The night range a hatchling red-eyed tree frog needs
A hatchling red-eyed tree frog, fresh from the tadpole stage, thrives when nights ease down into the high sixties to low seventies Fahrenheit rather than staying at full daytime warmth. Daytime conditions in the mid to high seventies give the froglet the energy to hunt and digest, and a modest night dip mirrors the forest canopy it evolved for and supports normal rest.
What a hatchling cannot cope with is a sharp fall. A room that turns cold overnight, an enclosure against a winter window, or air conditioning blowing across the glass can pull temperatures well below that safe band. A froglet has almost no body mass to buffer the change, so it simply becomes cold, sluggish, and unwilling to feed.
Setting up gentle, controlled night warmth
Measure temperature where the hatchling red-eyed tree frog actually sleeps, at leaf height, not on the room wall. Place a reliable digital thermometer probe in the enclosure and check it last thing at night and first thing in the morning for several days whenever the season changes or the enclosure moves rooms.
If extra warmth is needed, supply it gently and under thermostat control, warming the air around one side of the enclosure so the froglet can choose a warmer or cooler leaf. Never rest a hatchling container directly on a heat source, and never aim a lamp into a small nursery enclosure overnight, because overheating a tiny frog in a confined space is as dangerous as chilling it. A stable gradient beats a single hot spot every time.
How a cold hatchling behaves, and what to do
A hatchling red-eyed tree frog that is too cold at night stays dull in colour, sleeps through its usual waking period, moves slowly when disturbed, and ignores fruit flies it would normally snap up. Repeated cold nights show up as a froglet that grows slowly, hunts weakly, and spends its time low in the enclosure near any faint warmth.
Correct the environment, not the frog. Move the enclosure away from drafts, windows, and exterior walls, warm the room or the controlled heat source gradually back into range, and mist with room-temperature dechlorinated water rather than cold water straight from a tap. Do not hold a cold froglet in warm hands to revive it, and do not offer food until it is moving normally at a proper temperature, because digestion slows to a crawl in a chilled frog.
When temperature worries become a vet conversation
Contact a veterinarian experienced with amphibians if a hatchling red-eyed tree frog stays limp or unresponsive after its enclosure has been back in range for a full night, develops swollen or bent limbs, or refuses food across several properly warm evenings. Bring your temperature notes, because a clear record of how cold it got and for how long helps the vet judge what they are looking at.
Night warmth is a habit, not a one-off setup, and habits are easier to keep when they are written down and dated. Recording the morning and evening readings for your hatchling in KinsLe through Pet Passport builds a history that travels with the frog, so a future keeper or vet sees the conditions it has actually lived in.