Uncovering Menopause in Tufted Capuchin Monkeys (Sapajus apella): Analyzing the Relationship between Estradiol, Aging, and Behavioral Estrus in a Captive Population Público
Whiteside, Elizabeth (Spring 2024)
Abstract
Menopause – the end of reproductive function – is a critical phase in a human female’s life; humans can live up to a third of their lives in a post-reproductive stage which is highly unusual among primates. As research on menopause in non-human primates expands, evidence of an age-related cessation of hormone production and fertility is most likely to be seen in other species of non-human primates with extended lifespans. In this study, I examine age-related effects on the concentration of estradiol in fecal samples from female tufted capuchin monkeys (Sapajus apella) to provide evidence for the occurrence of menopause in the oldest members of a captive population. I also validated and employed a human estradiol assay as an effective measurement of the menopausal transition in tufted capuchin females. In addition to investigating age-related hormone changes, I investigate how aging affects the frequency of behavioral estrus in individuals over the age of 30 to further explore the occurrence of menopause in tufted capuchins. I also examine the relationship between estradiol and estrus behaviors in normally cycling individuals to analyze how hormonal changes during the menstrual cycle may influence sexual soliciting behavior in tufted capuchins. Comparing adult (<30 years old) with old-age (over 30-year-old) individuals, I found that estradiol declines significantly with age. Additionally, in a biological validation with a female who had undergone an ovariectomy, I found a significant difference in the pre- versus post-operative estradiol concentration but no significant difference between the ovariectomized condition and the old-age individuals. In terms of behavior, I found that sexual soliciting, or estrus, behaviors decline with age. Unlike previous studies using progesterone, I did not find a strong correlation between high concentrations of fecal estradiol and the onset of estrus suggesting a decoupling of behavioral estrus from ovulation in capuchin monkeys and the potential for deceptive estrus to be occurring. Overall, these results suggest the occurrence of menopause in old-age, captive tufted capuchins and have implications for the capacity to use estradiol to explore menopause in other captively housed, long-lived primates.
Table of Contents
Overview 1
Menopause: Physiology & Expected Hormonal Profile 3
Estradiol & Estrus Behaviors: Honest or Deceptive Signaling? 6
RESEARCH QUESTIONS 10
METHODS 11
Study Site and Subjects 11
Hormones Collection & Extraction 11
Estradiol Assay Validation 12
Serial Dilution 13
Parallelism 13
Accuracy 14
Precision 14
Estradiol Concentrations 14
Biological Validation: Ovariectomy 15
Behavioral Observations 15
DATA ANALYSES 18
Validation 18
Estradiol Assays and Statistical Modeling 18
RESULTS 20
Analytical Validations 21
Serial Dilution 21
Parallelism 23
Accuracy and Precision 24
Estradiol and Old-Age Individuals 25
Effects of an Ovariectomy on Estradiol 28
Effect of Age on Estrus Behaviors 30
Relationship between Estradiol and Estrus 33
DISCUSSION 35
References 40
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Uncovering Menopause in Tufted Capuchin Monkeys (Sapajus apella): Analyzing the Relationship between Estradiol, Aging, and Behavioral Estrus in a Captive Population () | 2024-04-09 16:54:35 -0400 |
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