Body condition is the size, weight, and proportions of your gerbil. Males and females are built different and they have different profiles. One of the things judges look at is the top line and belly of your gerbil. These lines reflect how weight and muscle is distributed on your gerbil. The top line refers to the curve of your gerbils back from their ears to their tail. The belly is not always as easily seen but it can easily be felt in hand. Overweight gerbils have soft bellies that tend to touch your hand when they stand on you. Underweight gerbils their fur does not even brush against your palm.
In male gerbils you are looking particularly at their shoulders and the middle of their back. In gerbils that are obese or very overweight the topline is arched and is a smooth convex curve that is nearly circular from their ears to the base of the tail. Very large male gerbils often have a fat pad on their neck, sometimes referred to as a hump. This can cause the highest point along their top line to be above the shoulders. Gerbils with large fat pads are undesirable for show. They often lack muscle tone and are overly squishy. A smooth or flat top line is fairly flat from the ears to the high point at the hips. Male gerbils may have small fat pads that are present, but they are not so large that they disrupt the line from the ears to the rump.
A dipped top line is underweight. They have no extraneous fat on their bodies. This makes them look rather racy.
Type 1: High-ball
The topline is arched with a highpoint occurring between the shoulders and hip. The gerbil's back is very rounded, almost circular. It is common for the belly to hang low and touch the ground as they walk.
Type 3: Linebacker
The topline is flat, and rises straight from the ear to the hips. A fat pad is present on the shoulders, but is not pronounced. The belly is low, but it clears the grounds. Fur may spray around arm pits.
Type 5: Racer
The topline is flat, but may dip at the shoulder. The rump is weak, and more flat then round. The hips may be obvious. Overall the gerbil is under condition or under weight. The belly is high.
Type 2: Zebu Hump
The topline is uneven. There are two distinct high points along the back. One at the shoulder and at the hip. The fat pad on the shoulder is exceedingly large. The belly is often low, and touches the ground as they walk.
Type 4: Streamlined
The topline is flat, and rises straight from the ear to the middle of the back. A fat pad is present on the shoulders, but is not pronounced. The belly is high
Type 6: Ratty
The topline is concave, and dipped at the shoulder. The rump is weak, and more flat then round. The hips may be obvious. Overall the gerbil is under condition or under weight. The belly is high.