The ecology of a unique marsupial - mistletoe interaction

AMICO, GC; RIVAROLA, MD; CARLO, T; MORALES, JM

Mendoza, Argentina

Simposio; The 10 th International Mammalogical congress; 2009

The monito del monte (Dromiciops gliroides, Microbiotheriidae) is a nocturnal marsupial endemic to the northern portion of the temperate forests of southern South America. Monito del monte is an omnivorous species; however, during the summers consumes mainly fruits. It has been reported that this marsupial is the only animal involved in the dispersal of the mistletoe Tristerix corymbosus (Loranthaceae). The passage of mistletoe seeds through the marsupial´s gut is critical for germination. Dromiciops is a highly efficient disperser of the mistletoe’s seeds, depositing most of them on host branches. Recent theoretical work suggest that in animal dispersed plants, the spatial configuration of fruit bearing individuals can have strong effects on both the rate of fruit removal and on the scale and shape of dispersal kernels. To test these ideas, we explored how fruit removal by Dromiciops was related to the abundance of ripe fruits on focal plants and to neighborhood density. Furthermore, we looked at marsupial movements associated with resource abundance in the area. We selected 22 mistletoe plants for which ripe fruit abundance and removal was weekly recorded. In addition, we estimated mistletoe density around each focal plant within a 5 m radius. To determine the marsupial movements, we placed 50 traps in two grids (50x50 m). The traps were placed during four consecutive days per month from December to April 2009. Captured animals were fitted with pit tags and radio transmitters were placed to 28 individuals. These were followed during nights as well as during the day to register their movement. Fruit removal rate was associated with fruit abundance and to a lesser degree with neighborhood density. Dromiciops movements revealed strong site fidelity but we found occasional forays up to 150 meters in a night. We discuss the potential implications of Dromiciops behavior for mistletoe population dynamics.