Data from: New estimates indicate that males are not larger than females in most mammal species
Data files
Feb 16, 2024 version files 380.12 KB
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Num_Spp_perFamily.ods
4.43 KB
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Num_Spp_perOrder.ods
3.17 KB
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NumSpp_perFamily.csv
2.76 KB
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NumSpp_perOrder.csv
417 B
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README.md
4.50 KB
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Tombak_etal_SSDinMammals_FullDataSet.csv
226.93 KB
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Tombak_etal_SSDinMammals_FullDataSet.ods
137.91 KB
Abstract
Sexual size dimorphism has motivated a large body of research on mammalian mating strategies and sexual selection. Despite some contrary evidence, the narrative that larger males are the norm in mammals – upheld since Darwin’s Descent of Man – still dominates today, supported by meta-analyses that use coarse measures of dimorphism and taxonomically biased sampling. With newly available datasets and primary sources reporting sex-segregated means and variances in adult body mass, we estimated statistically determined rates of sexual size dimorphism in mammals, sampling taxa by their species richness at the family level. Our analyses of wild, non-provisioned populations representing >400 species indicate that although males tend to be larger than females when dimorphism occurs, males are not larger in most mammal species, suggesting a need to revisit other assumptions in sexual selection research.
README: New estimates indicate that males are not larger than females in most mammal species
https://doi.org/10.5061/dryad.280gb5mx0
These files include the R code and raw data used for all analyses and data visualizations in the associated manuscript:
Tombak KJ, Hex SBSW, Rubenstein DI. 2024. New estimates indicate that males are not larger than females in most mammal species. Nature Communications.
Description of the data and file structure
FILE LIST:
SSD_Paper_Code.R: R code used for analyses and generating figures in the manuscript and supplementary materials.
Tombak_etal_SSDinMammals_FullDataSet.csv: the full set of raw data used for analyses and data visualizations.
Tombak_etal_SSDinMammals_FullDataSet.ods: the same as above, in ods format.
Num_Spp_perFamily.csv: data on the number of species per family in each mammalian order with at least ten species, as well as the families of the order Pilosa sampled in our study. These data are from Burgin et al. 2018 (full citation below).
Num_Spp_perFamily.ods: the same as above, in ods format.
Num_Spp_perOrder.csv: data on the number of species in each mammalian order with at least ten species. These data are from Burgin et al. 2018.
Num_Spp_perOrder.ods: the same as above, in ods format.
DATA-SPECIFIC INFORMATION FOR: Tombak_etal_SSDinMammals_FullDataSet.csv and Tombak_etal_SSDinMammals_FullDataSet.ods
1. Number of variables: 18
2. Number of cases/rows: 666
3. Variable List:
Order: Mammalian order
Family: Mammalian family
Species: Common name of mammalian species
Scientific_Name: Latin name of mammalian species
massM: mean body mass, in grams, for adult males reported in the data source
SDmassM: standard deviation of the body mass for adult males reported in the data source
massF: mean body mass, in grams, for adult females reported in the data source
SDmassF: standard deviation of the body mass for adult females reported in the data source
lengthM: mean body length, in cm, for adult males if reported in the data source
SDlengthM: standard deviation of the body length for adult males if reported in the data source
lengthF: mean body length, in cm, for adult females if reported in the data source
SDlengthF: standard deviation of the body length for adult females if reported in the data source
n_M: sample size (number of individuals measured) corresponding to the mean body mass reported for adult males in the data source
n_F: sample size (number of individuals measured) corresponding to the mean body mass reported for adult females in the data source
n_Mlength: sample size (number of individuals measured) corresponding to the mean body length, if reported, for adult males in the data source
n_Flength: sample size (number of individuals measured) corresponding to the mean body length, if reported, for adult females in the data source
Comments: notes on the data, individuals sampled, exclusions/inclusions, or how the data reported from the original source were used to calculate the measures needed in our study
Missing data code: NA
Source: data source
DATA-SPECIFIC INFORMATION FOR: Num_Spp_perFamily.csv and Num_Spp_perFamily.ods
1. Number of variables: 4
2. Number of cases/rows: 81
3. Variable List:
Order: Mammalian order
Family: Mammalian family
Num_Spp: The number of extant species in the family (from Burgin et al. 2018)
FivePercent_Spp: Five percent of the number of extant species in the family
DATA-SPECIFIC INFORMATION FOR: Num_Spp_perOrder.csv and Num_Spp_perOrder.ods
1. Number of variables: 3
2. Number of cases/rows: 17
3. Variable List:
Order: Mammalian order
Num_Spp: Number of extant species in the order (from Burgin et al. 2018)
FivePercent_Spp: Five percent of the number of extant species in the order
Sharing/Access information
Data was derived from the following sources:
- Burgin, C. J., Colella, J. P., Kahn, P. L. & Upham, N. S. How many species of mammals are there? J. Mammal.99, 1–14 (2018).
- See list of sources from which the body mass and body length data for each mammalian species sampled were derived in Tombak_etal_SSDinMammals_FullDataSet.csv or Tombak_etal_SSDinMammals_FullDataSet.ods.
Code/Software
All analyses and data visualizations were generated in RStudio version 4.3.2. The R packages used were ggplot2, gridExtra, dplyr, tidyr, viridis, KneeArrower, and see. Microsoft Powerpoint was used for final compilation of some of the figures (described in the R code attached).
Methods
These data on sex-segregated body mass means and variances were collected from the literature, including existing published datasets and from primary sources. We sampled mammalian families according to their species richness (including the orders and families comprising at least 10 species). We excluded data from sexually immature, captive-bred or food-provisioned, or pregnant individuals when these data were distinguished or when it was indicated that they were mixed into the data (see Methods section in manuscript for the few exceptions). Estimates from museum specimens were generally not used as we wished to make within-population comparisons between the sexes, and domesticated species were excluded apart from semi-domesticated free-ranging reindeer (Rangifer tarandus). Whenever sex-segregated means and variances for body length were presented alongside body mass data in a study included in the dataset, these data were also harvested. Prior to analyses, we filtered the full dataset (attached here) by sample size such that a minimum of 9 males and 9 females were required for inclusion, based on an analysis of the relationship between sample size and 95% confidence intervals for mean body mass (see R code), and removed rows for any duplicated species, keeping only the row with the highest combined (male + female) sample size for each unique species (subspecies were treated as different populations of the same species). Analyses were performed in RStudio (version 4.3.2) and the code used for analyses and data visualization are also appended here.