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Animals : an open access journal from MDPI2023; 13(1); doi: 10.3390/ani13010176

Laissez-Faire Stallions? Males’ Fecal Cortisol Metabolite Concentrations Do Not Vary with Increased Female Turnover in Feral Horses (Equus caballus).

Abstract: Stress responses can be triggered by several physical and social factors, prompting physiological reactions including increases in glucocorticoid concentrations. In a population of feral horses (Equus caballus) on Shackleford Banks, North Carolina, females previously immunized with the immunocontraceptive agent porcine zona pellucida (PZP) change social groups (bands) more often than unimmunized females, disrupting the social stability within the population. We assessed the effects of increased female group changing behavior (or female turnover) on individual male stress by comparing fecal cortisol metabolite (FCM) concentrations among stallions experiencing varying amounts of female group changing behavior. FCM concentrations did not significantly correlate with female turnover. Similarly, FCM concentrations were not dependent upon the timing of female group changing behavior. These findings suggest that female turnover rate has little influence on physiological measures of stress in associated stallions. That said, Shackleford stallions experiencing increased female turnover do engage in behaviors typically associated with stress (increased vigilance, highly escalated male-male conflicts). Future work should compare FCM concentrations across time within populations and among populations managed under different strategies to better isolate factors influencing stallion stress physiology. Such studies are especially important if we are to determine how changes in female behavior related to immunocontraception impact physiological and behavioral indicators of stress for non-target animals. Finally, our study highlights the importance of considering both physiological and behavioral measures when investigating animal responses to potentially challenging situations.
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Publication Date: 2023-01-03 PubMed ID: 36611784PubMed Central: PMC9817692DOI: 10.3390/ani13010176Google Scholar: Lookup
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  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research investigates whether the disruptive behavior of female horses, particularly their frequent changes in social groups, impacts the stress levels of male horses, measured through cortisol levels in their feces. Surprisingly, the study finds no correlation between female behavior and cortisol levels in males, hinting that males do not physiologically stress over such disruptions.

Introduction and Methodology

  • The study was conducted on a population of feral horses on Shackleford Banks, North Carolina.
  • In this population, it was observed that females who had been immunized with the contraceptive agent porcine zona pellucida (PZP) changed social groups more frequently than those who had not been immunized.
  • This behavior was seen to disrupt the social stability of the population.
  • The researchers sought to understand whether this increased female group changing behavior, or female turnover, had any effect on the stress levels of the individual male horses.
  • They measured the stress by comparing the levels of cortisol metabolite in the feces of stallions who were experiencing different amounts of female group changing behavior.

Results

  • The results revealed that the fecal cortisol metabolite (FCM) concentrations did not significantly correlate with female turnover.
  • In other words, the stress levels of the stallions did not seem to increase as a result of frequent changes in the female social groups.
  • Additionally, there was no significant change in FCM concentrations based on the timing of female group changing behavior.

Implications and Future Directions

  • Despite the lack of physiological stress indicators, the stallions did show behavioral changes like increased vigilance and escalated male-male conflicts which are typically associated with stress.
  • This hints that changes in female social groups do affect stallions, but this effect is not reflected in cortisol levels.
  • Future research should focus on comparing FCM concentrations across time within and among populations managed under different strategies.
  • It is crucial to understand how changes in female behavior, especially those associated with immunocontraception, can impact the stress indicators of non-target animals.
  • The study underlines the significance of considering both physiological and behavioral measures when studying animal responses to challenging situations.

Cite This Article

APA
Jones MM, Nuñez CMV. (2023). Laissez-Faire Stallions? Males’ Fecal Cortisol Metabolite Concentrations Do Not Vary with Increased Female Turnover in Feral Horses (Equus caballus). Animals (Basel), 13(1). https://doi.org/10.3390/ani13010176

Publication

Animals : an open access journal from MDPI
ISSN: 2076-2615
NlmUniqueID: 101635614
Country: Switzerland
Language: English
Volume: 13
Issue: 1

Researcher Affiliations

Jones, Maggie M
  • Department of Natural Resource Ecology and Management, Iowa State University, 2310 Pammel Dr., Ames, IA 50011, USA.
  • School of Natural Resources and Environment, University of Florida, P.O. Box 116455, Building 0724, 103 Black Hall, Gainesville, FL 32611, USA.
Nuñez, Cassandra M V
  • Department of Biological Sciences, The University of Memphis, 3774 Walker Avenue, Ellington Hall, Room 239, Memphis, TN 38512, USA.

Grant Funding

  • 1744592 / National Science Foundation
  • project IOW05509 / USDA National Institute of Food and Agriculture Hatch Multistate Funding

Conflict of Interest Statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

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Citations

This article has been cited 5 times.
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  5. Górecka-Bruzda A, Jaworska J, Stanley CR. The Social and Reproductive Challenges Faced by Free-Roaming Horse (Equus caballus) Stallions. Animals (Basel) 2023 Mar 24;13(7).
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