Messaggioda Maria » gio dic 28, 2006 3:45 pm
[quote]Messaggio inserito da DelorenziDanilo
le yniphora...
quante ce ne saranno in natura!
ho letto 400 esemplari.. ma chissà..
deve essere stupendo vederle dal vivo..
quelle della foto tra l'altro è una coppia! speriamo nei piccoli!!
Dear Danilo,
In the meantime, I have got some details regrading history of Ampijoroa Forest Station, and current status of G. yniphora in Madagascar. It could be interesting for some members of Tarta Club Italia, and I am repeating the whole text avaialble with me now, as follows:
Captive Breeding of Geochelone yniphora in Madagascar
Throughout the 1970's and early 1980's, the Malagasy Government (Direction des Eaux et Forets: DEF) maintained a captive breeding facility for confiscated native land tortoises at the Ivoloina Forestry station in Toamasina (Tamatave) on the island's humid (windward) east coast.
On a visit to the Ivoloina facility in January 1984, the senior author found the tortoise collection to include 43 adult G. radiata (21 male, 22 female) and 7 adult G. yniphora (5 male, 2 female), all confined together in a small thatched shed (area 22.5 m, or 2.2 tortoises/sq. m). In spite of space limitations the tortoises appeared well cared for and in good health. The G. radiata had been breeding successfully for several years. About 50-60 eggs were laid annually and incubated in closed wooden boxes of sand under ambient temperature conditions. Each year, 20-30 hatchlings emerged after an incubation period of 8-12 months (A. Befeno, personal communication, 1984). In January 1984, there were 144 captive bred young G. radiata at the Ivoloina facility, ranging in age from recent hatchlings to 5 year olds. The largest captive bred animals (1979 hatch) had carapace straight lengths of 82-125 mm (X=105 mm; N=6), and noticeable pyramiding of the carapace scutes.
In contrast to the prolific reproduction of G. radiata, no egg laying was reported for the G. yniphora as Ivoloina. Although confined in cramped quarters with adult G. radiata, it was observed that G. yniphora males made clear interspecific discrimination as both episodes of male combat and courtship in G. yniphora were noted during the brief visit.
Because the Ivoloina site did not possess climatic conditions comparable (i.e., distinct wet-dry season contrasts) to that found in the natural range of G. yniphora, it was earlier recommended in the Species Recovery Plan (Juvik et al., 1982) that the Ivoloina animals be relocated to a west coast forestry facility in the Mahajanga area (some 100 km east of Baly Bay) where general environmental conditions were more appropriate.
In 1986, with support from the World Wildlife Fund, the Jersey Wildlife Preservation Trust (JWPT) in cooperation with the Malagasy DEF, established a G. yniphora captive breeding facility at the Ampijoroa Forestry station near Mahajanga. In September 1986, the Ivoloina G. yniphora (5 male, 2 female) were transferred to Ampijoroa. More recently, additional captive held G. yniphora from villages in the Soalala area have been donated to the Ampijoroa breeding program, bringing the adult tortoise population at the facility to 20 animals (8 males, 12 females) in October, 1991. The first captive breeding success at Ampijoroa was achieved in 1987 with the emergence of a single hatchling G. yniphora. By the end of 1989 a total of 21 captive hatchlings had been produced, including 12 in 1989 alone, from 7 clutches totaling 25 eggs (Reid et al., 1989). In 1990 there were a further 10 hatchlings, and for 1991, there are 55 eggs under incubation (Reid, pers. comm. November, 1991). Eggs have been left to incubate in situ in outdoor tortoise pens, with wire screen covers placed over nest sites to provide protection from predators. Natural incubation periods have ranged from 168-266 days and are apparently correlated with wet-dry season onset and duration (Reid, 1990a).
Wild Populations of G. yniphora: Status and Prospects
Based on field surveys during the early and mid 1970's, Juvik et al. (1981) documented the presence of wild G. yniphora populations at four different dry forest locations in the Baly Bay area:
1. North Ankoro (tortoise seen in wild, see Andrianarivo, 1977)
2. Cape Sada (several tortoises seen in wild)
3. East of Andanivato (fresh tortoise dung)
4. Forest patches between Anky and Antanandava (fresh tortoise dung)
More recent surveys in 1983 and 1986 (Curl et al., 1984, 1985 and Curl, 1986a) collected considerable anecdotal information (and documented a substantial number of captive tortoises in villages) but failed to uncover or confirm any new wild populations beyond those listed above.
In January 1990, Don Reid, the Madagascar based conservation officer with JWPT, spent two weeks in the Baly Bay region surveying G. yniphora populations and potential protected area sites. Reid was unable to visit the forest locality north of Ankoro (Anjaha) on the west side of Baly Bay but visits to this area in April, 1991 by local Malagasy nature protection officials confirmed the continued presence of a significant G. yniphora population in the Belambo forest to the north and east of Ankoro. This habitat area may well prove to be as important as Cape Sada for G. yniphora conservation and is currently the focus of ongoing field work.
Reid (1990b) also interviewed villages at Antanandava concerning the status of G. yniphora populations inhabiting remaining forest patches to the north. These dry forest areas were reported to have been heavily degraded by fire and cattle grazing over the past few years, with villagers convinced that no tortoises remained in the area. Reid (1990b) did find one adult G. yniphora in the wild, in a small (30 hectare) dry forest "island" (surrounded by palm/grass savanna) in the Betheta/Anamboho area. Reid (1990b) also visited Cape Sada and confirmed the earlier recommendations of Juvik et al. (1982) and Curl et al. (1985) that Cape Sada is the most appropriate site for initial protected area status based on the following factors:
a) 200-250 hectares of suitable tortoise habitat (little affected by burning) which could potentially support up to several thousand tortoises;
b) the absence of a permanent human population or intensive human utilization of the area;
c) ease and economy of constructing a pig/cattle barrier fence across the Cape Sada peninsula (about 2 km); and
d) the convenience of access (by boat) from the administrative center of Soalala.
Juvik et al. (1982) gave specific design specifications on a mesh and barbed wire pig fence for Cape Sada, based on successful fencing techniques used to control feral pigs in Hawaii Volcanoes National Park. According to Reid (1990b) local Malagasy authorities expressed some concern that villagers near Cape Sada might well find alternative uses for valuable fencing materials. This potential problem can possibly be overcome by employing local villages in fence constructing and maintenance and providing each nearby village with some fencing material for pig traps and garden protection.
In a recent uncritical review of the literature on G. yniphora conservation, Burke (1990) draws several unsupported and errant conclusions which only detract from ongoing conservation efforts for the species. Perhaps confused by contradictory assertions on the persistence of vegetation boundaries around Baly Bay (Curl et al., 1984, 1985 and Curl 1986b), Burke (1990) concludes there is little evidence for ongoing tortoise habitat degradation, and that "the situation of the wild angonoka (G. yniphora) may be somewhat less precarious than previously thought." Such contentions are merely "wishful thinking" in view of recent field work results (Reid, 1990b), and our own (Kiester and Juvik, in preparation) assessment of regional habitat change based on comparative analysis of early aerial photography (1949) and recent hand-held Space Shuttle photography and Landsat thematic mapping images (both from December, 1990). Although preliminary remote sensing analysis indicates that some forest fragments have disappeared over the 41 year interval, other forest patches have retained their boundaries virtually unchanged (e.g., the Antanandava Forest). Ground surveys, however, indicate that even in these persistent forest fragments human induced habitat degradation is diminishing the quality if not the quantity of the areas for native wildlife. These conclusions are consistent with the recent work of Andrianarivo (1990) who studied dry forest cover changes from satellite data for a nearby area (Mahajamba Bay) in western Madagascar. Although Andrianarivo found little net change in total forest cover between 1973-84, ground surveys revealed qualitative forest ecosystem decline in the form of reduced tree basal area and lower densities for arboreal lemurs.
Burke (1990) also asserts that Cape Sada is unsuitable for a nature reserve because its small size (200-250 hectares of tortoise habitat) would probably not support a viable tortoise population. If pigs and cattle were effectively excluded (by fencing) from Cape Sada, G. yniphora would remain the only significant terrestrial herbivore in an ecosystem which could easily support several tortoises per hectare, or a total population exceeding 1,000 animals. It should be noted that much larger tortoises (G. gigantea) exist at average densities of 17/hectare on the south coast of Aldabra Atoll, some 600 km to the north of Baly Bay (Hnatiuk et al., 1976). We agree that Cape Sada comprises less than ideal habitat size, however there is simply no realistic alternative at the present time given current land use trends and cultural practices in the region.
Warmest regards, Marco