In a world-first pilot study, researchers from the University of South Australia (UniSA) have used video footage of insects to extract their heart rates without touching or disturbing them.
The innovation, published in the Archives of Insect Biochemistry and Physiology, could transform how scientists monitor the health and stress levels of arthropods, that account for more than 80% of animal species.
Taking footage from smartphones, social media videos and digital cameras, the researchers used sophisticated signal processing methods to monitor the heart activity of ants, bees, caterpillars, spiders, grasshoppers and stick insects.
Unlike mammals, arthropods have an open circulatory system in which blood fills the body cavity, bathing the internal organs and tissues. Their heart is located on the top (dorsal) side of their body in the abdomen.
Led by UniSA PhD candidate Danyi Wang and her supervisor Professor Javaan Chahl, the study demonstrates that subtle body movements captured on standard digital or smartphone cameras can be analysed to reveal accurate and detailed cardiac activity in a range of insect species.
Unlike traditional methods that require physical contact or immobilisation, this technique allows insects to remain free, without disrupting their natural behaviour.
"Insects are vital to our ecosystems, and understanding their physiological responses to environmental change is essential," Wang says.
"Existing methods to measure insect' vital signs are invasive, however. Our method preserves their natural behaviour while providing accurate insights into their heart activity."
The extracted heart rates closely matched the physiological ranges recorded via traditional techniques, validating the system's accuracy.
Senior author Prof Javaan Chahl says the system successfully captured heart rates across multiple insect species, detecting physiological differences influenced by factors such as wing morphology and temperature.
"From ants with heart rates of around 50 beats per minute, to bees reaching 119bpm, our results consistently aligned with established reference values," Prof Chahl says.
"What's exciting is that this was all achieved without attaching sensors or disturbing the insects in any way."
One of the most impressive validations came from caterpillar recordings, where the team compared their video-derived cardiac signals to data from infrared contact sensors in previous studies. The shapes and frequencies were almost identical.
The study also revealed interesting inter-species variations. For example, spider heart rates varied significantly, reflecting differences between species rather than activity levels, since all subjects were at rest during filming.
Advanced image processing techniques, including motion tracking algorithms and magnification, were applied to detect tiny movements associated with heartbeats. These signals were analysed using spectral filtering and transformed into frequency data to isolate the heart rate.
According to Prof Chahl, the study marks an important step forward in insect research.
"Non-invasive cardiac monitoring offers tremendous potential; not just for studying insect health, but also for understanding environmental stressors, pesticide effects, or even the wellbeing of social insects like ants and bees, where heart signals can provide insights into colony health and behaviour."
His team has previously used a similar technique with digital cameras to remotely extract cardiac signals in humans and wildlife.
The researchers hope to test the system in the field and refine it by using machine learning to improve the accuracy across different body types and light conditions.
"With more refinement, this could become a cost effective and valuable tool in the ecological research toolkit," says Wang. "It gives us the ability to listen to the hearts of the smallest creatures without harming them."
'Extracting Cardiac Activity for Arthropods Using Digital Cameras: Insights from a Pilot Study' is published in the Archives of Insect Biochemistry and Physiology. DOI: 10.1002/arch.70076
A video demonstrating the experiment is available at: redback_final.mp4 - Google Drive
