Dense and sparse aggregations in complex motion: Video coupled with simulation modeling

Investigations into the complex behaviors of aggregations of highly mobile animals have not used the link between image processing technology and simulation modeling fruitfully to address many fundamental ecological issues. Examples include population censusing, which remains difficult despite the demonstrated ecological importance of assessing abundance and density of organisms. We introduce a theoretical framework that connects thermal infrared video imaging with an individual-based simulation model-an approach that appears to be applicable to a diverse set of aggregated, highly mobile, nocturnal animals. To demonstrate the framework two applications are presented. The first is a dense aggregation of Brazilian free-tailed bats (Tadarida brasiliensis) that exhibits an emergence pattern that has complex dynamics and the second is a sparse local aggregation of agricultural pest moths whose dynamics are insipid. The first application uses individual-based modeling to mimic the behavior in the video of bats during a nightly emergence from a cave and to provide reliable estimates of the numbers, and associated error bounds. The second application uses video recordings of sparse aggregations to provide consistent estimates of the numbers of flying noctuid moths recorded over a corn and cotton-dominated agroecosystem in south-central Texas. This does not use a mathematical model because error estimates tend to be small.