Bats are another group of mammals with a good chance to be seen, especially in spring time and in the summer, when they are more active, hunting flying insects (all the Buenos Aires’ bats are insectivorous). Two species are the most common ones: the Hoary Bat (Lasiurus cinereus) and the Brazilian free-tailed Bat (Tadarida brasiliensis).
Reptiles and amphibians
The fish fauna of the Río de la Plata basin is of sub-tropical/tropical origin, and shares many of its species with the Amazon basin, although much less biodiverse, especially in this latitude with a temperate weather. Before the beginning of the twentieth century, with the industrialization of the area originating an intensive pollution activity that continues till today, the Río de la Plata hosted a wealthy environment with a rich species assemblage now very modified. In addition, the construction of damns in several points of the main basin’s rivers (Paraná and Uruguay) has interrupted the natural migration of many species that used to migrate southward in the summer, and the opposite direction in winter. This has damaged very much their populations.
The group of the invertebrates is well represented here, with some very remarkable species. Following are just some of the most notable common (or easy to see) invertebrates, among the insects and the arachnids.
Among the insects there is a group that must be mentioned separately: the diurnal butterflies. Many of them find their southernmost limit of distribution here. That’s the case of the Morpho genera, which finds its southernmost limit in the continent with the Argentine Flag (Morpho epistrophus argentina). With around 10 centimeters of length between the tips of their white/light blue colored wings, it’s one of the largest Buenos Aires’ butterflies. It is common in the riverside forest of the delta of the Paraná River, Martin Garcia Island, and the Natural Reserve of Punta Lara (near the city of La Plata). In the reserves of Buenos Aires it's possible to find it in Ribera Norte and Vicente López, although its presence is occasional y the Reserva Ecológica Costanera Sur. Among the most remarkable Neotropical genera of butterflies is the Diaethria. One species of this genus reaches the riverside forests of the Río de la Plata: the “Eighty” (Diaethria candrena). Its name comes from the number “80” legible in the ventral side of its hind wings.
There are also some interesting species of moths, including members of the Sphingid family (Hawk Moths).
Other remarkable insects in the area, among a plethora of others, are the Camoati wasps (Polybia scutellaris), a species of social wasp, which is black and very small, but builds a very characteristic huge nest; and the Rhinoceros Beetle (Diloboderus abderus).