Endangered species considered too rare to save may avoid extinction if conservation work tackles the threats facing them, experts said yesterday.
A study by researchers in the UK and US raises hopes for the remaining small populations of animals such as the mountain gorilla, Amur (Siberian) tigers and Puerto Rican parrots.
Fewer than 1,000 mountain gorillas, approximately 450 Siberian tigers and 70 wild Puerto Rican parrots remain, with populations of the three species well below levels believed to be needed to ensure they survive.
Previous conservation studies suggested that 5,000 individuals were needed as a “minimum viable population” in any species to prevent it going extinct, a figure used to guide whether it is worth introducing conservation efforts to try to save them.
But the new study, published in the journal Trends in Ecology and Evolution, said no single “magic” number can be used as a yardstick for whether a species might survive. Instead, the size of the population needed varies between and within species and depends on the circumstances in which it is found, including the threats facing it.
The study showed that estimates of the numbers needed for a species’ survival were typically reduced from thousands to hundreds if the population was relatively stable.
The Bengal tiger, which numbers fewer than 5,000 in the wild, could be saved if the threats facing it are tackled. The Komodo monitor is also thought to be below the 5,000 threshold but steps are already being taken to create protected areas and prevent trade in the species which could mean it survives.
But while the sun bear and orang-utan both exist in numbers exceeding 5,000, they are subject to extreme pressure from habitat loss and are likely to go extinct without urgent action to protect them.
Researchers warn against complacency over protecting animals because even large populations can be at risk.
They point to the extinction of the passenger pigeon which numbered three to five billion in north America in the 1800s but vanished largely because of hunting.
Study co-author Dr Philip Stephens, of the school of biological and biomedical sciences at Durham University, said: “Populations usually show rapid declines as a result of human activities such as hunting and habitat conservation.
“The results of the study are encouraging and show that, if we can remove the negative effects of human activities, even relatively small populations could be viable in the long term.”