For quite some time now I have been exploring remote ridges and gullies in the Waiʻanae Mountains to look for rare native plants and animals.

Much of the Waiʻanae Mountains lie in the rain shadow of the Koʻolau Mountains and makes the Waiʻanae Mountains significantly drier.  But since Mount Kaʻala — the highest point on Oʻahu — receives considerable rainfall, the Waiʻanae Mountains have a broader range of ecosystems and are more biologically diverse.

Like the rest of the island, most of the Waiʻanae Mountains have been over-run with invasive plants like strawberry guava, clidemia, and christmas berry.  But if you diligently search the remote parts of the mountains you can still find some small little pockets where rare native plants and animals still remain.

One of the rarest endemic trees is māhoe (Alectryon macrococcus).  Perhaps its most distinctive feature is its trunk which has many folds and furrows.  The tree bears bright red good eating fruits which were gathered by the Hawaiians for food. The leaves are pinnately compound with oval-shaped, asymmetrical, net-veined leaflets.


Māhoe was once widespread on the leeward sides of all the Hawaiian Islands but is now almost completely gone.  The tree is now on the federal list of endangered species.  Their main threats today are from the black twig borer which drill into their branches and kill the trees and rats which eat their fruits and prevent the next generation of plants from germinating.

Even rarer is mēhamehame (Flueggea neowawraea) — a giant in the native forest reaching heights of 100 feet with trunks 7 feet in diameter.  The wood is extremely hard and dense and were made into weapons by the Hawaiians.  When Joseph F. Rock first collected mēhamehame from Kapua on the Big Island in 1912 the trees were already extremely rare.  Since then, black twig borers have decimated their numbers.  The tree above is literally half-dead — the tree on the right side of the crack is dead.  A few branches on the top living side of the tree has leaves and a green shoots emanate from the bottom of the tree.   The tree is not doing well but is still alive.

The leaves are pinnately compound with leaflets alternating from the stem.   The tree has thin, papery, oval leaves, 1.5 to 5 inches long and 1 to 3 inches wide, which are green on the upper surface and pale green on the lower surface.  The tree has separate male and female plants.  On Oʻahu, only 28 mēhamehame trees remain.  The tree is on the list of endangered species.

One of the encouraging things about mēhamehame is that efforts are being made to collect seeds, germinate them in the greenhouse, and outplant them in the wild.  This mēhamehame sappling is over 6 feet tall.

One of the cool things about being in remote sections of the Waiʻanae mountains, is that you can see native insects like this koa butterfly or Hawaiian blue (Udara Blaackburni).   The cute little butterfly is about half-an-inch long with iridescent turquoise colored wings.

Another really cool thing to see are tiny little happyface spiders (Theridion grallator) whose body is smaller than a grain of rice — about three-quarters of an inch long with legs extended.  I always get a kick searching the foliage to find these cute little creatures.

Perhaps the rarest of the creatures is pupu kuahiwi or the sanguine litter snail (Laminella sanguinea).  The snail is about half-an-inch long and has a red colored shell with zig-zag markings. Visiting remote gullies of the Waiʻanae Mountains is always an adventure — you can never tell what you will find.


Flueggea neowawraea, Center for Plant Conservation

Alectryon macrococcus, Wikipedia,

Flueggea neowawraea, Mēhamehame, Wikipedia

Recovery Plan for Multi-Island Plants, US Fish and Wildlife, Dept of the Interior