I went on another backpacking trip with the O’ahu Army Natural Resources Program — this time to the Central Wai’anae Mountains — to survey a population of endangered kahuli or Oahu Tree Snails (Achatinella mustelina) and to record the sounds tradition says they make.
According to Hawaiian tradition, kahuli “sing”, “chirp” or “whistle”. One of the places where they were renown for singing was Nu’uanu Valley. The summer home of Kamehameha III — located near the waterfalls of Luakaha and Lulumahu — is named Kaniakapupu — “the singing of the snails”. Also known as “pupukanioe” or “pupu kuahiwi”, kahuli are featured in a well-known name chant for Queen Kapi’olani about the flowers, winds and places of Nu’uanu.
Science on the other hand does not believe they sing. Biologists point out that snails have no lungs, vocal chords or other anatomy that would enable them to “sing”, “chirp”, or “whistle”. Furthermore, kahuli have been in captivity for decades and no one has ever hear them make any audible sound. The Kahuli Recording Team — lead by Robert Wai (shown in the photo below) — aims to reconcile the gulf between tradition and science. The team hypothesizes that the snails can make an audible sound under certain conditions and that this could be the underlying kernel of truth behind the tradition that the snails “sing”.
Kahuli were once so common that if you shook a tree it would rain snails. Sadly, this is no longer the case and kahuli are now an endangered species on the brink of extinction. Kahuli have been in decline for over a hundred fifty years and the snails are long gone from Nu’uanu Valley The only surviving populations reside in the remotest parts of O’ahu. In order to access the snails at night when they are active, we joined the O’ahu Army Natural Resources Program on an overnight survey to count their numbers.
Because the snails are mostly nocturnal, Vince Costello from the Army and the Kahuli Recording Team — Rex Williamson, Steve Young, and Robert Wai (from left to right) have an early dinner before we embark on our night time surveying and recording activities.
While having dinner, I was pleased to see a number of adult kahuli no more than three-quarters of an inch long on the underside of ‘ala’a leaves (Pouteria sanwichensis). There is considerable variation on the marking of this particular species of tree snail — Achatinella mustelina. This individual has attractive light brown plaid and white bands that spiral up the spire of the shell. Achatinella snails are endemic only to the island of O’ahu and can be found no where else in the world.
When darkness descended on the native forest, we headed out into the papala kepau (Pisonia), kopiko (Psychotria), ‘ie’ie (Freycinetia), and other native plants to count the snails. Kahuli are much easier to spot in the dark when their glossy shells reflect the light from your flashlight.
Over the course of the night we counted 386 Achatinella mustelina snails, an appreciable number, but less that the 421 counted during the last night survey in 2006. Their numbers are declining at this location. One of the factors hampering their comeback is their low reproductive rate. Unlike most other snails who lay scores if not hundred of eggs at a time, kahuli are unique in that they give live birth to a single offspring up to 4 times a year. Since they sexually mature at age 4 and have a lifespan of 10 years, they produce at most 28 offspring during their entire lifetime.
Other native snails were also in the immediate area. We saw many Auricullela ambusta snails which are considerably smaller than Achatinella mustelina. The white shells of adults grows no larger than a quarter inch long and the lip of their shells have a distinctive flare. I was pleased to photograph three of them on successive blades of ‘ie’ie leaves that whorled up the central stem.
During our search for snails we found a tree with 17 kahuli that had feeding tracks all over the bark of the tree. Achatinella snails graze on microscopic algae and fungi that live on the surface of the bark and leaves of trees. Notice how the tracks weave back and forth and how their radula — scraping tongue of the snail — often leaves a series of circular marks.
After waiting for the kahuli to awaken from their slumber, we videotaped the nocturnal animals as they crawled about to feed at night. Unfortunately, we were not able to detect any audible sound coming from the snails and there was no sound to record. Here are some short video clips put together showing the movement of the kahuli as they moved from side to side. Since observing snails in real time is like watching grass grow, the video footage above has been speeded up and condensed into a 38 second video-clip.
During our survey of the Achatinella snails we stumbled upon 26 Euglandina rosea snails. This carnivorous snail is a major predator of kahuli that was originally brought to Hawaii in the 1950s from Florida to control a population explosion of African snails. Unfortunately, these predatory snails prefer to hunt native snails and are creditted with the further decline of kahuli and extinction of other native snail species. Fortunately, the O’ahu Army Natural Resources Program is devising and implementing a number of strategies to reduce their predation on native snails.
One of the more poignant moments was when we found several Euglandina egg cases that would have hatched into voracious carnivors. Euglandina snails lay eggs multiples times a year and produce up to 600 offspring per year. With such a high reproductive rate compared to Achatinella, which produces only 4 offspring per year, it is little wonder that native snails are in serious trouble.
While we were disappointed that the kahuli did not make any audible sounds we could detect, we were pleased to see that appreciable numbers of kahuli can still be found at this location and that a number of strategies are being implemented to protect them from predation.
Many thanks to Vince Costello and Kapua Kawelo of the O’ahu Army Natural Resources Program for taking us to this site and for making these investigations possible.
“Aia i Nu‘uanu ko lei nani – He Lei no Kapi‘olani”, Nuuanu, Oahu – The Land: Winds, Pacific World
Euglandina rosea, Global Invasive Species Database
Native Hawaiian Plants, UH Department of Botany
Status and Trends of the Nation’s Biological Resources – Hawaii (Euglandina Reproductive Rate), National Wildlife Service