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.
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Agrell J, Wolff JO, Ylönen H (1998) Counter-strategies to infanticide in mammals: costs and consequences. Oikos 83:507–517
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 29:102–106
Asa CS, Goldfoot DA, Garcia MC, Ginther OJ (1980) Sexual behavior in ovariectomized and seasonally unovulatory pony mares (Equus caballus). Horm Behav 14:46–54
Asa CS, Goldfoot DA, Ginther OJ (1983) Assessment of the sexual-behavior of pregnant mares. Horm Behav 17:405–413
Bain AM (1969) Foetal losses during pregnancy in the thoroughbred mare; a record of 2562 pregnancies. N Z Vet J 17:155–158
Becker SD, Hurst JL (2009) Female behaviour plays a critical role in controlling murine pregnancy block. Proc Roy Soc Lond B 276:1723–1729
Berger J (1983) Induced abortion and social factors in wild horses. Nature 303:59–61
Berger J (1986) Wild horses of the Great Basin: social competition and population size. University of Chicago Press, Chicago
Bowling AT, Touchberry RW (1990) Parentage of Great Basin feral horses. J Wildl Manage 54:424–429
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 55–82
Bruce HM (1959) An exteroreceptive block to pregnancy in the mouse. Nature 184:105
Bruce HM (1960) A block of pregnancy in the mouse caused by proximity of strange males. J Reprod Fertil 1:96–103
Crowell-Davis SL (2007) Sexual behavior of mares. Horm Behav 52:12–17
Duncan P (1982) Foal killing by stallions. Appl Anim Ethol 8:567–570
Ebensperger LA (1998) Strategies and counterstrategies to infanticide in mammals. Biol Rev 73:321–346
Gray ME (2009) An infanticide attempt by a free-roaming feral stallion (Equus caballus). Biol Let 5:23–25
Hayes KEN, Ginther OJ (1989) Relationship between estrous behavior in pregnant mares and the presence of a female conceptus. J Equine Vet Sci 9:316–318
Hedberg Y, Dalin AM, Forsberg M, Lundeheim N, Sandh G, Hoffmann B, Ludwig C, Kindahl H (2007) Effect of ACTH (tetracosactide) on steroid hormone levels in the mare—part B: effect in ovariectomized mares (including estrous behavior). Anim Reprod Sci 100:92–106
Hooper RN, Taylor TS, Varner DD, Blanchard TL (1993) Effects of bilateral ovariectomy via colpotomy in mares—23 cases (1984–1990). J Am Vet Med Assoc 203:1043–1046
Horugel U, Pohle D (2008) Causes of abortions of horses in Saxonia from 2002 to 2007. Prakt Tierarzt 89:644–647
Hrdy SB (1979) Infanticide among animals—review, classification, and examination of the implications for the reproductive strategies of females. Ethol Sociobiol 1:13–40
Kaseda Y, Khalil AM, Ogawa H (1995) Harem stability and reproductive success of Misaki feral mares. Equine Vet J 27:368–372
Kirkpatrick JF, Turner JW (1991) Changes in herd stallions among feral horse bands and the absence of forced copulation and induced abortion. Behav Ecol Sociobiol 29:217–219
Kolter L, Zimmermann W (1988) Social-behavior of przewalski horses (Equus-przewalskii-przewalskii) in the Cologne zoo and its consequences for management and housing. Appl Anim Behav Sci 21:117–145
Kowalewski MM, Garber PA (2010) Mating promiscuity and reproductive tactics in female black and gold Howler monkeys (Alouatta caraya) inhabiting an island on the Parana River, Argentina. Amer J Primatol 72:734–748
Labov JB (1981) Male social status, physiology, and ability to block pregnancies in female house mice (Mus musculus). Behav Ecol Sociobiol 8:287–291
Labov JB, Huck WU, Elwood RW, Brooks RJ (1985) Current problems in the study of infanticidal behavior of rodents. Quart Rev Biol 60:1–20
Lee JI, Kim IH (2007) Pregnancy loss in dairy cows: the contributing factors, the effects on reproductive performance and the economic impact. J Vet Sci 8:283–288
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 44:479–488
Morehead JP, Blanchard TL, Thompson JA, Brinsko SP (2002) Evaluation of early fetal losses on four equine farms in central Kentucky: 73 cases (2001). J Am Vet Med Assoc 220:1828–1830
Paisley LG, Mickelsen WD, Frost OL (1978) Survey of incidence of prenatal mortality in cattle following pregnancy diagnosis by rectal palpation. Theriogenology 9:481–491
Penzhorn BL (1984) A long term study of social organization and behavior of Cope mountain zebras Equus zebra zebra. Ztschr Tierpsychol 64:97–146
Platt H (1973) Etiological aspects of abortion in thoroughbred mare. J Comp Pathol 83:199–205
Pluháček J, Bartoš L (2000) Male infanticide in captive plains zebra, Equus burchelli. Anim Behav 59:689–694
Pluháček J, Bartoš L (2005) Further evidence for male infanticide and feticide in captive plains zebra, Equus burchelli. Folia Zool 54:258–262
Rambags BPB, Colenbrander B, Stout TAE (2003) Early pregnancy loss in aged mares: probable causes and possible cures. Pferdeheilkunde 19:653–656
Ryder OA, Massena R (1988) A case of male infanticide in Equus przewalskii. Appl Anim Behav Sci 21:187–190
Stokes ME, Davis CS, Koch GG (2000) Categorical data analysis using the SAS system, 2nd edn. SAS Institute Inc., Cary
van Noordwijk MA, van Schaik CP (2000) Reproductive patterns in eutherian mammals: adaptations against infanticide? In: van Schaik CP, Janson CH (eds) Infanticide by males and its implications. Cambridge University Press, New York, pp 322–360
Vanderwall DK (2008) Early embryonic loss in the mare. J Equine Vet Sci 28:691–702
Wolff JO, Macdonald DW (2004) Promiscuous females protect their offspring. Trends Ecol Evol 19:127–134
Zharkikh TL (1999) The cases of infanticide in the Przewalskii horses in Askajnia-Nova. Vestn zool Suppl 11:80–82
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.
Communicated by M. Festa-Bianchet
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Bartoš, L., Bartošová, J., Pluháček, J. et al. Promiscuous behaviour disrupts pregnancy block in domestic horse mares. Behav Ecol Sociobiol 65, 1567–1572 (2011). https://doi.org/10.1007/s00265-011-1166-6
- Foetal loss
- Domestic horse
- Bruce effect
- Sexual behaviour