The first rule for a frog: look far more than you touch
A green tree frog breathes and drinks through its skin, and that skin absorbs oils, salts, and residues from dry human hands quickly enough to harm it. So this species' quick health check is an exercise in disciplined observation, done at night with the enclosure light low, and any unavoidable handling is done with clean, wet, powder-free gloved hands or wet bare hands rinsed in dechlorinated water, for seconds rather than minutes. Judge everything against the frog's active hours: a frog asleep in a curled, tucked posture by day is behaving normally, while the same frog awake should be upright, glossy, and interested in the world.
Skin: moisture, colour, and surface
Read the skin first, because for an amphibian it is both coat and lung. It should look evenly moist with a healthy sheen, smooth across the back and flanks, without dry, crusty, or fuzzy patches, unusual spots, sores, or a reddened belly and inner thighs. Green tree frogs shift colour between bright green and duller olive or brown tones with light, temperature, and mood, so colour alone is a weak signal; texture and moisture are the reliable ones. A frog that looks dry while sitting beside available water, or whose skin appears slimy and discoloured in patches, has given you a finding worth acting on rather than photographing for another week.
Eyes, posture, grip, and body shape
The eyes should open fully at night, clear and matching, with no cloudiness, swelling, or discharge, and the frog should track a moving insect with obvious focus. Posture tells the strength story: a healthy frog sits upright on strong limbs, toe pads spread and gripping leaf, glass, or branch so securely that it can sleep vertically. View the body from above and the side for shape; it should be gently plump, neither bony along the back and hips nor uniformly swollen, since general swelling in a frog can reflect fluid problems that move faster than most reptile illnesses. A frog sprawled flat, unable to right itself, or slipping repeatedly from surfaces it once held needs help promptly.
Soaking, shedding, and the night feed
Watch the water behaviour. Green tree frogs soak in their dish to hydrate, usually sitting with the lower body submerged, and a frog spending nearly all its time in the water, or never approaching it, is departing from its pattern in opposite, equally informative directions. Shedding in frogs is easy to miss because they eat the shed skin, often seen as odd yawning and wiping motions with the feet, which are normal and not distress. The night feed is the final test: a well frog snaps at suitable insects with speed and accuracy, and a frog that misses repeatedly, strikes weakly, or ignores food across several nights after dark is showing you appetite or vision trouble.
Escalation for a fast-moving amphibian
Frog problems can progress quickly, so lower your threshold. Contact an exotics vet promptly for skin sores or discolouration spreading across the body, general swelling, an inability to sit upright or grip, an eye that will not open, or a frog found limp on the enclosure floor. Do not wait out several days of appetite loss in an animal this small. Bring your water and misting routine details, since a vet will ask about them first. A dated log in KinsLe Pet Passport, holding this frog's observations and routine in one place, makes that conversation precise.