The animals and plants of our planet are becoming extinct under the pressure of civilization. The scientists have counted that one species vanishes from Earth every hour. The mammoth, passenger pigeon, gare-fowl, Steller`s sea cow - these are the most well-known of extinct species, but hundreds of species are next in turn. Can the scientists forecast what species is the first in this succession and what species is not under the threat of complete extinction? If the answer is known, the effort and funds intended for the preservation of natural resources could be distributed correctly. Leonard Polishchuk, Ph. D. (Biology), research assistant of the Chair of General Ecology, Faculty of Biology, Lomonosov Moscow State University, has found a mathematical index of animal vulnerability.
It is common knowledge that the species of large animals that propagate themselves slowly and produce scarce posterity extinct earlier than others. Therefore, Leonard Polishchuk was looking for the characteristic of extinction risk among common demographic and ecological parameters. The researcher analyzed several parameters for 90 species mammal inhabiting the territory of the former USSR: life interval, quantity of litter, body weight of a sexually mature female, annual prolificacy and the number of posterity that each specific animal species produces within the entire lifetime. Applying the logistic regression method, he compared the above parameters to the probability of these species` registration in the Red Book. The most appropriate characteristic has appeared to be natural annual prolificacy, i.e. the number of daughters born by a female within a year.
The leaders of this index have turned out to be the rodents: common shrew (11.4), rabbit (10.5), Pallas` pika and steppe mouse-hare (8.8 è 7.9), field mouse (7.7), Alpine hare and European hare (5.0 è 4.4) - these species are well-known for their vitality.
About one third of all investigated species is characterized by the index exceeding 2.9. Almost all the species registered in the Red Book are grouped closer to the end of the list - their production/mortality ratio is lower than the above value. The list is ended by the walrus (0.17), bison (0.20), and the sea-otter (0.25), which were on the verge of extinction in the 19th century.
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