Emiliano Donadio

Diet, Morphology, and Interspecific Killing in Carnivora

Interspecific killing is a key determinant of the abundances and distributions of carnivores, their prey, and nonprey community members. Similarity of body size has been proposed to lead competitors to seek similar prey, which increases the likelihood of interference encounters, including lethal ones. We explored the influence of body size, diet, predatory habits, and taxonomic relatedness on interspecific killing. The frequency of attacks depends on differences in body size: at small and large differences, attacks are less likely to occur; at intermediate differences, killing interactions are frequent and related to diet overlap. Further, the importance of interspecific killing as a mortality factor in the victim population increases with an increase in body size differences between killers and victims. Carnivores highly adapted to kill vertebrate prey are more prone to killing interactions, usually with animals of similar predatory habits. Family‐level taxonomy influences killing interactions; carnivores tend to interact more with species in the same family than with species in different families. We conclude that although resource exploitation (diet), predatory habits, and taxonomy are influential in predisposing carnivores to attack each other, relative body size of the participants is overwhelmingly important. We discuss the implications of interspecific killing for body size and the dynamics of geographic ranges.

DIETS OF THREE SPECIES OF ANDEAN CARNIVORES IN HIGH-ALTITUDE DESERTS OF ARGENTINA

Abstract We present the 1st data on the diet of the Andean mountain cat (Leopardus jacobitus), and the 1st on the colocolo (Leopardus colocolo) and the culpeo (Lycalopex culpaeus) in high-altitude deserts of northern Argentina, based on fecal analysis. Feces of Andean mountain cats and colocolos were distinguished by DNA analysis. The Andean mountain cat (n = 57) was the most specialized, relying heavily on southern mountain vizcachas (Lagidium viscacia). The colocolo (n = 504) also was specialized, consuming mostly cricetine rodents and tuco-tucos (Ctenomys). The culpeo (n = 399) was a generalist, consuming all prey items that the cats used, and a greater variety of invertebrates. Short-tailed chinchillas (Chinchilla chinchilla) were found in 3 culpeo feces, indicating that this rodent, considered extinct in Argentina, is still present in the wild. Both southern mountain vizcachas and tuco-tucos have a patchy distribution, indicating that very large areas may be required to support populations of the cats that depend on these prey species.

Feeding ecology of the Andean hog-nosed skunk (Conepatus chinga) in areas under different land use in north-western Patagonia

Abstract We studied the feeding ecology of the Andean hog-nosed skunk ( Conepatus chinga ) in three areas with different land use in Patagonia. Two areas were heavily grazed by sheep or horses and wild exotic herbivores and the third area was lightly grazed by cattle. In each area, we assessed skunk diet, prey abundance and carrion availability. Skunks were generalist feeders, with invertebrates composing the bulk of their diet, but also consumed small vertebrates and carrion. Differences in diet composition were found among areas, mainly because skunks consumed more beetle larvae in the sheep area and more cricetines and spiders in the exotic-herbivore area. All prey but rodents were significantly more abundant in spring and summer than in fall and winter, but skunk diets were similar among seasons. In the sheep area, where the soil was most disturbed, we found reduced abundances of invertebrate prey and rodents. High consumption of beetles during autumn and winter when these were least abundant and in the sheep area indicates that skunks had a preference for beetles and their larvae. We conclude that Andean hog-nosed skunks in Patagonia might be negatively affected by reductions of their main prey due to soil and plant alterations by livestock.

Juvenile and adult mortality patterns in a vicuña (Vicugna vicugna) population

Abstract Neotropical ungulates are poorly understood with regard to age-specific mortality and how it relates to different mortality causes. During January 2008–April 2011, we investigated mortality patterns of calf (<1 year old) and adult vicuñas (Vicugna vicugna) in west-central Argentina. Specifically, we analyzed whether birth mass, birth date, and sex of radiomarked vicuña calves affected 1st-year survival; quantified cause of death for marked calves and unmarked adults; and explored how primary productivity and quality of forage and diet related to body condition of adult vicuña carcasses. Birth mass was a strong predictor of 1st-year survival: a 1-kg (∼18%) increase in birth mass resulted in a 54% decline in the risk of death. Further, low survival rate in 1 calendar year was associated with low mean birth mass during that year, but not with population density and forage quality in the previous year. Puma (Puma concolor) predation accounted for ≥49% (n = 93) and 91% (n = 89) of the mortality in calves and adults, respectively. Body condition of adult vicuñas killed by pumas varied seasonally and correlated with seasonal changes in primary productivity and forage and diet quality. Our results highlighted the importance of puma predation and low birth mass as proximate causes of vicuña mortality. How environmental factors (e.g., early summer precipitation) influence forage and ultimately mortality has yet to be determined. Resumen En ungulados Neotropicales, la relación entre la mortalidad especifica por edades y sus causas ha sido poco estudiada. Entre enero de 2008–abril 2011, investigamos los patrones de mortalidad de crías (<1 año de edad) y adultos de vicuñas (Vicugna vicugna) en el Parque Nacional San Guillermo, ubicado en los Andes centrales de Argentina. En este trabajo analizamos la relación entre el peso al nacer, la fecha de nacimiento y el sexo de las crías con la probabilidad de supervivencia durante el primer año de vida; cuantificamos las causas de muerte en crías y adultos; y exploramos la relación entre la productividad primaria, calidad del forraje y calidad de la dieta y el estado nutricional de las carcasas de vicuñas adultas. El peso al nacer fue un buen indicador de la supervivencia durante el primer año de vida: un incremento de 1-kg (∼18%) en el peso al nacer resultó en una declinación del 54% en el riesgo de muerte. Adicionalmente, un bajo promedio del peso al nacer en un año estuvo asociado con una baja tasa de supervivencia durante ese año, pero no con la densidad poblacional ni calidad del forraje en el año previo. La depredación por puma (Puma concolor) explicó ≥49% (n = 93) y 91% (n = 89) de la mortalidad en crías y adultos, respectivamente. La condición corporal de las vicuñas adultas cazadas por pumas varió estacionalmente. Este patrón estuvo asociado con cambios estacionales en la productividad primaria, la calidad del forraje y la calidad de la dieta en vicuñas. La influencia de factores ambientales (e.g., precipitación al inicio del verano) sobre el forraje y, en ultima instancia, la mortalidad todavía debe ser determinada.

Linking predation risk, ungulate antipredator responses, and patterns of vegetation in the high Andes

Whether large carnivores indirectly influence vegetation via prey behavior remains controversial because available evidence is largely correlational, and recent field experiments have found weak associations between risk experienced by prey and vegetative responses to herbivory. We combined observational data and a field experiment to test whether an ambush predator—the puma (Puma concolor)—affected the antipredator behavior of its primary ungulate prey—the vicuña (Vicugna vicugna)—which in turn had cascading effects on vegetation. We predicted that strong protective effects of pumas on vegetation would be most apparent in habitats where cover and terrain (i.e., physical complexity) facilitated the ambushing strategy of pumas. In 3 different habitats, we evaluated the relationships among predation risk, vicuña behavior, and—by deploying vicuña exclosures— vegetation structure and productivity. We also examined habitat-specific rates of vegetative regrowth. Risky habitats presented high physical complexity, a disproportionately large number of vicuñas killed by pumas, and high relative abundance of pumas. In these habitats, vicuñas displayed strong antipredator behaviors and exclosures did not affect vegetation, suggesting that pumas indirectly protected plants. Conversely, a safe habitat presented low structural complexity, a disproportionately low number of vicuñas killed by pumas, and low relative abundance of pumas. Here, vicuñas relaxed antipredator behaviors and exclosures had strong effects on vegetation. In 1 habitat deemed as risky, however, cascading effects were offset likely because water and nutrients were readily available to plants and regrowth was rapid. Our results show that large ambush carnivores can positively affect vegetation via nonconsumptive effects on their prey, and that these effects are habitat mediated. However, primary productivity modulated the strength of such effects, with high primary productivity dampening the observed cascading effects.

A method to estimate body mass and relative age of exotic lagomorphs in the southern Neotropics

Exotic prey species can dramatically alter trophic interactions by functionally replacing native prey species. This pattern has been observed in the southern Neotropics, where introduced haresLepus europaeus Pallas, 1778 and rabbitsOryctolagus cuniculus (Linnaeus, 1758) have become the staple prey for native predators. Despite their importance as prey, no data are available on the mass and relative age of the lagomorphs on which native predators feed. We used linear regression models to predict the mass of lagomorphs from their hind-foot length, and investigated the influence of sex, season, and collection site on this relationship. Hind-foot length was a good predictor of body mass for both species and accounted for 58.4 and 71.6% of the variability in body mass for hares and rabbits, respectively. Sex and season significantly influenced the relationship, whereas the effect of collection site was negligible. Hind-foot length was also a good predictor of age class for hares and rabbits, allowing the discrimination between nonreproductive and reproductive classes for both species. Future research can use this method to determine the biomass and age class of exotic lagomorphs consumed by predators.