Rediscovery of rodents (Genus Nesoryzomys) considered extinct in the Galapagos Islands

The history of the endemic rodents of the Galapagos Islands began with the discovery of the first Galapagos rice rat species by Charles Darwin in 1835 and the last species was described as recently as 1980. Unfortunately, of the seven described species known to occur in the islands during the past 150 years, only two were known to be extant to 1995. Since then, two expeditions to the Galapagos Islands have been conducted to survey endemic rodent populations. The first confirmed the existence of a small endemic rice rat, Nesoryzomys fernandinae, on Fernandina, known previously only from owl pellet remains found in 1979. In 1997, an expedition to Santiago revealed a population of the larger rice rat N. swarthi, a species collected alive only once in 1906 and considered extinct in all recent literature on the Galapagos Islands. Survey efforts on Santa Cruz resulted only in the collection of introduced rodent species (Rattus rattus, R. norvegicus and Mus musculus). The extant species of native rodents in the Galapagos Islands now number four: N. narboroughi and N. fernandinae on Fernandina; N. swarthi on Santiago; and Oryzomys bauri on Santa Fe. Three species are found on islands where no introduced rodents or cats occur, whereas only one (N. swarthi) co-exists with R. rattus and M. musculus. Nesoryzomys darwini and N. indefessus on Santa Cruz and O. galapagoensis on San Cristobal are still considered extinct. Strategies for conservation should include monitoring islands for introduced rodents and cats, development of emergency plans in the event of introductions, and captive management.