Jaime E. Jiménez

Invaders without frontiers: cross-border invasions of exotic mammals

We address cross-border mammal invasions between Chilean and Argentine Patagonia, providing a detailed history of the introductions, subsequent spread (and spread rate when documented), and current limits of mammal invasions. The eight species involved are the following: European hare (Lepus europaeus), European rabbit (Oryctolagus cuniculus), wild boar (Sus scrofa), and red deer (Cervus elaphus) were all introduced from Europe (Austria, France, Germany, and Spain) to either or both Chilean and Argentine Patagonia. American beaver (Castor canadensis) and muskrat (Ondatra zibethicus) were introduced from Canada to Argentine Tierra del Fuego Island (shared with Chile). The American mink (Mustela vison) apparently was brought from the United States of America to both Chilean and Argentine Patagonia, independently. The native grey fox (Pseudalopex griseus) was introduced from Chilean to Argentine Tierra del Fuego. Few spread rates are available: the lowest are 10 km/yr and correspond to American beaver and American mink; intermediate rates are observed in muskrat and rather questionably, in grey fox; the highest rates (10–20 km/yr) are found among European hare and European rabbit. Because of their frequent migration, it is difficult to estimate the natural spread rate for wild boar and red deer. Not all mammal invasions in Chilean and Argentine Patagonia have been methodical advances of species; some involve an overlap of invasion fronts, with advances and retreats, and perhaps with re-invasions to different areas of either country. Because national policies with regard to introduced species may differ between countries sharing porous borders, it seems advisable to coordinate such policies in order to prevent the entry of unwelcome invaders.

EFFECT OF SAMPLE SIZE, PLOT SIZE, AND COUNTING TIME ON ESTIMATES OF AVIAN DIVERSITY AND ABUNDANCE IN A CHILEAN RAINFOREST

Abstract The bird assemblage of a southern temperate rainforest on Chiloé Island, southern Chile, was studied during the breeding season of 1993–1994. The modified variable-circular plot method was used to examine the effects on the estimated overall density and species richness of birds when the size of the plot, duration at the plot, and number of plots were varied, one variable at a time. A total of 459 individuals of 24 species was recorded on 18 plots sampled for a maximum of 10 min with unlimited distance. When increasing either the plot size, sampling length, or number of plots, the number of species detected increased at a decreasing rate, but without reaching an asymptote. The estimated density decreased with increasing plot size, increased with sampling length, and did not change with increasing plot number. However, the precision substantially improved. Plots of 40-m radius counted for 10 min detected 78% of the species found in larger plots and rendered an overall bird density of 34 individuals/ha, almost twice as many as the only comparable study found. On average, more than 75% of all species detected were within 40 m of the observers, using a 4-min sampling period at five plots. The migrant omnivorous flycatcher Elaenia albiceps was the most abundant species (22% of total counts), followed by the hummingbird Sephanoides galeritus, the tapaculo Scelorchilus rubecola, the treecreeper Aphrastura spinicauda, and the parakeet Enicognathus ferrugineus. These species, which were the most common in other studies conducted in similar temperate South American forests, showed species-specific responses to changes in the sampling variables.

Seasonal food habits of the endangered long-tailed chinchilla (Chinchilla lanigera): the effect of precipitation

Summary Based on the content of feces, we studied the food habits of the endangered rodent Chinchilla lanigera . On a seasonal basis, during two years of contrasting rain levels (1992 = 242 mm; 1993 = 123 mm), we collected chinchilla feces from El Cuyano ravine, adjacent to the Chinchilla National Reserve in north central Chile (31° 29′ 10.8″ S, 71° 03′ 43.9″ W). The main plant species eaten was the perennial graminoid Nassella chilensis . Chinchillas showed a broader trophic niche during the rainy year, than during the dry year, consuming 55.5 and 40.7% of the 38 and 27 plants available, respectively. Within the wet year the diet differed less between winter and summer (Horn similarity index R 0 = 0.58) than within the dry year (R 0 = 0.83). Between years, the diet differed more during winters (R 0 = 0.20) than during summers (R 0 = 0.52). Chinchillas are folivorous, using a feeding pattern of a generalist species. The opportunistic feeding behavior of chinchillas may be an adaptation to the harsh conditions and high variability in food availability triggered by fluctuations in rainfall among years in the arid north central Chile.

Estación Biológica Senda Darwin: Investigación ecológica de largo plazo en la interfase ciencia-sociedad

This article discusses Senda Darwin Biological Station and the work of the scientists who study the anthropological role in ecological processes there.

Feeding habits of guanacos Lama guanicoe in the high Andes of North-Central Chile

The guanacoLama guanicoe Muller, 1776 has a wide distribution along the Andes and Patagonia. We studied the feeding behaviour of a guanaco population that lives over 4100 m altitude in the Andes of north-central Chile. By contrasting the diet of guanacos during a dry year with that of a wet year and comparing it with the plant availabilities in the field, we tested the hypothesis that the guanaco is a generalist herbivore. We predicted that under such extreme habitat conditions guanacos should consume whatever plant species are available in the environment, especially in a dry year, when vegetation is scarcer. In addition, we compared its diet at three different age classes. We estimated the diet through the microhistological analysis of plant remains found in guanaco pellets collected during January of 1997 (ie after a dry year) and 1998 (ie after a wet year; 41 vs 495 mm, respectively). Then, we computed dietary preferences, food niche-breadth, and food-niche overlap between years and among age classes. Vegetation cover and plant species richness were higher during the wet than during the dry year. The most common plants in the environment were perennial graminoids and legumes. Contrary to our prediction, the guanaco preferred a few plant species, showing a relatively narrow diet breadth that changed little between years differing in plant abundances. The diet proportions differed among the three age classes, however. Our data indicate that at least in this high-elevation population, guanacos are selective and non-opportunistic herbivores. This specialized feeding behaviour is puzzling given the energetic demands of living in a harsh environment with low availabilities of resources. The hypothesis that this is due to the lower palatability of the plants not eaten, remains to be tested.

The raptors of Torres del Paine National Park, Chile: biodiversity and conservation

Quince especies de rapaces (Falconiformes y Strigiformes) se reproducen y otras dos posiblemente se reproducen en el Parque Nacional Torres del Paine (Patagonia chilena), la mayor riqueza de especies de rapaces documentada hasta ahora en Chile. Entregamos descripciones de cada especie de rapaz en Torres del Paine, incluyendo informacion sobre peso, habitat, dieta, residencia, conservacion, y observaciones miscelaneas en el Parque. Comparamos la riqueza de especies de rapaces en Torres del Paine con aquella en localidades bien estudiadas del centro y norte de Chile, y especulamos sobre las causas de la mayor diversidad de rapaces observadas en el Parque. Determinamos los macronichos de las rapaces en Torres del Paine, describiendo principalmente su uso de dos tipos de habitats predominantes y de nueve tipos de recursos alimentarios. Examinamos las relaciones de nicho trofico en un conjunto de cuatro rapaces consumidoras de micromamiferos, a la luz de sus diferentes ecologias y tamanos corporales. Esbozamos un programa de monitoreo para las rapaces de Torres del Paine, bajo el criterio que estas especies indicadoras pueden ayudar a prever posibles disfunciones de los procesos ecosistemicos basicos que determinan las condiciones relativamente pristinas aun prevalentes en el Parque

Underestimation of Abundances of the Monito Del Monte (Dromiciops gliroides) due to a Sampling Artifact

Abstract The monito del monte (Dromiciops gliroides) is an arboreal marsupial found only in austral South American temperate rain forests. Its conservation is a priority as the only extant species of the order Microbiotheria. We investigated whether the apparent low abundances reported for D. gliroides are real, or reflect a sampling artifact. We used wire-mesh and Sherman live traps, devices for recording tracks and hair, 2 types of bait, and 2 trap placements (ground level and 1.5–2.5 m high) in an old-growth forest in southern Chile. Type of bait and placement height affected captures of D. gliroides. The most efficient trapping combination (wire-mesh traps baited with banana, and placed above ground) yielded capture rates of up to 11%, and a relative population density of 21 ± 5 individuals/ha (mean ± SE), whereas traditional methods used for sampling small mammals were not effective. The sampling artifact uncovered here may have important future management and conservation implications.

Foxes, people and hens: Human dimensions of a conflict in a rural area of southern Chile

Los conflictos entre humanos y carnivoros han sido reconocidos como una de las mayores amenazas para la conservacion de carnivoros. Cuando existe ganado menor o aves domesticas disponibles, es esperable que pequenos carnivoros depreden sobre estas. Centinela -un area rural localizada en el sur de Chile y donde coexisten zorros chilla {Lycalopex griseus Gray) y pequenos agricultores- fue escogida como area de estudio. Para entender los posibles conflictos entre agricultores y zorros, evaluamos los conocimientos locales, experiencias, y actitudes hacia este zorro, asi como el manejo de los animales domesticos usando una encuesta. Casi un tercio de los encuestados reportaron la perdida de aves domesticas en el ultimo ano como consecuencia de la depredacion por parte de chillas. Estudios simultaneos de la dieta de chillas mostraron resultados coincidentes con esas denuncias. La mayoria de los participantes del estudio (67.4 %) manifesto actitudes negativas hacia la chilla. Las perdidas de aves parecieran estar relacionadas con su manejo, debido a que ningun agricultor reporto perdidas cuando las gallinas se encontraban encerradas en gallineros. Esto sugiere que el encierro permanente de las aves podria ser un metodo efectivo de prevencion de las perdidas. Las actitudes negativas se reflejaron tambien en el hecho de que la mayor parte de los encuestados reporto haber eliminado zorros chillas en al menos una ocasion.

Potential impact of the Alien American Mink (Neovison vison) on Magellanic woodpeckers (Campephilus magellanicus) in Navarino Island, Southern Chile.

The American mink (Neovison vison) has been described as one of the worst invasive species in the northern hemisphere. Although some studies on the mink exist for the southern hemisphere, aside from impacts on marine and freshwater birds, its effect on other components of the biota is not well understood. Here, as a result of 3 different studies, we report evidence for the mink as a predator of the Magellanic woodpecker (Campephilus magellanicus). To our knowledge, these are the first evidences of predation on this charismatic and endemic woodpecker and indicate that mink might have a more widespread impact on forest birds than was initially suspected.

Matrix composition and corridor function for austral thrushes in a fragmented temperate forest

Although it is widely recognized that animal movement may be facilitated by corridors and hindered by the matrix, the influence of matrix composition on the use of corridors still remain poorly understood. We used translocation experiments and state-space models to assess if the movement response of the frugivorous bird, the austral thrush, to riparian forest strips varies depending on matrix composition (open pasture vs. eucalyptus plantation). In agricultural landscapes, the directions displayed by most birds when moving in the open pasture matrix were consistent with an edge-following behavior. Riparian strips also functioned as passive drift fences in agricultural landscapes, with strips being used as conduits for movements once birds entered into a riparian strip. Our results suggest that visual perception of riparian strips by birds is hampered by the complex habitat structure in the eucalyptus matrix and that the use of riparian strips as habitat is conditioned by the surrounding matrix.