A family history: Effects of parental age on offspring life-history traits in bighorn sheep
Data files
May 02, 2025 version files 60.31 KB
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dataLongevityDad.csv
5.54 KB
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dataLongevityMum.csv
13.57 KB
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dataLRSDad.csv
12.99 KB
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dataLRSMum.csv
7.17 KB
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dataMassDad.csv
5.75 KB
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dataMassMum.csv
11.88 KB
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README.md
3.41 KB
Abstract
Long-term fitness effects of parental age could affect population dynamics, as age structure can vary considerably over time. Few studies of wild animals, however, have examined the possible long-term fitness consequences of parental age. Based upon 50 years of data on wild bighorn sheep, we investigated how parental age affected three offspring traits – mass at three years, longevity, and female lifetime reproductive success. We also tested for a survival filter which could mask or increase fitness effects of parental age. Our results showed a significant, quadratic negative association between maternal age, offspring longevity and female lifetime reproductive success. Offspring born to mothers aged 5-6 years lived about 2 years longer and weaned about 1.5 lambs more than siblings born to mothers aged 12-13 years. The effect of paternal age was not significant. There was also a positive association between the longevity of mothers and offspring. We did not detect any effects of parental age on mass at three years for offspring of either sex. These results demonstrate the presence of persistent maternal age effects in a long-lived species. The sex-specific effects support the importance of analyzing maternal and paternal age effects separately, as well as effects on female and male offspring. This study advances our understanding of evolutionary processes and population dynamics in wild long-lived mammals.
Dataset DOI: 10.5061/dryad.7d7wm3868
Description of the data and file structure
This dataset contains information on individual sheep, including their ID, sex, mass at 3 years old, birth and death years, parental information, and reproductive traits.
Files and variables
File: dataLongevityDad.csv
Description: This dataset contains information on offspring longevity in relation to paternal age and longevity. It includes details on the focal individual's birth and death years, parental identifiers, and the number of adult females in the population.
Variables
- ID: Unique identifier for each sheep.
- idSex: Sex of the focal individual (*F * for female, M for male).
- idLongevity: Longevity, in years, of the focal individual (the offspring).
- birthYear: Year the individual was born (the cohort).
- deathYear: Year the individual died (corresponding to the last sighting).
- mumID: Unique identifier for the individual's mother (dam).
- dadID: Unique identifier for the individual's father (sire).
- dadLongevity: Total lifespan of the father (years).
- dadAgeAtConception: Age (years) of the father at the time of offspring conception (also simply dadAge in some analyses).
- fem: Number of females older than 2 years in the population.
File: dataLongevityMum.csv
Description: This dataset is structured similarly to dataLongevityDad.csv, but focuses on maternal age and longevity effects on offspring longevity. It includes additional variables specific to the mother.
Additional Variables (not in dataLongevityDad.csv):
- mumAge: Age, in years, of the mother at the time of offspring birth.
- mumLongevity: Total lifespan of the mother (years).
Files: dataMassDad.csv and dataMassMum.csv
Description: These datasets contain information used for mass analyses. All variables, except the following, are defined consistently with the previous datasets. The data are divided into father and mother files, focusing on paternal and maternal influences on the offspring’s mass.
Variables:
- massAt3yoFall: Body mass, in kg, of the offspring measured in the fall of their third year.
- fem3yo: Number of females older than 2 years in the population when the offspring was 3 years old.
Files: dataLRSMum.csv and dataLRSDad.csv
Description: These datasets are used for analyzing lifetime reproductive success (LRS) in relation to parental age and longevity. The datasets are divided based on whether the focus is on maternal or paternal effects on offspring LRS. All other variables are defined consistently with previous datasets.
Variables
- nbLbWeaned: The number of lambs successfully weaned by the focal individual (offspring); this variable is recorded for females only.
- nbLbProduced: The total number of lambs born to the focal individual (offspring), regardless of survival; this variable is recorded for females only.
- Note: For paternal LRS, we retained the full dataset, including missing values marked as 'NA', because the reproductive success of males (fathers) is less completely documented than that of females (mothers).
Code/software
Microsoft Excel, Numbers, LibreOffice.