in a remote location at about 9,000' on Mauna Loa; another two carcasses were recovered this August. The condition of the remains fingered cats as the likely culprits. Although it is not known how long cats have roamed the subalpine, it is certain that continued predation will result in the petrel's extirpation.
The emerging picture is of a once incredibly numerous seabird species that nested on all of Hawai`i's main islands. Its population has now dwindled and contracted to a relatively small number of birds that find their primary refuge within protected national park lands. The future of `ua`u, (and that of all Hawai`i's native ground nesting birds) depends on control of alien predators around nest sites. Live trapping is the preferred control method; kill trapping risks injury to non-target species, including petrels. Pet owners are a part of the solution when they neuter all cats that are let outdoors and take unwanted house pets to Humane Society shelters, rather than abandon them in the wild.
Early Hawai'ians named the Dark-rumped petrel after its distinctive drawn out "ooo--aa--ooo" call heard on spring and summer evenings as the birds flew to their nests from the sea. At that time, `ua`u filled the air with haunting howls and uncanny wailings, "combining such a number of sounds as to make it both indescribable and unforgettable." The designation endangered resonates with an ominous tone, yet means there is still time . . .time to save a bird that once darkened Hawai'ian skies.
Trouble in Paradise
The Hawai'ian Archipelago was once celebrated as islands of evolution; now they are islands of extinction. The arrival of people changed forever the conditions that fostered the original diversity of life. Forests disappeared as people cleared the land to plant crops and establish communities. Polynesian and other settlers introduced numerous alien plants and animals, some of which thrived in their new homes and multiplied. Their impact has been catastrophic: pigs destroy the understory of tree fern and �ohi'a forests. Their muddy wallows provide breeding grounds for mosquitoes that transmit avian malaria and pox to native birds. Mongoose, cats and rats eat native birds and their eggs. Alien plants such as firetree and banana poka displace vast areas of Hawai'ian forests. The onslaught of introduced plants and animals caused the extinction of countless native species and continues to threaten Hawai'i's unique life forms.
During 1,500 years of human immigration and settlement, largely due to alien invasions and habitat destruction, 63 uniquely Hawai'ian bird species (owls, geese, rails, eagle, honeycreepers, etc.) have faced the finality of extinction. Nearly three quarters of the documented extinctions in the United States are Hawai'ian species; more than half of Hawa'ii's original bird species are gone.
Today, Hawai'i is home to 25% of all the endangered plants and birds in the United States. Six endangered bird species seek refuge in Hawai'i Volcanoes National Park, dependent directly on the remaining portions of native habitat now under siege by alien invaders.
Saving an Ecosystem
Hawai'i Volcanoes National Park is an island within an island. It is shelter for what remains of the once-rich tapestry of Hawai'ian life - a tapestry unravelled by an alien species. In some areas of the park, natural habitats are damaged beyond recovery. The park concentrates its energies on the most biologically diverse habitats and those that offer the best chance for successful restoration. The immediate strategy is to control or eliminate the most disruptive alien plant and animal pest. Park crews erect fences to keep out feral animals; track and kill feral pigs; and pull out or cut down firetree, banana poka, guava, and ginger. As native plant communities reestablish themselves, populations of Hawai'ian honeycreepers, nene, Kamehameha butterflies, and happyface spiders may flourish.
In recognition of its outstanding natural values, Hawai'i Volcanoes has been honored as an International Biosphere Reserve and a World Heritage Site. The park continues to mend the fabric and promote the lasting vitality of this remnant of pristine Hawai'i.
The first pigs (Sus scrofa) brought to the Hawai'ian Islands by Polynesians nearly 1,500 years ago, were small domesticated animals. European wild boars were introduced to the Islands in the late 18th century. They became feral (wild) and spread into grasslands, open-canopy woodlands, and closed-canopy forests. Wild pigs pose a serious threat to endemic (unique to Hawai'i) plants and animals, and may be the greatest current modifiers of Hawai'i's remnant native forests.
Pigs with selective appetites prefer certain native plants. Tree ferns, orchids, lilies, and other Hawai'ian endemics evolved in the absence of mammals (except for a bat and a seal), reptiles, and amphibians. Their defenselessness is obvious in the contradiction of terms used to describe the island's vulnerable life forms. . .nettleless nettle, mintless mint, briarless greenbriar, and stinkless stinkbug.
The pig, a secretive, highly adaptive opportunist, seeks and destroys native plant communities without regard for rare or endangered status. Rooting and rutting, digging and degrading, pigs eliminate endemics, and spread and fertilize aliens.
Another alien menace, the mosquito (Culex quinquefasciatus), breeds in water that collects in pig wallows, and eaten-out tree fern hollows. Mosquito bites infect birds with microorganisms causing avian malaria and bird pox. Hawai'i's native birds, with little or no natural immunity, suffer death and disfigurement.
"Here comes Peter Cottontail, hopping down the bunny trail . . . " may ring as a sweet refrain to some, but to rangers at Hawai'i Volcanoes National Park it sounds an intruder alert that cannot be ignored. According to Tim Tunison, Chief of Resources Management, the recent sightings of rabbits running wild in the upland forest of Mauna Loa pose a "hare-raising" prospect. If rabbits became established in the park, and multiplied out-of-control, years of effort in trying to protect and promote the recovery of native plants and wildlife would be destroyed.
During the past several years, there have been singular sightings of rabbits at Halape, Chain of Craters Road, Thurston Lava Tube, Steam Vents, Kilauea Military Camp, Kipuka Puaulu, and the Hilo boundary. They have also been spotted on the loose in adjacent subdivisions "just a hop, skip, and a jump away."
These rabbits are believed to be intentionally released domestic European rabbits, the kind sold at pet stores. Most island residents are unaware of the destructive potential of these cuddly, doe-eyed creatures. And pet owners who tire of their animals may think the park a perfect dumping ground. Yet, nothing could be further from the truth.
To a rabbit, the Hawai'ian forest is a salad bar, all-you-can-eat. Because native plants evolved in isolation, free from the grazing pressures of chompers and stompers, there are rarely any nasty thorns, obnoxious odors, or unpleasant tastes to deter a rabbit's incessant nibbling. Bunnies find the young leaves, seedlings, and buds of trees, shrubs and ferns simply irresistible.
Those large front teeth that give Bugs Bunny his distinctive "Uh, what's up Doc?" grin grow continuously, and can quite effectively girdle and strip bark from trees. Six rabbits can eat as much as a single sheep. Their 20 foot long digestive systems are designed to allow consumption of huge quantities of low nutritive value food and are adapted to absorb all the available nutrients.
Rabbits have existed for more than three-and-a-half million years; their footprints have been found in fossilized rock in Africa. First domesticated about 4,000 years ago, their ability to multiply is legendary. A wild doe can have up to seven litters of six to eight young a year during the three most fertile years of her life; her pups are weaned at six to eight weeks. It is estimated that a single pair of rabbits and their progeny can potentially produce almost 13 million rabbits in that three year time period. In Hawai'i, feral cats and dogs, mongooses, barn owls, pueo (Hawai'ian owl) and `io (Hawai'ian hawk) are potential predators.
Lessons learned at Haleakala National Park on Maui reinforce the urgency of immediate and intensive control methods. In July 1990, rangers there spotted several rabbits running loose near the Hosmer Grove campground. Inspection of the area by biologists showed that rabbits were living and reproducing over an area of 60 acres in surrounding shrubland.
An all-out eradication program ensued. Nearly 100 of the elusive creatures were trapped, shot, and snared over the next six months, with the last rabbit caught in May 1991. Haleakala National Park research scientist Lloyd Loope estimated that without successful eradication efforts, bunny numbers would have swelled into the millions in just a few years time. (NOTE: An apologetic former pet owner anonymously confessed to having released six unwanted rabbits near Hosmer Grove in October 1989.)
The State of Hawai'i has long recognized the destructive capability of wild rabbit populations and early-on enacted legislation to stave off such ecological calamity. It is illegal to intentionally release rabbits, and state law allows for the killing of any unconfined rabbit. Rabbits kept outdoors are legally required to be housed in a hutch that's off the ground so that these master diggers don't tunnel their way to freedom with their sharp, ever-growing toenails.
A pet rabbit can live for many years, requires a clean, secure, and sheltered living space, and a daily supply of pellets, and fresh food and water. Rabbit owners who can no longer care for their animals are encouraged to turn them over to the Hawai'i Humane Society. The shelter maintains a "wish list" of folks waiting to adopt bunnies. A preferable alternative is to avoid the impulse to acquire a pet that one is not committed to caring for over the long-term, especially during springtime's ". . . hippity, hoppity. . ." Easter season.
Park rangers consider any rabbit sighting a serious, potentially disastrous, omen. If visitors see a rabbit in the park, they should note the time and exact location, and immediately call the division of resource management at (808) 985-6087. And "for Peter's sake," never abandon a rabbit in the wild.
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