Abstract The Isla Palacio Natural Monument is a protected natural area in the province of Misiones, which was established after creating the reservoir due to the dam built on the Urugua-í stream. It was an area very studied in the mid-20th century by different naturalists and scientists. After several decades of transformation of its environment and 21 years of periodic censuses, its flora and fauna inventory is presented. Nine amphibians, 16 reptiles, 141 birds, 37 mammals, and 104 floristic species were recorded. Despite its small size, the area is home to species of particular value for conservation and, above all, it preserves a historical, folkloric, and cultural reference.

Resumen El Monumento Natural Isla Palacio es un área natural protegida de 160 hectáreas en la provincia de Misiones que fue establecida luego de la creación del embalse producto de la represa construida sobre el Arroyo Urugua-í. Fue muy estudiada a mitad del siglo XX por distintos naturalistas y científicos. Tras varias décadas de transformación de su entorno se presenta un inventario de su flora y fauna luego de 21 años de relevamientos periódicos. Fueron registrados nueve anfibios, 16 reptiles, 141 aves, 37 mamíferos y 104 especies de flora. A pesar de su escasa superficie, el área alberga especies de valor especial para la conservación y sobre todo, conserva una referencia histórica, folclórica y cultural.

The knowledge of the species present in a natural protected area provides indispensable information to valorate it correctly and to plan its management. The private natural reserve El Morejón is located in Campana Department, Buenos Aires province, and 340 ha are protected, with natural and semi-natural environments in Pampas ecoregion. The reserve has several artificial lagoons, two water courses that go across it, grasslands, flood plains, sedges and forest relicts. The objective of this work was to compile an inventory of the biodiversity of vertebrates registered in the reserve over eight years of periodic surveys. A total of 243 vertebrate species were recorded: 61 fishes, 150 birds, 11 mammals, 10 reptiles and 11 amphibians. Representative species of the environments protected in the reserve were recorded, as well as threatened species such as the Long-winged Harrier (Circus buffoni), the capybara (Hydrochoerus hydrochaeris) and the D’Orbigny’s turtle (Trachemys dorbigni). The recorded biodiversity over the years turned out to be much higher than expected and these surveys allowed us to conclude that this anthropic wetlands can host numerous communities, being areas of breeding, refuge and migratory scale of fauna. In spite of the surface, proximity to urbanizations and the industrial activities that take place in the reserve surroundings, the contribution of voluntary conservation is important for their protection, especially in ecoregions scarcely represented in the federal system of protected areas.

El conocimiento de las especies presentes en un área natural protegida brinda información indispensable para valorarla correctamente y planificar su manejo. La reserva natural privada El Morejón se encuentra localizada en el Partido de Campana, provincia de Buenos Aires y protege 340 ha de ambientes naturales y semi-naturales de la ecorregión pampeana. La reserva cuenta con varias lagunas, dos cursos de agua que la atraviesan, pastizales, llanuras de inundación, pajonales y relictos de bosques. El objetivo del presente trabajo fue confeccionar un inventario de la biodiversidad de vertebrados registrados en la reserva a lo largo de ocho años de relevamientos periódicos. Se registraron un total de 243 especies de vertebrados: 61 peces, 150 aves, 11 mamíferos, 10 reptiles y 11 anfibios. Se registraron especies representativas de los ambientes que están protegidos en la reserva y además especies amenazadas como el gavilán planeador (Circus buffoni), el carpincho (Hydrochoerus hydrochaeris) y la tortuga pintada (Trachemys dorbigni). La biodiversidad registrada a través de los años resultó ser muy superior a la esperada y los relevamientos nos permitieron concluir que estos humedales de origen antrópico pueden albergar numerosas comunidades, siendo áreas de cría, refugio y escala migratoria de fauna. A pesar de la superficie, cercanía a urbanizaciones y las actividades industriales que se desarrollan en el entorno de la reserva es importante el aporte de la conservación voluntaria para su protección, en especial en ecorregiones escasamente representadas en el sistema federal de áreas protegidas.

Abstract The humpback whale (Megaptera novaeangliae) is distributed among most oceans and seas of the globe (except Mediterranean Sea). These whales migrate from feeding regions in the Antarctic waters to breeding areas in tropical and subtropical seas. Here we report the stranding of a female young humpback whale, which was founded dead in the vicinity of the Talavera Island, in the Paraná River Delta, Buenos Aires Province, Argentina. From the analysis of mitochondrial cytochrome c oxidase subunit I gene sequences, two novel haplotypes were found, totalizing four haplotypes described for the species. In the La Plata River Basin this species was found only twice at the end of the XIX century. Thus, the new finding constitutes an important addition to the list of cetaceans that occurs in Uruguay, Paraná and La Plata Rivers.