496.

Galapagos Rice Rat

Aegialomys galapagoensis

French: Oryzomys des Galapagos / German: Galapagos-Reisratte / Spanish: Rata arrocera de Galapagos

Other common names: Galapagos Aegialomys, Galapagos Oryzomys

Taxonomy. Mus galapagoensis Waterhouse, 1839, San Cristobal (Chatham) Island, Galapagos Islands, Ecuador.

Aegralomys galapagoensis includes Oryzomys bauri, with type locality in Santa Fe (Barrington) Island, Galapagos Islands. Monotypic.

Distribution. Galapagos Is; recorded on Santa Fe, San Cristobal, and Santiago (James) Is, but may only be extant on Santa Fe I.

Descriptive notes. Head-body 106-152 mm, tail 120-173 mm, hindfoot 28-34 mm, ear 14-23 mm; weight 62-103 g. Male Galapagos Rice Rats are larger, heavier, and more vagile than females. Fur is soft, lax, dense, and long. Dorsum is yellow or copper, weakly grizzled with grayish or brownish; venter is grayish yellow. Mystacial vibrissae are dense and thick but very short, not reaching pinnae when laid back. Dorsal surface of hindfootis covered by very white and long hair. Ears are small (c.10% of head-body length), densely covered by short hair; outer hair is creamy and yellowish, and inner hair is light yellow. Ungual tufts are dense and long. Interdigital and plantar pads are developed, and thenar and hypothenar are fleshy. Tail is hirsute, shorter than headbody length, unicolored, and dark brown, with c.20 scales/cm and without terminal tuft. Hindfoot is short (c.21% of head—body length). Chromosomal complementis 2n = 56, FN = 58.

Habitat. Xeric vegetation. Galapagos Rice Rats were recorded near a sandy beach that led directly to rough ground with large boulders covered by a narrow strip of very dense but low halophytic vegetation 5-10 m wide before it opened into Opuntia echios (Cataceae) forest with sparse understory.

Food and Feeding. The Galapagos Rice Rat eats seeds, fruits, and invertebrates. On Santa Fe Island,it has been observed eating placenta of the Galapagos Sea Lion (Zalophus wollebaeki).

Breeding. Reproduction is restricted to the warm season (January-April) and occurs after annual rains; in more humid periods, females produce more embryos. Survival rate is high and does not differ between males and females, reaching up to 599 days but averaging 165 days for males and 167 for females.

Activity patterns. The Galapagos Rice Rat is diurnal and nocturnal. It is terrestrial.

Movements, Home range and Social organization. No information.

Status and Conservation. Classified as Vulnerable on The IUCN Red List. History of decline and likely extinction of Galapagos Rice Rats on San Cristobal Island, with increase and spread of introduced species, has been well documented. Introduction of exotic rats such as the Roof Rat ( Rattus rattus) and the House Mouse ( Mus musculus) to Santa Fe Island remains the main threat to the Galapagos Rice Rat. History suggests that it could easily go extinct due to invasive predators and competitor species, and this should be a conservation priority.

Bibliography. Allen (1892), Clark (1980), Gardner & Patton (1976), Patton & Hafner (1983), Percequillo (2015k), Prado & Percequillo (2016, 2017), Swing & Guerra (2015), Thomas (1894), Vallejo & Boada (2017c), Waterhouse (1839).