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Land Snails at Honouliuli Preserve
Posted: January 12, 2009
One of my favorite places to see native land snails is on Palehua-Palikea Ridge in Honouliuli Preserve on the Waianae Mountains of Oahu.
The Palehua-Palikea Trail is located above Makakilo and is by far the most accessible place to see native land snails. The Nature Conservancy of Hawaii offers guided hikes once a month on the 4-mile round trip hike.
Palehua means “lehua place” in Hawaiian and aptly describes the many varieties of lehua (Metrosideros polymorpha) that thrive at Honouliuli. Honouliuli means “dark, dark harbor” for the dark fertile ahupua’a (traditional land division) that extends south from the spine of the Wai’anae Mountains at Pu’u Hapapa to the shores of Kaihuopala’ai (West Loch of Pearl Harbor).
Since the snails are active mostly at night, the best time to see them is just before sunrise. In order to see active snails moving on the vegetation I start hiking an hour before first light. In the photo above, ohia lehua branches frame the waterways of Pu’uloa (Pearl Harbor) as the sun prepares to inch its way over the horizon.
Snails are moisture-loving creatures. As a result, the best time to see active snails is when the mountain tops are shrouded in clouds, moisture condenses on the vegetation, and the leaves are covered in dew. Since the very act of moving results in moisture loss — snails lose water in the slime trails they leave behind — they retract into their shells and stay put when no moisture is available, especially in times of drought.
Oahu tree snails are an endangered species that are heavily preyed upon by rats and carnivorous snails. Prior to the management of Honouliuli Preserve by The Nature Conservancy, rats devoured snails in great numbers. The photo above shows decades-old shells that were broken into and eaten by rats.
For the past decade or so, The Nature Conservancy has implemented measures to reduce the rat population in areas where snails are known to live.
Just before sunrise an adult native tree snail (Achatinella mustelina) with amazing markings on its shell just over three-quarters of an inch long crawls over pilo leaves covered in dew. All species of Achatinella snails are critically endangered.
This cute little juvenile Achatinella mustelina has an intricate pattern on its shell and is just under than three-eights of an inch long.
Once the sun rises over the horizon, Achatinella snails usually crawl to the underside of leaves, retreat into their shells, and sleep for the day. The photo above is an adult Achatinella concavospira snail just under three-quarters of an inch long with alternating bands of white and brown on its shell. The shape of the shell of this species of Achatinella is different — more bulbous at the bottom — from other Achatinella snails and resembles the shape of a turban.
While Achatinella snails get the most attention for their attractively colored and patterned shells, other snails live at Honouliuli Preserve too. This pair of Auricullela ambusta snails a quarter inch in length have shells that are more stretched out and have a pronounced flare on the lip of the shell. While Auricullela ambusta snails are not an endangered species, they are found only in a few places and are not commonly seen.
Brown tornatellinid snails are so tiny that you need a magnifying glass to see them clearly. The snail above is just over 1 millimeter in length. While tornatellinid snails are not endangered, they too are not commonly seen in Hawaii. Closely related species in the tornatellinid genus of snails are widely distributed across the Pacific and Indian Oceans from Mauritius in the west, the Galapagos to the east, the Bonin and Izu Islands of Japan to the north, and New Zealand to the south. As a result, tornatellinid snails are believed to have existed since Palaeozoic times to acquire its present distribution.
In addition to the native Hawaiian land snails pictured above, there are other snail species — namely Amstra and Laminella snails (which I have yet to see and photograph) — that live in the Honouliuli Preserve. Stay tuned for more snail explorations.
MAHALO
Many thanks to the Nature Conservancy of Hawaii for their efforts to protect the native plants and animals at Honouliuli Preserve and for permitting me to go there to photograph them.
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SOURCES
Big efforts to save a tiny animal by Stephanie Lum
Hike Schedule – Honouliuli Preserve, The Nature Conservancy of Hawaii
Honouliuli Preserve, The Nature Conservancy of Hawaii
Manual of Conchology, Second Series: Pulmonata, Vol XXIII, By Pilsbry, Henry Augustus, b. 1862; Cooke, Charles Montague, 1874-1948, The Conchology Department, University of Philadelphia, 1915-1916
Personal Communication with Daniel Chung, University of Hawaii and Bishop Museum
[...] all mollusk findings. I don’t know that I’ll get to see any, but Hawaii has very cool land snails, many of which are endemic. They also have invasive snails. I’ll tell you about what I see [...]