Duration and reliability of placental scars in the Norwegian lemming Lemmus lemmus (L.)

Abstract

The development of placental scars and the correlation between the number of scars and the number of young born, was studied in Norwegian lemmings Lemmus lemmus (L.) from a laboratory colony. The 55 females used were separated into series where the number of young, the number of litters and the length of the post-natal period varied. Placental scars were visible for at least 190 days after the birth of a litter. There was considerable variation in the appearance of the most recent scars, and they could not be used for age determination or to separate different litters. In females with one, two or three litters, each scar showed 0.14, 0.25, and 0.06 too many young ones. A significant correlation between the number of scars and the number of young could only be shown in females with one litter. When the number of scars was below 15, the correlation was significant, irrespective of the number of litters. The correlation decreased with increasing number of scars. Possible explanations could be total or partial abortions, common placentas or fusion of scars.

Keywords

• Mammalia
• Rodentia
• demography
• population dynamic
• controlled condition