Bruce Leslie worked on Cousin from January to March 2006 as a visiting warden from Kruger National Park in South Africa to Cousin as part of Nature Seychelles' Experience Exchange Programme (EXP) under the GEF/World Bank Project. Bruce reports on his experience on Cousin and Seychelles.
It is almost impossible to explain to someone who has never visited an oceanic island and experienced the wildlife which inhabit these amazing places what it is actually like. Most people will not actually appreciate how different continents and oceanic islands are in terms of the fauna and flora and how the natural selection processes such as predation or the lack of predation have played in shaping the endemic wildlife found on these geographically isolated areas, such as the Seychelles.
Fairy terns don't build nests, they just put their eggs on a branch© B. Leslie
Fairy tern chick about two weeks old © B. Leslie
Hawksbill turtle coming up Cousin beach to lay eggs © B. Leslie
Bruce tagging a hawksbill turtle © H. Tanskannen
To date my entire 19 year career in conservation has been spent in protected area management in Southern Africa, very far away from any oceanic island. I remember studying about island bio-geography during my collage days and been fascinated as to how dynamically natural selection processes influences isolated populations of any species and their development over time. One just has to be reminded of the Galapagos Islands and think of the numerous wonderful documentaries which have been produced over the years to appreciate how speciation is influenced by factors such as geographic isolation, climatic differences and vegetation and how these factors effect similar but yet geographically isolated populations of the same species over time. Darwin’s Finches are the perfect example of this. So when the opportunity arose for me to get involved in the Cousin Island Special Reserve visiting wardens exchange program I jumped at the opportunity. There was definitely no need to be pushed!
Coming from a protected area such as the Kruger National Park in Southern Africa where predation and avoiding been eaten is an important way of life, Island life is totally on the opposite end of the scale- everything is in your face! I don’t recall any thing ever running away to escape my presence. The most one can expect was a squawk from a White –tailed Tropicbird just to inform you not to stand on its nesting site by accident.
During my stay the White-tailed Tropicbirds, Fairy Terns, Audubon’s and Wedge-tailed Shearwaters where nesting by the thousands. While the Lesser Noddy, Brown Noddy and Bridled Tern numbers steadily increased. Just prior to my departure in mid March the Bridled Terns and a few Brown Noddy’s had started courting and nesting. Some of my most memorable times on Cousin where just sitting on the hill top or granite out crop over looking the sea trying to understand how the ecology functioned and fitted together. For example; what are the linkages between the marine and terrestrial ecosystems and how do they function together?
Very basically I now realize that an island to a seabird is just a big over sized platform which provides a stable and convenient environment on which to lay an egg and raise and fledge a chick. However to the other animals and plants stuck to the terrestrial environment or island the sea birds play an important role in nutrient cycling from the marine environment. This occurs in the form of gwano and other by products such as dead and decaying seabirds which die from natural causes or fish which is dropped to the ground while feeding a chick. This nutrient enriched environment in turn provides rich soils for a variety of plants and trees. This then provides structure within and upon which both terrestrial and seabirds can nest.
The geology of the island was exceptionally fascinating and obviously in a continual state of flux, driven on the short term by the north westerly and south westerly monsoon winds.While the rising and falling sea levels during the inter-glacial periods over the last several million years or so had a significant effect on the island geomorphology.
Today the importance of the monsoon winds is obvious in its effects on beach erosion and sediment transportation and deposition. Literally thousands of tons of beach sand is transported from one side of the island to the other and back each year. This has a short term effect on the day to day operations of the island staff as tourists visiting the island have to be beached by the island boat at the safest location where the beach profile is conducive to safe beaching of the boat. In turn hard corals cannot establish on the inshore lime stone reef which is continually been exposed and covered by the moving sands. However on a seasonal basis the exposure of the inshore lime stone reef provides a surface for alga beds to develop which are frequented by hundreds of Convict Surgeon fish, mullet and other fish. These fish feed on the algae during the high tides.
If you were part of the Hawksbill Turtle population utilizing the dune crest as a potential nesting site then you may also be faced with the probability that your nesting site may well be eroded by wave action and lost to the sea for good. But considering that a single hawksbill female may visit the island to nest two to three times in a single season. The natural beach erosion taking place together with egg predation by ghost crabs on the turtles eggs at nesting sites must play an important part in controlling the numbers of hatchlings going to sea. However Hawksbill Turtles are an endangered species and it is therefore important to reduce these negative impacts by relocation of potentially negatively effected nesting sites to safer areas.
By far the most important lesson to be learnt by these oceanic islands is the devastating effect that alien invasive fauna and flora have on our protected areas and environments within which we live. We know how bad alien invasive plants or animals can be to the endemic species within our respective countries, but nowhere has it ever been so blatantly obvious as to the devastating effects invasive aliens are having on indigenous or endemic species as observed in the Seychelles. Just one visit to a neighboring island during my stay at Cousin high lighted this point. Cousin Island Special Reserve can boast of 80 000 breeding pairs of Lesser Noddy, 1700 pairs of Brown Noddy, 4000 pairs of Fairy Terns, 600 Bridled Terns, 3000 pairs of White Tailed Tropic birds, 5000 pairs of Audubon’s Shearwaters and 14 000 pairs of Wedge-tailed Shearwater’s utilizing the island as a breeding ground over the year. This is simply due to the fact that there are no alien invasive mammalian predators such as cats and rats. However on an island such as Curieuse you will be lucky if you spot one of these birds nesting there let alone flying over. A very sad state of affairs just because of the presence of an alien rat!
My stay as a visiting warden on Cousin Island Special Reserve has been an amazing learning experience which I was fortunate enough to obtain. Many thanks to both Nature Seychelles, South African National Parks and the Honary Rangers of SANParks for affording me this extraordinary opportunity.