Promiscuous behaviour disrupts pregnancy block in domestic horse mares
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Based on questionnaires from horse breeders, we found that bringing a pregnant mare which had been mated away from home into a vicinity of a familiar male who was not the father of her foetus increased probability of pregnancy disruption. These mares aborted in 31% of cases, while none of those mated within the home stable aborted. Repeated sexual activity either by a stallion or dominant gelding from the normal home group was observed shortly after the mare came from away-mating. Pregnant mares isolated from home males by a fence were even seen soliciting them over the fence. We speculate that, once returned to the home “herd”, and introduced to familiar males, mares were more likely to terminate their pregnancy to save energy and avoid likely future infanticidal loss of their progeny by dominant male(s) of the home social group. This is a newly discovered phenomenon where a mare manipulates the male’s paternity assessment by promiscuous mating. It may explain a common increased incidence of foetal loss in domestic horses occurring in nearly 40% of pregnancies. We conclude that the common practice of transporting the mare for mating and then bringing her back to an environment with males, stallions or geldings, which did not sire the foetus, is the main cause of high percentages of pregnancy disruption in domestic horses.
KeywordsFoetal loss Domestic horse Bruce effect Sexual behaviour
We thank Petr Šimeček, Adam Dušek and other colleagues from the department for discussion to Sarah Blaffer Hrdy for encouragement and Joy Tripovich and Rory Putman for improving English. This work was supported by the Ministry of Agriculture of the Czech Republic (grant number MZe 0002701404).
Conflict of interest
The authors declare that they have no conflict of interest.
- Aldomy F, Hussein NO, Sawalha L, Khatatbeh K, Aldomy A (2009) A national survey of perinatal mortality in sheep and goats in Jordan. Pak Vet J 29:102–106Google Scholar
- Berger J (1986) Wild horses of the Great Basin: social competition and population size. University of Chicago Press, ChicagoGoogle Scholar
- Boyd L, Keiper R (2005) Behavioural ecology of feral horses. The domestic horse: the origins, development, and management of its behaviour. Cambridge University Press, Cambridge, pp 55–82Google Scholar
- Horugel U, Pohle D (2008) Causes of abortions of horses in Saxonia from 2002 to 2007. Prakt Tierarzt 89:644–647Google Scholar
- Lucas Z, Raeside JI, Betteridge KJ (1991) Noninvasive assessment of the incidences of pregnancy and pregnancy loss in the feral horses of Sable Island. J Reprod Fert Supplement No 44:479–488Google Scholar
- Pluháček J, Bartoš L (2005) Further evidence for male infanticide and feticide in captive plains zebra, Equus burchelli. Folia Zool 54:258–262Google Scholar
- Rambags BPB, Colenbrander B, Stout TAE (2003) Early pregnancy loss in aged mares: probable causes and possible cures. Pferdeheilkunde 19:653–656Google Scholar
- Stokes ME, Davis CS, Koch GG (2000) Categorical data analysis using the SAS system, 2nd edn. SAS Institute Inc., CaryGoogle Scholar
- Zharkikh TL (1999) The cases of infanticide in the Przewalskii horses in Askajnia-Nova. Vestn zool Suppl 11:80–82Google Scholar