By Sandhya Sekar
Keeping track of the number of wild animals killed illegally has never been easy. From counting carcasses, to looking at official records and trade logs, managers have had to innovate. Now, a recent paper in the journal Biological Conservation has suggested simple recipe-book mathematics as a tool to get more accurate numbers.
As populations change over time, they follow certain patterns when they are not disturbed in any way. After counting populations and getting real time data overtime, scientists can use simple mathematical equations to predict what will happen to the population in the future. Known as population modeling, this is a tool that can tease out the secret history of a population from numbers.
Karpagam Chelliah, Harshavardhan Bukka and Raman Sukumar from the Indian Institute of Science in Bangalore, India, used mathematics to understand population trends in the elephant. They developed a model that uses three ratios to describe a population: the sex ratio, the ratio of old males to young males, and the proportion of adult males. Together the researchers were able to use these ratios to predict how many elephants were poached over a certain period of time.
“Getting accurate information about age of elephants maybe a problem, but an approximate classification like old and young is possible when out counting elephants,” said first author Karpagam Chelliah. When tested with real data from two populations, one of Asian and one of African elephants, the model predicted with reasonable accuracy the number of elephants poached in both.
“These two populations are excellent to test the model because they present an interesting contrast. While males of both species are killed for ivory, the tusked female African elephant is also poached but the tuskless female Asian elephant is virtually immune to such harvest,” the authors note in the paper. The model does make certain simplifying assumptions - it assumes constant birth rate and death rate, and that no new animals are entering or leaving a population, which is unrealistic considering natural populations. But the researchers still feel confident that their model provides accurate results. More....