Final answer:
The best method to investigate mammalian body temperature ranges is through measurement in a controlled lab setting. Biotelemetry can be used to collect simultaneous body temperature and heart rate data, providing insight into an animal's metabolism. Small mammals like squirrels need to eat periodically during hibernation due to their higher surface area to volume ratio and lower fat reserves compared to larger animals like bears.
Step-by-step explanation:
The investigation into whether different species of mammals have different ranges of body temperatures can be approached with a combination of the methods listed, but the most precise and informative method would be measuring the body temperature of mammals in a controlled laboratory setting. This method allows researchers to control for external variables and obtain accurate, reproducible data. Observing behavior or surveying populations can provide supplementary data but are less controlled and can introduce variables that might skew the body temperature data. Analyzing data from previous studies can also be valuable, especially when combined with new observations to give depth to the understanding of mammalian thermoregulation.
To design an experiment collecting both body temperature and heart rate, one could use modern biotelemetry devices as referenced in the example of studying hibernating bears. These devices could be non-invasively attached to the mammals and would record body temperature and heart rate simultaneously. Combining data on body temperature with heart rate can reveal insights into the animal's overall metabolism, as heart rate is typically correlated with metabolic rate, which in turn influences body temperature.
Mammals stay warm using insulation like fur, fat, or feathers and dissipate heat through methods such as sweating, or in the case of furry animals, adjustments in the position of their fur via arrector pili muscles. While larger animals like bears can survive on their fat reserves during hibernation, small mammals like squirrels must eat periodically as they have less fat reserves and higher surface area-to-volume ratios, which make them lose heat more quickly.