Galapagos rice rats

Extinct in 1929-1934
  • Galapagos Rice rats
  • Galapagos Rice rats

Galapagos rice rats – one of the few land mammals on Galapagos and an excellent example for evolution

Because of the large distance between the Galapagos and the South American continent, land mammals are of course rare on the Galapagos. Only two species of bats, which were probably blown over by storm, and a few rodents can be found on the islands. Before the arrival of man, the only species of rodents to occur in Galapagos were the Rice rats (Cricetidae). Formerly there were three genera with seven endemic species. Mostly, each of them could be found only on one island of the archipelago.
Such an evolution of endemic species on islands caused by isolation and their adaptation to a new environment can be observed also in other parts of the world. Also in Japan, on Okinawa and two Ryukyu Islands lives an endemic rat, the arboreal Ryukyu long-tailed giant rat (Diplothrix legata).This species is unique and no other related species are known and the origin and phylogeny of this tree rat is still not yet fully understood.

Galapagos rice rat drawn in 18th century

Galapagos rice rat drawn in 18th century (Click to view larger image)

The endemic Galapagos Rice rats were classified into three genera, namely Nesoryzomys with five species, Megaoryzomys with one species and Aegialomys again with one single species but two subspecies. But the introduction of the ubiquitous Ship rat and the increasing number of settlers on the Galapagos are believed to have led to the extinction of four of these species.

Portrait of Charles Darwin The hispid cotton rat which is relative to the Galapagos rice rat

Portrait of Charles Darwin
(Click to view larger image).

The hispid cotton rat which is relative to the Galapagos rice rat
(Click to view larger image).

The Galapagos Giant rat (Megaoryzomys curioi) is known from Isabela and Santa Cruz Island. With a body length of more than 20 cm it was a rather large species. It likely met its demise when European settlers introduced invasive species to the island. It was the only species of the genus Megaoryzomys. Although historic records do not hint at the existence of the Galapagos Giant rat and the bones are only known from late Quaternary and subfossil cave deposits, this species is considered to have very recently become extinct. The possibility of the involvement of a climate change by an El Nino as well as the involvement of feral dogs, cats, pigs, and black rats in its extinction is also suggestive of this recent extinction.

Beagle the Navy ship for Survey Adventure log of the Beagle(Red line of this map)

"Beagle" the Navy ship for Survey
(Click to view larger image).

Adventure log of the "Beagle"(Red line of this map)
(Click to view larger image).

Another extinct Rice rat is one subspecies of the Galapagos Rice rat (Aegialomys galapagoensis), which is found with one subspecies (A.g.bauri) in the dry shrub-land on Fernandina Island and formerly a second subspecies (A.g.galapagoensis) also on San Cristobal, where Charles Darwin captured several live specimens on his cruise with the “Beagle” in 1855. It is believed that this subspecies became extinct only decades after Darwin's visit and the next specimens collected were subfossil remains found in 1984 in lava tubes. The closest relative of this Galapagos Rice rat is the Yellowish Rice rat (Aegialomys xanthaeolus), which is found on the South American continent in coastal Ecuador and Peru and which is currently the only formally recognized mainland species of this genus.

The landscape of Fernandia island Adventure log of the

The landscape of Fernandia island
(Click to view larger image).

Ryukyu long-tailed giant rat which is endemic to Okinawa,Japan
(Click to view larger image).

The cinnamon-brown Darwin’s Galapagos mouse (Nesoryzomys darwini) is another Rice rat species that lived on Santa Cruz Island. It measured 20.4-22.2 cm and its tail was shorter than the body length (about 80%). The Darwin’s Galapagos mouse was probably nocturnal and inhabited burrows or rock crevices under bushes. Only four specimens exist, collected in 1929. The species is extinct since 1930 and its extinction may have been caused by competition and disease created by the introduction of nonnative brown and black rats.
The second extinct Rice rat species of this genus, which lived formerly on Santa Cruz and Baltra, is the Indefatigable Galapagos mouse (Nesoryzomys indefessus). This species was larger than the Darwin’s Galapagos mouse and had a body length of almost 30 cm. Its tail measured 10.8-11.7 cm. The Indefatigable Galapagos mouse lived probably across the whole island and was seen in 1934 for the last time. It became extinct definitely in the 1930ies, probably due to the introduction of Black rats (Rattus rattus) too.

Cape lion Enclosure in LOST ZOO

Galapagos Rice rats in LOST ZOO
(Click to view larger image).

Although the Galapagos Rice rats are rather small and not very impressive animals, our Lost Zoo is happy and proud to keep these very rare rodents from the Galapagos Islands, because these rats are a great example for evolution and natural selection and adaptation to new habitats. The Galapagos Rice rats will inhabit a nice, large glass vitrine in a small moon light house, where the visitor can observe the nocturnal animals and their activities during the normal visiting hours, when we have daylight outside of the building but darkness inside.

Executive Curator

Galapagos rice rats

Except two species of bats the Galapagos Rice rats are the only mammals which have ever lived on the Galapagos Islands before the humans came to the islands. The closest relative is the Yellowish rice rat which lives in coastal Ecuador and Peru.

Body length: 20-30 cm (depending on the species).

Tail length: 11-15 cm.

Habitat:Dry shrub land, living in the burrows or rock crevices under bushes.

Extinction: 1929-1934, when European settlers introduced invasive species to the islands.

Galapagos Rice rats