Javier A. Pereira

Time Partitioning Favors the Coexistence of Sympatric Crab-Eating Foxes (Cerdocyon thous) and Pampas Foxes (Lycalopex gymnocercus)

Abstract Crab-eating foxes (Cerdocyon thous) and pampas foxes (Lycalopex gymnocercus) are very similar in body size and food habits, with distributional ranges that overlap extensively in South America. We used camera-trap records of both species obtained at the Iberá Nature Reserve (INR), northeastern Argentina, to test the hypothesis that, when living in sympatry, they reduce competition by using different habitats and by being active at different times. Camera-trap records obtained at 2 additional sites inhabited by only 1 of these species, the Atlantic Forest of Misiones (AF) and Lihué Calel National Park (LCNP), were used to determine the activity patterns of these foxes when living alone. At INR, we set 41 camera-trap stations in 2 habitats (shrubland forest and flooded grassland), and in 2 treatments per habitat (with or without cattle). Three stations also were set in gallery forests. We obtained 540 photographs of crab-eating foxes (289 records) and 175 photographs of pampas foxes (115 records) in 1,521 camera-trap days. At LCNP, 27 camera-trap stations (1,002 camera-trap days) provided 109 records of pampas foxes. At AF, 195 camera-trap stations (11,689 camera-trap days) provided 103 records of crab-eating foxes. At INR, crab-eating foxes were more frequently recorded in forest habitats, whereas pampas foxes preferred opened grasslands. However, both species were found in all habitats and their recording rates were not negatively correlated. At INR, crab-eating foxes were nocturnal, with peaks of activity after dusk and before dawn, a pattern similar to that observed at AF and elsewhere. At INR, pampas foxes showed a peak of activity between 0000 and 0400 h and another between 1000 and 1300 h, a pattern that differed from that observed at LCNP and other places, where the species is mostly nocturnal. At INR, pampas foxes reduced their activity at times when activity of presumably dominant crab-eating foxes was high, which may facilitate their coexistence.

Numerical and Spatial Responses of Geoffroy's Cat (Oncifelis geoffroyi) to Prey Decline in Argentina

Abstract We examined the numerical and spatial responses of Geoffroys cats (Oncifelis geoffroyi) to a prey decline in central Argentina between April 2002 and November 2003. The 2nd year of the study coincided with a severe drought. Relative abundance of brown hares (Lepus europaeus) declined from 5.6 individuals/10 km during the predrought period to about 0.6 individuals/10 km during the drought. Small-rodent biomass also showed the lowest level for the study area during the drought of 2002–2003 (134.5 g/ha). During the predrought and drought periods, 3 male and 1 female, and 1 male and 9 female Geoffroys cats, respectively, were radiotagged and monitored. Home ranges for males of the predrought period averaged 202.8 ha ± 156.8 SD and that of the single female was 27.3 ha. During the drought period, 4 females occupied an average home range of 254.9 ± 254.1 ha, and the home-range size of the single predrought female increased by a factor of 2. No obvious change in mean daily distance traveled between the 2 periods was observed. Geoffroys cats predominantly used habitats of dense cover during the predrought period, but they became more habitat generalists during the drought. Recruitment of juveniles was only recorded during the predrought period, and all monitored Geoffroys cats dispersed or died of starvation after the prey decline. Consequently, density of Geoffroys cats dropped from 2.9 individuals/10 km2 before the drought to 0.3 individuals/10 km2, probably because of food scarcity. This is the 1st study to examine the spatial ecology of a small wild cat species under nutritional (energetic) stress in South America.

EXPOSURE TO SELECTED PATHOGENS IN GEOFFROY’S CATS AND DOMESTIC CARNIVORES FROM CENTRAL ARGENTINA

Wild carnivores share a high percentage of parasites and viruses with closely related domestic carnivores. Because of increased overlap and potential contact with domestic species, we conducted a retrospective serosurvey for 11 common carnivore pathogens in 40 Geoffroy’s cats (Leopardus geoffroyi) sampled between 2000 and 2008 within or near two protected areas in central Argentina (Lihué Calel National Park, La Pampa, and Campos del Tuyú National Park, Buenos Aires), as well as five domestic cats and 11 domestic dogs from cattle ranches adjacent to Lihué Calel Park. Geoffroy’s cats had detectable antibody to canine distemper virus (CDV), feline calicivirus (FCV), feline coronavirus, feline panleukopenia virus (FPV), Toxoplasma gondii, Leptospira interrogans (serovars Ictero/Icter and Ballum), and Dirofilaria immitis. None of the wild cats had antibodies to feline herpesvirus, feline immunodeficiency virus (FIV), feline leukemia virus, or rabies virus. Domestic dogs had antibodies to CDV, canine adenovirus, canine herpesvirus, and canine parvovirus. Antibodies to FPV, FCV, FIV, and T. gondii were found in domestic cats. We provide the first data on exposure of free-ranging Geoffroy’s cats to pathogens at two sites within the core area of the species distribution range, including the first report of antibodies to CDV in this species. We encourage continued monitoring for diseases in wild and domestic carnivores as well as preventive health care for domestic animals, particularly in park buffer zones where overlap is greatest.

Mammalia, Didelphimorphia, Chiroptera, and Rodentia, Parque Nacional Chaco and Capitán Solari, Chaco Province, Argentina

We studied the small mammal assemblage (bats, marsupials and rodents) of Parque Nacional Chaco and Capitan Solari (Chaco Province, Argentina) based on captures and analysis of owl pellets. Twenty-one species were recorded during a brief survey, including two marsupials, seven bats, and twelve rodents. In addition, we documented the first occurrence of the bat Lasiurus ega in the Chaco Province, and extended to the southwest the distribution of the didelphid marsupial Cryptonanus chacoensis and the oryzomyine rodent Oecomys sp. We also provided a second occurrence site in the ents Calomys laucha and Holochilus brasiliensis . Identified taxa belonged to species that are typical of the Humid Chaco ecoregion of Argentina.

Habitat-specific demography and conservation of Geoffroy's cats in a human-dominated landscape

Abstract The understanding of the spatial structure and dynamics of populations can guide conservation decisions, but studies of this type focused on small (< 7-kg) carnivores are rare. We compared survival, reproduction, and dispersal of radiocollared Geoffroys cats (Leopardus geoffroyi) in a protected area and adjacent cattle ranches in Argentina to assess the effects of livestock management and its associated disturbances (i.e., hunting by humans) on the demography of this felid. Thirteen cats in the park and 13 in the ranches were radiotracked for up to 556 days in 2007–2008. We evaluated the Geoffroys cat population trajectory at the landscape level using a stage-structured, stochastic matrix model based on our estimated vital rates. The study occurred during a prolonged drought, likely affecting estimated vital rates. Survival in the ranches was 52% lower than in the park; mortalities were due to intraguild predation in the park and were human-related in the ranches. Dispersal from the ranches was 32% lower than from the park and dispersal distances were up to 128 km. The number of cubs per litter was similar between areas. Assuming persistence of drought conditions and estimated vital rates, the simulated metapopulation rapidly collapsed and cat survival on ranches was the vital rate to which the model was most sensitive. Because projected climatic scenarios predict increased drought frequency for the region, we explored management options that would enhance chances of persistence, simulating 2 “adaptation” strategies: hunting restrictions on ranches and expanding protected areas. More than doubling of cat survival on ranches or a 9-fold increase in protected area extension would be required, involving major investments, to avoid the extinction of this cat metapopulation if droughts become prevalent. Our analysis may be helpful to improve our predictive capacity to identify new threats and facilitate adaptation strategies for Geoffroys cat or other similar carnivores. Resumen La comprensión de la estructura espacial y la dinámica de las poblaciones pueden guiar decisiones de conservación, pero los estudios de este tipo centrados en pequeños carnívoros (< 7 kg) son raros. Se comparó la supervivencia, reproducción y dispersión de gatos monteses (Leopardus geoffroyi) equipados con radiocollar en una zona protegida y campos ganaderos adyacentes en Argentina, para evaluar los efectos del manejo ganadero y sus disturbios asociados (p.e., la cacería) sobre la demografía de este felino. Trece gatos en el parque y 13 en los campos fueron monitoreados por hasta 556 días durante 2007–2008. Se simuló la trayectoria de la población monitoreada a nivel del paisaje utilizando un modelo matricial estocástico estructurado por edades, basado en las tasas vitales estimadas. El estudio tuvo lugar durante una sequía prolongada, lo que probablemente afectó las tasas vitales estimadas. La supervivencia de los gatos en los campos fue 52% menor que en el parque; la mortalidad se debió a depredación intragremio en el parque y estuvo mayormente relacionada al hombre en los campos. La dispersión desde los campos fue 32% menor que desde el parque y las distancias de dispersión fueron de hasta 128 km. El número de crías por camada fue similar entre áreas. Asumiendo la persistencia de la sequía prolongada y las tasas vitales estimadas, la metapoblación simulada declinó rápidamente, siendo la supervivencia de los gatos en los campos la tasa vital más sensible para el modelo. Dado que los escenarios climáticos proyectados predicen una mayor frecuencia de sequías para la región, se exploraron opciones de manejo para mejorar las posibilidades de persistencia de esta población, simulando dos “estrategias de adaptación”: restricciones de cacería en los campos y ampliación del área protegida en el paisaje estudiado. Para evitar la extinción de esta metapoblación si las sequías se hacen frecuentes, sería necesario incrementar a más del doble la supervivencia de los gatos en los campos o aumentar 9 veces la extensión de superficie protegida en el paisaje, lo que implica importantes inversiones de manejo. Nuestro análisis puede ser útil para mejorar la capacidad de predicción en la identificación de nuevas amenazas y para facilitar estrategias de adaptación para el gato montés u otros carnívoros similares.

Trophic interactions among plains vizcacha (Lagostomus maximus), greater rhea (Rhea americana), and cattle in a wetland of the Paraná River Delta Region, Argentina.

The plains vizcacha (Lagostomus maximus) and the greater rhea (Rhea americana) are considered to compete for forage with cattle in agroecosystems of South America. The aims of this research were to analyze the diet diversity and the trophic niche breadth of these three herbivores where they share a wetland area in Argentina, and to assess the extent of food niche overlap throughout the year. The three species all showed relatively narrow trophic niches in all seasons, which defines them as selective feeders. Vizcacha and cattle showed the highest (54.8%) mean food niche overlap throughout the year. A low overlap was observed between greater rhea and the other two herbivores, except in Winter (61.2% greater rhea and cattle). Vizcacha showed the highest mean diet diversity, and diet diversity was similar, but lower, in greater rhea and cattle. According to the results, if livestock raising increases and a scenario of competition is considered, the vizcacha is likely be the most affected species, because its foraging areas are restricted to the surroundings of its fixed burrows. On the other hand, greater rheas have an opportunistic foraging behavior and can move into areas where cattle are absent.

Spatial organization and social dynamics of Geoffroy’s cat in the Brazilian pampas

Geoffroys cat (Leopardus geoffroyi) is a small Neotropical felid whose social behavior remains poorly understood. We used simultaneous radiotelemetry (4 males and 3 females) and camera trapping to examine the spatial structure and dynamics of a population of this species in the Brazilian pampas (part of the Uruguayan Savannah ecoregion), including assessment of interindividual genetic relatedness. Home ranges (HRs) and core areas of males were larger than those of females. Males were significantly heavier than females, and linear regression analyses indicated that body mass of males significantly influenced HR size, whereas the relationship was not significant for females. When we performed a joint analysis comparing our data to those reported previously for other study sites, we observed the same patterns. We detected extensive HR and core area overlap among most of our monitored individuals, with no clear sex-based pattern. Moreover, our molecular data indicated that most of the sampled individuals were unrelated, and that the levels of HR and core area overlap were not significantly influenced by genetic relatedness. These results suggest that some interindividual tolerance and relaxation in territoriality may occur in Geoffroys cat. We detected only minor changes in HR and core area size and overlap between seasons, indicating that the spatial structure we observed was temporally stable. On a broader perspective, our cross-site comparisons illustrate the usefulness of performing multiple ecological studies employing comparable methods at different locations to better understand the ecology of wild felid populations.

Determinants of capybara presence in afforestations of the lower delta of the Paraná river, Argentina

The delta of the Paraná River in Argentina represents the southernmost stronghold for capybaras (Hydrochoerus hydrochaeris), but this area is highly modified due to commercial afforestations with Salicaceae. Water management (e.g. drainage of marshes) and land protections (e.g. polders) are carried out to improve field conditions for developing afforestations. To assess determinants of capybara presence within polder afforestations, its presence was surveyed in 2011–2013 along with 35 habitat and human-related variables at two spatial scales, in 53 watercourse-side sites. Using logistic regression, a habitat model was developed. Capybaras were present in 52.8% of sites. Water depth at the center of the watercourse had the strongest positive effect on capybara presence, followed by cover of reed marshes and cover of grass bush on the banks. Cover of adult poplar plantations showed a significant negative effect on capybara presence. Watercourses within polder afforestations can provide habitat for capybaras, although their use by these rodents depends on factors interacting at different scales.