Look at the carapace on the turtle's back (the so-called thirteen hexagons). There are circles on each shell, and each circle represents a year. You can also look at the belly spots of turtles in the sky. Each belly spot has a circular pattern, which is represented by each circle in a year (some have two circles or no circles).
Different turtle species, ring marks and other factors will also affect the accuracy of age. For old turtles or turtles with unclear concentric rings, there are artificial turtles raised in greenhouses. Although they are large, they are hard to see on the growth line. The approximate age can only be estimated by estimating its appearance characteristics. Judging the size and youth of the turtle by the color and clarity of the lines on the back of the turtle, the older the lines are deep and clear; If the lines are light and unclear, they are young. Some scientists are using bone age calculation to determine the age of turtles. In fact, bones are also said by growth lines, so the bone age and biological age are basically the same, but this method is too professional.
For experienced professionals, you can also judge the turtle's age by measuring its body length and weight. There are precedents for the mature age, adult nail length and weight of turtles. We can roughly calculate the turtle's age by measuring the relevant data and comparing it with the average value. By measuring the length of the tortoise shell, compare the sizes accordingly. Under normal circumstances, the tortoise of 1-3 years old is about 6 cm long, less than 10 cm; Turtles with a shell length exceeding 10 cm are all adults. If the tortoise is not fully grown, you can roughly estimate its age. The age of the tortoise can also be roughly known by its weight. Usually 15g is 1 year, 50g is 2 years old, 100g is 3 years old, and 200g is 4 years old. Of course, these are all based on the usual experience.
However, it is generally inaccurate to estimate the turtle's age by its length and weight. Turtles of the same species grow much faster in the south than in the north, and grow and gain weight faster under artificial feeding conditions, especially in winter. Between different kinds of turtles, such as turtles of the same age and Burmese turtles, the weight of the latter may be more than ten times that of the former. A poor quality turtle shell will make the turtle look older than its actual age. For example, a tortoise has been malnourished for several years, and its shell may be rough and uneven, which may make people misunderstand its age. When guessing the age, don't care too much about the appearance of the tortoise.