Jaime R. Rau

Trophic Relations of the Southernmost Populations of Dusicyon in Chile

Etude comparative de la niche ecologique et du regime alimentaire de D. griseus, D. culpaeus, D. fulvipes. Degre de chevauchement

Comparative demography and diversity of small mammals in precordilleran temperate rainforests of Southern Chile

Small mammals were studied in two southern Chilean temperate rainforests in the precor-dillean Andes during 2 low-rainfall years following the 1982 El Nino event. Forests had somewhat different levels of canopy, shrub, and herbaceous cover, and species richness of trees but most of the same plants. Most captures were of four sigmodontine rodents, Akodon olivaceus, Abrothrix longipilis, Abrothrix sanborni , and Oligoryzomys longicaudatus ; five other species and a putative hybrid were recorded. Maximum numbers were in January–July (late summer to winter) and lower numbers in August–December (late winter to early summer). All species had seasonal reproduction in September–April (spring to autumn). A. olivaceus and A. longipilis generally were long-lived, whereas survival rates were low for O. longicaudatus . Responses after the 1982 El Nino were small, and some populations increased during 1984. Populations of A. olivaceus fluctuated more than those of A. longipilis ; those of A. sanborni were low and O. longicaudatus was sporadic and irruptive. Lower-elevational Chilean and precordilleran Argentine forests have similar species composition, but differences in demography and dominance of the former by more widespread, omnivorous A. olivaceus , animalivorous-fungivorous Abrothrix , and granivorous O. longicaudatus . Opportunities for immigration may explain greater homogeneity of populations of small mammals in Chilean rainforests relative to Argentine ones. Although responses to El Nino and subsequent droughts were weak, flowering episodes of bamboo ( Chusquea ) can have strong effects due to increased availability of food.

Raptor habitat management and its implication on the biological control of the Hantavirus

Rodents have a high impact on human activities, producing economical losses and diseases. One of these diseases is Hantavirus syndrome, whose reservoir is Oligoryzomys longicaudatus. Raptors are the natural biological controllers of rodents, being, therefore, our efficient and effective allies. Despite the existing legal dispositions for protection, 11 of the 33 species of raptors in Chile have conservation problems. We evaluated the effectiveness of nest boxes for Tyto alba, as a way to increase its population and propose a procedure for the biological control of O. longicaudatus. The study area was the National Reserve Lago Peñuelas, Valparaíso, Chile. The variation of population density before and after the installation of the nest boxes was established both for T. alba and rodents. The results show that the nest boxes installed dramatically increased the population and the total density of T. alba, and a significant reduction of the abundance of small mammals was stated. We propose a methodological diagram for the biological control of the reservoir of the Hantavirus, which we have been implementing since 2001.

Estado de arte del conocimiento de las aves rapaces de Chile: Situación actual y proyecciones futuras

El creciente interes a nivel mundial por el estudio de las aves rapaces ha generado la necesidad de identificar las prioridades de investigacion para asi enfocar los esfuerzos de conservacion sobre ellas. En Chile, las primeras investigaciones se inician en 1891, y el numero de publicaciones se ha incrementado considerablemente durante las ultimas decadas. Basados en la informacion publicada entre los anos 1970 y 2011 evaluamos el estado de conocimiento de las aves rapaces de Chile con el proposito de identificar aquellos topicos donde todavia la informacion es deficiente o insuficiente para determinar que tipo de informacion debe priorizarse. Analizamos la informacion de acuerdo a la especie, especies agrupadas (rapaces diurnas y nocturnas), temas de investigacion y area geografica donde se realizaron los estudios. Encontramos que el numero de publicaciones aumento linealmente con el tiempo, pero esta tendencia ha sido fuertemente sesgada hacia solo dos especies (Tyto alba y Geranoaetus polyosoma). La mayor cantidad de estudios realizados en Chile se centraron en el conocimiento de la dieta, con un interes mas acentuado en las rapaces nocturnas que en las diurnas. Los temas de investigacion restantes solo fueron mediana o escasamente considerados. Las aves rapaces menos estudiadas fueron las migratorias (Buteo swainsoni, Pandion haliaetus, Circus buffoni), las especialistas del bosque templado de Sudamerica austral (Strix rufipes, Accipiter bicolor, Buteo ventralis y B. albigula) y aquellas pertenecientes al genero Phalcoboenus, la mayoria de las cuales se encuentran con problemas de conservacion. Los estudios por areas geograficas fueron similares entre rapaces diurnas y nocturnas. Cabe destacar que se observo una alta concentracion de los estudios en las cercanias de Santiago, capital administrativa de Chile. Concluimos que las prioridades de investigacion deben focalizarse sobre: (a) las especies escasamente estudiadas y con problemas de conservacion, (b) temas de investigacion tales como migracion, densidad poblacional, taxonomia, manejo, parasitos y uso y seleccion de habitat, y (c) las especies que habitan ambientes remotos, paisajes fragmentados y/o modificados por el hombre y areas altamente pobladas.

Rodent Prey of the Barn Owl Tyto alba and Short-Eared Owl Asio flammeus During Winter in Agricultural Lands in Southern Chile

We compared the consumption of rodent prey by barn owl Tyto alba and short-eared owl Asio flammeus during winter in agricultural areas in southern Chile. Diets were studied on the basis of pellets collected during the winters of 1986, 1987 and 1996. Both owl species consumed a large number of different rodent prey (8–9 species), but they preyed more often on the olivaceus field mouse Abrothrix olivaceus (56% and 52% of all individual prey, respectively) and long-tailed pygmy rice rat Oligoryzomys longicandatus (12.6% and 18.6%, respectively). The diet of the two owl species largely overlapped (95%). The diet diversity of barn owls and short-eared owls was not statistically different and accordingly they showed a similar evenness in diet. The geometric mean weight of rodent prey (GMWP) for short-eared owls (33 ± 1.36 g) was significantly greater than that of barn owls (28.3 ± 1.81 g). No significant difference was found between the proportion of native and introduced rodent prey consumed by barn and short-eared owls. The high diet similarity between both owl species could be a result of convergencies in hunting modes and activity time, similar body mass, or homogeneous rodent prey distribution and abundance in the agricultural areas we studied. The higher GMWP for the short-eared owl was probably caused by the fact that it preyed on the largest rodent prey in our study sites, the Norwegian rat Rattus norvegicus. According to our rodent trapping in the field, barn and short-eared owls appear to be opportunistic rather than selective predators in agricultural areas in southern Chile.

Trophic ecology of two raptors, Barn Owl (Tyto alba) and White-tailed Kite (Elanus leucurus), and possible implications for biological control of Hantavirus reservoir in Chile

ABSTRACT Raptors are important predators of various species of small mammals, which renders them of economic importance since their prey may be either disease vectors or reservoirs which represent health problems, or economically important through the damage they cause to crops and stocks. The long-tailed rice rat Oligoryzomys longicaudatus is a reservoir and vector of Hantavirus, a disease of increasing importance in various Latin American countries. The nocturnal Barn Owl (Tyto alba) and the diurnal White-tailed Kite (Elanus leucurus) appear to be the most significant predators of this species. Here, we characterize the diet of these two raptors and analyze their trophic specialization and dietary selectivity using published information, pellet analysis, and field abundances of small mammals. Both raptor species positively selected O. longicaudatus in their diets to suggest that they could be potential controllers of the Hantavirus reservoir in Chile, both in natural and agricultural ecosystems. Predation on O. longicaudatus by these two raptors is interesting because they have complementary activity periods, a condition which enables them to share the same prey without having strong interference.

Phenological synchrony between the austral thrush Turdus falcklandii (Passeriformes: Turdidae) and its food resources within forests and prairies in southern Chile

BackgroundFrugivorous birds are phenologically linked to the fruits that they eat. When there is less fruit in seasonal environments, frugivorous birds complement their diet by eating invertebrates. The depth of the phenological link between frugivorous birds and their dietary resources has not been studied until now. The objective was to determine the possible phenological synchrony between the Austral thrush (Turdus falcklandii) and its dietary resource, fruits and annelids, found in the fragmented forests in the South of Chile.ResultsThe numbers of thrushes, annelids, and fruits in fragments of native forest and anthropogenic grassland in Chiles Lake District were estimated annually. Spatial variation (i.e., forest and grassland) and seasonal variation (i.e., the period of greatest fruit growth and least fruit growth) on thrushes, annelids, and fruits were analyzed with a nonparametric Scheirer-Ray-Hare extension for the Kruskal-Wallis test. The graphic representation of the seasonal variation of thrushes, annelids, and fruits was carried out using cubic spline routines. It was found that there are seasonal changes in the dietary resources of these birds. During the period of greatest fruit production, there was a trend towards a higher number of thrushes in the forest where there was a greater availability of ripe fruit in relation to the nearby grasslands. In the grasslands, the annelids demonstrated a trend towards greater quantities in comparison with the forest. There was a positive and significant correlation between the thrushes and the annelids and fruits, indicating phenological synchrony between this bird and its dietary resources.ConclusionsTherefore, we concluded that the thrush responded numerically and functionally to the variations in its resources. The result of our research underlines the importance of grasslands in maintaining thrush populations, with this bird acting as one of the most important seed dispersers in the temperate southern forests of Chile.

Genetic divergence analysis of the Common Barn Owl Tyto alba (Scopoli, 1769) and the Short-eared Owl Asio flammeus (Pontoppidan, 1763) from southern Chile using COI sequence

Abstract In this paper new mitochondrial COI sequences of Common Barn Owl Tyto alba (Scopoli, 1769) and Short-eared Owl Asio flammeus (Pontoppidan, 1763) from southern Chile are reported and compared with sequences from other parts of the World. The intraspecific genetic divergence (mean p-distance) was 4.6 to 5.5% for the Common Barn Owl in comparison with specimens from northern Europe and Australasia and 3.1% for the Short-eared Owl with respect to samples from north America, northern Europe and northern Asia. Phylogenetic analyses revealed three distinctive groups for the Common Barn Owl: (i) South America (Chile and Argentina) plus Central and North America, (ii) northern Europe and (iii) Australasia, and two distinctive groups for the Short-eared Owl: (i) South America (Chile and Argentina) and (ii) north America plus northern Europe and northern Asia. The level of genetic divergence observed in both species exceeds the upper limit of intraspecific comparisons reported previously for Strigiformes. Therefore, this suggests that further research is needed to assess the taxonomic status, particularly for the Chilean populations that, to date, have been identified as belonging to these species through traditional taxonomy.

Alimentación del cisne de cuello negro Cygnus melanocoryphus (Aves: Anatidae) en un humedal marino de Chiloé, sur de Chile

El considerar a Cygnus melanocoryphus como un herbivoro generalista que se alimenta de las algas y pastos marinos mas abundantes en los humedales - entre ellos los costeros - que habita, permite suponer la existencia de interacciones aun no reportadas entre esta ave acuatica y los cultivadores de algas marinas del sur de Chile, por ello el objetivo de este estudio fue conocer la alimentacion de C. melanocoryphus en un humedal marino del sur de Chile, en donde tradicionalmente se ha realizado el cultivo del alga pelillo (Gracillaria chilensis). El trabajo se desarrollo durante el invierno de 2011 en el humedal marino de bahia Caulin (41o49’S; 73o38’O), en isla grande de Chiloe, sur de Chile. C. melanocoryphus destino la mayor parte de su tiempo a la alimentacion, observandose en esta ave una conducta alimenticia de herbivoro selectivo hacia el consumo no estricto pero preferente del alga Ulva taeniata. El ciclo de marea afecto la distribucion espacial de C. melanocoryphus; durante los periodos de marea baja estos se concentraron en la zona intermareal alimentandose de las frondas de U. taeniata retenidas o asentadas en los sistemas de cultivo de G. chilensis. Mientras que durante los periodos de marea alta C. melanocoryphus ingreso a la zona supramareal siguiendo las frondas de U. taeniata en la deriva de las corrientes, observandolos alimentarse tambien de los pastos salados (Distichlis spicata y Selliera radicans) dominantes en la zona estuarina (fuera del agua). El conocimiento obtenido permite proponer la hipotesis de un servicio ambiental brindado por C. melanocoryphus a los algueros del humedal, mediante la remocion del alga U. taeniata desde los sistemas de cultivo de G. chilensis liberando su competencia por sustrato y luz para crecer.

Evaluación de dos métodos de análisis dietarios aplicados en la Bandurria Theristicus melanopis (Gmelin 1789) y el Queltehue Vanellus chilensis (Molina 1782)

Los estudios dietarios contribuyen a comprender la ecologia de las aves y son relevantes en programas de conservacion de los organismos. Contrastamos los metodos de analisis dietarios fecales y estomacales en la Bandurria y en el Queltehue, para evaluar su sensibilidad para discriminar las presas consumidas. La diversidad y la abundancia de presas detectadas fueron mayores en los estomagos que en las heces en ambas especies de aves. El Queltehue no mostro una asociacion en el numero de categorias troficas, ni una similitud en la composicion taxonomica de la dieta entre ambos metodos, lo que sugiere que los analisis fecales no son confiables y pueden conducir a interpretaciones erroneas de la ecologia trofica de esta especie de ave. La Bandurria mostro una alta asociacion en el numero de presas entre ambos metodos y la composicion taxonomica y abundancia de presas en las heces fue concordante con la detectada en los estomagos, sugiriendo que los analisis fecales entregan resultados confiables y coherentes entre ambos metodos de analisis dietario; se recomienda su uso complementado con metodos moleculares de analisis de contenido estomacal como los isotopos estables si el objetivo de la investigacion es desarrollar estudios a largo plazo.