A Two-Year Ecological Study of Norway Rats (Rattus norvegicus) in a Brazilian Urban Slum

Abstract

The Norway or brown rat (Rattus norvegicus) is among the most ubiquitous of rodents. However, the lack of studies describing Norway rat populations from tropical areas have limited our understanding regarding their demography and seasonal dynamics. In this study, we describe seasonal pattern in the abundance, reproductive parameters, and morphometrics of Norway rat populations in Salvador, Brazil. Rodents were trapped over four seasonal trapping periods (2013–2014) from three valleys. A total of 802 Norway rats were trapped over the course of the study over 7653 trap-nights. Norway rat abundance was high, but there was no significant differences between seasons. The reproductive parameters (e.g. frequency of pregnant and lactating females) did not show statistical differences between seasons. Female rats collected in the rainy season were heavier and older than females from the dry season. Salvador rats had a high incidence of pregnancy and birth rate (estimated birth rate of 79 young per year) compared to previous studies. The information generated is critical for the understanding of the ecology of Norway rat, the main reservoir of Leptospira in Salvador. However, future studies examining the effect of rodent control programs aimed at reducing populations, and determining rates of recovery, will further clarify our understanding of population dynamics.

Synanthropic rodents as virus reservoirs and transmitters

“…Although little information is currently available on the size of the population of synanthropic rats, some indicators allow the subjective estimation of their presence, such as the presence of excrement, marks on walls, trails on the ground, food sources, or the visual observation of rodents and/or the damage caused by them [9][10][11] .…”

“…To evaluate the size of rodent populations, the concept of the 'minimum known number' is used 12 , where individuals have to be captured and recaptured to estimate the infestation rate. This statistical formula can be simplified by multiplying the number of animals caught in a trap in a single catch by 100 11,13 .…”

The helminth community of a population ofRattus norvegicusfrom an urban Brazilian slum and the threat of zoonotic diseases

“…During the necropsies, performed for purposes of a larger project on leptospirosis (Costa et al . 2015 b ; Panti-May et al . 2016), fecal samples were collected directly from the intestines and placed in 10% formalin for subsequent analysis.…”

“…2014 a ). However, we also estimated age in days [age(d)] using a statistical model derived from published age–weight growth curve for wild rats (Calhoun, 1962), as described by Panti-May et al . (2016) (see Supplementary Fig.…”

“…The Norway rat, Rattus norvegicus Berkenhout (1769), has been the most successful invasive mammalian species, exhibiting tolerance to a wide range of temperatures, a high reproductive rate and adaptability to rural and urban environmental modification (Long, 2003; Vadell et al . 2014; Panti-May et al . 2016; Puckett et al .…”