How can a rat's temperature be measured? - briefly
Core temperature is typically obtained with a calibrated rectal thermistor probe inserted a few centimeters into the anal canal. Surface temperature can be recorded rapidly using a non‑contact infrared thermometer aimed at the dorsal skin.
How can a rat's temperature be measured? - in detail
Accurate assessment of a rat’s core temperature is essential for physiological and pharmacological studies. Several techniques are routinely employed, each with specific procedural steps, equipment requirements, and limitations.
Rectal thermometry remains the most direct method. A lubricated, flexible probe (typically 1.5 mm diameter) is inserted 2–3 cm into the anal canal. The probe connects to a digital thermometer with a resolution of 0.1 °C. Measurements are taken after the animal is gently restrained, avoiding excessive stress that could alter temperature. Calibration against a certified reference thermometer should be performed before each session. The method provides rapid readings but may cause discomfort and requires brief handling.
Infrared thermography offers a non‑contact alternative. An infrared camera calibrated for small‑animal emissivity (≈0.98) records surface temperature over the dorsal thorax or tail. Ambient temperature and airflow must be controlled to prevent artefacts. While the technique eliminates handling stress, it reflects peripheral rather than core temperature and is sensitive to fur density and vasomotor changes.
Tympanic thermometers, adapted for rodents, measure heat emitted from the ear canal. A miniature probe is inserted gently into the external auditory meatus. The device provides readings comparable to rectal measurements when calibrated correctly. Limitations include anatomical variability of the ear canal and the need for anesthesia to prevent movement.
Implantable telemetry devices deliver continuous core temperature data. A sterile, biocompatible sensor is surgically placed in the peritoneal cavity or subcutaneously, with a radio‑frequency transmitter beneath the skin. Data are streamed to a receiver, allowing real‑time monitoring without repeated restraint. Surgical implantation requires aseptic technique, postoperative analgesia, and periodic device calibration. The high cost and surgical burden restrict use to long‑term studies.
Subcutaneous temperature chips, similar to telemetry but without active transmission, are read with a handheld scanner. The sensor is implanted under the dorsal skin, and temperature is obtained by placing the scanner over the implantation site. This approach reduces surgical complexity but provides only intermittent data points.
Selection of an appropriate method depends on experimental goals, required temporal resolution, animal welfare considerations, and available resources. For short‑term studies demanding precise core values, rectal thermometry or tympanic measurement under brief anesthesia is advisable. For longitudinal investigations where stress minimization is paramount, telemetry implants offer the most comprehensive solution. All techniques mandate regular calibration, consistent environmental conditions, and adherence to institutional animal‑care protocols.