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By Frances Caflisch, Conservation Technician II
Merlin Edmonds, Weed Control Coordinator
Jordan Guss, Weed Control Technician II
and Chiemi Nagle, Predator Control Coordinator
The steady hum of the engine intensifies as the Hughes 500 helicopter lifts over the ridge marking the edge of Upper Limahuli Valley. Through the clouds below we can see the complex topography and viridescent canopy of the hanging valley, bordered by precipitous 2,000-foot cliffs. A typical Monday morning commute for the conservation staff of Upper Limahuli Preserve offers breath-taking views of waterfalls, rivers, deep mysterious valleys, and towering peaks as we travel above the island’s interior to the verdant north shore of Kauaʻi.
Located at the eastern end of Kaua‘i’s Nāpali coast, the Upper Limahuli Preserve ranges from 1,600-3,330 feet above sea level in the wao akua1, encompassing 1,068 surface acres of relatively pristine native forest. Home to incredibly rare flora and fauna, Limahuli is one of the most biodiverse valleys in Hawai‘i. In 2009, a 3.5-mile long ungulate-proof fence was installed to protect habitat critical for the successful breeding of ‘ua‘u and ‘a‘o2, two critically endangered seabirds which are central to the valley’s biodiverse ecosystem. To enhance protection of the preserve, NTBG staff work on two main programs: Predator Control and Weed Control. The goal of the predator control team is to reduce harm from non-native predators such as cats, rats, pigs, and barn owls. The weed control team focuses on stemming the incursion of habitat-destroying plants such as Himalayan ginger, Australian tree fern, and Koster’s curse3.
Left: A transport helicopter on a small landing zone in the Upper Limahuli Preserve. Photo by Frances Caflisch. Right: A 3.5-mile-long ungulate-proof fence protects critical seabird breeding habitat in the Upper Limahuli Preserve. Photo by Jordan Guss.
Our pilot banks the helicopter suddenly to account for an unexpected gust of wind and sets the skids down onto the narrow landing zone, the powerful rotor blades sending leaves fluttering wildly. Mist sweeps over the slopes as white caps foam up in the distant sea. We unload our supplies for the week, carefully securing our gear as the helicopter lifts off.
It takes several trips to carry everything up the trail to the WeatherPort, our 16’ x 20’ home away from home for the next five days. The campsite, constructed in 2010, serves as a refuge from the wet environment, and has all the essentials for comfortable mountain living — solar panels and battery, water catchment, propane stove, and cozy bunk beds.
Weatherport in the Upper Limahuli Preserve. Photo by Jordan Guss.
Over the weekend, cellular trail cameras recorded two feral cats prowling along the fenceline. These motion-activated cameras transmit photos via email, allowing us to monitor traps daily and respond quickly when needed. Constant monitoring of trails and traps is especially crucial during the ‘ua‘u and ‘a‘o nesting season from March through December.
Upper Limahuli Preserve holds one of the world’s largest monitored ‘a‘o colonies, however ‘a‘o and ‘ua‘u populations have steadily declined due to habitat loss and predation by introduced species such as feral cats. Though domestic and feral cats are the same species, they differ in impact and behavior. Feral cats are unsocialized, cannot be handled, frequently diseased, and survive in the wild, hunting for food. Cats kill adult seabirds, chicks, and eggs, catastrophically reducing breeding success.
Huddled around our detailed LiDAR4 map of the preserve we systematically study where and when the cats were sighted to determine a plan. We decide that leghold traps are the best option for this situation. These spring-operated traps consist of rubber-padded jaws which, under tension, will rapidly close around the predator’s foot, gripping it firmly. When camouflaged and set directly in the trail, they are very effective for predators that have demonstrated trap-avoidance behavior.
We pack up the traps and gear and set out, splitting into two teams. As we depart, the air is cut by the sharp cry of a pueo5, freefalling from high above before soundlessly flapping to a glide a few meters overhead, examining us with its piercing golden eyes.
Left: Jordan Guss holds an ‘A‘o (Newell’s shearwater) chick. Photo by Merlin Edmonds. Right: Pueo (Hawaiian short-eared owls) photographed using a Reconyx trail camera.
We arrive at one of our most successful and often-used trap sites where the trail along the fence narrows between earthen walls. We drop our packs onto the soft earth with a heavy clanging thud. Using a hand pick, Frances excavates shallow holes in which to nestle the legholds and conceals them with dry leaves, making sure nothing will prevent the jaws from closing. Our goal is to make the area with the traps indistinguishable from the rest of the trail. Other bulky vegetation is added to block access points and funnel cats into the trap site.
Weary from the day’s efforts but buoyed by the optimism of freshly set legholds, we flag the site and record our data. In the distance we hear the distinctive fluttering wingbeats of a flock of ‘apapane6 as they alight upon ʻōhiʻa7 flowers to feed. We check that our trail cameras are obstruction-free and aimed at the trap site. As we pack our gear and head home, the setting sun’s golden glow softens the air and shadows grow long.
Reconvening at the WeatherPort, the teams discuss their leghold sites and place wagers on which traps will be successful. After a hearty communal dinner, we enjoy a few games of hanafuda8, followed by quiet activities like reading, knitting, and stargazing. The evening calm is marked by a veritable symphony of chirping crickets.
On Tuesday morning we perform our daily remote trap check. Seeing that all the traps are still open, we decide to focus on cliffside weed control, one of our most exciting, yet dangerous tasks. We set off down the steep trail carrying our overstuffed packs. Misty wisps of clouds drift across the tops of stately ʻōhiʻa; sparkling ‘ōlapa9 trees dance in the slight breeze, shaking off the morning dew. During a recent drone survey, we spotted a dense area of highly invasive Himalayan ginger on the steep cliffs below our campsite, an area packed with ‘ua‘u and ‘a‘o burrows.
“On rappel!” Jordan yells as he lowers himself slowly over the cliff’s edge, boot spikes scrabbling on the slippery basalt, while the rest of us busy ourselves doublechecking each others’ knots and anchors, and gathering our tools — herbicide, handsaw, machete, and an iPhone for data collection and photos. We carefully make our way down the vertical slope, picking out invasive plants to treat, guiding each other to targets by shouting directions. The rhythmic chop-chop-chop of machetes echoes along the cliffside. Beautiful native plants densely cascade around us: hāpu‘u, ho‘i‘o kula, and ʻamaʻu10. We are excited to see delicate shrubs in the Campanulaceae family like ʻōhā wai, hāhā, and ‘ōpelu11.
Staff rappelling on a sheer cliff face in the Upper Limahuli Preserve. Photo by Merlin Edmonds.
Upon reaching a patch of ginger, we cut the growing fronds, stack them to one side, clean the rhizomatous root-ball to expose the work area, then proceed to make hundreds of small slices in each root-mass, finishing by carefully spritzing herbicide on all the rhizomes. A data entry is made for each weed kill, and a protective “hale”12, using the large waxy ginger leaves, is built over the remains of the patch to prevent the rain from washing away our hard work.
Merlin Edmonds beside a patch of invasive Himalayan ginger. Photo by Chiemi Nagle.
In the early afternoon, Chiemi calls out to the group in excitement. While roping down a narrow deeply-shaded gulch, she discovered a new individual of Melicope quadrangularis, a critically endangered shrub in the Rutaceae. Known only from the Wahiawa mountains of southern Kauaʻi, this rare alani13 was discovered in Upper Limahuli Preserve in 2012. While tagging the alluring plant with a POPREF14 code, we find one solitary fruit low on the stem which we cover with a mesh bag in hopes of collecting for future propagation.
At the end of the day, muddy and exhausted but buzzing from the exciting rare plant discovery, we pack up our gear and hike back to camp. Recapping the day’s activities, we are reminded of the significance of removing invasive species in this fragile habitat. Over 25 seabird burrows were spotted throughout the day, some of them new discoveries.
Left: Pu‘e (Lobelia kauaensis) in bloom. Photo by Merlin Edmonds. Right: Kōlea (Myrsine linearifolia). Photo by Jordan Guss.
As the forecast Kona low-pressure system rolls in, the mountains become shrouded in clouds and a light rain begins, expected to last for the remainder of the trip. The crew continues with the tasks begun earlier in the week. Traps are monitored remotely and shockingly, a third cat shows up on camera. Other rodent traplines are checked and there are always more weeds to treat.
On our last morning, as the darkness gives way to the pre-dawn light, we listen to the donkey-like braying of the ‘a‘o and the ethereal cooing of the ‘ua‘u as the last birds head out to sea to hunt for the day. The final morning of a trip can be an apprehensive affair, as weather dictates if we can return home after another difficult work week or if we must stay until the conditions improve. Sunrise reveals that we are indeed socked in by dense clouds. After communicating with the pilot, we go on standby, ready to fly out at a moment’s notice. We continue our typical Friday morning routine of packing, cleaning and hauling gear down to the landing zone, albeit with a heightened sense of urgency.
The wao akua eventually grants us a well-timed break in the clouds, just long enough for two extraction flights. As the second flight lifts off and swoops down through the billowing clouds, we catch one last glimpse of the WeatherPort as it disappears in the mist. Following the stream low through the valley, as the helicopter swoops up and over the eastern ridge, Merlin has time to reflect on the importance of the work we do in Upper Limahuli Preserve. Outside our fence, previously pristine native habitat is being steadily inundated by invasive weeds and destroyed by non-native browsing mammals. As native ecosystems face habitat loss, introduced predators, and climate change, it is more important than ever to maintain these pu‘uhonua15, these refugia, as places where irreplaceable endemic species can continue to thrive for future generations.
Upper Limahuli Preserve on the North Shore of Kaua‘i encompasses over a thousand acres of native forest and is home to incredibly rare flora and fauna. Photo by Chiemi Nagle.
[1] Spiritual region inhabited by gods, a place with limited human interaction
[2] Hawaiian petrel, Pterodroma sandwichensis and Newell’s shearwater, Puffinus auricularis newelli
[3] Hedychium gardnerianum, Sphaeropteris cooperi, and Miconia crenata
[4] Light Detection and Ranging: remote sensing method of measuring variable distance to the Earth
[5] Hawaiian short-eared owl, Asio flammeus sandwichensis, endemic subspecies
[6] Hawaiian honeycreeper, Himatione sanguinea, endemic
[7] Metrosideros polymorpha, the most abundant tree in Hawai‘i
[8] Traditional Japanese nature-themed card game
[9] Cheirodendron platyphyllum, a native species in the ginseng family
[10] Cibotium glaucum and C. nealiae, Hoiokula sandwicensis, Sadleria cyatheoides and S. squarrosa
[11] Clermontia fauriei, Cyanea fissa, and Lobelia hypoleuca
[12] Hawaiian word for house or dwelling signifying a sheltered place
[13] Hawaiian name for many species in the genus Melicope
[14] Unique identifier for a specific population sample or site within an ecological or genetic database
[15] Hawaiian word for “place of refuge” or “sanctuary”
