Seleção de microhabitat por pequenos mamíferos em fragmentos florestais no município de Cerro Largo - Rio Grande do Sul

Abstract

Microhabitat variables consist of environmental characteristics that affect, directly or indirectly, the individual's movement behavior, and therefore determine which parts of the home range will be more intensely used. This study investigates the microhabitat chosen by four small mammals species (Akodon montensis, Oligoryzomys flavescens, Oryzomys sp. and Didelphis albiventris) in two forest fragments of Cerro Largo – state of the Rio Grande do Sul, Brazil. The small mammals were captured in live traps (Sherman and Tomahawk) disposed during ten consecutive nights, seasonally, from April 2015 to July 2016. In each trap season, 42 trap points were instaled, with two traps in each point , totaling an effort of 4480 traps night. In the same trap points, thirteen variables related to microhabitat were measured: soil cover, which could be leaf litter, rocks, herbaceous vegetation and uncovered soil; vegetation structure between the ground until 50cm high; vegetation structure between 50cm to 100cm high; vegetation structure between 100cm to 150cm high; number of trees (separated into three subcategories considering the Perimeter at Breast Height (PBH): PBH 10-30cm; PBH 30-60cm and PBH +60cm); canopy high; canopy cover and fruits. Some of the variables they was collected, show a high correlation values, and were grouped using a Principal Component Analises or between a avarage. A Generalized Linear Model, with Poisson distribution was performed with this nine remaining variables and the abundance of the four species at each trap point. The analyses indicated that Akodon montensis is positively influenced by fruits, trees with PBH +60cm, vegetation structure, and PC2, which means positively influenced by herbaceous vegetation e negative by rocks, and presented a negative influenced by canopy cover. Oligoryzomys flavescens presented a positively influenced just by vegetation structure, and a negative influenced by trees with PBH between 30 to 60cm and the PC1, which means positive relation with rocks and negative relation with herbaceous vegetation. Oryzomys presented a positive influenced by vegetation structure and fruits, and a negative influence by trees with PBH between 10 to 30cm and the PC1, which means they positive selected places with high litter availability. Didelphis albiventris presented positive relation with fruits and trees with PBH between 30 to 60cm. Is possible infer that due to the differences presented between the species, regarding the use of microhabitat, the same presented a segregation in the spatial resource partition , with probably is a better alternative than competing for them.