Cock-tailed Tyrant Alectrurus tricolor (Vieillot, 1816), a Vulnerable South American grassland specialist, is facing substantial habitat loss due to land-use change by agricultural and forestry expansion. This study aims to assess the current distribution and suitable habitat availability for Cock-tailed Tyrant using species distribution modelling (SDM) and recent distributional data from the Global Biodiversity Information Facility (GBIF). Occurrence data from 1,583 records, mapped by season and habitat type, were used to generate a MaxEnt model with a high predictive accuracy (AUC = 0.974). Results revealed three main distributional clusters: one in Brazil, another spanning Mato Grosso do Sul, Paraguay and north-eastern Argentina, and a separate group in the Bolivian lowlands. Seasonal analysis found no significant distributional shifts, supporting previous findings of the species’ non-migratory behaviour. Key environmental contributors to habitat suitability included ecoregion type, precipitation, and vapour pressure. The predicted suitable habitat covers approximately 177,753 km². These findings underscore the urgent need for conservation efforts focusing on critical grassland habitats, particularly within the Cerrado, Southern Cone Mesopotamian grasslands, and Beni savanna biomes. Sustainable land-use practices, grassland restoration, and periodic habitat reassessments are essential to preserve Cock-tailed Tyrant populations and support the biodiversity of South American grasslands.

Grasshoppers are one of the most predominant insects in the grasslands of the southern Pampas. In this region, Dichroplus elongatus, Dichroplus maculipennis, Dichroplus pratensis and Borellia bruneri are the most abundant species and have the greatest economic importance. This study aimed to assess the relationship between temporal changes in the density of these species and climate variables associated with temperature and rainfall over an 11-year study period., We monitored 22 sites in different areas of Laprida county from 2005 to 2016. A total of 25 grasshopper species were collected. The most abundant species were D. maculipennis and B. bruneri which reached the highest densities from 2008–2009 to 2010–2011. The rainfall accumulated from September (RAS) to the sampling date and the number of rainy days (RD) largely explained the density variation of B. bruneri. Besides RD and RAS, winter rainfall, rainfall accumulated from October to the sampling date, and thermal amplitude of October (TAO) influenced the density of D. maculipennis. Our results indicated that seasons with less rainfall and fewer RD favored these two species’ abundance. We identified that the RD and TAO contributed significantly to variations in the density of D. elongatus. In contrast to the other two species, we recorded D. elongatus in seasons with high rainfall and high RD. A better understanding of the climate influence on the life cycle of these economically important insects may identify key factors in their population dynamics which in turn may improve management options.

Phosphorus uptake by grass species from natural South American grasslands can change depending on root and leaf attributes capable of determining higher, or lower, relative growth rate. The aim of the current study is to investigate whether leaf and root attributes capable of determining leaf and root area production in native C4 grass species Axonopus affinis and Andropogon lateralis are related to higher relative growth rate (RGR), P uptake capacity (maximum P influx; Imax) and concentration. Species grown in 2-litre pots with added nutrition solution were subjected to two treatments, namely 5 μM P l−1 and 30 μM P l−1. Solution aliquots (10 ml) were collected for 30 hours at the end of the study to determine P concentrations. RGR was 3.6 and 2.8 times higher in A. affinis than in A. lateralis in treatments with 5 μM P and 30 μM P. Axonopus affinis recorded the highest P concentration in leaf tissue. This outcome was associated with Imax 85% higher in A. affinis. High RGR was associated with larger leaf and root surface area per dry mass unit, as well as with high P influx capacity and with higher affinity transporters. These species often prevail in areas accounting for greater natural fertility and are more responsive to phosphate fertilization.

Production and endoparasitism of first grazing season Holstein heifers and steers were investigated over two grazing seasons. Studies were conducted on low-lying peaty soil. In year 2000, 40 animals were included in a 2×2 factorial, replicated experiment with two sexes (steers v. heifers) and two stocking rates (SR): normal v. low (840 v. 420 kg live weight per ha at turn-out) in a set stocking grazing system. Mean grass heights over the entire season were 6·3±4·8 cm (mean±s.d.) at normal SR and 9·8±6·1 cm at low SR. Mean daily live-weight gain during grazing was significantly (P<0·001) lower at normal SR (256±147 g) compared with low (468±142 g) but sex did not significantly affect the daily gain. Serum pepsinogen levels, indicating uptake of gastric nematodes, were higher at normal SR and consistently higher in steers compared with heifers, although not significantly. In 2001 the experiment included 80 animals in a 2×2 factorial experiment with two sexes (steers v. heifers), two grazing systems (set stocking and two-paddock rotation) and four replicates. Pasture quality was low, 570 g digestible organic matter per kg organic matter and 139 g crude protein per kg dry matter on average, independent of grazing system. Mean daily live-weight gain was not significantly affected by grazing system. A tendency (P=0·07) to lower daily gain for the heifers than for steers was observed (427±161 g v. 474±138 g). Lower levels of pasture contamination with parasites were observed in the paddocks without grazing up to mid July but otherwise rotation did not prevent parasite infections. It is concluded that first grazing season steers and heifers have the same potential for growth when grazing marginal areas with low pasture quality. Set stocking or the two-paddock rotation scheme did not affect productivity or level of parasite infection at the end of season. Parasite infections became a problem at high SR. SR is an important factor for both daily live-weight gain per animal and total production per ha. However, due to the very heterogeneous structure of marginal areas there is a need for other indicators than kg live weight per ha at turn-out in order to define a clear relationship between stocking rate and production.

As part of a study on the ecological strategies related to adaptation to the subterranean habitat of genus Ctenomys (tuco-tucos), a natural population of C. talarum was live-trapped at Necochea (Buenos Aires Province, Argentina) with the aim of providing information on its population ecology. Population size was consistently low throughout the study and was related to the low habitat productivity. Mortality rates were low, although for juveniles the estimations were higher than for adults. Individuals have an average life expectancy of 22-25 months, but some individuals lived at least three years. Reproductive activity started by July and ended by March, when last known pregnancies were recorded. This long reproductive season allowed a gradual incorporation of young over an extended period of time, with a restricted period of recruitment lacking. Sex ratio did not depart from 1:1 and appears to be density dependent. The spatial distribution of individuals was clumped and corresponded to the patchy distribution of suitable habitats. The results are compared and contrasted with those from previous demographic studies performed in other conspecifics as well as in other subterranean rodents.