A hatchling Argentine tegu needs a genuinely warm night
A hatchling Argentine tegu should be kept around the high seventies to low eighties Fahrenheit overnight, roughly twenty-six to twenty-eight degrees Celsius, and its enclosure should not be allowed to drift down into the low seventies while it is small. That is warmer than many lizards need after dark, and it reflects where this species starts life: hatchlings emerge in the South American summer and grow at maximum speed through warm days and warm nights. An adult tegu tolerates a cooler night and a seasonal slowdown, but copying adult conditions for a hatchling stalls the growth and appetite the first months are meant to build.
Why night warmth drives a hatchling tegu's growth
A hatchling Argentine tegu's night temperature decides how well it uses its food. This species eats rich, frequent meals as a baby, and digestion continues overnight in the burrow where the tegu sleeps buried in substrate. A tegu that cools deeply every night digests slowly, wakes sluggish, basks for hours before it will eat, and converts far less of each meal into growth. Kept warm overnight, the same hatchling emerges active, reaches its basking spot quickly in the morning, and feeds with the strong appetite keepers expect from this species. Night warmth is therefore not a comfort detail for a baby tegu; it is part of its feeding system.
Holding the night range without light or guesswork
A hatchling Argentine tegu's basking lamps go off at night, so the overnight warmth must come from a light-free source on a thermostat. A ceramic heat emitter or a radiant panel sized to the enclosure, controlled by a thermostat with its probe at floor level in the cooler half, is the usual way to hold the high seventies without lighting the enclosure or cooking the warm end. The burrow matters too: deep, slightly moist substrate in a hide holds warmth and humidity around a sleeping hatchling far better than a bare floor. Check that the warm end can still offer a slightly warmer pocket than the cool end, because even at night a tegu adjusts its temperature by moving.
Checking the temperature in the burrow, not just the air
A hatchling Argentine tegu's night warmth should be verified where the animal actually sleeps. A thermometer reading the air near the top of the enclosure says little about the floor of the hide, where substrate, height, and distance from the background heater can leave a cold pocket. Place a probe or a small digital thermometer at substrate level inside or beside the sleeping hide and read it late at night, after the basking lights have been off for hours. Record a few nights in a row when the weather turns colder, because a room that cools overnight in autumn is the classic way a tegu setup that tested fine in summer starts failing its hatchling.
What a too-cold night pattern looks like in a baby tegu
A hatchling Argentine tegu kept too cold at night changes gradually rather than collapsing. It starts emerging later each morning, spends longer flattened under the basking light before moving, eats smaller meals or skips days it used to feed, and grows noticeably slower than its early pace. Its droppings may show poorly digested food, a sign meals are passing through a gut that never got warm enough to work on them. Correct the night warmth first and watch appetite over the following days; if a warmed hatchling still refuses food or looks lethargic through the day, a reptile vet should examine it. KinsLe's Care Teams let a household assign this tegu's evening warmth check to a named helper, each night's reading marked complete with a timestamp.