The closest I've found is these two behaviors:
Tail carry: rats may pick up their tails in their mouths and carry them. May be a form of displaced maternal behavior by mother rats. Pregnant rats who are deprived of all nesting material still attempt to build nests by carrying their tails again and again to the chosen nest site. Mother rats with nursing litters may
retrieve their own tails to the nest.
Drag (another rat): A rat graps another rat's skin in its teeth and attempts to pull the rat in a particular direction. Dragging may be seen in mother rats. Price and Belanger (1977) examined the behavior of mother rats toward intruders and found that 33% of females dragged or pulled intruders, usually toward the nest. The mother rats targeted the neck 61.4% of the time, the side 28.3% of the time, the tail 8.7% of the time, and the ear 1.6% of the time. Dragging adult rats may be a component of maternal aggression.
Wiesner and Sheard (1933) observed that lactating female rats may drag their mates and adult offspring toward the nest. Lactating rats may even drag young rabbits or kittens as well. This dragging tends to decrease as lactation wanes, which suggests that dragging is linked with normal pup-carrying. Adult rats may simply be a "supernormal" stimulus for the retrieval response, and the mother may drag them because they are too big to be lifted and carried.
Here's the source website which may go a long way to helping you understand ratty tendencies you'll observe:
http://www.ratbehavior.org/Glossary.htm
and main page:
http://www.ratbehavior.org/RatBehaviorMain.htm