Correction factors for prey size estimation from PenguCams.

Area of Science:

• Marine biology
• Animal behavior
• Ecological research

Background:

• Animal-borne cameras provide unprecedented views of wildlife behavior.
• Traditional prey analysis relies on post-consumption examination, limiting detailed behavioral insights.
• Accurate prey size estimation is crucial for understanding predator feeding ecology and energy transfer.

Purpose of the Study:

• To develop and validate a method for accurate prey size measurement using animal-borne camera footage.
• To establish a correction factor (pixel:mm ratio) for converting video pixels to real-world measurements.
• To assess the influence of salinity and medium (air vs. water) on this correction factor.

Main Methods:

• Utilized PenguCam footage to determine the pixel:mm ratio by measuring a 2 cm grid paper.
• Recorded footage at various distances (10-60 cm) and salinities (0-35 psu) under controlled temperature and pressure.
• Developed linear equations to predict correction factors across different distances.

Main Results:

• Found no significant variation in correction factors across different water salinities.
• Observed significant differences in correction factors between water and air due to refractive index variations.
• Demonstrated the applicability of the method using footage from Humboldt, Tawaki, and King penguins.

Conclusions:

• The developed method provides a reliable tool for quantifying prey dimensions from animal-borne camera data.
• This technique enhances the study of predator-prey interactions by enabling precise prey size and energy content analysis.
• The findings support wider application of animal-borne cameras in ecological research, particularly in marine environments.