ABSTRACT

This chapter illustrates calculations of numbers of terrestrial vertebrates. It also explains the advantages and disadvantages of the calculations. Accuracy and precision refer to different concepts. Two sources of error exist: bias and sampling. Bias systematically distorts an estimate. The advantage of narrow limits is the ability to detect small differences. Counts may be absolute or relative. A census method requires detection somehow of the animals but what proportion of the population is detectable. The calculations also assume that all members of the population have an equal probability of being counted. Counting methods are simple in principle but may have pitfalls when comparing two estimates. The conditions under which the counts were made must be comparable. The simplest way to determine the size and composition of a population is by a direct visual count of the animals.