Location and General Description
Malpelo Island (3¸59'05N - 81¸35'28W) is a small isolated Pacific island, 270 miles to the west of Colombia and south of Panama. It is one of several oceanic islands in the eastern tropical Pacific, along with Cocos Island and the Galapagos. The main island itself is roughly 8 km2, its elongate shape is 2.5 km long and 800m wide at its widest point, and is surrounded by a number of smaller rock outcroppings.
Climate is maritime and wet tropical, with high humidity and abundant rainfall. Temperatures average around 280 C, and the majority of the rainfall. There are no areas of permanent fresh water on the island, although frequent rains accumulate and passe through temporary rock pools, seeps, and springs throughout the islands.
Malpelo is an oceanic island, and the only island on the Malpelo Ridge, a solitary volcanic submarine ridge that extends northeast-southwest with a length of 150 miles and a width of 50 miles. The island had a volcanic origin, and geological surveys estimate that it was once 8 to 10 times larger than its present size, and maritime weathering has eroded the island and has formaed steep cliffs and sea-caves along its sides (Stead, 1975). Very little soil occurs on the island due to lack of parent material, and heavy erosion combined with steep surfaces. The exception is at higher elevations and where surfaces are flat. There are three distinct peaks, the highest of which is Cerro de la Mona, reaching 376 meters above sea-level. The steep cliffs which surround the island contain abundant sea-caves.
Vegetation on the island is sparse and is concentrated in areas which offer surface soil, and protection from high winds and erosion. The predominant vegetation are algae, mosses, and lichens which grown on vertical rock faces which receives fresh water. In areas with permanent soil are patches of grass and in restricted areas scrub is known to occur. The fern Pityrograma dealbata is found in association with these plants (Wolda 1975). This scant vegetation is the basis for a complex community of animals including two species of lizards, a land crab, and a number of invertebrates.
Considering the islands and their surrounding waters as a whole, Malpelo represents the confluence of biogeographical elements from the Galapagos, Cocos Islands, mainland Colombia, and even the Indo-Pacific. The terrestrial flora and fauna of Malpelo Island is not particularly diverse or extraordinary, however the island and it's surrounding rocky outcroppings contains important breeding and nesting grounds for a number of sea-birds and are host to a number of endemic vertebrate species. No native mammals or amphibians exist on the island, and to date no records exist of either having been introduced. Human contact with the island is minor and infrequent, and the difficulty of access has spared the islands being "seeded" with livestock by passing mariners, as has been the fate of so may other islands in the Pacific and around the world.
Among the birds, the dominant components are the extensive colonies of breeding seabirds. The most abundant of these being the orange-billed form of the masked booby (Sula dactylatra granti), whose range is restricted to the eastern Pacific Ocean - which nests almost exclusively here and on islands of the Galapagos (Pitman & Jehl 1998). Population estimated for this species on Malpelo Island are approximately 24,000 individuals, making this the second largest Masked Booby colony in the world (Pitman et al 1995). The only other bird species known to breed on the island is swallow-tailed gull (Craegrus furcatus), with an estimate of 50 pairs. Other species that regularly occur at Malpelo and most likely breed in small numbers include: red-billed tropicbird (Phaethon aenthereus), red-footed booby (Sula sula), black noddy (Anous minutus), brown noody (A. stolidus), white tern (Gygis alba), and great and magnificent frigatebirds (Frigata minor and F. magnificens, respectively).
Reptiles are the only other terrestrial vertebrate group to occur naturally on the island, and are represented by three species, all endemic to the island - an anole (Anolis agassizi), an anguid lizard (Diploglossus millepunctatus), and a gecko (Phyllodactylus transversalia) (Huey 1975; Kiester 1975; Rand et al. 1975). D. millepunctatus is among the largest of the anguid lizards and is one of the most conspicuous elements of the fauna on the island (Kiester 1975; Savage et al. 1993). All of these lizards feed on insects and the occasional crab, however D. millepunctatus has the unusual habit of eating fish dropped by birds feeding their young, and on carrion of dead birds.
Insufficient information is available to provide a detailed description of the vegetation on this island. Other than the information above, we have very limited survey information (Wolda 1975). It is likely however that several endemic species occur, particularly among the lichens, algae, and moss.
The marine flora and fauna of Malpelo and the surrounding islands is extraordinary, and is discussed greater detail in Glynn & Ault (2000) and Birkland et al. (1975).
The terrestrial species on Malpelo Island remain in relatively good condition. That is to say no exotic species have thus far been introduced, no permanent human habitations exist, and the island is otherwise unchanged by mankind. A military garrison is in place on the island and houses several people at any given time. At present, Malpelo Island is recognized as a Fauna and Floa Sanctuary (IUCN category IV, gazetted 1995).
Types and Severity of Threats
The military garrison, established in 1986, raised concerns about the possibility of introduced pests that might hitch a ride on personel, luggage, or food and supplies. As of the writing of this paper this has not yet been reported.
Justification of Ecoregion Delineation
The island of Malpelo was classified as its own ecoregion due to distance from the mainland and from other islands, and for its unique and endemic species assemblage which includes two lizard species (Graham 1975).
Birkleland, C., D.L. Meyer, J.P. Stames, and C.L. Buford. 1975. Subtidal Communities of Malpelo Island. Pages 44-46 in J. Graham, editor, The Biological Investigation of Malpelo Island, Colombia. Smithsonian Contributions to Zoology, No.176.
Glynn, P.W., and J.S. Ault. 2000. A biogeographic analysis and review of the far eastern Pacific coral reef region. In: Coral Reefs, March, 19 (1): 1-23.
Huey, R.B. 1975. A new gecko from Malpelo Island (Sauria: Gekkonidae: Phyllodactylus). Pages 44-46 in J. Graham, editor. The Biological Investigation of Malpelo Island, Colombia. Smithsonian Contributions to Zoology, No.176.
Pitman, R.L., L.B. Spear, and M.P. Force. 1995. The marine birds of Malpelo Island, Colombia. Colonial Waterbirds 18(1): 113-119.
Pitman, R.L. and J.R. Jehl. 1998. Geographic variation and reassessment of species limits in the "masked" boobies of the eastern Pacific Ocean. Wilson Bulletin, 110 (2):155-170.
Rand, A.S. G.C. Gorman, and W.M. Rand. 1975. Natural history, behavior, and ecology of Anolis agassizi. Pages 27-38 in J. Graham, editor. The Biological Investigation of Malpelo Island, Colombia. Smithsonian Contributions to Zoology, No.176.
Savage, J.M. and K.R. Lips. 1993. A review of the status and biogeography of the lizard genera Celestus and Diploglossus (Squamata: Anguidae), with description of two new species from Costa Rica. Revista de Biologia Tropical, 41: 817-842.
Wolda, H. 1975. The ecosystem on Malpelo Island. Pages 22-26 in J. Graham, editor. The Biological Investigation of Malpelo Island, Colombia. Smithsonian Contributions to Zoology, No.176.
Prepared by: Jan Schipper
Reviewed by: In process