Researchers enhance wildlife studies with novel prey measurement technique using animal-borne cameras

A team of international scientists, led by researchers from the University of Otago, has introduced a groundbreaking method to improve the accuracy of prey size estimation using footage captured by animal-borne cameras. This innovative approach, published in PeerJ Life and Environment, enhances our understanding of predator-prey interactions in natural habitats by refining a critical tool for ecological research.

Animal-borne cameras, such as the "PenguCams" used in this study, allow scientists to witness behaviors and predator-prey interactions that were previously inaccessible. The team, including researchers from the University of Otago, the Tawaki Trust, the Global Penguin Society, the Antarctic Research Trust, and CONICET in Argentina, developed a set of correction factors that enable accurate measurement of prey size directly from video footage. These measurements help scientists estimate the energy content of prey and offer unprecedented insight into wildlife feeding behavior.

By capturing footage from Humboldt, Tawaki, and King penguins, the researchers established correction factors for converting pixel-based measurements into real-world dimensions. These correction factors account for variables such as distance, refraction, and distortion, providing a practical tool for precise size estimations. Notably, the study found that correction factors differ significantly between air and water environments due to differences in light refraction but remain consistent across varying salinity levels.

“We created a new way to study marine predators through animal borne camera footage. The correction factor allows measurements to be taken directly from video footage using a simple method. This innovative technique allows energetics of the prey to be calculated which can help explain the decisions made by predators during foraging. ” said lead author Mr. Owen Dabkowski. 

The research involved testing video footage of a reference object (a grid of known dimensions) at various distances, salinities, and angles. The team used these findings to create linear models predicting correction factors for distances beyond the tested range, broadening the utility of their work. For practical application, the study also provides a quick-reference table and example footage demonstrating how the method works in real-world scenarios.

Key findings from the study include:

• Salinity levels (ranging from freshwater to 35 PSU) have no significant impact on correction factors in water.
• Significant differences exist in correction factors between air and water due to variations in light refraction.
• The method accounts for distortion effects, such as barrel distortion in water and pincushion distortion in air, to ensure precise measurements.

This advancement is poised to benefit marine and terrestrial researchers alike, enabling more accurate studies of ecological interactions and contributing to the conservation of species like penguins.