Breathing you can see
A healthy lizard at rest breathes quietly with its mouth closed, the throat and flanks moving in a slow, easy rhythm. The first visible sign of a respiratory problem is that rhythm changing. The mouth is held slightly or widely open — gaping that is not part of temperature regulation because the lizard is not on its hot basking spot but sitting in a cool corner doing it. You may see the head raised and tipped back, or the whole front of the body propped at a steep angle against a branch or the glass, a posture lizards adopt because breathing is easier with the airway straightened. Look closely at the nostrils and the corners of the mouth for bubbles or strands of mucus, and watch for the sides heaving with obvious effort or the throat puffing unevenly.
Breathing you can hear
Put your ear near the enclosure in a quiet room, ideally in the evening when the lizard is settled. Respiratory trouble often announces itself as sound before it is dramatic to look at: a wheeze as air moves in or out, a faint clicking or popping with each breath, or an occasional squeak. Sounds that appear when the lizard is handled and then vanish may simply be a huff of protest, but sounds that repeat at rest, breath after breath, are a finding. Note when you first heard them and whether they are getting louder or more frequent across days — that progression is exactly the detail a vet will ask about and exactly the detail memory blurs.
The behaviour that arrives with it
Breathing difficulty drains a lizard's budget for everything else. Appetite fades first — a lizard that usually strikes at food starts watching it pass. Basking drops away or becomes strangely constant, activity shrinks, and the animal spends long stretches with its eyes closed in a spot it would normally avoid. Some lizards stop bothering to right their posture or move away when approached. Treat the combination as the message: visible or audible breathing change plus a lizard going quiet and off its food is a much stronger signal than either alone, and in prey animals that suppress symptoms, a lizard showing this much is usually further along than it looks.
Why the setup is part of the picture
Respiratory infections in lizards are frequently the visible end of an invisible husbandry problem. Temperatures running too cool suppress the immune system and are the classic background; humidity far off the species' needs, dusty or dirty substrate, and stale, poorly ventilated air all contribute. While you arrange the vet visit, check the enclosure honestly with a thermometer and hygrometer rather than the dials on the equipment: measure the basking spot and the cool end as the lizard experiences them. Write down what you find. Correcting a cold enclosure matters for recovery, but do not delay the appointment to experiment with the setup first — a lizard already breathing with effort needs treatment and husbandry fixed in parallel, not in sequence.
How fast to act, and what not to do
Book the vet the same day you see laboured or open-mouth breathing, and within a day or two for sounds or mucus without obvious effort — sooner always wins with small reptiles. Transport the lizard warm, in a secure ventilated box, with handling kept to a minimum, since a struggling breathless animal stresses fast. Do not try to open the mouth to look inside, do not offer food to tempt it, and skip home remedies such as steam sessions or leftover medicines from another pet; they waste the window in which treatment works best. When you arrive, the dated notes in the lizard's KinsLe Pet Passport — first sounds heard, appetite changes, the enclosure temperatures you measured — let the vet start from evidence instead of reconstruction.