Mole-Rat Pregnancy Checks

The first chance I got to really hold and touch a mole rat was when learning how to perform pregnancy checks. Mole rats breed throughout the year, and because we need to know when the pups are born, it is best to be able to make predictions for how far along each mother is. This is done in two ways. The first way is to look at the changes in weight. Based on a few years of monitoring, we know now sort of how to tell when a pregnant female will be due and if she even is pregnant based on big changes in weight.

The other way is more….tactile. For this, each queen is removed and the abdomen is carefully manipulated to feel for shapes that might be pups. The tricky part is doing this and not getting bit. The queen is held by the tail, and generally they stay facing forward for most of it. However, some will immediately reach around to try and bite, and it can be difficult to get a good feel.

Their gestation period is around three months, and usually the pups can be felt when there is a little over a month left. At first you feel small round shapes a little bigger than a pea. When there is closer to a month left, the shapes feel more like lima beans. With 2-3 weeks left, you can start to feel the skulls with little bodies attached. The best way to tell how many individuals there are is by skulls, although it can start to feel quite confusing the closer they are to birth. The size isn’t always the best factor to determine how far along either, since a queen with only one pup will have a much larger pup at birth than one with three or four.

The maximum number of pups is probably about six, although some females have seven nipples (yep, 7). Based on the pregnancy checks, both weight and physical manipulation, we try to predict birth dates. The closer it gets, the more frequently we check the nest, up to once a day. Once the pups are born, we take them out and give them their individual ID numbers and first dye marks.

We also take pictures of their head patches, which are visible on the skin before they even grow hair. The head patches are mostly pretty unique and easy to tell apart. We try to do this quickly, then return the pups to the nest. The newborn pups are quite squirmy and surprisingly mobile, and the hair starts to come in very quickly. It is very fun to compare litters at different stages and watch them become more and more independent.

This is G1F010, or Panda Queen as I call her. She is a pregnant female with the unique panda head patch. Only a few of the mole rats in the lab have this type of headpatch, and it is definitely the coolest.