One of the chief reasons among the following for the depletion in the number of species making it endangered is

The sudden decrease in the number of species has been observed. The main reason for the decrease includes the activities like hunting and poaching. The animals are killed for skin, teeth, ivory, etc. These activities are performed for the benefits obtained from the animals after killing them, which causes loss of animal species. These activities result in the adding more number of species in the list of endangered animals.