スミソニアン国立動物園さんのインスタグラム写真 - (スミソニアン国立動物園Instagram)「🐘 Instead of counting numbers alone, a better way to save wild elephants is to determine their "demographic tipping point," or when the population is no longer self-sustaining. Large animals, like the Asian elephants, have evolved to grow and mature at a different rate than many smaller species monitored by organizations like the International Union for the Conservation of Nature (IUCN). At 22 months, elephants have the longest gestation period of any mammal. They hit sexual maturity when they are 10 or 11 years old, but females don’t start having calves until they are 13 and can only reproduce every three to four years. But in reality, most females only reproduce every six years. Despite their evolutionary tactics of living longer and having fewer calves during their lifetimes, Asian elephants are evaluated with the same lens as species that have shorter lifespans and more offspring. Shermin de Silva, a former James Smithson Fellow, and Peter Leimgruber, research ecologist at the Smithsonian Conservation Biology Institute, may have found an approach for monitoring elephants that takes their specific biology and ecology into account. The approach is to take a more focused look at populations, rather than global numbers, and make decisions based on “demographic tipping points,” or the point when the growth rate of a population switches from positive to negative. A positive growth rate would signify a growing population, while a negative would signal a decline. If the population is declining, it is critical for scientists to identify the causes to help create conservation strategies to combat them. Most Asian elephant populations have already past their demographic tipping points and the populations are in decline. The hope is that the approach will bring greater awareness to the status of all populations and become part of the toolkit, to determine when a species is heading towards extinction. #WorldElephantDay #WeSaveSpecies #Elephants #Ecology」8月13日 8時30分