Estimating the abundance of wild animals is essential to the protection of the environment, management of stocks and monitoring species at risk of extinction. 

Many animals, including marine animals such as whales, are difficult to detect visually, so we rely on acoustic surveys to listen to the animal vocalizations. These surveys are passive; the researcher travels along a path and stops periodically to listen for a particular species.

There are many issues that arise when converting a collection of vocalizations to an estimate of the number of individuals. Determining whether a particular vocalization comes from a new or previously detected animal is often impossible to determine. It is also often impossible to determine whether or not a particular vocalization arose from a single individual or from several animals. It must also be taken into account that some individuals will simply escape detection.

Dr. Julie Horrocks works with students and collaborators to apply modern statistical techniques to help solve these problems. She and her team hope that these techniques can be applied to help monitor the populations of other species, such as birds and bats, that are more easily detected acoustically rather than visually. These techniques could also be applied to estimating population sizes for species that can only be detected by smell, or chemical trace.