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.

Investigating non‐random assemblages emerging in response to environmental gradients is relevant to understand mechanisms and processes affecting biodiversity. Species may be filtered from fractions of environmental gradients that limit dispersal, survival or ontogenetic development, which ultimately leads to biotic complementarities among sites. Non‐random assemblages as a response to environmental filtering have been widely demonstrated in Amazonian forests, but are rarely assessed in non‐forest ecosystems such as macrophyte meadows covering lakes. In this study, we sampled 50 plots (50 m long, 6 m wide) along continuous macrophyte meadows in a lake system in the lower Amazon River. Our main goal is to test the effects of distance from the lake bank, macrophyte height and composition (frequency of morphotype occurrence), air temperature and physicochemical properties of water (pH, dissolved oxygen, depth and temperature) on frog α and β‐diversity estimates, and frequency of species traits occurrence (abundance‐weighted body size, toe pads, foot webbing and tadpole habit). We found 16 species, for which local assemblages quantified by α and β‐diversity estimates were not random, but predicted by macrophyte height, morphotype composition and water depth. We have explicitly shown that species are filtered from fractions of these gradients through ecomorphological relationships, since morphological traits and tadpole habits were also selected by the vertical stratification provided by the vegetation cover and water depth. Overall, we present an investigation of assemblage ecology that is relevant to conservation, because the results suggest biotic complementarities within habitats that are rarely considered as distinct biogeographic units from the surrounding várzea forests. Abstract in Portuguese is available with online material.

Ecological succession in tropical savannas is limited by seasonal fire, which affects habitat quality. Although fire may cause negligible or positive effects on animals occupying savannas, most short-term studies (months to a few years) are based on a single temporal sampling snapshot, and long-term studies (decades) are rare. We sampled four lizard species in Amazonian savannas to test the effects of fire and vegetation cover on lizard densities at two temporal scales. In the short-term, we use three sampling snapshots to test the effects of fire and vegetation cover on estimated lizard densities over the subsequent 1–5 years. In the long-term, we test the effects of fire and changes in vegetation cover over 21 years on current lizard density differences. In the short-term, species responses were usually consistent with foraging and thermoregulation modes. However, the results were not consistent among species and years, although the variances in species density explained by year as a random factor were generally low. In the long-term, the main effects of fire and vegetation cover show that lizard densities may change spatially, but not necessarily temporarily. Wildfire is a natural resource of savannas and apparently have little impact on resident lizards of that ecosystem.

We present a case of human intoxication due to a snakebite by the opisthoglyphous dipsadid Thamnodynastes lanei. A 26-year-old man was bitten on the right hand and was not medicated. Bleeding lasted a few seconds, while paresthesia, chills, and headache persisted for up to 10 hours. The pain disappeared after a week, and the edema, itching, and prickling persisted for another 3 days. Although this patient’s symptoms were typical of bites by South American opisthoglyphous snakes, they persisted longer than those of bites by some congeneric species. Our report adds a species to the list of medically relevant snakes.

No abstract