Biodiversity

Mar

2026

The Young Coconut Crab

Gerald McCormack, CINHT

Is it true that hermit-crabs develop into Coconut Crabs?

Juvenile and adult coconut crabs – Cook Islands – Gerald McCormack

The Coconut Crab (Birgus latro) is the world’s largest land-crab, often reaching 5kg. They take 7-12 years to reach sexual maturity, and can live more than 50 years. They are nocturnal omnivores, with a preference for coconut meat. Traditional names for large Coconut Crabs include: Unga, Unga Kaveu, Ūngākave‘u, Kaveu, Unga Koveu, and Unga Puku‘ara. Names for smaller ones include Toromimi and Unga ‘Onu.

Adult Coconut Crabs usually live within a few hundred metres of the shore, although they sometimes wander inland more than a kilometre. Years ago I met a large blue one on the summit of Mount ‘Ikurangi (485m elevation and about 2.5km from the shore).

Coconut Crabs are usually blue although some are dull orange-red. The colour is not related to age or sex.

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Mar

2026

Cook Islands Green Turtle, ‘Onu – a migratory turtle

Gerald McCormack, CINHT

Turtle tourism has become a popular year-round activity in Rarotonga, with both Government and civil society groups working to make it safer for turtles and people. The industry is built around “resident” Green and Hawksbill Turtles.

Green Turtle – Gerald McCormack

Recently, Te Ipukarea Society (CI News 22 Feb. 2025) reported 90 Green and 19 Hawksbills. They highlighted one Green Turtle seen in Avaavaroa Passage since 2021 as “a good example of a ‘residential turtle’ that is quite happy spending its days in Vaimaanga”. The following article will focus solely on Green Turtles, which have a distinct lifecycle compared to Hawksbill Turtles.

The presence of around 90 “residential” Green Turtles is a dramatic change from the 1980s and ’90s when such turtles were very rarely seen. What caused this dramatic change? Has there been a local population boom? Have these migratory turtles found a good home and stopped migrating? Can these “resident” turtles contribute to the survival of their endangered species?

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Mar

2026

The Kura on Ātiu – the 10th anniversary

Gerald McCormack, CINHT

Ten years ago, on 24^th April 2007, Air Rarotonga flew 27 Kura (Rimatara Lorikeets, Vini kuhlii) on a direct flight from Rimatara to Ātiu, where the bird had been absent for 200 years.

Map showing route the Rimatara Lorikeets took to get to Ātiu and eventually Mitiaro

This was the first transboundary reintroduction of a bird in the Pacific and was reported by more than 130 major news outlets around the world. TVNZ showcased the event with Greg Parker’s “Spirit of the Queen” documentary, which is on YouTube at www.youtube.com/kokamedia.

In pre-historic times the Kura were found throughout the Southern Cooks and eastward to Rimatara and Rurutu in French Polynesia. It had been lost on all islands, except Rimatara, by the over-harvesting of its red feathers for personal adornment.

The purpose of the reintroduction project was to establish a second population to maintain the Kura within its former natural range in case it were devastated on Rimatara by an invasion of Ship Rat(Rattus rattus). The Natural Heritage Trust and MANU, the Ornithological Society of French Polynesia, took six years to negotiate approvals with government agencies and the Rimatara community, which gave the birds into the care of Rongomatane Ariki and the Ātiu community.

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Mar

2026

The Bottle Gourd (Hue, ‘Ue) of ancient Polynesia

Gerald McCormack, CINHT

The ancient Polynesians brought many plants into Polynesia from Melanesia and Asia. Was this the source of the Bottle Gourd or did it come from the Americas?

In the Cook Islands there are 39 useful, or formerly useful, plants that were purposefully introduced by the Polynesian settlers before contact with Europeans. In addition there are 17 weedy plants that were probably accidentally introduced in those ancient times, although some are used in herbal medicines and might have been purposeful introductions. In total: about 56 Polynesian Introduced plants.

Among the Polynesian Introduced plants there are two that probably came from the Pacific coast of South America: the Sweet Potato (Kūmara, Kūara, Ipomoea batatas) and the Bottle Gourd (Hue, ‘Ue, Lagenaria siceraria).

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Mar

2026

Frigatebirds – Our Vulnerable Pirates

Great Frigatebird Courtship – Donna O’Daniel

Gerald McCormack, CINHT

Frigatebirds are the largest seabirds residing in the Cook Islands, with wingspans of 180-220cm. They are uniformly black above, and black or black with a white breast below; their wings are long, angled, and sharp tipped; their tails are long, and deeply split into two sections. They do not nest on Rarotonga, or on any inhabited Southern Group island, although they often soar over the coast of inhabited islands when there is a storm at sea. As a result they are sometimes called Storm Birds or Hurricane Birds. It is not clear why frigatebirds congregate at islands during storms, but it is probably because they find flying at sea more difficult and if they land on the water they usually die.

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Biodiversity

The Young Coconut Crab

Cook Islands Green Turtle, ‘Onu – a migratory turtle

The Kura on Ātiu – the 10th anniversary

The Bottle Gourd (Hue, ‘Ue) of ancient Polynesia

Frigatebirds – Our Vulnerable Pirates

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