The one fact everything else hangs on
Pet African pygmy hedgehogs are not British hedgehogs. They come from warm climates, they have no safe hibernation physiology, and a cage that drifts cold — especially overnight in winter, when household heating drops — can trigger a hibernation attempt that suppresses his body systems and can kill him. The sitter does not need a lecture on hedgehog biology, but they do need this completely: his cage must stay in its normal warm range, around the low-to-mid twenties Celsius, around the clock, for the whole stay. Not the room in general — his cage, measured where he sleeps.
The thermometer routine
Show the sitter the thermometer fixed at cage level and make checking it a named, twice-daily job: once in the morning, once before bed, because the dangerous dip happens in the small hours after the heating clicks off. The reading should look boring — the same warm figure every time. A reading drifting downward is not a wait-and-see; it is an instruction to act that day: check the heat source is on and working, check the cage has not been moved near a window or outside wall, and add the backup fleece or hide insulation you have left ready. Leave a written note of what the reading normally is, so the sitter is comparing against a number, not guessing what 'warm enough' means.
How his heat source works — and its backup
Walk the sitter through the actual equipment before you leave: the ceramic heat emitter or heat mat, the thermostat that controls it, and where the dial or probe should sit. A sitter who does not know the thermostat exists can defeat the whole system by tidying the probe out of the cage. Agree the winter backup plan too — what to do if the heater fails or the power cuts: spare fleece layers, a microwave heat pad if you use one, and moving the cage to the warmest internal room of the house. In winter, that failure plan is not pessimism; heating faults happen exactly when the weather is coldest.
Recognising a hedgehog who has got cold
Describe the signs concretely. A hedgehog attempting hibernation feels cold on his belly — the sitter should know how his tummy normally feels warm against a palm — and he may be wobbly on his feet, slow to uncurl, or balled tight and unresponsive when handled. His appetite drops and he may not have used his wheel. None of these signs should be watched overnight to 'see how he goes'; cold is the emergency for this species, and the response starts immediately.
Warming him — slowly — and getting help
The correct first aid is gradual warmth from the sitter's own body: the hedgehog held against their skin under a jumper or fleece, warming over tens of minutes, never plunged into warm water and never placed directly on a hot surface, because rapid reheating is its own shock. While he warms, the sitter phones a vet for guidance — a hedgehog who has been cold needs checking even if he perks up, because the attempt may not be the only problem. Writing all of this — the target range, the thermometer checks, the warming steps, the vet's number — into his KinsLe Care Pass means the sitter has the whole routine in hand at 3 a.m., not a memory of a chat in your kitchen.