Amphibians of Aruba, Curaçao, and Bonaire
A. Geography, climate, extended dry periods, tankis and earthen dams, and vegetation Aruba, Curaçao, and Bonaire, together with the Venezuelan islands of Los Monjes, Islas Aves, Los Roques, La Orchila, and La Blanquilla form an archipelago north of the Venezuelan coast. Biogeographically, these islands do not belong to the West Indian region; their flora and fauna are mainly of South American origin. There are many endemic elements in the fauna, largely derived from South American ancestors. This justifies the view that these islands form a small, but distinct, zoogeographical subregion belonging to the South American realm (Wagenaar Hummelinck 1940). The fauna (Wagenaar Hummelinck 1940) and especially the flora (Stoffers 1956) both contain West Indian elements too. Wagenaar Hummelinck makes a distinction between older and newer West Indian fauna. The West Indian elements are especially strong in the flora. Stoffers states the following (about the Dutch Leeward Islands):
Of the species with a more restricted distribution the West-Indian plants (35)
are the most numerous, the South American element being represented by only
22 species. The vegetation of the Leeward group therefore resembles the flora of
the Antilles, rather than the flora of South America, at least from a floristic point of
view. However, physiognomically the vegetation corresponds more to that of the
dry region of northern South America.
Perhaps this area (the Monjes–La Blanquilla archipelago) should be considered an intermediate zone between the West Indies and the South American realm. The Venezuelan islands of Los Monjes, Islas Aves, Los Roques, La Orchila, and La Blanquilla are devoid of amphibians. Of the islands covered in this chapter, Curaçao is the largest with a surface area of 444 km2. Aruba has a surface area of 190 km2 and Bonaire 289 km2 (including Klein Bonaire with 7 km2). Their climate is rather arid compared to most Caribbean islands, with a mean annual rainfall of 409 mm, 557 mm, and 463 mm respectively (Meteorological Service of Netherlands Antilles and Aruba). Aruba is the most arid of the Dutch islands, while the western parts of
Curaçao receive the most rainfall; the mean temperature across the archipelago is about 28°C. The hilly areas receive slightly more rain, and rainfall can be quite variable from year to year. Dry years have only 200–300 mm of rain, while the maximum is about 1,100 m. The driest year on record for Curaçao is 1914, which saw an average of 207.9 mm. Every century there occur several extended periods of drought with practically no rain (van Buurt 2010) (Figs. 10.1–10.3).