How do mammals react when the environmental temperature is much higher than their body temperature in a short term?

I'd think they still consider to increase the heat loss rather than doing to reduce the heat gain.

Generally they try to cool themsleves evaporatively, like sweating or panting.

Exactly. I heard it put generally that "Mammals pay their heat bills with water" in a seminar recently.

 

A few have oddball strategies, like camels who tolerate increased body temperatures during the day so they can dump heat at night, thereby minimizing water loss. But most rely on evaporative cooling for the most part.

 

Mokele