U.S. Department of Agriculture: Animal and Plant Health Inspection Service


Date of this Version

March 2005


Published in Wildlife Research 32 (2005), pp. 259-263.


The accurate estimation of wildlife population density is difficult and requires considerable investment of resources and time. Population indices are easier to obtain but are influenced by many unknowns and the relationships to actual population densities are usually unclear. Wildlife biologists, whether in the public or private sector, often find themselves in difficult situations where a resource manager or landowner wants good information, quickly, at low cost, and without clear objectives. In many situations, in addition to establishing clear objectives, a budget and timeframe, a biologist must understand and deal with the reality of many logistical concerns that will make the achievement of the objectives difficult or impossible. The situation is often complicated because the biology and ecology of the species of interest may be poorly understood in the specific setting and the species may be very rare or strongly influenced by current or past human activities. Methods to monitor a wildlife population may need to be tested or validated, extending the time and resources needed to complete the assigned task. In this paper, I discuss many of the challenges faced and the decisions to be made when a biologist is requested to provide useful, timely information on the status of a wildlife population.