Variance in offspring sex ratio and maternal allocation in a highly invasive mammal

Skewed sex ratios at birth are widely reported in wild populations, however the extent to which parents are able to modulate the sex ratio of offspring to maximize their own fitness remains unclear. This is particularly true for highly polytocous species as maximizing fitness may include trade-offs between sex ratio and the size and number of offspring in litters. In such cases, it may be adaptive for mothers to adjust both the number of offspring per litter and offspring sex to maximize individual fitness. Investigating maternal sex allocation in wild pigs (Sus scrofa) under stochastic environmental conditions, we predicted that, under favorable conditions, high quality mothers (larger, older) would produce male-biased litters and invest more in producing larger litters with more males. We also predicted sex ratio would vary relative to litter size, with a male-bias among smaller litters. We found evidence that increasing wild boar ancestry, maternal age and condition, and resource ava..., This study was conducted at the Savannah River Site (SRS), a 78,000 ha U.S. Department of Energy facility located in Aiken, Barnwell, and Allendale counties, South Carolina, USA. We sampled from live-trapped (and consequently released for other studies, e.g., neonate survival [Chinn et al. 2021]) and humanely-euthanized according to established protocols (A2015 12-017) wild pigs throughout the year between March 2017 and July 2019. We collected fetal data, tissue for genetic analysis, and morphological measurements from females >27 kg to quantify litter and maternal attributes (n = 160). We weighed and measured each female dorsally from snout to base of tail. We calculated a standardized body condition index (subsequently referred to as maternal condition) for each individual as mass/length (LaBocha et al., 2014). We measured extraneous fat reserves, a quantitative measurement of maternal nutritional condition, from culled females and used it as a proxy for local resource availabilit..., All analyses were performed in R 4.0.5 (R Core Team, 2021). We used package lme4 (Bates et al. 2015) for some analyses., # Chinn et al. 2023 Variance in offspring sex ratio and maternal allocation in a highly invasive mammal

[https://doi.org/10.5061/dryad.pzgmsbcrz](https://doi.org/10.5061/dryad.pzgmsbcrz)

Manuscript citation: Chinn, S. M., Smyser, T., & Beasley, J. C. (2023). Variance in offspring sex ratio and maternal allocation in a highly invasive mammal. *Ecology and Evolution*, *13*(5), e10136.

\## Corresponding author: Dr. Sarah M. Chinn, [[e-mail]](mailto:[e-mail])

These are original data for the manuscript published in Ecology and Evolution. This file explains all variables in the dataset that accompany Chinn et al. 2023 (Ecology and Evolution).

For data not collected for a specific variable are represented by 'NA' in the datasets.

## Description of the data and file structure

\# 1. Dataset: Chinn.et.al.2023_SexRatioData.csv

Analyses: Sex Ratio Triver-Willard (GLM), Allocation Williams (LM), Fig5a Allocation vs boar ancestry, Fig5b Allocation vs maternal cond...