Nene Goose and Accumulated Environmental Impact

Abstract

Accumulated environmental impact on the Nene, or Hawaiian, Goose commenced with man's occupation of the Islands some 1,200 to 1,400 years ago. During that period, the Nene population fell from an estimated 25,000 birds to an estimated 30 birds by 1949. The losses were due to man's direct activities on the Islands and the impact of other animals and organisms introduced by man.

Restoration of the Nene to a portion of its former range began over 40 years ago and has been only marginally successful. Captive propagation of the Nene, both on and off the islands, played a major role in this restoration effort. The program has suffered from lack of resources, insufficient initial and follow-up field work, and lack of genetic diversity in the captive population.

This early and long running effort to restore the Nene has afforded us an opportunity to reflect on various aspects of the program and apply the lessons learned to more recent attempts involving other species. It is probably not too late to apply some of these lessons to the Nene itself, but efforts appear to be stalled, and we are in danger of losing this species once again. This article will discuss Nene biology, history, predators, restoration, and genetic management and emphasize the lessons learned.

Biology

The Nene (Branta or Nesochen sanduicensis) is one of 30 bird species classified as endangered in Hawaii. It is a member of the subfamily Anserinae which includes whistling ducks, swans and true geese. The origin of this small terrestrial goose has been debated for years, as has its classification. The Nene has been included in the genus Branta because of its apparent affinities with the Canada Goose. This possible ancestry is reinforced yearly by the presence of a few Canada Geese and Brant on the Islands in the winter. Others have argued for a southern hemisphere origin, linking it to the Orinoco Goose (Nesochen jubatus) or the Cereopsis Goose (Cereopsis novaehollandiae). This question should be resolved in the very near future, through rapidly developing DNA classification analysis.

The Nene is nonmigratory even to the extent that it seldom moves from one island to another. It is taller, has shorter wings, and a slightly longer, turned down bill than other geese of similar weight. Additional adaptations to its island habitat include occupying a smaller range than any other goose, standing upright and feeding on berries, herbs and shrubs. The bulk of its legs is 2 5 % greater than other geese, and the tendons of the toes are stronger. Its adaptation to climbing and running over rough ground include flexible, elongated toes, reduced webbing, large nails and protective pads on the soles of the feet.

Currently, Nenes live in kipukas, vegetated areas among the more recent lava flows between 5, 000 and 8,000 feet. It usually breeds at two years old and has the ability to copulate out of water. Unlike most other birds, it comes into breeding condition with decreasing day length, which means it breeds on Hawaii starting in October or November and on into February. Nests are usually found under pukeawe bushes. The species lays small clutches, two to three eggs, and the eggs are large in comparison to body size, both of which are typical of island birds. The incubation period is 30 days. The young have a long fledging period, 70 days. The productive life of a wild Nene is usually over by 12 years of age, and an old bird is 15 years. In captivity, the birds live and produce for a longer period. One bird is known to have lived for 42 years.

 History

The Hawaiian Islands began to appear one to ten million years ago with the big island of Hawaii among the youngest. In recent times, the Nene was found only on this island, but there is fossil evidence to suggest that it also occurred on Maui, Kauai and Molokai. The goose ranged from elevations of 8, 000 feet down to sea level.

The first Polynesians arrived on the Islands between 500 and 750 A.D., and the accumulated environmental impact we are dealing with today started at that time. This early impact came from the dogs and cats, and possibly pigs and rats, which they brought with them and from man's harvest for food. The lowland populations suffered the most from the encroachment of these settlers. The Nene was able to survive into the historic period on Hawaii and maybe Maui because these were the only islands in the chain with subalpine zones that provided suitable habitat for the Nene but not for Polynesians.

When the sailing ships began to arrived in the late 1600s and early 1700s, the natives gave the geese to the ships' crews, often in exchange for rats, which the Polynesians considered a delicacy. The islanders also domesticated the geese and used them as watch geese. By the early 1800s, the population estimates of 25,000 birds began to decline rapidly as the direct activities of man and indirect agents of man's activities had overwhelming impacts. Man's direct activities included...