The Ecology of Ha`ahue Valley
Northwestern Ua Huka, Marquesas Islands
(0—1500 ft elev.)
K. R. Wood
P. O. Box 745, ‘Ele‘ele, Kaua‘i, HI 96705, firstname.lastname@example.org
[region explored by the author 19—21 Jun 2004]
MARQUESAS: Ua Huka,
(8°S/139°W), lies 312 kilometers from the Marquesas Fault Line hot spot, volcanic island of 3.24 million years, 82 sq kilometer area, maximum altitude of 884 meters.
Northwestern valley of Ha`ahue.
Between the period of June 19—21, 2004 the author, along with field partner S. Perlman, visited Ha`ahue (S 08°53.827’—W 139°35.894’), a remote mesophytic valley on the northwestern side of Ua Huka. We were dropped off and picked up by the captain of a small local fishing vessel the Tai Oa II.
Ha`ahue is bordered on the south by Vaipaia valley and to the north by Hanainamoa and Ha`ahevea, respectively. This northwestern region is called the Terre Deserte. Ha`ahue and its adjacent valleys rise in elevation from sea level and run east to around 2000 ft where they reach the dividing ridge that separates them from the large inland valley of Vaipae`e. Soils are of a fine texture and medium brown color. Leaf litter is abundant with small pebble-size to boulder-size basalt mixed with the substrate.
Between approximately 0—700 ft elev., Ha`ahue and its neighboring valleys are characterized by the occurrence of a great Pisonia grandis forest, many of which reach a girth of three meters and heights of up to 15 or 20 m. Interspersed within the great Pisonia trees are very large Ficus prolixa banyans that will spread even wider than the Pisonia with their stilt-like roots. Another emergent tree is the non-native Aleurites moluccana. Scattered below these giants there lies a thick Sapindus saponaria understory forest with several dry to mesic forest trees. The most common in their order of abundance include Hibiscus tiliaceus, Xylosma suaveolens subsp. pubigerum, Maytenus crenata, Cordia lutea, Cyclophyllum barbatum, Cordia subcordata, Glochidion marchionicum, Waltheria tomentosa, Guettarda speciosa, Thespesia populnea, and Celtis pacifica. Caesalpinia bonduc is a common native liana in this region. Native herbs include Peperomia blanda var. floribunda and Waltheria indica, with coastal sedges and grasses of Chrysopogon aciculatus, Leptochloa xerophila, Cyperus javanicus, and Cyperus cyperinus. In basalt coastal seeps and on a tidal shelf along the northern end of Ha`ahue bay the indigenous grass Paspalum distichum grows in the salt spray with the common non-native vine Ipomoea alba.
Above 800 ft elevation the forests of the drainage becomes dominated by Pandanus tectorius, yet the ridgelines bordering the drainage remain dominated by Sapindus saponaria, Xylosma suaveolens subsp. pubigerum, Dodonaea viscosa, and Maytenus crenata, with occasional trees of Wikstroemia coriacea and Psydrax odorata. The saprophytic vine Decaisnina forsteriana was relatively common along the ridges between 1200—1500 ft elev. where it was only observed on Xylosma. In addition, the native vine Stephania japonica var. timoriensis was scattered in this area. Native ferns in the upper valley include, Nephrolepis biserrata, Phymatosorus grossus, Asplenium nidus, and Tectaria jardinii. Above 1400 ft elev., patches of the indigenous fern Dicranopteris linearis and grass Miscanthus floridulus became more common. This zone appears to have been severely altered with few native trees remaining and patches of the non-native Psidium guajava. The degradation of this area may be the result of fire, horses, and goats.
Large sections of the valley slopes from sea-level to 1500 ft elev. are seriously impacted by the presence of goats. The author estimates he saw up to 400 goats in the region. In addition, pigs were observed in the lower and upper valleys, yet were limited to just a few. As a result of grazing goats several weeds have covered large sections of the valley especially Ocimum gratissimum, Elephantopus mollis, and Senna occidentalis. Other non-native shrubs in their order of abundance include Triumfetta rhomboidea, Jatropha gossypiifolia, Sida acuta, Asclepias physocarpa, Asclepias curassavica, and Achyranthes aspera var. aspera. Weedy non-native trees include Psidium guajava, Morinda citrifolia, and a few Coffea arabica. Weedy non-native herbs in their order of abundance include Ageratum conyzoides, Cyanthillium cinereum, Synedrella nodiflora, Acanthospermum hispidum, Desmodium triflorum, Chamaesyce hirta, Crotalaria retusa, Indigofera suffruticosa, Mimosa pudica var. unijuga, Abrus precatorius, Salvia coccinea and Portulaca oleracea. Weedy non-native vines include Ipomoea alba and Passiflora foetida. Weedy non-native sedges and grasses include Oplismenus compositus, Kyllinga nemoralis, Chloris barbata, Urochloa reptans, Eleusine indica, and Rhynchelytrum repens.
Cultivated trees, especially in the lower valley include Cocos nucifera, Cordyline fruticosa, Inocarpus fagifer, Mangifera indica, Tamarindus indica, Carica papaya, and Citrus aurantifolia.
Fresh-water Mollusca and Gobies. The main stream of Ha`ahue and adjacent valleys are characterized by large rough-textured basalt boulders strewn along the course and interspersed with smooth smaller stones and occasional flat, slippery water-running slides. Small 2—4 m tall cascades were common along the stream with little plunge-pools at their bases. Ha`ahue and Ha`ahevea had several confluences where smaller tributary streams meandered down from the valley sides and joined the main stream. Darting brown-black gobies of approximately 3—5 cm in length were common around the lower plunge-pools. Of particular interest were the abundance of 10—20 mm long cone-shaped fresh-water snails of a medium brown-green color and with slight longitudinal red-purple lines detailing some of their 5—7 whirls. These snails seemed to prefer the steeper smooth-basalt runs and were easily observed with their long, slender cone shape. In one particular passage up a 5 m tall cascade that had carved out pool-cavities worn from falling water, the author observed hundreds of these snails laying together on the bottom of a 25 cm deep bowl-like pool. On reaching in to examine them more closely, it was evident that they were all alive and carrying out some particular process of their life-cycle.
Sections of the streams above 900 ft were tight-walled on both sides with larger cascades of 7—15 m., which were difficult to traverse, yet with caution surmountable. These sections were dominated by Pandanus and interspersed with Hibiscus tiliaceus, Sapindus saponaria, and Cordia subcordata.
Pihiti, Ultramarine lorikeet, Vini ultramarina (Loriidae): At least three pair of the ultramarine lori were seen in the middle valley section of Ha`ahue around 300—700 ft elev.
Komako, Marquesas Reed-Warbler, Acrocephalus mendanae (Sylviinae): The Marquesan warbler was seen from the coast-line to the top of Ha`ahue Valley. They seemed to prefer the dense closed forest understory and were often seen hopping from branch to branch, tilting their heads and trying to catch assorted prey. The warblers were seen eating lizards, insects and fruit. The author estimates approximately 100 birds were observed.
Pati`oti`o, Iphis Monarch, Pomarea iphis (Monarchinae): At least 20 pair of the Iphis Monarch was seen during my exploration of the three coastal valleys of Ha`ahue, Hanainamoa and Ha`ahevea. Males were black with white mottling on the belly, females and immatures light brown above, white below. They were observed foraging in the dense Sapindus forests.
Kuku, White-capped Fruit-Dove, Ptilinopus dupetithouarsii (Columbidae): Several pair of the white-capped fruit-doves were observed around mid-valley 300—700 ft elev. These birds could be seen taking long flights across the valleys and often settling into the Ficus prolixa banyans.
Kopekapeka, Marquesas Swiftlet, Aerodramus ocistus (Apodidae): Several hundreds of the Marquesan swiftlets could be seen throughout the day gliding in circular patterns low over canopy and forest edge or close to the ground and above degraded slopes of Ocimum gratissimum and Elephantopus mollis. They were mostly seen in large groups of 30—50 individuals.
Brown noddy, Anous stolidus (Sterninae): The brown noddies seemed to spend their days out at sea. In the early evening thousands of ko`io (brown noddy) would fly into Ha`ahue and adjacent valleys. One evening as I returned in the early dark through the Pisonia forest of the lower valley I could hear and see the ko`io finding their nests in the tops of these great Pisonia.
Common Fairy-Tern, Gygis alba (Sterninae): Well over a thousand fairy-terns were observed along the coastal zone and circling the lower Pisonia forests. They seemed to be present during the day, but were in much greater numbers in the early evening.
Kaveka, Sooty Tern, Sterna fuscata (Sterninae): Hundreds of sooty terns could be seen flying above the water along the coast-line.
Brown Booby, Sula leucogaster (Sulidae): Several brown boobies were seen and heard perching in the upper branches of the Pisonia trees in the early evening.
Red-Footed Booby, Sula sula (Sulidae): A few red-footed boobies could be seen flying above the coastal Pisonia forest.
Lesser Frigatebird, Fregata ariel (Fregatidae): Several lesser frigates were observed circling the northern end of Ha`ahue and settling in the Pisonia trees of that region. One bird, which appeared to be a female (i.e., black with white breast and black throat), was observed in this area throughout our stay.