# Electrocardiographic parameters and heart rate variability in free-ranging Jaguars (Panthera onca) immobilized with tiletamine–zolazepam–dexmedetomidine

## TL;DR

This study examines heart activity in wild jaguars under anesthesia to help improve veterinary care for these animals.

## Contribution

The study provides new electrocardiographic data and heart rate variability for jaguars under a specific anesthetic protocol.

## Key findings

- Electrocardiographic parameters varied between sexes, ages, and body weights of jaguars.
- Heart rate variability did not differ significantly among the studied parameters.
- The anesthetic combination used has not been previously described in wild felids.

## Abstract

Understanding the physiology and particularities of wild felids is important for improving the ability of veterinary medicine to contribute to the preservation of these species. Thus, the objective of this study was to describe the electrocardiographic parameters and heart rate variability (HRV) of wild jaguars (Panthera onca) captured in Brazil. The anaesthetic protocol used for chemical restraint of the animals involved the drug combination of tiletamine and zolazepam (7 mg/Kg) along with the α2 adrenergic (receptor) agonist dexmedetomidine (10 µg/Kg). The 42 electrocardiographic reports from 39 animals were categorized (sex, estimated age, and body weight) and statistically analysed; 25 females and 14 males between two and 21 years old with a mean weight of 80.96 ± 23 kg were analysed. During the examination, the mean heart rate maintained by the animals was 99 bpm, with a maximum heart rate during the examination of 122 bpm and a minimum heart rate of 93 bpm; the values were comparable with the reference values for large felids. Electrocardiographic parameters differed between the sexes (p < 0,05) (P wave amplitude, QT interval and ST segment) and between the estimated ages (P wave amplitude) and the body weight (P wave amplitude and S amplitude) of the animals. The HRV determined by electrocardiogram did not differ (SDNN 52.89 ± 50.37, rMSSD 59.99 ± 59.79, ApEntropy 0.47 ± 0.36, CVI 3.03 ± 1.35, CSI 1.75 ± 0.82, alpha 1 DFA 0.821 ± 0.264, alpha 2 DFA 0.689 ± 0.385); however, the effect of tiletamine–zolazepam in combination with an anaesthetic agent such as dexmedetomidine (an α2 adrenergic receptor) has never been described. Since this anaesthetic protocol has currently been used effectively in wild felids, the description of electrocardiographic parameters and HRV in free-ranging jaguars seems to be particularly important for future studies of the autonomic tone in the sedation of this species.

The online version contains supplementary material available at 10.1186/s12917-026-05285-2.