MATING BEHAVIOR OF THE MEXICAN MOUSE OPOSSUM (Marmosa canescens) IN CUIXMALA, JALISCO, MEXICO.

The Mexican mouse opossum (Marmosa canescens sinaloae) is the smallest species among the Mexican marsupials. This is an endemic species to Mexico with a geographic range from Sinaloa to Chiapas, along the Pacific coast, to the Yucatan Peninsula (Ceballos and Miranda, 1986) where it inhabits mainly in tropical dry deciduous and tropical semideciduous forests. Although some general aspects on its biology are known (Barness and Barthold, 1969; Alvarez del Toro, 1977; Ceballos and Miranda, 1986), there is not any previous information on the mating behavior of this species. On July 27th, 1993, the mating behavior of the Mexican mouse opossum (Marmosa canescens sinaloae) was recorded in a tropical dry forest in western Mexico (19a24’59'’ N, 104a58’33'’,W). Observations were made in the ChamelaCuixmala Biosphere Reserve, located 45 Km NW of Barra de Navidad, Jalisco. Physical and biotic characteristics are described elsewhere (Bullock, 1986; Ceballos and Miranda, 1986; Arizmendi et al., 1991, Lott, 1993; Garcia and Ceballos, 1994). Observations were made around 18:28 hrs in a sunny afternoon with minimum and maximum air temperature of 22 and 24oC, respectively. Rains had been considerable with about 606 mm of precipitation since the beginning of June (raining season) and were close to the annual average precipitation rate of 748 mm (Bullock, 1986). At 18:28 hrs a Mexican mouse opossum male was detected walking on the ground litter, 3 m away from a female with her offspring. The offspring was in a dead empty tree of 1.5 m high and 0.2 m in diameter, with an entrance opening at the top. The male climbed the tree and entered the nest. After 4 minutes both male and female emerged. The female stayed at the nest entrance while the male was moving around the nearest branches for almost 5 minutes. Suddenly, the male approached to the female so that they were face to face. The male either passed food to the female of simply touched her snout; this could not be determined because of the vegetation between animals and observers. Both opossums started to make loud noises (resembling suction with saliva) for approximately 3 minutes. Then they went to a nearby branch, 4 cm in diameter, which was 1.8 m above the ground. They suspended themselves up side down by wrapping their tails around the branch. The tail was their only support, and there was nothing between them and the ground. The male grabbed