Telemetered temperature monitoring in preweanling Mongolian gerbils (Meriones unguiculatus)

Like most small mammals, Mongolian gerbils (Meriones unguiculatus) are born without the ability to maintain core body temperature (T_b). Breeding adults, juvenile alloparents, nest materials, and other litter mates probably contribute to the maintenance of core body temperature in neonates, but the relative role of each factor is unknown. We developed a procedure allowing biotransmitters to be implanted into 9-day-old pups for use with a radiotelemetry system. Experiment 1 demonstrated the development of thermoregulatory capacity over postpartum days 11, 15, and 19. Pups at 11 days of age lacked thermoregulatory capacity, and maintained T_b only slightly above the ambient temperature (15°C) of the testing environment. The transition from poikilothermy to homeothermy was clearly accomplished by day 19, with pups maintaining T_b of 35.8 ± 0.2°C for at least 100 min. Experiment 2 measured T_b in 11- and 12-nest materials, litter mates, or both mainained higher T_b during a 40-min test than those without these resources. Our methodology minimizes disruptions and the thermal consequences associated with other invasive (rectal probe thermistors) and noninvasive (e.g., infrared thermography) procedures.