A long term study of small mammal populations in a Brazilian agricultural landscape

Abstract

Long-term monitoring of small mammal populations is very important to understand the variations in temporal abundance on a large time scale, which are related to ecological, economic and epidemiological phenomena. The aim of this study is to monitor the populations of the marsupials Didelphis aurita and Philander frenatus and the rodents Nectomys squamipes, Akodon cursor and Oligorysomys nigripes in a locality of typical Brazilian rural landscape, Sumidouro Municipality, Rio de Janeiro State, Brazil. A mark-recapture study was conducted during five years. We analyzed the population dynamics, the reproduction and age structure of these species. Both marsupials presented higher population sizes in the end of wet period and beginning of the dry period, which can be explained by the seasonal reproduction which begins in the middle of the dry period and ends in the last months of the wet period. N. squamipes reproduced throughout the year but mostly during rainy periods, due to the close association of this rodent to resources found in the water. Higher survivorship and recruitment rates were in the end of the wet season. The rodent A. cursor had an opportunist reproduction, resulting in high turnover rates. Survivorship increased with the effects of the dry periods. O. nigripes showed a clear annual pattern of population cycle with peaks during the dry season. The rodents did not show potential to present outbreaks and become agricultural pests. The annual population cycles of O. nigripes and the unique peak of A. cursor population during five years highlight attention to their importance as wild reservoirs of the hantavirus disease. Their ecological characteristics associated to their opportunistic behavior make these species prone to be good reservoirs of zoonoses.

Population Ecology of Hantavirus Rodent Hosts in Southern Brazil

“…These population dynamics patterns agree with other studies on Sigmodontinae ecology in both Atlantic Forest landscape types, Mixed Ombrophilous Forest, 45,48,49 and Dense Ombrophilous Forest. 44,47,74,75 Hantavirus exhibited a seasonal pattern with higher prevalence in spring/summer, when population sizes were lower and both reproductive activity and numbers of adults were higher. This pattern was also witnessed for other hantavirus genotypes in North 52,56 and South America.…”

“…47,75 This low abundance and instability on O. nigripes populations may be playing an important role to keep JUQV-like at low frequency.…”

“…[40][41][42][43][44][45][46][47][48][49] Notwithstanding the great diversity of rodents in Brazil (about 240 species), 50,51 consequently providing a high potential for many new hantavirus hosts, no studies have considered the infection dynamics. Population ecology studies are crucial for understanding the temporal patterns of infection in host populations and furnishing data on epidemiology, outbreak prediction, and risk of human infection.…”

The Role of Wild Rodents in the Transmission of Schistosoma mansoni in Brazil

“…Human populations were also diagnosed and treated. With this design, we obtained results that have enabled us to raise the small mammal fauna of the area (D'Andrea et al, 1999), understand the pattern of population dynamics of the water-rat (Bonecker et al, 2009;D'Andrea et al 2007;Gentile et al 2000) and its habitat use (Gentile & Fernandez 1999), understand aspects of the relationship between S. mansoni and N. squamipes Gentile et al, 2006), and adapt procedures and techniques to local particularities. In Pamparrão, which is a low endemicity area, the population dynamic study of the waterrat showed that it reproduced throughout the year, predominantly during the rainy periods.…”

“…In the Encanto locality, where schistosomiasis present at a medium endemicity, another phase of the study was conducted over four years to evaluate the effects of chemotherapy treatment in the infected human population on the rate of rodent infection and to compare diagnostic methods. During this phase, we also studied the population dynamics of the rodent N. squamipes, the infection rate of schistosomiasis on the water-rat populations and its change over time, and different methods for S. mansoni diagnosis (Bonecker et al, 2009;Gentile et al, 2006). The population dynamics of N. squamipes were in accordance with other studies and with the Pamparrão study, where the reproduction of the animals occurred throughout the year but primarily during rainy periods, a trend that is related to the close association of this rodent to resources found in water (Ernest & Mares, 1986;Gentile et al, 2000).…”