Hair Cortisol and Testosterone Concentrations in Relation to Maturity and Breeding Status of Male Feral Horses
Steroid-hormone concentrations from non-invasively obtained biomarkers, like hair, can provide a representation of circulating hormones diffused over relatively long time periods (e.g., weeks or months). The hormone cortisol is often associated with physiological or even psychological stress, while...
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MDPI AG
2023-06-01
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| Series: | Animals |
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| Online Access: | https://www.mdpi.com/2076-2615/13/13/2129 |
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| author | Sarah A. Medill David M. Janz Philip D. McLoughlin |
| author_facet | Sarah A. Medill David M. Janz Philip D. McLoughlin |
| author_sort | Sarah A. Medill |
| collection | DOAJ |
| description | Steroid-hormone concentrations from non-invasively obtained biomarkers, like hair, can provide a representation of circulating hormones diffused over relatively long time periods (e.g., weeks or months). The hormone cortisol is often associated with physiological or even psychological stress, while testosterone is strongly associated with male development and reproductive success. Increasingly, studies are using hormone levels derived from hair to make inferences among both domestic animals and wildlife. For horses, all previous hair hormone analysis has been done on companion or working animals. We evaluated the levels of hair cortisol (<i>n</i> = 153) and testosterone (<i>n</i> = 48) from 136 feral horses living on Sable Island, Canada that have been part of a long-term individual-based study since 2008. This population has been undisturbed and unmanaged for over 50 years, and exhibits the natural social organization for horses, harem defense polygyny. Hair samples were collected in mid to late summer and the segment analyzed corresponds with hair grown during, and following, the peak of the reproductive season. Social position was determined based on the male’s role as either a dominant breeding Stallion (Stallion), a non-breeding subordinate male (tag), adult Bachelor (5 years old or older), or Immature male (2–4 years of age). While there was no difference in hair-cortisol concentration among any class of adult males (i.e., Stallion, tag, or Bachelor), Immature males had significantly lower hair cortisol concentrations than the other groups (<i>p</i> = 0.001). Hair testosterone levels among the four social positions were significantly higher among Stallions (<i>p</i> = 0.04). Hair testosterone concentration was also significantly related to the probability of a male being either a Bachelor or Stallion and was the only variable remaining in AIC<sub>c</sub> model selection (<i>p</i> = 0.016, AIC<sub>c</sub> = 32.3, Null AIC<sub>c</sub> = 38.8). While not a significant relationship, Stallions had a negative correlation between hair cortisol concentrations and testosterone (R<sup>2</sup> = −0.20, <i>p</i> = 0.383), and Bachelors, conversely, had a positive association (R<sup>2</sup> = 0.43, <i>p</i> = 0.246). Our observations of hormone concentrations in relation to physiological, social, or reproductive parameters in this population suggest trends that are similar to what has been established using blood or other matrices. |
| first_indexed | 2024-03-11T01:48:07Z |
| format | Article |
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| institution | Directory Open Access Journal |
| issn | 2076-2615 |
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| last_indexed | 2024-03-11T01:48:07Z |
| publishDate | 2023-06-01 |
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| spelling | doaj.art-749388550ca44154be2b10e3af9a66f22023-11-18T16:03:23ZengMDPI AGAnimals2076-26152023-06-011313212910.3390/ani13132129Hair Cortisol and Testosterone Concentrations in Relation to Maturity and Breeding Status of Male Feral HorsesSarah A. Medill0David M. Janz1Philip D. McLoughlin2Department of Biology, University of Saskatchewan, Saskatoon, SK S7N 5C8, CanadaDepartment of Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, SK S7N 5B4, CanadaDepartment of Biology, University of Saskatchewan, Saskatoon, SK S7N 5C8, CanadaSteroid-hormone concentrations from non-invasively obtained biomarkers, like hair, can provide a representation of circulating hormones diffused over relatively long time periods (e.g., weeks or months). The hormone cortisol is often associated with physiological or even psychological stress, while testosterone is strongly associated with male development and reproductive success. Increasingly, studies are using hormone levels derived from hair to make inferences among both domestic animals and wildlife. For horses, all previous hair hormone analysis has been done on companion or working animals. We evaluated the levels of hair cortisol (<i>n</i> = 153) and testosterone (<i>n</i> = 48) from 136 feral horses living on Sable Island, Canada that have been part of a long-term individual-based study since 2008. This population has been undisturbed and unmanaged for over 50 years, and exhibits the natural social organization for horses, harem defense polygyny. Hair samples were collected in mid to late summer and the segment analyzed corresponds with hair grown during, and following, the peak of the reproductive season. Social position was determined based on the male’s role as either a dominant breeding Stallion (Stallion), a non-breeding subordinate male (tag), adult Bachelor (5 years old or older), or Immature male (2–4 years of age). While there was no difference in hair-cortisol concentration among any class of adult males (i.e., Stallion, tag, or Bachelor), Immature males had significantly lower hair cortisol concentrations than the other groups (<i>p</i> = 0.001). Hair testosterone levels among the four social positions were significantly higher among Stallions (<i>p</i> = 0.04). Hair testosterone concentration was also significantly related to the probability of a male being either a Bachelor or Stallion and was the only variable remaining in AIC<sub>c</sub> model selection (<i>p</i> = 0.016, AIC<sub>c</sub> = 32.3, Null AIC<sub>c</sub> = 38.8). While not a significant relationship, Stallions had a negative correlation between hair cortisol concentrations and testosterone (R<sup>2</sup> = −0.20, <i>p</i> = 0.383), and Bachelors, conversely, had a positive association (R<sup>2</sup> = 0.43, <i>p</i> = 0.246). Our observations of hormone concentrations in relation to physiological, social, or reproductive parameters in this population suggest trends that are similar to what has been established using blood or other matrices.https://www.mdpi.com/2076-2615/13/13/2129cortisoltestosteronenon-invasive samplinghairdominanceferal horse |
| spellingShingle | Sarah A. Medill David M. Janz Philip D. McLoughlin Hair Cortisol and Testosterone Concentrations in Relation to Maturity and Breeding Status of Male Feral Horses Animals cortisol testosterone non-invasive sampling hair dominance feral horse |
| title | Hair Cortisol and Testosterone Concentrations in Relation to Maturity and Breeding Status of Male Feral Horses |
| title_full | Hair Cortisol and Testosterone Concentrations in Relation to Maturity and Breeding Status of Male Feral Horses |
| title_fullStr | Hair Cortisol and Testosterone Concentrations in Relation to Maturity and Breeding Status of Male Feral Horses |
| title_full_unstemmed | Hair Cortisol and Testosterone Concentrations in Relation to Maturity and Breeding Status of Male Feral Horses |
| title_short | Hair Cortisol and Testosterone Concentrations in Relation to Maturity and Breeding Status of Male Feral Horses |
| title_sort | hair cortisol and testosterone concentrations in relation to maturity and breeding status of male feral horses |
| topic | cortisol testosterone non-invasive sampling hair dominance feral horse |
| url | https://www.mdpi.com/2076-2615/13/13/2129 |
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