Uso do espaço vertical por marsupiais (Didelphimorphia: Mammalia) através da utilização de ninhos artificiais em um fragmento de floresta atlântica

Abstract

Different sampling methods have been developed to analyze space use and vertical stratification by mammals. The artificial nesting technique allows the analysis of the activities and use of these refuges by animals without influencing their behavior. In this study, the use of vertical space by marsupials was characterized by the use of artificial nests in an area of the Atlantic Forest in Sergipe, Northeastern Brazil. This study also presented unprecedented data on the use of plant resources in the construction of these nests. Sampling was realized at two sampling sites, with 60 capture stations/site arranged with two artificial nests at 1.5 m and 3 m high. The nests were monitored biweekly between April/2022 and May/2023. The formats of the occupied shelters were defined in terms of the organization of the plant material. Differences in records between the vertical strata of each species and between the strata and species were tested. Vertical segregation was measured using the niche overlap. The relationship between precipitation and the number of occupied nests/month, as well as the relationship between the animal's body size and the area of the shelter constructed, was investigated. The variation in the number of shelters built among the four types (cocoon, shell, few leaves, and vertical leaves) for each species was evaluated. In some cases, green leaves were recorded from 125 shelters with dry leaves. Only 24 nests were occupied (19.2%), one of which had two sub-adult individuals of Marmosa murina. Marmosa demerarae was more frequent at 3.0 m while M. murina did not differ in the use of strata. The frequency of nests records between the strata differed among these species. A high niche overlap was recorded (0.834). Leaves belonging to the families Rubiaceae (in 100% of the nests), Melastomataceae, Phyllanthaceae, and Erythroxylaceae were identified. There were no differences between the different types of shelters built by the species. There was no relationship between monthly nest occupancy and precipitation or between the animal's body size and the built area. In general, M. demerarae and M. murina use artificial nests in the two selected strata and build shelters with preferably dry leaves. Furthermore, the use of leaves corroborates with other studies that indicate the use of plant material by these animals. However, there appear to be no specific selection criteria with for the random use of leaves from the ground. The record of M. murina individuals in the same nest may indicate early formation of pairs or cooperative construction to increase protection. The use of Rubiaceae leaves in all shelters may be related to their wide representation of the location. The construction of the “cocoon” shelter by M. murina suggests increased protection against predators, whereas M. demerarae appears to have used its shelters more than once. Field observations indicated that shell-type shelters and with few leaves at the bottom corresponded to the initial formation of the cocoon-type nest construction process. These results contribute to increasing knowledge on the marsupials of Sergipe, and this is the first study to characterize the composition of the plant material used in these animal shelters.