Two recent articles about zoos caught my attention. The first shows that zoos can be an unanticipated pathway for the introduction of non-native species. In an analysis of 63 zoos in Spain, researchers discovered that "75% of the zoos studied were found to be problematic, while 14% of the animal housing was evaluated as 'insecure' against the possibility of escape." And, “Of the 1,568 animal houses studied, 221 were insecure against the threat of the species housed in them escaping, 167 housed non-indigenous species (potentially dangerous to the environment), and of these 21 housed invasive species”. To solve the problem the researchers recommend "not allowing animals to walk freely within the zoo grounds, and ensuring there is a physical barrier marking the zoo boundaries, and preventing individuals from escaping through drains, sewers or any other channels." Further studies on other zoos are much-needed to prevent zoos from becoming unwelcome corridors for the introduction of non-indigenous species.
Another article on zoos dealt with the challenges of geriatric animals who are kept in captivity. While this surely is a problem that needs to be dealt with as long as animals are kept in zoos and kept alive beyond what might be their natural lifespan, I was surprised to read that "Animals tend to live longer while in captivity" and that they "live twice as long as their wild counterparts." There's at least one significant exception for members of species that should never be kept in zoos in the first place. Thus, it's well-known for example, that Asiatic elephants show compromised survivorship when compared to wild elephants in protected populations; see also. Even if some individuals live longer than expected in zoos compared with their wild relatives, this isn't a compelling argument to keep animals in zoos. For more on some of the misleading claims made by zoos see and also.