Lactating red squirrels experiencing high heat load occupy less insulated nests.

Area of Science:

• Mammalian physiology
• Animal ecology
• Thermoregulation

Background:

• The heat dissipation limit hypothesis posits that heat loss constrains milk production in lactating mammals.
• This constraint is particularly relevant for species nesting in insulated environments.
• Understanding nest selection is crucial for comprehending mammalian reproductive strategies.

Purpose of the Study:

• To test the heat dissipation limit hypothesis in free-ranging red squirrels (Tamiasciurus hudsonicus).
• To investigate if lactating squirrels select nests with lower insulation during periods of increased heat load.

Main Methods:

• Observational study of free-ranging red squirrels during lactation.
• Assessing nest insulative properties in relation to ambient temperature and litter mass.
• Monitoring environmental conditions and reproductive status of the squirrels.

Main Results:

• Lactating red squirrels with large litter masses occupied nests with lower insulative value during warmer ambient temperatures.
• Nest selection was influenced by conditions that increase heat load.
• Results align with predictions derived from the heat dissipation limit hypothesis.

Conclusions:

• Free-ranging mammals may select nests based on insulative value to manage heat load.
• Nest insulation plays a role in both heat conservation and heat dissipation for lactating mammals.
• The findings support the broader applicability of the heat dissipation limit hypothesis in explaining mammalian reproductive adaptations.