Table 4.

Results of mixed-effects regression models showing significant predictors of trauma and reproductive success in four large breeding groups over an 11-year period (2003–2013).

Final model results*	β, P-value	Regression model specification
Trauma frequency =		Negative binomial regression model (glmer.nb function in R)
Intercept	1.420
Group age (years since formation) +	0.138, p<0.001
Sex ratio (# breeding aged females/males) +	0.030, p=0.005
Group (random effects term)
Reproductive Success =		Linear Gaussian regression model (lmer function in R)
Intercept	84.791
Individual space (meters per animal) +	−0.249, p=0.008
Trauma rate (# trauma/group size) +	−0.116, p=0.039
Sex ratio (# breeding aged females/males) +	−0.419, p=0.041
Group (random effects term)

^*All models included a term accounting for variation in the dependent variable due to group membership. With the size of the dataset, we could only account for varying intercepts, not varying slopes as well.