You'd probably find that the diurnal species such as sand snakes, boomslang and especially the lizards are still active because the area still gets quite hot during the day, but the nocturnal things tend to disappear in May/early June or even earlier if I go herping in early May
. My theory is actually that it is not the temperatures that make them hibernate or become REALLY inactive in that area. I think it is actually the lack of available fluids as the area gets really dry, so snakes can't risk dehidrating and be active for long periods without sufficient water...
You can of course go and cause permanent damage to the environment by flipping termite mounds just in case something is hiding in them...but I'd recommend not to do that
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