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Ontogenesis of endocrine function in silver foxes under domestication
Abstracts /Applied Animal Behaviour Science 44 (1995) 257-281
273
Lambs’ attachment to their mother: Importance of the first sucking bouts R. Nowak Laboratoire de Comportement Animal, CNRS/lNRA, 37380 Nouzilly, France
Abstract
In lambs, attachment to the mother occurs within 24 h after birth. The association of maternal cues with neonatal rewards is believed to provide the basis of this early bonding. I attempted to determine whether sucking was a potent reinforcer in the establishment and maintenance of the attachment process by covering temporarily the udder of the ewe. Newborn lambs (34) were assigned to one of three treatments: they had free access to the udder (group 1) or were prevented from sucking for 6 h either at birth (group 2) or at the age of 3 days (group 3). When tested in a two-choice situation at 24 h of age, lambs from groups 1 and 3 discriminated their mother from an alien ewe (time near mother vs. alien (mean f SE): group 1, 222.7 + 25.5 s vs. 42.7 f 19.7 s, PcO.01; group 3, 210.4+ 15.0 s vs. 61.5* 16.0 s, P
Ontogenesis of endocrine function in silver foxes under domestication I.N. Oskina Institute of Cytology and Genetics, Novosibirsk, Russia
Abstract
For decades, a model experiment with silver foxes ( Vulpes vulpes) selected for defensive behavior has been carried out at this Institute. Certain hormonal systems and their underlying mechanisms were altered in these foxes. The changes concerned pituitary-adrenal and reproductive functions. In the present study, we took account of the fact that the status of steroid hormones in the developing organism has an influence on many reproductive characteristics, persisting through puberty and
214
Abstracts /Applied Animal Behaviour Science 44 (1995) 257-281
manifest in adulthood. We compared the function of the adrenals and gonads during development in females selected for domestic pattern of behavior ( 16 tame animals) and enhanced defense responses to man (13 aggressive animals). Plasma cortisol was significantly lower in tame than aggressive counterparts aged 2-8 months (P < 0.01) . The differences in the course of changes in plasma progesterone between tame and aggressive foxes were similar, although smaller than those of cortisol during this period. The pattern of changes for plasma estradiol was the reverse. In tame females, its estradiol was significantly higher as early as at 3 months (P < 0.05)) and its rise was more sharp during puberty. As a result, the level of plasma estradiol in tame foxes was twice as high as that in aggressive foxes at the ages of 6, 7 and 8 months (P < 0.01). Thus, selection of foxes for domestic behavior has affected the time course of establishment of the function of the gonads and adrenals during development.
Parent-offspring conflict in pigs E.A. Pajorapb, D. Fraserb, D.L. Kramera aDepartment of Biology, McGill University, Montreal, Que. H3A lB1, Canada bCentre for Food and Animal Research, Bldg. 94, Agriculture and Agri-Food Canada, Ottawa, Ont. KlA OC6, Canada
Abstract We tested the hypothesis that sows and piglets are in conflict over parental investment. We assigned 41 multiparous sows to pens confined with their litters (C-sows, n = 17) or pens where they could leave the litter at will (get-away pens, n = 24). Sows in get-away pens were divided into those that spent more than 50% of their time away from piglets (leavers, L-sows, n = 15)) and those that spent less (behaviourally confined, BC-sows, n =9). L-sows nursed less frequently, had a shorter premassage and milk ejection, lost less weight, and returned to oestrus sooner than C- or BC-sows. Compared with piglets of C- and BC-sows, piglets of L-sows ate more creep feed, vocalised to their absent mother, had a higher rate of contact when the sow was present, and did not, lose weight on the day after weaning. With increasing litter age, L-sows terminated a higher proportion of nursings while C- and BC-sows spent a higher proportion of time lying on the udder. These results support the hypothesis that sows and litters are in conflict over the amount of milk provided and that piglets and sows can bias parental investment toward their own optimum.
273
Lambs’ attachment to their mother: Importance of the first sucking bouts R. Nowak Laboratoire de Comportement Animal, CNRS/lNRA, 37380 Nouzilly, France
Abstract
In lambs, attachment to the mother occurs within 24 h after birth. The association of maternal cues with neonatal rewards is believed to provide the basis of this early bonding. I attempted to determine whether sucking was a potent reinforcer in the establishment and maintenance of the attachment process by covering temporarily the udder of the ewe. Newborn lambs (34) were assigned to one of three treatments: they had free access to the udder (group 1) or were prevented from sucking for 6 h either at birth (group 2) or at the age of 3 days (group 3). When tested in a two-choice situation at 24 h of age, lambs from groups 1 and 3 discriminated their mother from an alien ewe (time near mother vs. alien (mean f SE): group 1, 222.7 + 25.5 s vs. 42.7 f 19.7 s, PcO.01; group 3, 210.4+ 15.0 s vs. 61.5* 16.0 s, P
Ontogenesis of endocrine function in silver foxes under domestication I.N. Oskina Institute of Cytology and Genetics, Novosibirsk, Russia
Abstract
For decades, a model experiment with silver foxes ( Vulpes vulpes) selected for defensive behavior has been carried out at this Institute. Certain hormonal systems and their underlying mechanisms were altered in these foxes. The changes concerned pituitary-adrenal and reproductive functions. In the present study, we took account of the fact that the status of steroid hormones in the developing organism has an influence on many reproductive characteristics, persisting through puberty and
214
Abstracts /Applied Animal Behaviour Science 44 (1995) 257-281
manifest in adulthood. We compared the function of the adrenals and gonads during development in females selected for domestic pattern of behavior ( 16 tame animals) and enhanced defense responses to man (13 aggressive animals). Plasma cortisol was significantly lower in tame than aggressive counterparts aged 2-8 months (P < 0.01) . The differences in the course of changes in plasma progesterone between tame and aggressive foxes were similar, although smaller than those of cortisol during this period. The pattern of changes for plasma estradiol was the reverse. In tame females, its estradiol was significantly higher as early as at 3 months (P < 0.05)) and its rise was more sharp during puberty. As a result, the level of plasma estradiol in tame foxes was twice as high as that in aggressive foxes at the ages of 6, 7 and 8 months (P < 0.01). Thus, selection of foxes for domestic behavior has affected the time course of establishment of the function of the gonads and adrenals during development.
Parent-offspring conflict in pigs E.A. Pajorapb, D. Fraserb, D.L. Kramera aDepartment of Biology, McGill University, Montreal, Que. H3A lB1, Canada bCentre for Food and Animal Research, Bldg. 94, Agriculture and Agri-Food Canada, Ottawa, Ont. KlA OC6, Canada
Abstract We tested the hypothesis that sows and piglets are in conflict over parental investment. We assigned 41 multiparous sows to pens confined with their litters (C-sows, n = 17) or pens where they could leave the litter at will (get-away pens, n = 24). Sows in get-away pens were divided into those that spent more than 50% of their time away from piglets (leavers, L-sows, n = 15)) and those that spent less (behaviourally confined, BC-sows, n =9). L-sows nursed less frequently, had a shorter premassage and milk ejection, lost less weight, and returned to oestrus sooner than C- or BC-sows. Compared with piglets of C- and BC-sows, piglets of L-sows ate more creep feed, vocalised to their absent mother, had a higher rate of contact when the sow was present, and did not, lose weight on the day after weaning. With increasing litter age, L-sows terminated a higher proportion of nursings while C- and BC-sows spent a higher proportion of time lying on the udder. These results support the hypothesis that sows and litters are in conflict over the amount of milk provided and that piglets and sows can bias parental investment toward their own optimum.