Abstract
The Pantanal is a South American biome characterized by extensive plains and stark environmental seasonality. Several habitats are subject to annual flooding, forcing small mammal species to aggregate in dry forest patches, which most likely influences their population dynamics and life history strategies. In order to investigate the seasonal influence on the life history traits of these small mammals, we conducted a 2-year mark-recapture study in the southeastern region of the Brazilian Pantanal (Nhecolândia) and analyzed the population dynamics of the most abundant small mammal species with the jackknife estimator. A trapping effort of 21,560 trap-nights resulted in 615 individuals in 1,171 captures (success = 5.43%). Three species of rodents - Oecomys mamorae (Thomas, 1906), Thrichomys pachyurus (Wagner, 1845), and Clyomys laticeps (Thomas, 1841) - and three species of marsupials - Gracilinanus agilis (Burmeister, 1854), Thylamys macrurus (Olfers, 1818), and Monodelphis domestica (Wagner, 1842) - were obtained. The most abundant species was O. mamorae, followed by G. agilis and T. pachyurus. Oecomys mamorae was more abundant in the wet season and presented an opportunistic reproductive strategy. Gracilianus agilis displayed increased population sizes in the dry season and synchronized, seasonal reproduction during the rainy season. Thrichomys pachyurus had a small population size, delayed response to variations in environmental conditions and higher reproductive rates in the dry season. All species revealed different life history strategies (seasonal, opportunistic or delayed response to environmental variations), coinciding with periods of higher resource availability in order to maximize survival.
Highlights
The Pantanal is a vast, flat wetland located in central South America, composed of a mosaic of habitats
Studies conducted in markedly seasonal habitats such as the Venezuelan Llanos (AUGUST 1983, 1984, VIVAS & CALERO 1985, 1988, VIVAS 1986, SORIANO & CLULOW 1988, O’CONNELL 1989), the Cerrado gallery forests (MARES & ERNEST 1995, VIEIRA 1997) and the Poconé Pantanal (ARAGONA & MARINHO-FILHO 2009) have confirmed that small mammal populations are influenced by seasonal dynamics
The three most abundant species had population dynamics influenced by the seasonality of the Pantanal, each in different ways
Summary
The Pantanal is a vast, flat wetland located in central South America, composed of a mosaic of habitats. The region is subject to annual, summer flooding, during which much of the Pantanal becomes inundated (ADÁMOLI 1987), confining animals to small areas (KEUROGHLIAN et al 2009) This pattern has several consequences for the local fauna related to habitat and resource availability. Reproduction of most species begins at the end of the dry season and is intensified during the wet season in the northern Pantanal (ARAGONA & MARINHO-FILHO 2009). This region displays several features strongly associated to Cerrado physiognomies, featuring drier areas in comparison to the southeast Pantanal (ADÁMOLI 1987)
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