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The Bruce effect revisited: is pregnancy termination in female rodents an adaptation to ensure breeding success after male turnover in low densities?

  • Pregnancy termination after encountering a strange male, the Bruce effect, is regarded as a counterstrategy of female mammals towards anticipated infanticide. While confirmed in caged rodent pairs, no verification for the Bruce effect existed from experimental field populations of small rodents. We suggest that the effect may be adaptive for breeding rodent females only under specific conditions related to populations with cyclically fluctuating densities. We investigated the occurrence of delay in birth date after experimental turnover of the breeding male under different population composition in bank voles (Myodes glareolus) in large outdoor enclosures: one-male-multiple-females (n = 6 populations/18 females), multiple-males-multiplefemales (n = 15/45), and single-male-single-female (MF treatment, n = 74/74). Most delays were observed in the MF treatment after turnover. Parallel we showed in a laboratory experiment (n = 205 females) that overwintered and primiparous females, the most abundant cohort during population lows in thePregnancy termination after encountering a strange male, the Bruce effect, is regarded as a counterstrategy of female mammals towards anticipated infanticide. While confirmed in caged rodent pairs, no verification for the Bruce effect existed from experimental field populations of small rodents. We suggest that the effect may be adaptive for breeding rodent females only under specific conditions related to populations with cyclically fluctuating densities. We investigated the occurrence of delay in birth date after experimental turnover of the breeding male under different population composition in bank voles (Myodes glareolus) in large outdoor enclosures: one-male-multiple-females (n = 6 populations/18 females), multiple-males-multiplefemales (n = 15/45), and single-male-single-female (MF treatment, n = 74/74). Most delays were observed in the MF treatment after turnover. Parallel we showed in a laboratory experiment (n = 205 females) that overwintered and primiparous females, the most abundant cohort during population lows in the increase phase of cyclic rodent populations, were more likely to delay births after turnover of the male than year-born and multiparous females. Taken together, our results suggest that the Bruce effect may be an adaptive breeding strategy for rodent females in cyclic populations specifically at low densities in the increase phase, when isolated, overwintered animals associate in MF pairs. During population lows infanticide risk and inbreeding risk may then be higher than during population highs, while also the fitness value of a litter in an increasing population is higher. Therefore, the Bruce effect may be adaptive for females during annual population lows in the increase phases, even at the costs of delaying reproduction.show moreshow less

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Metadaten
Author:Jana A. Eccard, Melanie Dammhahn, Hannu Ylonen
DOI:https://doi.org/10.1007/s00442-017-3904-6
ISSN:0029-8549
ISSN:1432-1939
Pubmed Id:http://www.ncbi.nlm.nih.gov/pubmed?term=28791488
Parent Title (English):Oecologia
Publisher:Springer
Place of publication:New York
Document Type:Article
Language:English
Year of first Publication:2017
Year of Completion:2017
Release Date:2020/04/20
Tag:Breeding strategies; Dip test; Infanticide; Myodes voles; Sexual conflict; Sexual selection
Volume:185
Page Number:14
First Page:81
Last Page:94
Funder:Finish Academy of Science (Suomen Akatemia); German Science Foundation (DFG) [EC361/11-1]
Organizational units:Mathematisch-Naturwissenschaftliche Fakultät / Institut für Biochemie und Biologie
Peer Review:Referiert