Recognition of Dizygotic and Monozygotic Twin Lambs By Ewes

• Published in: Behaviour 1993, Vol.127 (1-2), p.119-138
• Main Authors: Romeyer, Alain, Porter, Richard H, Poindron, Pascal, Orgeur, Pierre, Chesne, Patrick, Poulin, Nati
• Format: Article
• Language: English
• Subjects: AGNEAU; Amniotic fluid; Animal ethology; Biological and medical sciences; BREBIS; COMPORTAMIENTO MATERNAL; COMPORTEMENT MATERNEL; Computer Science; CORDERO; EWES; Fundamental and applied biological sciences. Psychology; Gender discrimination; GESTATION MULTIPLE; Identical twins; LAMBS; Life Sciences; Mammalia; MATERNAL BEHAVIOUR; Mothers; MULTIPLE BIRTHS; Odors; OVEJA; PARTOS MULTIPLES; Psychology. Psychoanalysis. Psychiatry; Signatures; Twins; Udders; Vertebrata
• ISSN: 0005-7959; 1568-539X
• DOI: 10.1163/156853993X00452

To assess the underlying bases of the phenotypic traits by which lambs are recognized, ewes' responses to both dizygotic and monozygotic twins were observed. When tested several hours post-partum, ewes discriminated between their familiar lamb and its same-sex dizygotic twin that had been isolated at birth. The latter twins were nonetheless treated more positively than were unfamiliar alien lambs. A similar pattern of results was obtained for ewes tested with familiar and isolated monozygotic twins, and an unfamiliar alien lamb. To assess the possible influence of the differential pre-test treatments of familiar and isolated twins and the role of maternal chemical labels in offspring discrimination, the above experiments were replicated with the familiar lamb confined to a mesh cage that prevented maternal licking and nursing. Although isolated dizygotic twins were accepted to a lesser extent than their caged familiar twins, levels of maternal acceptance/rejection did not differ between the isolated twins and unfamiliar alien lambs. In contrast, isolated monozygotic twins were not treated differently than their caged familiar twins, but they were nonetheless distinguished from unfamiliar alien young. These latter data tentatively suggest that ewes may have discerned a greater resemblance between familiar and isolated MZ twins than between DZ twins of these two categories. It therefore appears that lambs' individually distinctive signatures reflect an interaction between genetically influenced processes and non-genetic factors (e.g. environmental or metabolic). /// Chez les ovins, l'agneau nouveau-né possède une signature olfactive individuelle qui sert de base à la sélectivité du lien mère-jeune. Quatre expériences ont été réalisées afin de préciser les facteurs génétiques et environnementaux intervenant dans la constitution de cette odeur. Dans une première étude, nous avons comparé les capacités de discrimination maternelle chez des mères de jumeaux dizygotes de même sexe. Le premier des jeunes restait en interaction normale avec sa mère pendant quatre heures, tandis que le second était isolé de tout contact dès la naissance, de même qu'un agneau étranger. Dans ces conditions, les mères ont clairement discriminé entre leur agneau familier (bien accepté), et le jumeau isolé (moins bien accepté). Cependant, elles ont traité ce dernier de façon plus positive que l'étranger. Dans une deuxième étude, la même comparaison a été effectuée, mais chez des mères de