title: Pup mortality in laboratory mice--infanticide or not?
abstract: BACKGROUND
  Despite being the most commonly used mammal in biomedical research, problems with perinatal mortality in mice have received little attention and the causes of pup death are still poorly known. Females are often housed alone with their litters and since the lost pups are generally eaten, it is commonly assumed that the mother has killed them. However, more detailed observations than have been reported previously in the literature are required to establish if the cause of death is infanticide. Litter loss can only be prevented efficiently after underlying causes have been carefully investigated and interpreted. The aim of this study was to investigate if females actively kill their pups by observing the behaviour of females and pups in litters that later were lost. We used video recordings of females that lost their entire litter to observe females in detail from parturition until the pups died. In total, 10 C57BL/6 females (wildtype and the knockouts Hfe-/- and β2m-/-) were studied, housed in Makrolon II cages with or without access to a small amount of nesting material.
  
  
  RESULTS
  Three of the females had pups that were never seen moving, and another three females had one or two pups that never moved, indicating that some pups were most likely still-born. In five females with live-born pups, detailed observations from the time when a pup was last seen moving until it died were possible to carry out. We observed females eating dead offspring and interacting with both moving and dead pups. However, we never observed a pup stop moving when manipulated by the female, nor were any wounds seen in the pups. Hence, we found no evidence of infanticide when studying females that had lost their entire litter.
  
  
  CONCLUSIONS
  These results suggest that other causes than infanticide plays a major role in mouse pup death, and stress the need for more systematic and careful investigations of the causality of litter loss.
authors.affiliation: Department of Animal Environment and Health, Swedish University of Agricultural Sciences,PO Box 234,532 23 Skara, Sweden. elin.weber@slu.se.
authors.forename: Elin M
authors.initials: EM
authors.lastname: Weber
authors.forename: Bo
authors.initials: B
authors.lastname: Algers
authors.forename: Jan
authors.initials: J
authors.lastname: Hultgren
authors.forename: I Anna S
authors.initials: IA
authors.lastname: Olsson
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001522:Behavior, Animal; D002190:Cannibalism; D005260:Female; D005786:Gene Expression Regulation; D000071020:Hemochromatosis Protein; D015395:Histocompatibility Antigens Class I / Q000235:genetics / Q000378:metabolism; D008425:Maternal Behavior; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011247:Pregnancy; D050497:Stillbirth; D001613:beta 2-Microglobulin / Q000235:genetics / Q000378:metabolism
chemical_list: D000071020:Hemochromatosis Protein; C499535:Hfe protein, mouse; D015395:Histocompatibility Antigens Class I; D008565:Membrane Proteins; D001613:beta 2-Microglobulin