Necromys lasiurus: Lessons From a 38-Year Study in an Amazonian Savanna

Abstract

Amazonian savannas are isolated patches of open habitats within an array of extensive tropical forest. The mammal fauna of the savannas in the Alter do Chão region (Santarém Municipality), is dominated by Necromys lasiurus, whose populations have been studied by researchers of the National Institute of Amazonian Research since 1983. Here, we summarize the studies and advances made so far to better understand aspects related to population dynamics and ecology of savanna rodents and the strategies they use to persist in an environment with frequent fires subject to global climatic influences. In the Amazonian savannas the species acts as a seed disperser and population fluctuations are related to invertebrate availability, but not with fire or vegetation structure. Global climate appears to affect N. lasiurus population dynamics at local scale (i.e., plot scale) but not at the regional scale of the Alter do Chão savannas. The long-term studies in Alter do Chão generated many advances about Necromys lasiurus population dynamics and ecology, including aspects relating to feeding, home range, animal-plant interactions, the effects of fire and climate change.

Life history variation of the Hairy-tailed Akodont (Necromys lasiurus, Rodentia, Sigmodontinae) in the Caatinga biome of northeastern Brazil

“…Conversely, low proportions of pregnant females were observed when population numbers were near their maximum. This pattern has been observed in other biomes—pregnant females are more common during the rainy season and population size is greatest during the dry season (Carmignotto et al 2014; Rocha et al 2017; Rosa et al 2021). While pregnancy in N. lasiurus has been recorded in both the dry season (Becker et al 2007) and wet season (Dietz 1983; Francisco et al 1995), it is most common during the wet season.…”

“…In general, there were fewer individuals in the wet season and more during the dry season. An increase in population size during the dry season is common both in the Cerrado (Carmignotto et al 2014; Rocha et al 2017) and in the Amazonian Savanna (Francisco et al 1995; Layme et al 2004; Rosa et al 2021).…”

“…These results are surprising because postpartum estrus has been observed in N. lasiurus (Hingst 1995) and because 90% of pregnant females were found in 1 month in the Amazonian Savanna (Francisco et al 1995). Rosa et al (2021:3) stated that N. lasiurus females are in a “perpetual cycle of gestation and lactation.” Interestingly, even though the study site used by Francisco et al (1995) and Rosa et al (2021) received more rainfall than any of our sites (>2,200 mm rainfall; Magnusson et al 2021), they reported strong reproductive seasonality.…”

“…This species is an important vector of several zoonoses, including bubonic plague (Tavares et al 2012) and Hantavirus (Figueiredo et al 2009)—its success as a disease reservoir has been attributed to its ability to utilize anthropogenic environments, its wide geographic distribution (Patton et al 2015), high densities (Vieira 1997; Becker et al 2007; Donalísio et al 2008; Talamoni et al 2008), and ability to shift food sources between seasons (Talamoni et al 2008). Although N. lasiurus is one of the most studied South American sigmodontine rodents (D'Elía et al 2008), particularly in the Amazonian Savanna (Magnusson et al 2021; Rosa et al 2021) and in the Cerrado (Becker et al 2007; Pires et al 2010), it has not been well studied within the Caatinga biome.…”

The relative importance of forest cover and patch-level drivers for phyllostomid bat communities in the Amazonian Savannas

“…The HAH has been tested in different anthropogenically fragmented landscapes (Melo et al 2017;Vieira et al 2018), but should also be expected to hold up for naturally patchy ecosystems, such as the Amazonian Savannas. The Amazonian Savannas are excellent natural laboratories for both ecological and conservation studies (e.g., Rosa et al 2021). They consist of highly heterogeneous landscapes, made up of different and highly contrasting habitat types (Mustin et al 2017), and as such they serve as excellent study areas to investigate the influence of landscape structure and composition, including forest cover, on different components of biodiversity (Bernard and Fenton 2007;Calle-Rendón et al 2020).…”