Table 1.

Results of the animal model analyses (which include only those variables identified by the reduced models) of absolute endocranial volume (millilitres). (Model 1: all-ages, model 2: adult-only (ages 3+). We fitted Bayesian MCMC animal models using the software MCMCglmm (see ‘Animal model analyses' section in Material and methods). CI, 95% Bayesian credible intervals; n.a., not applicable. Model 1 intercept gives the value for females at age 0 with mother's location at parturition being intermediate; model 2 intercept gives the value for females with mother's reproductive status as milk/winter.)

variable	effect	95% CI	p-value
model 1: all-ages (n = 873)
intercept	86.89	63.80–109.92	<0.001
males	14.39	11.43–17.70	<0.001
age 1	5.60	−0.59 to 11.69	0.09
age 2	16.17	7.49–26.88	0.004
ages 3+	17.16	6.21–27.86	<0.001
jaw length	0.79	0.67–0.92	<0.001
birth weight	2.71	1.51–4.00	<0.001
mother's location at parturition
Laundry greens	−1.38	−9.23 to 5.91	0.72
Mid glen	−2.79	−9.42 to 4.12	0.43
North glen	−1.72	−7.54 to 3.65	0.54
South glen	−4.45	−12.53 to 3.28	0.30
Shamnan Insir	−3.79	−10.91 to 2.18	0.27
random effects: posterior mean
birth year	19.31	0.0008–39.43	n.a.
mother's ID	1.93	0.0005–10.11	n.a.
animal	346.10	254.70–445.40	n.a.
residual	172.80	114.30–231.70	n.a.
model 2: adults-only (n = 561)
intercept	139.93	94.50–183.38	<0.002
males	19.19	14.57–23.92	<0.002
jaw length	0.70	0.53–0.88	<0.002
mother's reproductive status:
naive	3.21	−1.51–8.03	0.23
summer/true yelds	7.75	3.67–11.74	<0.002
random effects: posterior mean
mother's ID	12.97	0.0003–59.27	n.a.
animal	463.30	337.2–598.20	n.a.
residual	132.80	51.38–490.70	n.a.