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Heart Rate, Breathing Rate and Body Temperature Fell as Hand-reared Reindeer Calves Grew

Young reindeer standing among low vegetation
Research · Physiology

Daily measurements from eight hand-reared female calves of the Alaskan barren-ground subspecies (Rangifer tarandus granti) showed that heart rate, respiratory rate and body temperature changed systematically as the calves matured. The study was conducted in Alaska, USA. The calves were born in the wild and brought into care at about 1–5 days old, then followed to 23 weeks. One calf with chronic illness was excluded from the healthy-animal analyses.

Vital signs were usually measured 1–3 times a day while the calves were resting: heart rate was counted from the pulse or with a stethoscope, breathing rate from chest movements, and body temperature rectally. This repeated monitoring produced thousands of measurements across the growth period rather than a single check of each animal.

Normal values changed substantially with age

Across all measurements from the seven healthy calves, average heart rate was 89 beats per minute, respiratory rate 19 breaths per minute and body temperature 38.9°C. These pooled means are not single normal values for every calf age: heart and breathing rates were much higher during the first weeks and declined markedly towards weaning. Age explained the changes in all three vital signs better than body mass, so the authors recommend judging a calf against age-specific ranges rather than one fixed reference value.

The calves also showed a compensatory response when body temperature was higher. After accounting for age, a 1°C rise in body temperature was associated with roughly a 10% higher heart rate and a 7% higher respiratory rate. Faster breathing helps cervids lose heat through respiration, while a faster heart rate can support both that increased breathing and heat transfer through the circulation. The study could not determine whether this compensation was sufficient to restore normal temperature completely.

A fixed 40°C fever threshold was too high for these calves

The authors also tested whether 40.0°C — a fever threshold used for domestic lambs — was appropriate for young Rangifer. In the healthy calves, the upper age-specific normal range never exceeded 39.2°C, so waiting until 40°C would risk recognising fever late. They therefore recommend interpreting temperature, like the other vital signs, against age-specific ranges.

The study provides useful physiological baselines for captive-rearing and health monitoring, but the calves were hand-reared under managed conditions and all were female. The results should therefore not be treated as fixed reference values for free-ranging calves in different environments.

Sources and image credit

  1. Denryter, K., Pryor, J., & Puype, A. (2026). Physiological indicators of Caribou calf health and compensatory responses to physiological perturbations. Journal of Mammalogy, 107(4), 714–725. https://doi.org/10.1093/jmammal/gyag051Primary research article published online 9 June 2026. Eight hand-reared caribou calves were measured daily from birth to 23 weeks of age; one chronically ill calf was excluded from healthy-animal analyses. Mean heart rate was 89 beats/min, respiratory rate 19 breaths/min and body temperature 38.9°C. All three declined with age, while higher body temperature elicited compensatory increases in heart and respiratory rates.

Image: Francisco M. Marzoa Alonso / Wikimedia Commons — young reindeer photographed on Karhunkierros, Finland, July 2006; representative species image, not one of the Alaskan study calves · CC BY-SA 2.5 · Source

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