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Site description (2001 baseline):
Site location and context
This is the largest lake in Madagascar, situated 170 km north-east of Antananarivo and 7 km north of Ambatondrazaka. It lies in a tectonic basin 40 km long and 9.5 km wide, located between the Grand Angavo escarpment in the west and the Mangoro–Alaotra escarpment in the east. Its depth is 1.0–2.5 m during the low-water season and 4 m during the high-water season. The water is fresh, and turbid with suspended silt due to intense erosion of the deforested hills that surround the lake. The lake is fed by the Sasomanga and Sahabe rivers in the south, and by the Sahamaloto and Anony rivers in the north-west. The only drainage river, the Maningory, flows out of the north-eastern part of the lake. The lake-bottom sediments consist of thick layers of sand, black mud and grey clay. Natural, permanent marshes occur along the lake margin, especially in the southern part of the site. The largest are located to the south and east of the Antanamalaza peninsula and in the part drained by the Maningory. There are also wet grasslands. The lake vegetation was formerly dominated by water-lilies
Nymphaea, but these have decreased in extent due to competition with non-native water-hyacinth
Eichhornia and water-fern
Salvinia. In the marshes, sedges
Cyperus and reeds
Phragmites dominate. Secondary savanna covers the surrounding hills.
See Box and Tables 2 and 3 for key species. Eighty species are known from the site, of which 13 are endemic to Madagascar. Lake Alaotra is an exceptional site for waterbirds. It formerly held two highly threatened endemic species, which were probably confined to the lake, but which may now be extinct:
Tachybaptus rufolavatus and
Aythya innotata. The former was last recorded in 1985 and the latter in 1991. Furthermore, the flocks of
Anas melleri that occur on the lake constitute the largest congregations known for this species, and
Ardea humbloti also occurs regularly (in its only eastern site), though it is not proven to have bred.
Non-bird biodiversity: Lemur: Hapalemur griseus alaotrensis (CR). Carnivore: Salanoia concolor (VU).
Pressure/threats to key biodiversity
Human activities that pose a threat include the burning of marsh vegetation, poaching, intensive gill-netting, and conversion of marshes to rice-fields. The invasion of the lake by non-native vegetation, and the introduction of non-native fishes such as
Tilapia and
Ophiocephalus, have resulted in the loss of several native species of fish, waterbird and aquatic plant.
Recommended citation
BirdLife International (2024) Important Bird Area factsheet: Lake Alaotra NPA (Madagascar). Downloaded from
https://datazone.birdlife.org/site/factsheet/lake-alaotra-npa-iba-madagascar on 25/12/2024.
