Researchers have, for the first time, validated and tracked heart rate over long periods in conscious, unrestrained jaguars, using a small implantable cardiac monitor in captive animals at two Brazilian facilities. The study, published in Animal Biotelemetry, offers a physiological baseline that the authors say could eventually help conservationists detect stress in free-ranging big cats before visible behavioral changes or population declines appear.
Jaguars are top predators and key drivers of ecosystem health, and the paper’s authors note that the species is particularly vulnerable to habitat disturbances arising from both natural processes and human impacts. Yet the physiological responses of jaguars to increasing environmental pressures and habitat loss remain poorly understood. Because physiological stress and shifts in metabolic processes can occur before visible behavioral alterations or population declines, physiology can serve as an early-warning metric for conservation, and heart rate is a practical and informative parameter that reflects both acute and chronic responses to environmental change.
Baseline cardiac parameters remain undefined for most species, and existing reference values are often limited to anesthetized animals, which can distort readings. To address this gap, the team used the jaguar as a model for advancing heart rate monitoring approaches in keystone species, implanting a Reveal LINQ insertable cardiac monitor in seventeen captive jaguars at two Brazilian facilities, NEX and AMPARA.
After excluding one individual whose recordings were compromised by persistent T-wave oversensing artifacts, sixteen animals yielded high-quality heart rate recordings with a mean duration of 375 days. That long, continuous window in awake, freely moving animals is what distinguishes the dataset from earlier anesthetized measurements.
Across all individuals, mean heart rate over 2-minute intervals was 85 ± 28 beats per minute, with a range of 31 to 250 beats per minute. The wide range reflects the dynamic nature of cardiac activity in these animals, spanning resting states and periods of high activity.
Using generalized additive models, the researchers identified activity as the strongest predictor of heart rate, followed by time of day, ambient temperature, season, and whether the day was a weekday or a weekend. The modeling approach allowed the team to quantify how much each factor contributed to variation in cardiac rhythms over the long monitoring period.
The jaguars exhibited clear daily rhythms, with heart rate and activity peaking between 05h00 and 06h00 and again between 16h00 and 20h00. The evening peak aligned with the animals’ feeding schedules, which the authors interpret as reflecting anticipatory behavior, a physiological preparation for predictable events in the captive environment.
According to the study’s conclusion, these findings validated the insertable cardiac monitor as a safe and reliable tool for jaguar cardiac monitoring. The work also established a natural baseline for monitoring stress responses to anthropogenic threats in free-ranging populations, and provided a quantitative framework for optimizing welfare in ex situ facilities such as zoos and breeding centers.
The authors emphasize that understanding how apex predators respond to environmental and management-related factors from a physiological perspective, including heart rate, is important not only to assess how individuals cope with change, but also to predict potential population declines or shifts in trophic interactions, thereby improving conservation strategies. Incorporating heart rate monitoring via biologging can enhance understanding of how individuals respond to stressors, and the baseline values now documented for captive jaguars give researchers a reference point against which future measurements in free-ranging animals can be compared.
The study is an open-access research article published on 09 September 2026, authored by Rafaella Martini and colleagues, with contributions from researchers at multiple Brazilian institutions and collaborators including Timothy G. Laske and Rosana Nogueira Moraes.
Subject of Research: Long-term heart rate monitoring in captive jaguars using an insertable cardiac monitor
Article Title: Assessing heart rate in an apex predator: piloting biologging in jaguars (Panthera onca)
Article References: Martini, R., Leimgruber, P., Songsasen, N., Salomão Junior, J. A., Luczinski, T. C., Morato, R. G., Ribeiro, R. M., de Lima, M. S., Silva, S., Laske, T. G., & Moraes, R. N. (2026). Assessing heart rate in an apex predator: piloting biologging in jaguars (Panthera onca). Animal Biotelemetry. https://doi.org/10.1186/s40317-026-00495-9
Image Credits: AI Generated
DOI: 10.1186/s40317-026-00495-9
Keywords: jaguars, heart rate, biologging, insertable cardiac monitor, conservation physiology, Panthera onca, captive animals, stress response, daily rhythms, generalized additive models, Brazil, apex predators
News Source: Margaret Porter. (October 29, 2026). Heart rate biologging in jaguars establishes first cardiac baseline for the species. Scienmag.
