[rekabis]

Desertification, wet bulb temperatures, heat stress, loss of food in the environment, ecosystem collapse due to climate change happening too fast for ecosystems to migrate, and the massively increased range required to find food causing them to not find mates.

[RetroTechie]

To add: ratio of surface area (skin, sweating/cooling), versus volume/weight (muscle activity, biochemical processes etc).

The bigger the animal, the harder it is to keep cool.

[rekabis]

Yes, I tried to encapsulate that within the term “heat stress”, but thank you for laying that all out for those not in the know.