When chimpanzees and other primates are fearful or feel threatened, their nasal temperature drops. How do scientists sense this fear? Infrared thermography is how.
It wouldn’t make sense to attach a flexible thermometer to the face of a great ape, especially in an outdoor sanctuary, but a high-resolution thermal camera capable of detecting minute temperature shifts can do the trick.
Scientists at the University of Sussex in the UK are in fact deploying thermal imagery to study great apes in wild animal parks in the UK and rescue sanctuaries in Africa. Most of these apes have experienced previous trauma, and scientists are hoping that by evaluating stress levels, they can better manage rehab or pick out the animals for release or even target those who need more help, according to Gillian Forrester, professor of comparative cognition at the school of psychology at Sussex.
Here’s the thing about the chimp’s nose, something similar to human noses: instead of getting hotter and redder in tone when stressed or overwhelmed with fear, scientists know the nose actually gets a little colder as the nervous system reroutes blood in the face and nose to other sensory organs, such as the eyes and ears to help individuals look and listen for danger.
There’s even a term for the phenomenon: nasal dip. Using thermal sensing technology to detect the dip overcomes the limitations that ecologists face if they try to connect subjects to pulsometers, heart monitors or blood pressure gauges.
Infrared often used in industry for ape study
The Sussex team decided to rely on two different types of sensor technology in its ape studies—uncooled and cooled. Broadly speaking,
cameras and sensors that are labeled “uncooled” operate at ambient temperatures, while device makers chill infrared sensors down to cryogenic levels to achieve what’s known as “cooled” devices that are more precise.
These researchers picked the uncooled Flir T1K thermal camera and the cooled Flir A6301 for higher image detail in static settings, according to a statement from Flir, a subsidiary of Teledyne. It’s interesting that the A6301 relies on a cooled mid-wave infrared sensor (MWIR), and has been described in Flir’s spec sheet mainly for industrial applications far from the research study of apes. Flir lists main applications for the A6301 as follows: inline inspection and validation of package heat sealing, process control and monitoring for adhesives, quality assurance during paper and plastics production and remote monitoring of electrical/mechanical systems.
At a sanctuary, the Sussex team will play videos on a screen designed to elicit a negative stress response or a positive one. If an ape voluntarily watches the video, the researchers will use the cooled A6301 static camera to study nasal dip. The A6301 has a spectral range of 3 to 5 micrometers to allow detection of minute temperature differences.
The uncooled T1K will be used for portable shots with a zoom. Forrester said it will come in handy with the team visits Uganda in 2026 to study its first group of wild chimpanzees. “We’ll track them through their natural habitat with the Flir T1K and capture samples of their stress levels,” Forrester said in a statement provided by Flir.