Changes in herd stallions among feral horse bands and the absence of forced copulation and induced abortion

  title={Changes in herd stallions among feral horse bands and the absence of forced copulation and induced abortion},
  author={J. F. Kirkpatrick and John W. Turner},
  journal={Behavioral Ecology and Sociobiology},
SummaryForced copulation and induced abortion were investigated in a herd of feral horses inhabiting a coastal barrier island. Eight mares were diagnosed pregnant in August and October 1989 by means of urinary and fecal steroid metabolites, prior to documented changes in herd stallions. These mares were observed for harassment and forced copulation by the new stallions and for the presence of foals during the spring and summer of 1990. No incidents of harassment or attempts at forced copulation… 

Management of Wild Horses by Fertility Control: The Assateague Experience

The Assateague Contraceptive Project, a large-scale study of the effects of PZP treatment on women’s fertility, has revealed positive results in both the short and long-term.

Social grouping and maternal behaviour in feral horses (Equus caballus): the influence of males on maternal protectiveness

The rate of aggression between the stallion and foal was a significant predictor of maternal protectiveness, and mare protectiveness was significantly correlated with reduced reproductive success in the subsequent year.

Promiscuous behaviour disrupts pregnancy block in domestic horse mares

It is concluded 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.

Behavioral Factors Affecting Reproduction in Domestic Horses: Sociobiological Approach

Results of three consecutive studies considering infanticide as a male's reproductive strategy and a mare’s counter strategies against it are summarized to explain substantial part of the high incidence of domestic horse fetal loss.

Immunocontraception and increased longevity in equids.

An examination of direct effects of fertility control on two groups of treated animals shows a significant increase in longevity over non-treated animals that is associated with contraceptive treatment.

The Social and Spatial Organisation of Horses

A population of feral horses live in the southern Kaimanawa Ranges, New Zealand. These horses live in polygynous social groups with stable membership, called bands. The Kaimanawa horses were the

Sexual harassment and female gregariousness in the South American sea lion, Otaria flavescens

The behaviour of dominant males and their females in a breeding colony of Otaria flavescens was analysed to investigate the relationship between male harassment and female gregariousness in relation to the size of breeding groups.

How to escape male infanticide: mechanisms for avoiding or terminating pregnancy in mammals

The phenomenon whereby pregnancy may be inhibited or terminated when a female is exposed to non-sire males after mating is often, and rather generally, referred to as the ‘Bruce effect’. Widespread



Induced abortion and social factors in wild horses

  • J. Berger
  • Environmental Science, Biology
  • 1983
Evidence is presented that, rather than killing infants directly, invading males induce abortions in females unprotected by their resident stallions and these females are then inseminated by the new males.

Remotely-delivered immunocontraception in feral horses.

The objectives of this study were to determine the effectiveness of remote delivery, test the contraceptive effectiveness of a PZP vaccine in free-roaming feral mares, determine the contraceptives effectiveness of the vaccine in pregnant and nonpregnant mare, and evaluate the safety of the vaccines for use in pregnant mares.

Pregnancy Determination in Uncaptured Feral Horses

The objective was to develop a test of pregnancy in free-roaming feral horses that is accurate, inexpensive, does not require capture or handling, and does not disturb the population being studied.

Male-induced pregnancy termination in the prairie vole, Microtus ochrogaster.

Postimplantation as well as preimplantation pregnancy in prairie voles can be terminated by replacing the original stud male with an unfamiliar male. The pregnancy is disrupted by the ensuing

Estrone sulfate concentrations as an indicator of fetal demise in horses.

Serum or urinary estrone sulfate measurements provide a simple and accurate test for fetal viability after GD 44 in the mare and seemingly, products of conception are the major source of estrogen during early pregnancy, although there appears to be some ovarian contribution.

Infanticide and other reproductive strategies in the collared lemming, Dicrostonyx groenlandicus

Postparturition effects of unfamiliar males in the collared lemming (Dicrostonyx groenlandicus) are reported and the significance of these effects on reproductive strategies in this species is discussed.

Homosexual rape and sexual selection in acanthocephalan worms.

Acanthocephalan males have cement glands associated with the vas deferens, secretions from which seal the female vagina with a cap after copulation and so prevent subsequent insemination, and this work interprets the evolution of the cement gland and sexual behavior as the result of sexual selection.