There is no honest way to read a tree frog's age off its body. Frogs have no growth rings you can check without harming them, no teeth to age, and no grey coat to give the game away — and a rehomed frog usually arrives with nothing more than a previous keeper's estimate. Accept that estimate as a rough range, then judge the frog in front of you: how it hunts, climbs, calls, and holds condition tells you far more about the care it needs than a guessed birthday.
Why size is a poor clock
A tree frog's size is set largely by how it was kept. Generous feeding and warm conditions grow a frog quickly to adult size, sometimes within a year or so, while a cooler, leaner upbringing produces a smaller adult of exactly the same age. Two frogs of identical length can be years apart, and a large frog is not automatically an old one. Species matters as well: a big species such as a White's tree frog will dwarf a small species at every age, so compare your frog only against adults of its own kind.
Signs that point toward a senior frog
A cluster of changes, arriving gradually, is more telling than any single one. Older tree frogs often hunt less sharply, lunging at crickets and missing more often, or waiting for prey to wander close instead of stalking it. Night-time activity may shrink: less climbing to the highest perch, fewer and quieter calls from a male who once sang regularly, and longer stretches sitting in one favoured spot. Skin can look duller and less vividly coloured than in younger adults, muscle over the back and thighs may thin so the frog looks slightly bony around the hips, and the eyes may develop a mild cloudiness. Treat every one of these as a prompt to check the basics and consider a vet visit, not as proof of age — dehydration, low humidity, poor diet, and infection can produce the same picture in a young frog.
Build a baseline from arrival day
Because the past is missing, your records become the frog's history. Photograph your frog from above and the side on arrival, weigh it if you can do so without prolonged handling, and note appetite, strike accuracy, calling, perch choice, and soaking habits over the first month. Weigh and photograph monthly after that. A stable frog who eats well, soaks regularly, and holds weight is coping, whatever his age; a steady decline in weight, hunting, or activity is a trend a vet can act on, and it is far more useful evidence than anyone's guess at a hatch year.
Care that suits a possibly older frog
You do not need to rebuild the vivarium — you need to make its essentials effortless to reach. Place a wide, shallow water dish where the frog can climb in and out without a scramble, and keep a favourite perch and hide at a lower, easily reached height as well as higher up, so the frog chooses rather than struggles. Hold humidity and temperature steady in the species' normal range, since older frogs tolerate swings less well, offer appropriately sized live food at dusk when the frog is naturally active, and keep handling to the minimum a nocturnal, thin-skinned animal needs. If appetite fades, strikes keep missing, or weight falls, see a vet with reptile and amphibian experience promptly rather than assuming it is simply old age. Keeping your dated photos, weights, and appetite notes in KinsLe's Transferrable Profiles means that if this frog is ever rehomed again, the next keeper starts from your real observations instead of another guess.