My first recollection of Christmas Island was watching David Attenborough walk through masses of migrating red crabs at the beginning of the documentary series ‘Trials of Life’. It would be around 15 years later that I gained a broader understanding of the Island’s ecology while studying under the tuition of Pete Green at La Trobe University, and another 12 years before I took the opportunity to visit!
The main reason for my stay over seven days in the second half of July was to volunteer for the very fist Citizen Science Lizard Census. The captive recovery efforts and associated lizard census on Christmas Island focus on the Blue-tailed Skink Cryptoblepharus egeriae and Lister’s Gecko Lepidodacylus listeri, both now considered likely to be extinct in the wild. Further information on these two lizards and the work being undertaken to conserve them can be found here: http://www.nespthreatenedspecies.edu.au/news/new-territory-for-christmas-island-reptile-conservation
The opportunity for volunteer involvement in the captive recovery of critically endangered animals is often limited due to quarantine, security, training and supervision issues, so to be given the chance to participate in the program was a rare privilege.
I was fortunate to experience several parts of the program, including retrieving animals from their enclosures for checking over and counting, refurbishing the outdoor exclosures (open-air pens), and monitoring both lizard species and for introduced predators (giant centipedes and wolf snakes) at the soft release site. A highlight popular with many of the visiting Parks staff and volunteers is the bug sweep, holding nets out the car windows to collect insects (food for the lizards) as we drove up and down the sides of the runway at the airport!
The census took place at the Island’s Pink House, being Park’s main research centre and the site of the captive breeding facilities. It includes the appropriately named Lizard Lodge where both species are housed in enclosures. The Lister’s Geckos are also maintained outside in tents while the Blue-tailed Skinks are in the open-air exclosures, both protected within large aviaries.
The soft release site consists of approximately 0.25 hectares of regrowth forest surrounded by electric fencing to keep wolf snakes and centipedes out. Monitoring the released population of Blue-tailed Skinks involved walking 50 metre transects at regular intervals, counting every individual seen. As Lister’s Gecko is harder to detect, these were noted opportunistically while also spotlighting for centipedes and wolf snakes at night. Monitoring and evaluation of the soft release has been and is continuing to be undertaken by PhD student Jon-Paul Emery.
Not content with spending only one night searching for the Island’s nocturnal reptiles, a hint from a couple of the Park’s staff led me to a hot spot for viewing the Christmas Island Giant Gecko Cyrtodactylus sadleiri, where I was lucky enough to find two within an hour.
Although not quite as keen on exploring Christmas Island’s (nevertheless spectacular) marine life in the little spare time I had, my interest in freshwater ecology drew me to the Dales, one of the few parts of the Island supporting surface freshwater habitats. While there are no frogs on Christmas Island, I saw plenty of the red crab’s less well-known relative, the Christmas Island Blue Crab Tuerkayana celeste. This species is dependant on freshwater, but like the red crab, returns to the sea once a year to deposit its eggs.
Both red crabs and blue crabs were seen among the exposed roots of Tahitian Chestnuts Inocarpus fagifer growing around the shallow pool above the waterfall at Hughs Dale. Christmas Island (Glossy) Swiftlets also congregated around the pool, catching insects as they flew over the water.
While not often recommended, some forward planning and safety precautions enabled me to remain at the Dales for a couple of hours after dark. It was then that I heard a Christmas Island Hawk-owl (Boobook) calling, although had no luck seeing it. Freshwater prawns Macrobrachium lar were abundant in most of the dales, jumping about in the torchlight. This species has a marine larval stage, being widespread on tropical islands throughout the Indo-Pacific.
Before leaving Christmas Island, I also managed to get a brief glimpse of the Brown Gudgeon Eleotris fusca, considered to be the Island’s main freshwater native fish. Even so, it can also be found in brackish and estuarine waters, explaining its wide distribution from East Africa to French Polynesia. The Indonesian Short-finned Eel Anguilla bicolor also travels up the Dales and has been found in at least one of the Island’s partly freshwater (anchialine) caves.
The last stage of my trip involved a visit to the Cocos (Keeling) Islands where I had the opportunity to help monitor rat eradication works in preparation for the release of Blue-tailed Skinks on Pulu Blan. While the island is only about 2 hectares in size, the apparent success of the eradication there in such a short time not only demonstrates another impressive achievement, but the continuing passion and dedication of all those involved in the recovery program.
Thanks to the staff at Parks Australia, particularly Samantha Flakus, Hamish Noller, Kent Retallick, Brendan Tiernan and Will Copland for hosting me during most of my time on Christmas Island. Also to Trish Flores for generously guiding me around Cocos (Keeling) Islands.
David De Angelis.