Giant Land Tortoises are Super Weed-Eaters

For those who love weeding – watch out. You may soon be replaced by a giant tortoise! Giant land tortoises that eat weeds and avoid Kauai’s precious native plants sounds too good to be true, but it is a reality in the Mascarenes, a group of islands in the Indian Ocean east of Madagascar, and is proving to work on Kauai, too.

“I had to see this for myself,” said Dr. David Burney, Director of Conservation at National Tropical Botanical Garden, who has introduced two giant tortoises from the Sahara Desert to the native and Polynesian plant nursery at Maha’u’lepu.  “The tortoises don’t touch the native plants. They pull the weeds, apply the fertilizer, and germinate the seeds.”

Burney who has conducted research in Madagascar for more than three decades, learned of reintroducing turtles to island habitats from Owen Griffiths, the biologist and owner of both the La Vanille Crocodile Park and Tortoise Reserve on Mauritius, and the François Leguat Giant Tortoise and Cave Reserve on Rodrigues Island, two places where giant tortoises are clearing weeds so that native species can thrive. Burney, along with his wife Lida Pigott Burney, head of the Makauwahi Cave Reserve landscape restoration project, and Professor James Juvik, chairman of the Geography Department at the University of Hawaii at Hilo, decided the time was right for tortoise weeding in a small, fenced-in portion of the 17 acre reserve where they are growing thousands of native and Polynesian plants.

Juvik, a world authority on tortoises and advisor to the Burney’s, explained why these huge, lumbering reptiles, which have been around for 200 million years and out-lived the dinosaurs, were pretty successful at survival – until humans came around.

“Tortoises have been found in the fossil records of nearly every island and land mass in the world,” said Juvik. “They had a pretty good evolutionary tactic -- having their home on their back and a place to hide in when threatened. Then man came along, flipped them over and their shell became a cooking pot.”

Although the two African spurred tortoises (Geochelone sulcata),  who were brought to Kauai by Juvik, are not a species that once lived on Kauai, they serve a similar function to the Turtle-jawed Moa Nalo (Chelychelynechen quassus) – an extinct flightless duck found in the ancient layers of the Makauwahi Cave that browsed in ways similar to the land tortoises. 

“Kauai never had any land tortoises. So, our strategy is to use these tortoises as a surrogate for this ecosystem,” said Juvik. “The tortoises browse at the same height as the extinct Kauai duck, which probably ate the same plants.”

 Regarding the introduction of another non-native species to Kauai’s ecosystem, Juvik and the Burneys plan to keep these reptilian giants in secure fences – there is no intention to release them into the environment outside their native plant sites.

 "Unlike other detrimental alien species on Kauai -- rats, feral cats and feral goats,” Juvik explains, “the tortoises can be easily recalled if they prove to present some unanticipated negative impact."

 Funding is being sought to bring in additional tortoises of several different sizes and species. For more information or to visit the Makauwahi Cave Reserve emailmakauwahi@gmail.com or call (808) 482-1059.

Take the dirt road that leads past the Grand Hyatt Road,make a right at CJM Stables and park on the grass across from the "Hpwdy Partners" sign. Walk up the dirt road and go left toward the crest of the hill. You will find a marked path, the Makauwahi Cave and Sinkhole, and the foot bridge pictured above. The tortoises are located in the fenced in area of the field just mauka of the bridge. Happy Trails!