When only 20–30 individuals of a species remain in the wild, extinction seems almost inevitable. Difficulties in finding a mate and the risk of inbreeding heighten vulnerability. However, a new study shows that even such tiny groups of birds and mammals can not only survive but grow markedly with targeted human assistance.
Scientists from Monash University in Australia and the Zoological Society of London analysed the fate of all 147 species of birds and mammals whose numbers in the wild fell below 50 individuals from 1950 onward. For 141 species, subsequent dynamics could be traced. Of these, 51 species received direct conservation measures — captive breeding followed by release, translocation, or control of invasive predators.
The results were telling. Among the species that were helped directly, 61 percent recovered to a hundred or more individuals. Without such interventions, the share of successful recovery was only two percent, and 37 percent of species went extinct. The best outcomes were observed when measures to eliminate external threats were combined with direct support for the population.
A striking example is the Lord Howe woodhen. In the late 1970s, only 23 birds remained in the wild. Thanks to a combination of actions, the population grew to more than 1600 individuals. Such stories confirm that population size alone does not determine a species' fate.
At the same time, the risk of genetic weakening remains when the initial numbers are very small. The researchers emphasise that success requires not only time and resources but also addressing the root causes of decline — habitat destruction and invasive species.
Thus, active and comprehensive conservation can turn the tide even for the smallest populations, giving them a real chance of recovery.
