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.)

variableeffect95% CIp-value
model 1: all-ages (n = 873)
 intercept86.8963.80–109.92<0.001
 males14.3911.43–17.70<0.001
 age 15.60−0.59 to 11.690.09
 age 216.177.49–26.880.004
 ages 3+17.166.21–27.86<0.001
 jaw length0.790.67–0.92<0.001
 birth weight2.711.51–4.00<0.001
 mother's location at parturition
  Laundry greens−1.38−9.23 to 5.910.72
  Mid glen−2.79−9.42 to 4.120.43
  North glen−1.72−7.54 to 3.650.54
  South glen−4.45−12.53 to 3.280.30
  Shamnan Insir−3.79−10.91 to 2.180.27
 random effects: posterior mean
  birth year19.310.0008–39.43n.a.
  mother's ID1.930.0005–10.11n.a.
  animal346.10254.70–445.40n.a.
  residual172.80114.30–231.70n.a.
model 2: adults-only (n = 561)
 intercept139.9394.50–183.38<0.002
 males19.1914.57–23.92<0.002
 jaw length0.700.53–0.88<0.002
 mother's reproductive status:
  naive3.21−1.51–8.030.23
  summer/true yelds7.753.67–11.74<0.002
 random effects: posterior mean
  mother's ID12.970.0003–59.27n.a.
  animal463.30337.2–598.20n.a.
  residual132.8051.38–490.70n.a.