A common sight on the ground in the woodlands of Denis, and indeed throughout the central Seychelles archipelago is the Seychelles skink (Mabuya sechellensis). This species is endemic to the central Seychelles.
On Denis this coppery-brown lizard gets up to approximately 22-23cm in length – including its tail. It has a distinct pale stripe running from above the eye down the top of each flank fading out at the tail. This stripe is emphasised by rows of darker patches running above and below it (see photos). This pale stripe and the pale belly in turn make the flanks appear as a brown stripe. The striping varies in prominence from island to island with adults in some populations reportedly not having stripes.
On some islands the skink can reach very high densities (e.g. Cousin) but this is not the case here. On Denis one generally first notices a skink by a rustle in the undergrowth as it seeks to avoid our great marauding feet! The best way to observe them I have found is by moving off the paths into areas of broadleaved woodland and just finding a comfortable perch. Once still, one rapidly becomes aware of the movement of the skinks across the forest floor and they often approach as curiosity brings them in search of food.
Gerlach (2007) states that the skink has been introduced to Denis and some credence is provided to this idea by the fact that no skinks were recorded on Denis’ nearest neighbour Bird in 1908 (Fryer 1910) but were subsequently found in 1939 – a timeframe highly suggestive of a human vector. For Denis though it is not so conclusive. Skinks were recorded in 1908 and it is definitely possible that they could have arrived on Denis during its 14,000 year history through natural means – i.e. “rafting” on floating vegetation.
Regardless the skink, as a species endemic to the central archipelago, is treated as native species and serves an important role in the ecosystem feeding omnivorously on insects, fruit, detritus and carrion. Skinks also provide a source of food for moorhens and interestingly the endangered magpie-robin which is highly adept at swooping down on an unsuspecting young lizard and despatching it clinically by 2 or 3 hard “thwacks” against a stone before consuming it.
The skinks lay 2 or more oblong, leathery white eggs and cover them with soil. We do anticipate that as sea bird colonies increase on the island that the detritus they bring – small fish, droppings, eggs and dead birds – will see a corresponding increase in the skink population.
Refs:
Fryer, J.C.F. (1910). Bird and Denis Islands, Seychelles. Trans. Linn. Soc. Land. (2)14: 15-20.
Gerlach, J. (2007). Terrestrial and Freshwater Vertebrates of the Seychelles Islands. Backhuys Publishers. The Netherlands.
Wednesday, September 2, 2009
Friday, August 28, 2009
Catching-up…
Leave and then the frantic writing of a project proposal to meet the donor deadline have kept me from posting for nearly a month and away from the island for longer, so just a few quick bullets to bring the blog up to date:
- Great news from Rachel, we have now our third successful fledging of a Seychelles paradise flycatcher on the island which is most encouraging. Breeding activity has now ceased as is usual for this time of year.
- Vicki and Georgia headed home at the end of July. Their work on the Sooty tern project was very fruitful with numerous landings recorded and very encouraging behaviour displayed. We believe that the birds that visited the island this year are young adults that have not previously bred reconnoitring potential breeding sites for the future. If so this is indeed a very encouraging development. I look forward to receiving the write-ups of their work and also hopefully they will contribute a post or two to the blog.
- Jildou and Peter have finished their work on the warblers (Acrocephalus sechellensis) on Denis for this visit and dropped by to the office last week to update me on their findings. They were able to catch and ring 99 birds during their stay and estimate that the island population is about 150 - 175 birds. There are now approximately 75 territories on the island. Once independent, young birds leave their natal territories. There are therefore a certain number of birds “floating”. That is to say moving round the island looking for a territory of their own. On Cousin Island where the warbler population is at carrying capacity the birds exhibit cooperative breeding where the young, and particularly the females, often remain in their natal territory and help their parents raise the next generation of siblings. This different life tactic is utilised because the entire existing habitat is occupied and the bird’s evolutionary fitness is optimised by helping to raise its siblings and seeking over time to either inherit the territory or gradually establish a territory off the side of the existing one. The high proportion of unringed birds found in the population during this visit is evidence of ample successful breeding but also suggests a quite high rate of adult mortality. Of particular concern is that Jildou and Peter estimate that 1 in 5 of the adults shows evidence of scarring and injury around the head. Such injuries are not evident on the other island populations and once again suspicion points to the predatory impact of the invasive Mynah bird.
I don’t know when I will be going back to the island, but I do have a backlog of a few things I could post on so I will try and post a couple of times over the next week. Keep checking back for updates…
Monday, August 3, 2009
More on littoral crabs... new records for Denis Island.
I posted at length on the 5th of July on the Sally lightfoot crab (Grapsus tenuicrustatus) and was able to get a few good shots of the animals as waves broke over them. G. tenuicrustatus is a common sight on the sandstone formations to be found around the southern and eastern coastline of the island and is indeed the only rocky shore crab previous studies have recorded on the island. I was very interested therefore to find other species present in the southern rocks when I was trying to get photos of G. tenuicrustatus. They were much more shy than the “Lightfoots” and difficult to photo but I was able to get a few snaps sufficient for their identification.
Eriphia smithi – rough red-eyed crab, red-eyed reef crab, pebble crab
E. smithi has an indo-pacific distribution and is reportedly very common on east African coasts. It has various distinctive characteristics which when combined allow for species identification. Most apparent are the bright red eyes on white stalks and this immediately narrows down its identity, this coupled with the numerous spines on carapace edge behind the eyes and the large molariform tooth on the larger claw clearly identify it as E. smithi.
This is an interesting species that grazes on algae during the day but turns predator of crustaceans and molluscs at night. At low tide at night individuals have been reported to roam out up to 50m on to reef flats in search of prey before returning to their crevice hideouts (Vaninni et al 1989). Rock crevices play an important part in their lifecycle for seclusion and mating and individual crabs can remain loyal to a single retreat for 3 weeks or more. The southern reaches of the island seem ideal in this regard with numerous cracks and crevices in the sandstone and large reef flats that are exposed at low tide.
Geograpsus stormi – red nipper.
Now I can’t be sure of this identification as I do not yet have a full dorsal photo of this crab (it moved very rapidly and agilely over the rocks in its search of refuge) but judging from the colour of its legs and eyes and the presence of prominent long bristles on the legs I am fairly certain that it is a specimen of the rocky shore crab G. stormi .
G. stormi has a western Indian ocean to central pacific distribution (Richmond 1997) and has been noted for its consumption of rocky shore carrion. Interestingly Haig (1984) records G. stormi as only occurring on islands that fit the habitat category of “low islands with mangroves” - in this case citing the outer island atolls of Aldabra and Cosmoledo. She does however go on to note that it is likely that G. stormi (inter alia) will be found on islands without mangroves as more “collecting” is done.
References:
1). Cook Islands biodiversity Database (2009). http://cookislands.bishopmuseum.org/species.asp?id=7351
2). Haig, J. (1984). Land and freshwater crabs of the Seychelles and neighbouring islands. In: Stoddardt, D.R. Biogeography and ecology of the Seychelles islands. Junk Publishers, The Hague.
3). Richmond, M.D. (1997). A guide to the seashores of Eastern Africa and the Western Indian Ocean Islands. ISBN 91-630-4594-X.
4).Vaninni, M. et al (1989). Feeding habits of the pebble crab Erithia smithi. Marine Biology 100, (249 -252) 1989.
Eriphia smithi – rough red-eyed crab, red-eyed reef crab, pebble crab
E. smithi has an indo-pacific distribution and is reportedly very common on east African coasts. It has various distinctive characteristics which when combined allow for species identification. Most apparent are the bright red eyes on white stalks and this immediately narrows down its identity, this coupled with the numerous spines on carapace edge behind the eyes and the large molariform tooth on the larger claw clearly identify it as E. smithi.
This is an interesting species that grazes on algae during the day but turns predator of crustaceans and molluscs at night. At low tide at night individuals have been reported to roam out up to 50m on to reef flats in search of prey before returning to their crevice hideouts (Vaninni et al 1989). Rock crevices play an important part in their lifecycle for seclusion and mating and individual crabs can remain loyal to a single retreat for 3 weeks or more. The southern reaches of the island seem ideal in this regard with numerous cracks and crevices in the sandstone and large reef flats that are exposed at low tide.
Geograpsus stormi – red nipper.
Now I can’t be sure of this identification as I do not yet have a full dorsal photo of this crab (it moved very rapidly and agilely over the rocks in its search of refuge) but judging from the colour of its legs and eyes and the presence of prominent long bristles on the legs I am fairly certain that it is a specimen of the rocky shore crab G. stormi .
G. stormi has a western Indian ocean to central pacific distribution (Richmond 1997) and has been noted for its consumption of rocky shore carrion. Interestingly Haig (1984) records G. stormi as only occurring on islands that fit the habitat category of “low islands with mangroves” - in this case citing the outer island atolls of Aldabra and Cosmoledo. She does however go on to note that it is likely that G. stormi (inter alia) will be found on islands without mangroves as more “collecting” is done.
References:
1). Cook Islands biodiversity Database (2009). http://cookislands.bishopmuseum.org/species.asp?id=7351
2). Haig, J. (1984). Land and freshwater crabs of the Seychelles and neighbouring islands. In: Stoddardt, D.R. Biogeography and ecology of the Seychelles islands. Junk Publishers, The Hague.
3). Richmond, M.D. (1997). A guide to the seashores of Eastern Africa and the Western Indian Ocean Islands. ISBN 91-630-4594-X.
4).Vaninni, M. et al (1989). Feeding habits of the pebble crab Erithia smithi. Marine Biology 100, (249 -252) 1989.
Friday, July 24, 2009
Nature Notes & Bird Bulletin…
I am taking some leave in the coming weeks so posts will likely be scarce for a good few weeks. I will use this combined “Nature Notes & Bird Bulletin” post to summarise a few odds and ends from my last island visit.
Nature Notes
Magpie Robin News. We have experienced some considerable set-backs in recent months with several chicks lost to Mynah bird attacks and two adults lost to illness. This is a matter of real concern as the population has decreased to 20 birds which is the number we started with a year ago and we have lost more females than males from the adult population. It is urgent that we take measures to improve breeding success in the population. The estate has been assisting with localised habitat management creating higher quality feeding grounds in each territory. Meanwhile I am in final negotiations with the island under what conditions we can bring a marksman to the island to undertake a preliminary cull of the Indian mynah population. The Indian mynah (Acridotheres tristis) is an invasive alien species in Seychelles and a highly effective predator of the eggs and chicks of our rare endemic species – so we have to deal with it. On a positive note I encountered a family group of three birds on the path called “L’Allee Bodamye” I was walking from the central path junction in the island when I noticed a single SMR following me. I took the opportunity disturb the leaf litter with my feet in order expose the insects upon which the bird feeds and moved on. When I looked back there were three birds on the patch of scraped ground. Such a sight even today is significant as it represents approximately a 60th of the world’s entire population of this endangered species. So I turned to take a few photos. One of the adults on seeing that I had stopped however soon came forward making its “churring” aggressive call. So not wanting to stress the birds I cleared another patch of leaves and left them to their foraging.
L’Allee Sed. The path that leads from the west coastal path to the island’s main central junction (mentioned above) is called “L’Allee Sed” because it is formed by an avenue of casuarina trees. L’Allee Sed is one of the older features on the islands. Casuarina trees were likely planted on the island from the 1860s onwards to provide a better windbreak for the coconut plantations and I have found reference from 1907 to the stands on the island being a major feature. The L’Allee Sed is therefore recognised under the island’s management plan as an important historical and ecotourism feature of the island that needs to be maintained.
Sally lightfoot crabs. In my post of 5th July I wrote about this species of crab and its special adaptations to life in the breaking waves. I also mentioned that on occasion the cast off exoskeletons could sometimes be found. During my last trip I indeed find one on the southern rocks see photo in sidebar.
Bird Bulletin
Nature Notes
Magpie Robin News. We have experienced some considerable set-backs in recent months with several chicks lost to Mynah bird attacks and two adults lost to illness. This is a matter of real concern as the population has decreased to 20 birds which is the number we started with a year ago and we have lost more females than males from the adult population. It is urgent that we take measures to improve breeding success in the population. The estate has been assisting with localised habitat management creating higher quality feeding grounds in each territory. Meanwhile I am in final negotiations with the island under what conditions we can bring a marksman to the island to undertake a preliminary cull of the Indian mynah population. The Indian mynah (Acridotheres tristis) is an invasive alien species in Seychelles and a highly effective predator of the eggs and chicks of our rare endemic species – so we have to deal with it. On a positive note I encountered a family group of three birds on the path called “L’Allee Bodamye” I was walking from the central path junction in the island when I noticed a single SMR following me. I took the opportunity disturb the leaf litter with my feet in order expose the insects upon which the bird feeds and moved on. When I looked back there were three birds on the patch of scraped ground. Such a sight even today is significant as it represents approximately a 60th of the world’s entire population of this endangered species. So I turned to take a few photos. One of the adults on seeing that I had stopped however soon came forward making its “churring” aggressive call. So not wanting to stress the birds I cleared another patch of leaves and left them to their foraging.
L’Allee Sed. The path that leads from the west coastal path to the island’s main central junction (mentioned above) is called “L’Allee Sed” because it is formed by an avenue of casuarina trees. L’Allee Sed is one of the older features on the islands. Casuarina trees were likely planted on the island from the 1860s onwards to provide a better windbreak for the coconut plantations and I have found reference from 1907 to the stands on the island being a major feature. The L’Allee Sed is therefore recognised under the island’s management plan as an important historical and ecotourism feature of the island that needs to be maintained.
Sally lightfoot crabs. In my post of 5th July I wrote about this species of crab and its special adaptations to life in the breaking waves. I also mentioned that on occasion the cast off exoskeletons could sometimes be found. During my last trip I indeed find one on the southern rocks see photo in sidebar.
Bird Bulletin
- I am pleased to report that both Paradise flycatcher fledglings are alive and well. Rachel Bristol, the Flycatcher Project Officer, is currently out on the island to follow up on the population so I should have more detailed news soon.
- Sadly the ground-nesting Tropicbird to the south of the island that fledged its first chick in December appears to have abandoned its nest without breeding this time – there are few factors that may be involved and I will follow up on the site closely.
- I noted only 1 Crested tern on the island last weekend interesting as I had recorded my highest ever count of 15 only a few weeks ago (see Post of 8th June).
- Sooty terns are a common sight and sound overflying the island aside from the actual project area they are particularly notable displaying over the northwest coast at Pte Mme Guichard.
- I checked on the White tern chick, the rescue of which I reported on in my second post of 5th July and am happy to report that it is growing well see photo in sidebar.
Wednesday, July 22, 2009
Studying the Seychelles warbler population on Denis…
As mentioned in my post of 8th June arrangements had been made for some researchers from Groningen University in the Netherlands to come to Denis to undertake a study of the Seychelles warbler (Acrocephalus sechellensis). The Seychelles warbler was introduced to Denis in 2004 as part of its ongoing national conservation plan (see post of 08/06 for more info).
The researchers Jildou and Peter arrived three weeks ago and were straight into their work. The establishment of a new population on an island offers plenty of scope for research. Jildou and Peter will be investigating the warbler’s population growth since 2007 and undertaking a detailed survey to ascertain survival and reproductive success in the population. Jildou and Peter are working under the supervision of Dr Jan Komdeur who worked in Seychelles for several years in the late 1980’s and early 1990’s. Jan was the man responsible for the propagation of the warbler to other islands that has done so much to enhance the conservation status of this endemic species. His detailed research of the warbler and its habitat requirements enabled the transfer of birds from the then sole colony on Cousin island to the islands of Aride and Cousine and latterly Denis.
Jildou and Peter are looking in particular at female mortality. There is evidence from the previous Denis survey in 2007 that the warbler population was skewed, with more males than females. Birds on a new island with abundant vacant habitat undergo more rapid reproduction than they do in established populations simply because resources are more abundant. Breeding is an energy intensive activity particularly for the females. It is postulated that this investment by the females may detract from their longevity and hence the development of a skewed sex ratio in the population.
Jildou and Peter will therefore be monitoring levels of stress in the birds by taking blood samples and checking for levels of oxidative stress, they will also be looking at the level of stress hormones in warbler faecal samples. They are furthermore looking at the levels of immunocompetence in the birds by assessing a variety of physical characteristics of the birds – as stress can affect immunocompetence.
This research is very interesting and has various ramifications for the planning of bird translocations in the future. From a Denis viewpoint, we are particularly interested in an update on the status of the population, its distribution and habitat use as this will help inform decision-making with regard to vegetation management on the island.
Keep checking back for more updates on Jildou and Peter’s endeavours.
The researchers Jildou and Peter arrived three weeks ago and were straight into their work. The establishment of a new population on an island offers plenty of scope for research. Jildou and Peter will be investigating the warbler’s population growth since 2007 and undertaking a detailed survey to ascertain survival and reproductive success in the population. Jildou and Peter are working under the supervision of Dr Jan Komdeur who worked in Seychelles for several years in the late 1980’s and early 1990’s. Jan was the man responsible for the propagation of the warbler to other islands that has done so much to enhance the conservation status of this endemic species. His detailed research of the warbler and its habitat requirements enabled the transfer of birds from the then sole colony on Cousin island to the islands of Aride and Cousine and latterly Denis.
Jildou and Peter are looking in particular at female mortality. There is evidence from the previous Denis survey in 2007 that the warbler population was skewed, with more males than females. Birds on a new island with abundant vacant habitat undergo more rapid reproduction than they do in established populations simply because resources are more abundant. Breeding is an energy intensive activity particularly for the females. It is postulated that this investment by the females may detract from their longevity and hence the development of a skewed sex ratio in the population.
Jildou and Peter will therefore be monitoring levels of stress in the birds by taking blood samples and checking for levels of oxidative stress, they will also be looking at the level of stress hormones in warbler faecal samples. They are furthermore looking at the levels of immunocompetence in the birds by assessing a variety of physical characteristics of the birds – as stress can affect immunocompetence.
This research is very interesting and has various ramifications for the planning of bird translocations in the future. From a Denis viewpoint, we are particularly interested in an update on the status of the population, its distribution and habitat use as this will help inform decision-making with regard to vegetation management on the island.
Keep checking back for more updates on Jildou and Peter’s endeavours.
Sooty tern update…
Part of the island’s management plan is in effect about turning back the clock. The southern portion of the island has been identified for restoration. The long term goal is to take this area back, as close as we can, to its original state when first discovered by man. De Trobriand the discoverer of Denis in 1773 left us a fascinating and quite detailed description of the island and its wildlife.
One of the dominant seabird species found on Denis at that time was the Sooty Tern (Onychoprion fuscata). Today one of the first aspects of restoration we are broaching is an attempt to re-establish a breeding population of Sooty terns on the island. Whilst we do not have specific records on the history and fate of the original sooty tern colony, we can draw certain conclusions from the island’s known development history and it seems probable that the bird has not successfully bred on the island for some 150 years.
We are now into the second year of this project and as such work has never been previously undertaken with the Sooty tern we are breaking new ground and learning as we go along. In this second year we have refined our approach following the results of last year and it has definitely been more successful (Previous posts cover the earlier stages of the project see: 19/05/09 and 02/07, 21/09 & 13/10 2008).
The sooty tern project was the focus of much my attention during my last visit to the island and it was most encouraging. On the Thursday afternoon I observed a few birds circling and a couple on the ground but it was on the mornings of Friday and Saturday that things were much more interesting. GIF volunteers Vicki and Georgia have been working steadily on the project and I hope that one or both of them will post soon on their perspective on the project. Both of them were present on Friday morning and the project area was alive with activity. Up to 37 birds were to be seen on the ground at a time with many more circling low over the area and calling. The birds on the ground were observed courting and mating and interacting as if a colony was under formation – it was fascinating stuff. The occasional bird was still seen to attempt to mate with one of the models as well. The next morning was much the same with up to 35 birds being observed on the ground at any time this time with the birds in general occurring in a single group.
It is unlikely that we will see any egg-laying on the island this year as, despite the delay in the onset of the southeast monsoon, egg-laying commenced in the existing Sooty colony on Aride Island in early June. Nevertheless the results this year are much improved from last and we continue to learn more about the bird’s preferences and how we might better design the project next year. According to studies the Sooty tern does not return to breed until it is 6 or 7 years old so it may well be that the birds we are attracting are young adults that are reconnoitring potential breeding locations for next year – let’s hope they keep Denis in mind!!!
One of the dominant seabird species found on Denis at that time was the Sooty Tern (Onychoprion fuscata). Today one of the first aspects of restoration we are broaching is an attempt to re-establish a breeding population of Sooty terns on the island. Whilst we do not have specific records on the history and fate of the original sooty tern colony, we can draw certain conclusions from the island’s known development history and it seems probable that the bird has not successfully bred on the island for some 150 years.
We are now into the second year of this project and as such work has never been previously undertaken with the Sooty tern we are breaking new ground and learning as we go along. In this second year we have refined our approach following the results of last year and it has definitely been more successful (Previous posts cover the earlier stages of the project see: 19/05/09 and 02/07, 21/09 & 13/10 2008).
The sooty tern project was the focus of much my attention during my last visit to the island and it was most encouraging. On the Thursday afternoon I observed a few birds circling and a couple on the ground but it was on the mornings of Friday and Saturday that things were much more interesting. GIF volunteers Vicki and Georgia have been working steadily on the project and I hope that one or both of them will post soon on their perspective on the project. Both of them were present on Friday morning and the project area was alive with activity. Up to 37 birds were to be seen on the ground at a time with many more circling low over the area and calling. The birds on the ground were observed courting and mating and interacting as if a colony was under formation – it was fascinating stuff. The occasional bird was still seen to attempt to mate with one of the models as well. The next morning was much the same with up to 35 birds being observed on the ground at any time this time with the birds in general occurring in a single group.
It is unlikely that we will see any egg-laying on the island this year as, despite the delay in the onset of the southeast monsoon, egg-laying commenced in the existing Sooty colony on Aride Island in early June. Nevertheless the results this year are much improved from last and we continue to learn more about the bird’s preferences and how we might better design the project next year. According to studies the Sooty tern does not return to breed until it is 6 or 7 years old so it may well be that the birds we are attracting are young adults that are reconnoitring potential breeding locations for next year – let’s hope they keep Denis in mind!!!
Monday, July 20, 2009
Southeast monsoon.
Flying to Denis on Thursday 16th July it was clear that the southeast monsoon was blowing strongly and had finally, properly established. Seychelles has two seasons determined by the direction of the prevailing wind either the northwest trade winds or the southeast monsoon. The southeast monsoon has been very late establishing this year and this affects the habits of many animals notably the breeding activity of seabirds that rely on the seasonal winds and related currents to bring the small fish they need to breed and successfully raise a chick.
I hadn’t been to Denis for a couple of weeks and last time I was there the southeast was blowing intermittently. On Thursday the white caps of waves were visible throughout the flight from Mahe to Denis. As the plane descended and approached the island, choppy water was evident on the surrounding shoals and then I saw something that I have never previously seen. A plume of sand was being carried offshore from “Pte Mme Guichard” on the northwest point of the island, off the shoal and into deeper water.
I have been monitoring the cycles of sand movement on the northwest coast since December 2005 and there is definite evidence of erosion. The difficulty in assessing such changes however is the fact that there may well be ongoing long-term cycles of erosion and accretion for which we have no information. It is therefore not possible to see short term changes in coastal profile in the proper context. Such thoughts are further complicated by ongoing changes in global weather patterns and the related issue of sea level rise. It is important however to monitor trends in coastal erosion in particular on the shoreline where key infrastructure is located in order to inform management decisions.
On seeing this sand plume going offshore and into deeper water it occurred to me that such sand loss may be permanent. Normally when I fly into the island I have camera ready for in case of a good photo-opportunities but on this trip because of the cloudy weather and poor light I hadn’t bothered. So I had to scramble to get the camera and snap some shots… so not great but good enough to show the occurrence… see photos in sidebar.
There was further evidence of the onset and stabilisation of the wind on the island. The sand promontory at Pte Mme Guichard has been largely eroded – a usual part of the island’s beach profile dynamics. I had reported previously (see post of 8th May amongst others) about the recovery of vegetation a Belle Etoile on the east coast following the cessation of grazing cattle there. This had greatly changed the view of the area with the former open meadows and casuarina-framed vistas obscured by the dense growth and foliage of papaya thickets. Well the salt spray driven by the “southeast” wind has changed this dramatically the leaves are gone leaving the barren stems to point accusingly at the sky.
Another key issue related to the southeast monsoon is that it will also mean that the Sooty tern season should get properly underway… but that is the subject of another post…
I hadn’t been to Denis for a couple of weeks and last time I was there the southeast was blowing intermittently. On Thursday the white caps of waves were visible throughout the flight from Mahe to Denis. As the plane descended and approached the island, choppy water was evident on the surrounding shoals and then I saw something that I have never previously seen. A plume of sand was being carried offshore from “Pte Mme Guichard” on the northwest point of the island, off the shoal and into deeper water.
I have been monitoring the cycles of sand movement on the northwest coast since December 2005 and there is definite evidence of erosion. The difficulty in assessing such changes however is the fact that there may well be ongoing long-term cycles of erosion and accretion for which we have no information. It is therefore not possible to see short term changes in coastal profile in the proper context. Such thoughts are further complicated by ongoing changes in global weather patterns and the related issue of sea level rise. It is important however to monitor trends in coastal erosion in particular on the shoreline where key infrastructure is located in order to inform management decisions.
On seeing this sand plume going offshore and into deeper water it occurred to me that such sand loss may be permanent. Normally when I fly into the island I have camera ready for in case of a good photo-opportunities but on this trip because of the cloudy weather and poor light I hadn’t bothered. So I had to scramble to get the camera and snap some shots… so not great but good enough to show the occurrence… see photos in sidebar.
There was further evidence of the onset and stabilisation of the wind on the island. The sand promontory at Pte Mme Guichard has been largely eroded – a usual part of the island’s beach profile dynamics. I had reported previously (see post of 8th May amongst others) about the recovery of vegetation a Belle Etoile on the east coast following the cessation of grazing cattle there. This had greatly changed the view of the area with the former open meadows and casuarina-framed vistas obscured by the dense growth and foliage of papaya thickets. Well the salt spray driven by the “southeast” wind has changed this dramatically the leaves are gone leaving the barren stems to point accusingly at the sky.
Another key issue related to the southeast monsoon is that it will also mean that the Sooty tern season should get properly underway… but that is the subject of another post…
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