Extinct Giant Ducks Return to Makauwahi

May 7, 2012

Extinct Giant Ducks Return to Makauwahi – Sort of!

The extinct Turtle-jawed Moa Nalo (Chelychelynechen quassus) was a giant flightless duck
that grazed the understory in the forests of Kaua`i before humans.

Contrary to what you read in older books about Hawai`i, these islands had large grazers and browsers before humans arrived. But instead of pigs, goats, sheep, cattle, and deer, the guys who mowed the lawns and trimmed the hedges before human arrival were, of all things, giant flightless ducks and geese. Studies of their coprolites (fossil dung) showed that they were eating surprisingly fibrous things, such as leaves and fern fronds (James and Burney, 1997). Alas, these big waterfowl have been gone for centuries, but the fossil record of Makauwahi Cave shows that they once prevailed on the landscape nearby, including the Turtle-jawed Moa-nalo (Chelychelynechen quassus), the Nene Nui (Branta aff. hylobadistes), and a smaller flightless duck, the Kaua`i Mole-duck (Talpanas lippa), in addition to the surviving flying waterfowl, the Nene, Laysan Duck, and Koloa Maoli.

Jurassic Park notwithstanding, and despite the excellent preservation of DNA in the sediments of Makauwahi Cave, we will probably never see these species alive. But on a National Geographic- sponsored research trip to Mauritius and Rodrigues last spring in the southwestern Indian Ocean (Burney, 2011), David and Lida Pigott Burney became thoroughly convinced that this missing keystone element of Hawaiian ecology might be partially replaceable, at least in fenced native plant restorations at Makauwahi, with a four-legged reptilian equivalent – giant tortoises. These creatures are entirely non-invasive, easy to handle, fun for kids to ride on, and most importantly, readily available for the purpose with a minimum of importation paperwork. One large species in particular, the African Spurred Tortoise (Geochelone sulcata) is relatively inexpensive, sometimes even available for the price of the shipping, as people buy them as tiny cute pets from shops nationwide, and 20 years later, are faced with the dilemma of what to do with a 100-pound animal likely to outlive its owner by decades, even a century or more.

Giant tortoises like this African Spurred Tortoise (Geochelone sulcata) may be the closest
living surrogates for the extinct moa-nalo. This 175-pounder we call “Chel” is one of three now eating
the weeds in native plant restorations at Makauwahi Cave. (photo by Lida Pigott Burney)

Long story short, the Makauwahi Cave Reserve now has three large tortoises, the biggest one weighing in at 175lb. They’ve taken up residence in a one-acre paddock in the midst of “Lida’s Field of Dreams,” where thousands of natives trees, shrubs, and herbs, some quite rare, have been planted by volunteers and school children on abandoned agricultural land. Remarkably, as on Indian Ocean islands, they greatly prefer to eat invasive mainland weeds to the native plants. The latter, according to the theory, have physical and chemical defenses against grazing birds and reptiles (but not mammals).

After half a year, this experiment is working so well, with the tortoises mowing down the weeds and ignoring the native trees and shrubs, that plans are to expand the fenced area and get more tortoises. If the funding can be found, the plan is to get larger species, such as true giants of the tortoise world, the Aldabra tortoises of the Indian Ocean, and smaller ones, such as African Leopard Tortoises, that have been shown to specialize in pulling up the small weed seedlings.

With the help of a renowned tortoise expert, Prof. James Juvik of UH-Hilo, who gave a talk to about this idea to 70 visitors and volunteers at the Cave Reserve on January 7, the Burneys hope to carry out large-scale controlled experiments to thoroughly evaluate the efficacy of tortoises in landscape management in Hawaii. Meanwhile, come out and enjoy our docile lumbering reptiles!

References:

Burney, D.A., 2011. Rodrigues Island: Hope thrives at the François Leguat Giant Tortoise and Cave Reserve. Madagascar Conservation
and Development 6(1):3-4.

James, H.F., and D.A. Burney, 1997. The diet and ecology of Hawaii’s extinct flightless waterfowl:
evidence from coprolites. Biological Journal of the Linnean Society 62:279-
297.