Variance estimate for the Allen activity index

The Alien activity index, originally developed for monitoring dingo populat ions, is statistically described as a mixed linear model, from which a vari ance formula for the index is derived. The resulting formula requires input of variance component estimates, the estimation of which is accomplished u sing restricted maximum-likelihood estimation. An example is used to demons trate the calculation of the variance components and their use in the varia nce formula. Application of the variance formula substantially enhances the quantitative practicality of this useful index of wildlife populations.