A team of American cave explorers estimate there may be hundreds of caves yet to be explored on Mangaia in what one team member describes as ‘a ringed web of caves’ rich in geological and historical interest, including evidence of pre-historic exploration, writes Rod Dixon.

A group of nine American cavers has recently completed the second of a planned multi-season exploration of Mangaia’s cave systems.

Exploration was undertaken with research permission from the Prime Minister’s Office, the Aronga Mana of Mangaia and individual landowners.

The exploration project was supported by a small grant from the American National Speleological Society of the USA but was primarily self-funded.

According to team leaders Ben Hutchins and Emily Davis, 10 caves in three districts (Veitatei, Ivirua, and Tava’enga) were completely or partially surveyed during the team’s first 2023 visit to Mangaia. Cave lengths ranged from 17 metres to 2.5 kilometres (Tuatini cave, Veitatei), and a total of 6.1 kilometres of survey was accomplished.

While some cave passages were easy to walk through, the team also had to navigate low crawls, deep mud and water, and vertical pits and fissures, often with specialised equipment. 

A further 16 caves were explored in the second (2024) season, with an extra 8 kilometres of passage surveyed.

Caver Andrea Futrell in Ana Tautua, Tamarua (Photo – Shane Fryer, 2024)/ 24092009

Caves are now documented in each of the island’s six puna. Of these, Tautua, in Tamarua, is currently the longest, at nearly 4 kilometres. Tautua was described by one team member as “the most beautiful cave” she’d seen in over 40 years of caving around the world.

Altogether the team estimates there may be hundreds of caves yet to be explored in what one team member described as “a ringed web of caves”.

The team is producing detailed digital maps of all 25 caves surveyed to date: those surveyed in 2023 are already completed and have been provided to landowners, guides, the Aronga Mana, and the Cook Islands Research Council. The process of cave survey is painstaking, using Leica laser-range finders modified to record distance, compass direction, and inclination) with paper-sketches in three perspectives (plan, cross-section, and profile) that are ultimately scanned and used for drafting with computer software.

A stunning photographic inventory has also been created by team photographer Shane Fryer. These, together with maps of the caves, have been developed into large-format posters at the request of island authorities, appropriate for the local tourism office or tourism information kiosks. A set of maps was provided to the Mangaia School for use in the local curriculum.

An interesting discovery was evidence of the presence of early Mangaians in the far reaches of many of the cave passages, sometimes several kilometres in and beyond treacherous passages like vertical pits and canyons.

Caver Cyndie Walck in Ana Tuatini, Veitatei (Photo – Shane Fryer, 2023)/ 24092010

According to team rope specialist, Philip Rykwalder, “We found that most of the caves on Mangaia were originally explored with candlenut torches, and virgin passage (places where no human has previously visited) was rare.” “People were going very, very far into the passages, everywhere we went.”

Local guide Harris Ngai demonstrated to the team a traditional lighting method using candlenut kernels strung together on a coconut leaf midrib and burned down one by one. A single candlenut, according to Rykalder, produced the near equivalent of a carbide lamp’s light.

Early explorers of the cave systems appear to have used pieces of stalactites as directional markers, laying a course through the labyrinth of cave passages. More often than not, the bases of the broken off stalactite markers, still attached to the cave ceiling, show evidence of regrowth, sometimes many centimetres, a process that may have taken hundreds of years.

It’s speculated that such exploration may have had strategic value at a time when the caves were used as refuges from the island’s frequent wars. Knowledge of a cave’s multiple exits and entry points would have been significant in protecting a refugee group from attack. The group’s research permit did not include archaeological investigation, and all natural and cultural resources in the caves were consequently left untouched and in place.

Discussions with the Aronga Mana, community members and government employees indicated an interest in promoting cave tours as a form of eco-tourism.

In their first report, the cavers have made general and cave-specific considerations for tourism and the conservation of caves. Several caves (e.g., Tuatini, Te Rua Rere, Touroporu) have been historically used for tourism. These, along with additional caves (e.g., Ana o Ruanae) would be appropriate for wild cave tours if landowners wish. Other caves however are considered too delicate or too difficult for visitors.

Team leader Ben Hutchins stands beside a curtain of calcium carbonate, known as ‘draperies’ in the cave Te Ana te Rau, Karanga (Photo – Shane Fryer, 2024)/ 24092012

Team leader Ben Hutchins notes that “The caves of Mangaia are rich in cave pearls, columns, coralloids (popcorn), draperies, flowstone, helictites, moonmilk, phytokarst, rimstone, rootsicles, stalactites, and stalagmites.”

“In the stable cave environment, these … are protected from light, wind, rain, and most animals, and so, may remain preserved for thousands of years. But a careless footstep or poorly placed hand may permanently damage or destroy formations that are thousands of years old, crush rare cave-adapted organisms, or break priceless artifacts.”

Most caves visited had little recent vandalism and little pollution relative to caves in some other parts of the world. An exception was one cave found littered with a heavy accumulation of wooden, plastic and metal waste. According to the team’s report, cave conservation and sustainable cave tourism, can be enhanced where traditional stewards of caves ensure that tourists and guides employ what they call “‘soft’ caving techniques: a suite of best practices developed to minimise impact to caves, ensuring that they remain pristine and protected for future generations.

The sheer quantity of passages, abundance of impressive formations, and fascinating history and legends tied to specific caves on Mangaia makes the island, in the team’s estimation, a unique, and still largely to be explored, location.