Generally, animals are more difficult to collect than plants since they often hide in concealed places, or move very fast. Different types of nets and traps are used in capturing and collecting animals from aquatic, terrestrial and arboreal habitats.
To study the animal population of an area, a collection of Animals is made at ten different spots and the average number of each species of animals is found. This would give us an idea of the animal species which dominates the area. Although it is difficult to sample animals as they are mobile , their presence and distribution can be inferred. This can be done by
• looking for signs of their presence such ad nests, eggs, feathers , droppings, tracks, etc.
• studying the vegetation with which they are associated.
Capture - recapture method
Animals population may be estimated by yhr capture - recapture method. In this method, animals of one type in a particular area are caught , counted (A) , and marked with ink and released. The following day, the process is repeated and the number (A2) of Animals caught is recorded. At the same time , the number of marked animals (A3) , from the previous day, that were found in this sample are counted and recorded. The population of Animals present in the area is founded by using the following formula
Population in area = A1 x A2 ÷ A3
Collection is soil animals
To Carry out a population survey of soil animals in an area, soil samples are collected from several sites, chosen by tossing a quadrat randomly. A 25% sodium chloride solution is added to each soil sample and the animals are collected as they float in the solution. Alternatively, a Tullgren's funnel can Also be used to collect soil animals. This funnel is fitted with a wire gauze. The soil samples is placed on this gauze and heated on a lighted bulb. As the animals move away from the heat, they drop into a Container of alcohol below the funnel, an can be collected.
To carry out a population survey of earth worms, the sampling sizes, chosen by random tossing of a quadrat, are irrigated with 25% formalin solution. The earthworms are collected as they move to the surface of the soil.
