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The Nēnē evolved from the Canada Goose (Branta canadensis), which most likely migrated to the Hawaiian islands 500,000 years ago, shortly after the island of Hawaiʻi was formed. This ancestor is the progenitor of the Nēnē as is the prehistoric Giant Hawaiʻi Goose and Nēnē-nui (Branta hylobadistes). The Nēnē-nui was larger than the Nēnē, varied from flightless to flighted depending on the individual, and inhabited the island of Maui. Similar fossil geese found on Oʻahu and Kauaʻi may be of the same species. The Giant Hawaiʻi Goose was restricted to the island of Hawaiʻi and measured 1.2 m in length with a mass of 8.6 kg, making it more than four times larger than the Nēnē. It is believed that the herbivorous Giant Hawaiʻi Goose occupied the same ecological niche as the goose-like ducks known as moa-nalo, which were not present on the Big Island. Based on mitochondrial DNA found in fossils, all Hawaiian geese, living and dead, are closely related to the Giant Canada Goose (B. c. maxima) and Dusky Canada Goose (B. c. occidentalis).
Nēnē’s strong toes are padded and have reduced webbing, an adaptation that allows it to swiftly traverse rough terrain such as lava plains.
The Hawaiian name, Nēnē refers to the birds’ call.
It is believed that it once was common, with approximately 25,000 Hawaiian Geese living in Hawaiʻi when Captain James Cook arrived in 1778. However, hunting and introduced predators, such as Small Asian Mongooses, pigs, and cats, reduced the population to 30 birds by 1952.
Other threats include disease and parasites, inbreeding depression, loss of adaptive skills in captive-bred birds and dietary deficiencies. Feral cats carry a protozoan organism (Toxoplasma gondii) which causes toxoplasmosis, a disease that can be fatal in the species. Road-kills are an important threat on Hawai`i and probably on Maui. Indeed road-kills were found to be the most common cause of known adult mortality on Hawai`i from 1989 to 1999.
While breeding in captivity has been successful, recruitment in the wild is low in this species. Yearly average hatching success was only 55% (range 44-77%), probably because of introduced predators rather than inbreeding. A yearly average of only 30% (range 0-50%) of nestlings fledged, with most lost to starvation, dehydration and predation. Recruitment into the breeding population is low, with only 42% of tracked fledglings eventually attempting to breed. An average of 35% of the population breed each year, probably limited by food availability, which affects the females condition.
Currently, there are 1,241 Nēnēs thanks in a good part to San Diego Zoo Global's breeding program.
Rendered in DS4 without postwork. Credits: Plants (LB Botanicals), Sky (Flink's Sky Dome) Nēnē from Songbird ReMix Hawai'i (Ken Gilliland)
- May 5, 2012
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