Mahebdella miranda is giving us headaches. For two days we have slogged our way up the southern face of Morne Blanc in Morne Seychellois National Park. It has been screaming hot and the 300 metre ascent has us drenched in sweat by the time we reach the top.
Morne Seychellois Park is a "biosphere reserve zone" in that the defined area, which covers the bulk of northern Mahe, is given complete protection and the buffer zone around the park accommodates only certain kinds of commercial activities. Tea, lemon grass and mahogany plantations for example.
The steep trek begins at the top of the Indian Ocean Tea Factory's plantations and progresses through a zone of mixed endemic and introduced vegetation. In the lower regions, the ever-present eucalyptus trees Mark has grown to despise (he is allergic to them) dominate, with an odd mixture of wild-growing introduced Jackfruit and the vanilla orchid.
Quickly though, the forest becomes dense, dark and moist. By the time we are within 80 metres (vertical) of the summit it is completely indigenous with species unique to these islands and that have evolved in-place for millions of years. Birdsnest ferns, the stout 'koko maron', Curculigo seychellensis, and a variety of unusual palms like 'latannyen oban', Rosheria melanochaetes, and the eerie-looking Pandanus screw pines.
After scaring a local tenrec off the inclined path, we emerged into a lush summit zone with exposed granite boulders and crevasses overlain with lofty green shrouds of moss. A majestic buttressed 'kapesin', Northea hornei, rests untouched in the centre of that zone receiving substantial rain and cloud cover year-round, and it is from here that we have begun our work in earnest each day.
With the sun climbing quickly and the heat drying out the forest floor, even at these heights, we have had to move quite early (5.00 am) each day, well before daylight breaks. This leech is an odd one to be sure. It is the only member of the Haemadipsidae known to have eschewed the blood-feeding habits of its ancestors. The only abundant vertebrate up here is the frog Sooglossus gardineri which can be heard everywhere taunting us with its peeps. With a maximum size of 1 centimetre, it is smaller than the leech we are looking for, and thus not surprising that the leeches no longer rely on these for their nutrition. In fact, Mahebdella miranda, like some unrelated distant leech relatives, has managed to find a way to survive the changing environment in isolation by switching to a diet based on the abundant snail populations.
This intriguing observation made by a M. Benoit and reported by Lawrence Richardson a quarter century ago has us on our hands and knees in the leaf litter scrounging around for any and every gastropod we can find. Justin Gerlach, who with his father Ron established and run the Nature Protection Trust of the Seychelles, has confirmed this observation. Justin has published the most significant monograph of terrestrial molluscs in the Seychelles and it is on his advice that we have been struggling to the top of Morne Blanc each morning. So far we have had considerable success in finding the myriad molluscs, but none with a happy leech attached; nothing on the ubiquitous arboreal species that munch on the fresh leaves of 'bwa bannan', Gastonia crassa, none on the large round snails lurking in moist leaf litter, and none on the enormous and voracious snail introduced from Africa.
Perhaps it is too late in the year. The rains here are at their highest between December and February. Tomorrow we will try another locality in the Western region of the park.
By mid day we are exhausted from the climb as well as the grinding heat and humidity. We have yet to really take advantage of the spectacular beaches and snorkeling opportunities. Maybe towards the end of our time here after returning from Silhouette.
We have only tomorrow before heading to Silhouette for Idiobdella species. The camera is working better, now that we've fixed strands of copper wire across the batteries and thoroughly wrapped this $1,000 piece of equipment with about 50 cents worth of duct tape (that comes apart and needs replacing each day in the humidity). The laptop battery is holding a charge for only 20 minutes now that we've burned it down to 10% several times. That and Mark left on the headlights of our vehicle this morning necessitating a jump start from some friendly Seychellians. Obviously, our spirits are low. We need a break in our luck. It was so much easier when the leeches were interested in us!