Equine and Animal Cognition Reference Database -- Query Results

Bartos, L., Bartosova, J., Pluhacek, J., & Sindelarova, J. (2012). Promiscuous behaviour disrupts pregnancy block in domestic horse (Equus caballus) mares: A counterstrategy against possible male infanticide. In K. Krueger (Ed.), Proceedings of the 2. International Equine Science Meeting (Vol. in press). Wald: Xenophon Publishing. Abstract: It is a common practice that the domestic horse mare is removed from her home environment and transported elsewhere for mating. After conceiving she is returned back into her home environment and social group, containing often familiar stallions and geldings. If we presume that the behavioural adaptation for infanticide relevant for wild, or free-ranging horses has not be lost in domestication (and it is clear that it remains at least within feral populations), then we may expect that, unless prevented by fencing or other management measures, the dominant males in the home social group may subsequently attempt infanticide. Foetal loss is a common phenomenon in domestic horses, being usually substantially higher than that in other domestic ungulates reaching up to 40%. One adaptive response to infanticide risk in polygynous populations is the Bruce effect. Pregnant females terminate their pregnancies when exposed to a dominant strange male. Our previous studies on plain zebra suggested the possibility of the Bruce effect also in equids. In this study we therefore tested the presumption that the Bruce effect could explain foetal loss in domestic horses. Based on reproduction records from horse breeders, we have recently published 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 (Behav Ecol Sociobiol DOI: 10.1007/s00265-011-1166-6). 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. Therefore, there is probably some other mechanism than the Bruce effect leading to pregnancy block in the mare. 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. Additional data has now showed that if a mare was mated away from home and was brought into an environment containing mares only, she was less likely to abort than a mare returning to an environment containing familiar male or males. This further supports our above hypothesis. Supported by AWIN, EU FP7 project No. 266213. Keywords: foetal loss, domestic horse, Bruce effect, sexual behaviour https://references.equine-behaviour.de/show.php?record=5544
Pluhacek, J., Bartos, L., & Culik, L. (2006). High-ranking mares of captive plains zebra Equus burchelli have greater reproductive success than low-ranking mares. Appl. Anim. Behav. Sci., 99(3-4), 315–329. Abstract: Plains zebra live in harems that include one to six adult mares. Between these mares is a strong order of social hierarchy. The social rank of an equid mare is typically correlated with her age. Further, high-ranking captive plains zebra mares produce more surviving offspring than low-ranking mares. The objectives of this study were to, first, examined the factors that influence social rank of captive plains zebra mares, and second, test if high-ranking mares conceive earlier and if they have shorter inter-birth intervals than low-ranking ones. We observed three herds of captive plains zebra (a total of 18 mares) at the Dvur Kralove Zoo, Czech Republic. During the 831 h of observation, we recorded 1713 aggressive interactions (biting and offensive kicking) between the mares. These data were used to determine, for each mare, the total number of mares that dominated her in each period of social stability. The GLMM model revealed that older mares were dominated by a lower number of mares than the younger mares. We also found that the probability that a mare would conceive declined with the increasing number of dominant mares. Further, we tested the relationship between the number of dominant mares and the inter-birth interval using 29 intervals for 15 mares. These inter-birth intervals were divided into two groups. When a stallion was continuously present in the herd, the intervals lasted from one birth to the next birth (natural intervals). When a herd was without a stallion, the intervals lasted from the release of the stallion into the herd to the birth of foal (stallion-influenced intervals). The analysis revealed that the inter-birth intervals decreased with an increasing number of dominant mares and the natural intervals decreased with an increasing number of offspring successfully reared by a mare. This finding is the first one in equids and contributes to the previous findings that suggest that social status influences reproductive success. Keywords: Equus burchelli; Social hierarchy; Reproductive success; Inter-birth interval; Zoo; Zebra https://references.equine-behaviour.de/show.php?record=2228

Abstract: It is a common practice that the domestic horse mare is removed from her home environment and transported elsewhere for mating. After conceiving she is returned back into her home environment and social group, containing often familiar stallions and geldings. If we presume that the behavioural adaptation for infanticide relevant for wild, or free-ranging horses has not be lost in domestication (and it is clear that it remains at least within feral populations), then we may expect that, unless prevented by fencing or other management measures, the dominant males in the home social group may subsequently attempt infanticide. Foetal loss is a common phenomenon in domestic horses, being usually substantially higher than that in other domestic ungulates reaching up to 40%. One adaptive response to infanticide risk in polygynous populations is the Bruce effect. Pregnant females terminate their pregnancies when exposed to a dominant strange male. Our previous studies on plain zebra suggested the possibility of the Bruce effect also in equids. In this study we therefore tested the presumption that the Bruce effect could explain foetal loss in domestic horses. Based on reproduction records from horse breeders, we have recently published 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 (Behav Ecol Sociobiol DOI: 10.1007/s00265-011-1166-6). 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. Therefore, there is probably some other mechanism than the Bruce effect leading to pregnancy block in the mare. 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. Additional data has now showed that if a mare was mated away from home and was brought into an environment containing mares only, she was less likely to abort than a mare returning to an environment containing familiar male or males. This further supports our above hypothesis. Supported by AWIN, EU FP7 project No. 266213.

Keywords: foetal loss, domestic horse, Bruce effect, sexual behaviour

https://references.equine-behaviour.de/show.php?record=5544

Abstract: Plains zebra live in harems that include one to six adult mares. Between these mares is a strong order of social hierarchy. The social rank of an equid mare is typically correlated with her age. Further, high-ranking captive plains zebra mares produce more surviving offspring than low-ranking mares. The objectives of this study were to, first, examined the factors that influence social rank of captive plains zebra mares, and second, test if high-ranking mares conceive earlier and if they have shorter inter-birth intervals than low-ranking ones. We observed three herds of captive plains zebra (a total of 18 mares) at the Dvur Kralove Zoo, Czech Republic. During the 831 h of observation, we recorded 1713 aggressive interactions (biting and offensive kicking) between the mares. These data were used to determine, for each mare, the total number of mares that dominated her in each period of social stability. The GLMM model revealed that older mares were dominated by a lower number of mares than the younger mares. We also found that the probability that a mare would conceive declined with the increasing number of dominant mares. Further, we tested the relationship between the number of dominant mares and the inter-birth interval using 29 intervals for 15 mares. These inter-birth intervals were divided into two groups. When a stallion was continuously present in the herd, the intervals lasted from one birth to the next birth (natural intervals). When a herd was without a stallion, the intervals lasted from the release of the stallion into the herd to the birth of foal (stallion-influenced intervals). The analysis revealed that the inter-birth intervals decreased with an increasing number of dominant mares and the natural intervals decreased with an increasing number of offspring successfully reared by a mare. This finding is the first one in equids and contributes to the previous findings that suggest that social status influences reproductive success.