The dynamic trophic niche of an island bird of prey

Optimal foraging theory predicts an inverse relationship between the availability of preferred prey and niche width in animals. Moreover, when individuals within a population have identical prey preferences and preferred prey is scarce, a nested pattern of trophic niche is expected if opportunistic and selective individuals can be identified. Here, we examined intraspecific variation in the trophic niche of a resident population of striated caracara (Phalcoboenus australis) on Isla de los Estados (Staten Island), Argentina, using pellet and stable isotope analyses. While this raptor specializes on seabird prey, we assessed this population\u27s potential to forage on terrestrial prey, especially invasive herbivores as carrion, when seabirds are less accessible. We found that the isotopic niche of this species varies with season, age, breeding status, and, to a lesser extent, year. Our results were in general consistent with classic predictions of the optimal foraging theory, but we also explore other possible explanations for the observed pattern. Isotopic niche was broader for groups identified a priori as opportunistic (i.e., nonbreeding adults during the breeding season and the whole population during the nonbreeding season) than it was for individuals identified a priori as selective. Results suggested that terrestrial input was relatively low, and invasive mammals accounted for no more than 5% of the input. The seasonal pulse of rockhopper penguins likely interacts with caracara\u27s reproductive status by constraining the spatial scale on which individuals forage. Niche expansion in spatially flexible individuals did not reflect an increase in terrestrial prey input; rather, it may be driven by a greater variation in the types of marine prey items consumed

Phylogeography of the Patagonian otter Lontra provocax: adaptive divergence to marine habitat or signature of southern glacial refugia?

<p>Abstract</p> <p>Background</p> <p>A number of studies have described the extension of ice cover in western Patagonia during the Last Glacial Maximum, providing evidence of a complete cover of terrestrial habitat from 41°S to 56°S and two main refugia, one in south-eastern Tierra del Fuego and the other north of the Chiloé Island. However, recent evidence of high genetic diversity in Patagonian river species suggests the existence of aquatic refugia in this region. Here, we further test this hypothesis based on phylogeographic inferences from a semi-aquatic species that is a top predator of river and marine fauna, the huillín or Southern river otter (<it>Lontra provocax</it>).</p> <p>Results</p> <p>We examined mtDNA sequences of the control region, ND5 and Cytochrome-b (2151 bp in total) in 75 samples of <it>L. provocax </it>from 21 locations in river and marine habitats. Phylogenetic analysis illustrates two main divergent clades for <it>L. provocax </it>in continental freshwater habitat. A highly diverse clade was represented by haplotypes from the marine habitat of the Southern Fjords and Channels (SFC) region (43°38' to 53°08'S), whereas only one of these haplotypes was paraphyletic and associated with northern river haplotypes.</p> <p>Conclusions</p> <p>Our data support the hypothesis of the persistence of <it>L. provocax </it>in western Patagonia, south of the ice sheet limit, during last glacial maximum (41°S latitude). This limit also corresponds to a strong environmental change, which might have spurred <it>L. provocax </it>differentiation between the two environments.</p

Revista de Vertebrados de la Estación Biológica de Doñaña

Alimentación de la boga del Guadiana (Chondrostoma polylepis wi/lkommi, Stein. 1866) en la interfase río-embalse de Sierra Boyera (Córdoba. España)Predación del búho real (Bubo bubo) sobre la perdiz roja (Alectoris rufa): selección de edad y sexoAlimentación de la nutria (Lutra lufra L, 1758)en el Nordeste de la Península IbéricaDatos sobre la distribución espacialde micromamíferos en el Parque Nacionalde DoñanaGuía para el reconocimiento microscópico de los pelos de los mamíferos de la Patagonia.Sobre la distribución geográfica de Anaecypris hispanica (STEINDACHNER, 1866) (OSTEICHTHYES, CYPRINIDAE)Cronología del periodo reproductor de Rana temporaria L. en La Coruña (NW de España).Un nuevo caso de melanismo en Natrix natrix (LINNAEUS 1758) procedente de Fuente Dé (Santander)Nuevas citas de anfibios y reptiles para el SE de la Península Ibérica.Datos sobre la dieta invernal del Búho chico (Asia atus) en la provinvia de LeónLa Distribucióndel Mara (Dolichotis patagonum) según criterios ecológicos e históricosSolapamiento entre la dieta de la cabra montés (Capra pyrenaica) y la del muflón (Ovis musimon)Nota sobre dietas de carnívoros e índices de abundancia en una Reserva de caza del norte de España.Discriminación osteométrica en el géneroTalpa (LINNEO, 1758), en el norte IbéricoObservaciones sobre el comportamiento depredativo de algunos colúbridos Ibéricos en estado salvajePeer reviewe

Trophic ecology and the use of shelters and latrines by the Neotropical otter (Lontra longicaudis) in the Taquari Valley, Southern Brazil

This manuscript presents information about the ecology of Lontra longicaudis (Olfers, 1818) in the Taquari Valley, State of Rio Grande do Sul, southern Brazil. The study was carried out in two areas located in the Forquetinha Creek and in the Forqueta River from January to December 2003. The otters are specialist feeders (Bsta = 0.24), with a diet based mostly on fish, especially those of the families Loricariidae and Cichlidae. Most shelters used by the species were excavated burrows underneath tree roots, while shelters within rocks were used less frequently. The burrows showed great variation in size, being found on average 3.5 m (sd = 3.6 m) away from the margin and 2.5 m (sd = 1.2 m) above the water level. Scent marks were made preferentially on rocks and fallen tree trunks at the edge of the water. There was a tendency to increase the reutilization of latrines in detriment of using new sites throughout the sample period