(CN) – Conservation efforts narrowly focused on species risk of extinction are likely to miss other important road signs along the way. This is especially true of large animals, which reproduce and rebound slowly, argues a study focused on Asian elephants published Friday.
"We propose that conservation efforts for Asian elephants and other slow-breeding megafauna be aimed at maintaining their 'demographic safe space': that is, the combination of key vital rates that supports a non-negative growth rate,” explained lead author Dr. Shermin de Silva in the study published in scientific journal Frontiers in Ecology and Evolution. President of conservation group Trunks & Leaves, de Silva has been studying elephants since 2005.
The World Wildlife Federation estimates there are fewer than 50,000 Elephas maximus in the world. They can grow to be between 6.5 and 11.5 feet tall, weighing up to 11,000 pounds. Female Asian elephants begin to bear offspring around age 10, and typically only birth one calf every six years.
Typical population measurements focus on rate of decline or on groups that have shrunk down to unsustainable numbers. But research sponsored by Trunks & Leaves, the Smithsonian Conservation Biology Institute and the University of California, San Diego, highlights the need to identify demographic tipping points with species populations.
"Decisions based on trends in population abundance and distribution may fail to protect populations of slow-breeding, long-lived megafauna from irrevocable decline if they ignore demographic constraints,” researchers concluded in the paper. “For such taxa, we urge that effort be directed at understanding the interactions among vital rates governing population growth rates, rather than on predicting probabilities of extinction."
Rather than assign an arbitrary population goal, researchers are asking for a measurement that is more nuanced, though not necessarily harder to obtain in models.
This "tipping point analysis" rates a population's health "based on the species' physiological constraints and the population's time-averaged growth rate,” focused on managing the risks of decline, over extinction.
Employing mathematical models, researchers found an average Asian elephant population is likely to decline, even in ideal living conditions, when more than 7.5 percent of its females die off.
Of course population growth goals only go so far, if systematic threats contributing to population decline go ignored.
Asian elephants are smaller than their African cousins, and although a majority of them lack tusks, they remain susceptible to poaching. In addition to shrinking habitats, Asian elephant skin and parts are still largely trafficked. Additionally, calves are captured and sold in Myanmar and Thailand for as much as $33,000 an animal for use in the tourism trade.
"Measures to enhance survival of calves, and particularly females, are key to saving the Asian elephant," emphasized de Silva.
Though researchers focused on Asian elephants, this method can be applied to other large animals including giraffes and rhinos Bactrian camels and eastern gorillas as well.
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