Does this make sense?

[Yzmasmom]

My girls have hot sides that range 88 to 91. But, when they are IN the hot hut and lying on the probes, they will read 85 or 86 sometimes. Is this because they are lying on the probe but they are cold blooded so it skews the reading? It's not every time, but often.

[ShaneSilva]

I'm assuming you're talking about the probe to your thermometer not the thermostat right? And yes the snake laying on the probe would give you inaccurate readings.

[Yzmasmom]

Yes, the probe to the thermometer. It usually reads colder when they lay on it.

[Coluber42]

If you put any object at the ambient temperature of the enclosure (say 80 degrees) on top of the UTH and thermostat probe (let's say a sack of water for the sake of argument, since animals are actually mostly water), it will absorb heat from the heat mat as the temperature equalizes between heat mat and cooler object. If that cooler object is sufficiently well insulated so as not to lose much heat, and the heat mat is regulated with a thermostat, that object plus the probe will all end up at whatever temperature the tstat is set for.

However, if that sack of water has a larger exposed surface area and isn't perfectly insulated, it will lose heat to the surrounding air, and if the amount of heat it loses to the surrounding air is less than the amount produced by the heat mat underneath it, that object will not ever get up to the set temp of the tstat. Make sense so far?

And in the meantime, that object is still cooling the thermometer probe it is sitting on because the probe is in contact with it.

The way that an animal is different from a sack of water is that an animal's blood circulates through its body, whichh means that blood that gets warmed by being closer to the heater will then circulate away and dissipate that heat through other parts of the animal's skin. "Cold blooded" does not mean that the animal's blood is cold, it just means that it doesn't regulate its body temperature internally the way we do (via things like sweating, shivering, and varying the amount of circulation in the extremities). So a bettter way of thinking of it is that a snake is like a bag of water with a little pump that keeps the water circulating.

For that matter, if the surface temperature of the hot spot inside the warm hide is 90 degrees, the air temperature in that spot is going to be a few degrees cooler than that. That's fine, it's normal. In order to have thhe air temperature 90, you'd have to have a surface temperature that was dangerously hot. But having a surface temperature higher than the air temperature is normal in nature too; think about burning your feet on the sand on a sunny day. The sand will burn your feet, but the air is not anywhere near that hot.