Mónica I. Cona

Habitat use by guanacos (Lama guanicoe, Camelidae) in northern Patagonia (Mendoza, Argentina)

Strategies of habitat use of the guanaco were analyzed in early and late summer, when parturition and lactation increase nutritional needs and predation risk. The daily distribution of guanacos was followed by scan‐sampling, relief and soil were measured in each habitat, and vegetation was analyzed by the point‐quadrat method. Guanacos showed a selective habitat use, preferring open areas with grasslands, gentle terrain and low hiding cover. The density of guanacos was positively associated with the intensively eaten grass Panicum urvilleanum, and negatively associated with rocky soils, high shrublands and avoided plants. A weakening of the selective habitat use occurred when the abundance of guanacos increased in the study area during late summer, ceasing avoidance of poor and risky habitats.

Diet Selection by the Fossorial Rodent Ctenomys mendocinus Inhabiting an Environment with Low Food Availability (Mendoza, Argentina)

The seasonal diet of Ctenomys mendocinus was determined in a habitat of the Andean Precordillera, through microhistological analyses of stomach contents and in relation to food availability. Diet included 23 genera of plants and only 6 of them were consumed with frequencies higher than 4%. The grasses Stipa and Elymus comprised about 80% of the diet. A high proportion of aerial plant material was registered throughout the year suggesting a tendency to forage on the surface. Dietary selectivity was evidenced by a preferential consumption of grasses and avoidance of shrubs. Moreover, most dietary items frequently used were eaten in proportions that differed from their availabilities. This non-opportunistic feeding behavior, specialized in a few dietary items, did not agree with the one expected for a subterranean rodent inhabiting an environment with severe climatic conditions, low food availability and patchy distribution of food resources.

Management of Protected Areas and Its Effect on an Ecosystem Function: Removal of Prosopis flexuosa Seeds by Mammals in Argentinian Drylands

The ecological function of animal seed dispersal depends on species interactions and can be affected by drivers such as the management interventions applied to protected areas. This study was conducted in two protected areas in the Monte Desert: a fenced reserve with grazing exclusion and absence of large native mammals (the Man and Biosphere Ñacuñán Reserve; FR) and an unfenced reserve with low densities of large native and domestic animals (Ischigualasto Park; UFR). The study focuses on Prosopis flexuosa seed removal by different functional mammal groups: “seed predators”, “scatter-hoarders”, and “opportunistic frugivores”. Under both interventions, the relative contribution to seed removal by different functional mammal groups was assessed, as well as how these groups respond to habitat heterogeneity (i.e. vegetation structure) at different spatial scales. Camera traps were used to identify mammal species removing P. flexuosa seeds and to quantify seed removal; remote sensing data helped analyze habitat heterogeneity. In the FR, the major fruit removers were a seed predator (Graomys griseoflavus) and a scatter-hoarder (Microcavia asutralis). In the UFR, the main seed removers were the opportunistic frugivores (Lycalopex griseus and Dolichotis patagonum), who removed more seeds than the seed predator in the FR. The FR shows higher habitat homogeneity than the UFR, and functional groups respond differently to habitat heterogeneity at different spatial scales. In the FR, because large herbivores are locally extinct (e.g. Lama guanicoe) and domestic herbivores are excluded, important functions of large herbivores are missing, such as the maintenance of habitat heterogeneity, which provides habitats for medium-sized opportunistic frugivores with consequent improvement of quality and quantity of seed dispersal services. In the UFR, with low densities of large herbivores, probably one important ecosystem function this group performs is to increase habitat heterogeneity, allowing for the activity of medium-sized mammals who, behaving as opportunistic frugivores, did the most significant seed removal.

Seed removal by different functional mammal groups in a protected and grazed landscape of the Monte, Argentina

Fil: Miguel, Maria Florencia. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Aridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Aridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Aridas; Argentina

Dietary overlap of coexisting exotic brown hare (Lepus europaeus) and endemic mara (Dolichotis patagonum) in Northern Patagonia (Mendoza, Argentina)

Abstract Introduced brown hares are present across the distribution range of maras, which are endemic to Argentina’s open steppes. Food competition with exotic herbivores could be partially responsible for declines in mara populations. Diets of sympatric hares and maras were compared to detect dietary overlap according to food availability. Diets and availability were estimated using microhistological analysis and point-quadrat transects, over four seasons. Horn’s index estimated dietary overlap, Kruskal-Wallis ANOVA detected significant differences, and permutational multivariate analysis of variance (PerMANOVA) determined the multivariate response to factors. Grasses prevailed among available items and in both diets. Plant cover and richness increased in summer and forbs in spring. High dietary overlap decreased in autumn-winter, when hares ate more forbs and tall shrubs and less low shrubs than maras. Interspecific overlap was higher inside a protected area with higher food diversity, more forbs, and low shrubs. Both herbivores shifted to different foods as availability decreased. When forbs declined, they were less eaten by maras than hares. Broader habitat use allows hares to search for preferred forbs farther away than maras. The more adaptive hare could become a stronger competitor in impacted environments. Better food availability inside than outside the protected area is a feeding advantage for the coexistence of these herbivores.

Studying the quantity component of seed dispersal effectiveness from exclosure treatments and camera trapping

Abstract The quantity component of effectiveness of seed dispersal by animals is determined by two events: fruit removal (intensity of the interaction) and animal visitation to the plant (frequency of interactions). Considering dispersal of Prosopis flexuosa seeds as case study, this work aimed at investigating the strengths and weaknesses of the two methods for assessing the quantity component of seed dispersal effectiveness: exclosures and camera traps. Prosopis fruits were offered for 48 hr. Exclosure treatments were performed using two types of wire‐screen cages, allowing access to ants (“closed exclosure”) and to small mammals up to 100 g (“open to small mammals”), and a treatment without exclosure (“open to all removers”). The camera trapping experiment was carried out using vertically oriented cameras placed at approximately 1.80 m height and focused on the fruits. The cameras were set in “motion detect mode,” taking series of three consecutive photographs. The exclosures largely allowed estimation of fruit removal by size‐based groups of animals, but did not provide information on species identity. In contrast, camera traps were able to identify all visitors to species level and could not only determine the number of visits by each species but also the proportion of visits, which resulted in removal of fruits. Camera trapping allowed discriminating among small mammals playing different roles, without underestimating fruit removal by scatter‐hoarding species. The quality of estimation of the quantity component of seed dispersal is remarkably better when the camera trapping method is applied. Additional information obtained, such as activity patterns of visitors, can contribute to a better understanding of the seed dispersal process.