Marmosa mexicana (Merriam, 1897)

Russell A. Mittermeier & Don E. Wilson, 2015, Didelphidae, Handbook of the Mammals of the World – Volume 5 Monotremes and Marsupials, Barcelona: Lynx Edicions, pp. 129-186 : 138

11.

Mexican Mouse Opossum

Marmosa mexicana

French: Opossum du Mexigue / German: Mexiko-Zwergbeutelratte / Spanish: Marmosa de México

Taxonomy. Marmosa murina mexicana Merriam, 1897 ,

“Juquila, Oaxaca,” Mexico.

Four subspecies were traditionally recognized, but one of these, M. zeledoni, has been elevated to species status. Genetic analyses indicate the presence of two distinct taxa in what is currently known as M. mexicana , but the status of the remaining three, traditionally recognized subspecies (nominate, mayensis, and savannarum) needs to be properly addressed. Monotypic.

Distribution. S & SE Mexico (Tamaulipas, San Luis Potosi, Veracruz, Oaxaca, Chiapas, and the Yucatan Peninsula) and through Central America to E Panama, including two Caribbean Is (Isla de Roatan, Honduras, and Isla del Maiz Grande, Nicaragua).

Descriptive notes. Head-body 11-16.8 cm (males) and 9.4-13.3 cm (females), tail 15.2-22.8 cm (males) and 13-22.3 cm (females); weight 24-99 g (males) and 35-4— 56-7 g (females). Dorsal fur of the Mexican Mouse Opossum is rich reddish-brown and becomes a grayish-brown frosted with reddish-brown in older individuals. There is paler mid-rostral fur on head but no mid-rostral stripe. Black eyes are surrounded by dark brown or blackish-brown eye-rings that extend back to base ofears. Tail length is ¢.137% of head-body length, tail has fur on its proximal 10%, and its naked part is dark brown. Ventral fur has a stripe of yellowish or orangish fur, running from chin to anus and varying in width, bordered by yellowish or orangish gray-based fur on sides of chest, abdominal, and upper inguinal regions, sometimes also extending to sides of neck and inner parts of arms and legs. Feet are orangish to brown or whitish, and carpal tubercles are present in old males. Furis short overall, and there is a throat gland. Female Mexican Mouse Opossums lack a pouch and have 11-15 mammae, with 5-7 on each side, as well as an additional medial mamma. The Mexican Mouse Opossum has a 2n = 14 karyotype, with biarmed autosomes, a small acrocentric X-chromosome and a very small unidentified Y-chromosome. Skull size and shape are sexually dimorphic.

Habitat. Tropical and subtropical forests and shrubby habitats below elevations of 1600 m and dry and humid forests, pine-oak forests, mangroves, and scrublands.

Food and Feeding. Diet of the Mexican Mouse Opossum is composed mainly of insects and fruits, but occasionally it consumes small rodents, lizards, birds, and eggs. Fecal samples from a Panamanian cloud forest contained spores of arbuscular mycorrhizal fungi. Individuals were also seen feeding on the inflorescence of Calyptrogyne ghiesbreghtiana , a small palm, which may represent an important energy resource. In return, the opossum may act as a pollinator for the palm.

Breeding. Female Mexican Mouse Opossums make nests in trees, abandoned birds’ nests, underground burrows (with nest chambers located c¢.40 cm from the entrance), and sandbanks. These nests are c.4 cm in diameter, usually made of dried leaves. Females were found with attached young in March, May, and June, although a female caught in Veracruz was not sexually active in April. Reported litter sizes vary from two to 13 young;litters most frequently are of 11-13 young. Young that get detached from their mother emit a distress call, prompting the mother to pick them up with her forefeet and push them under her belly, so that they cling on her fur and reattach themselves.

Activity patterns. Mexican Mouse Opossums are active at night. They have been recorded visiting night-flowering palms, with peaks right after sunset and from 23:00 h to 01:00 h, but there are no additional data on activity patterns.

Movements, Home range and Social organization. The Mexican Mouse Opossum uses understory and the ground, spending more time in trees and using the ground occasionally. They are found in small trees and bushes up to 1-5 m high but also under logs and tree roots and among grasses. They seem to be more arboreal than ground dwelling because they are more frequently trapped off the ground.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Mexican Mouse Opossum has wide distribution, presumably a large population size, and a certain degree of tolerance for habitat modification.

Bibliography. Alonso-Mejia & Medellin (1992), Astua (2010), Biggers et al. (1965), Goodwin (1946), Gutiérrez et al. (2010), Hatt (1938), Hershkovitz (1992a), Mangan & Adler (2000), Reig et al. (1977), Rossi (2005), Rossi, Voss & Lunde (2010), Sperr et al. (2009), Voss et al. (2014).

Figures

65. Pygmy Opossum (Chacodelphys formosa), 66. Agricola’s Opossum (Cryptonanus agricola), 67. Chacoan Mouse Opossum (Cryptonanus chacoensis), 68. Guaiba Mouse Opossum (Cryptonanus guahybae), 69. Unduavi Mouse Opossum (Cryptonanus unduaviensis), 70. . Emilie’s. 9 Opossum.. Gracilinanus. (null), 71. Aceramarca Opossum (Gracilinanus aceramarcae), 72. Agile Opossum (Gracilinanus agilis), 73. Wood Sprite Opossum (Gracilinanus dryas), 74. Northern Gracile Opossum (Gracilinanus marica), 75. Brazilian Gracile Opossum (Gracilinanus microtarsus)

Distribution. S & SE Mexico (Tamaulipas, San Luis Potosi, Veracruz, Oaxaca, Chiapas, and the Yucatan Peninsula) and through Central America to E Panama, including two Caribbean Is (Isla de Roatan, Honduras, and Isla del Maiz Grande, Nicaragua).