Unlocking heart health: Advancing noninvasive monitoring in chimpanzees

Measuring the heart rate of great apes in captivity is essential for both health management and animal studies. However, most existing methods are either invasive or inaccurate.

Now, researchers from Japan have investigated the potential of using millimeter-wave radar technology to estimate heart rate from subtle body movements in chimpanzees. Their efforts will hopefully pave the way to better practices and techniques for monitoring heart rates in wild and captive primates. Their work has been published in the American Journal of Primatology.

Just like in humans, heart rate is a critically important and informative vital sign in nonhuman primates. Heart diseases are among the main causes of death of nonhuman primates in captivity, and monitoring their heart rate regularly can help veterinarians catch symptoms early.

Beyond the obvious health reasons, monitoring heart rate is also really useful in animal cognitive studies. For example, it has been well documented that a chimpanzee's heart rate changes under psychological stress, when emotionally aroused by images, or when encountering familiar humans.

Thus, it's no wonder a few techniques have been devised to measure heart rate in great apes. Besides standard contact measurements, the most prevailing one consists of attaching a wireless device to the animal to monitor and transmit its heart rate remotely. However, installing the device often requires anesthesia, which carries risks. Moreover, the device itself might cause stress to the animal or others in its group.

A less invasive approach is the estimation of heart rate from video feed, which has been tested in some species of primates. Still, the accuracy of these methods is quite sensitive to lighting conditions and the movement of the animals.

Against all these backdrops, a research team including Assistant Professor Takuya Matsumoto from Shinshu University, Japan, set out to find a better alternative.

In their latest study, the researchers investigated whether millimeter-wave radar-based techniques originally developed for humans could be used to measure heart rate in chimpanzees. The co-authors include Dr. Itsuki Iwata, Dr. Takuya Sakamoto, and Dr. Satoshi Hirata, all affiliated with Kyoto University.

In essence, the proposed approach involves emitting high-frequency electromagnetic pulses aimed at the chest of the animal and capturing the resulting echoes. From these echoes, one can detect subtle body movements, which are ultimately used to estimate heart rate using specialized algorithms.

Dr. Matsumoto highlights the study's motivation, "Millimeter-wave radar technology has been extensively developed for applications in automated driving and medicine, but after speaking with a radar researcher at a reception at an academic conference, we felt that it could open up a new field of study if applied to primates other than humans; thus, we began our joint research."

To test their approach, the researchers performed experiments during the annual health checks of two adult chimpanzees at Kumamoto Sanctuary, Wildlife Research Center, Kyoto University. During these checkups, the animals were anesthetized, and the radar system was hung about half a meter above their chest. Traditional electrocardiography (ECG) signals were also recorded and used to assess the accuracy of the radar-based technique.