Table 3.
A comparison of models analyzing variation in annual breeding success and calf survival in females aged 19 and over. All models were generalized linear mixed-effects models (GLMMs) with binomial errors and logit link function. Models were compared using AIC values, where the best-supported model for each trait is shown in bold italics. ΔAIC values are shown relative to the best-supported model. ELF(2) groups individuals by their early-life fecundity based on whether they reproduced in early life; ELF(3) is a factor grouping individuals based on whether they had 0, 1 or 2 or more calves before age 19 (see Materials and methods). For annual breeding success, we analyzed 7044 records from 401 reproductive females who survived at least until age 19; for calf survival, we analyzed 744 calves born to 333 mothers after the age of 19.
| Model | Structure | Breeding success | Calf survival | ||
|---|---|---|---|---|---|
| AIC | ΔAIC | AIC | ΔAIC | ||
| 0 | Null | 5526.22 | 3.32 | 842.95 | 22.24 |
| 1 | Age | 5522.90 | 0.00 | 839.51 | 18.80 |
| 2 | Age2 | 5524.46 | 1.57 | 838.17 | 17.46 |
| 3 | Age3 | 5526.07 | 3.18 | 830.50 | 9.79 |
| 4 | ELF(3) | 5526.74 | 3.84 | 834.68 | 13.97 |
| 5 | ELF(2) | 5526.16 | 3.26 | 844.94 | 24.23 |
| 6 | ELF(3) + Age | 5523.09 | 0.19 | 829.25 | 8.54 |
| 7 | ELF(3) + Age2 | 5524.65 | 1.76 | 829.79 | 9.08 |
| 8 | ELF(3) + Age3 | 5526.24 | 3.35 | 820.71 | 0.00 |
| 9 | ELF(2) + Age | 5522.66 | −0.24 | 841.36 | 20.65 |
| 10 | ELF(2) + Age2 | 5524.22 | 1.32 | 840.03 | 19.32 |
| 11 | ELF(2) + Age3 | 5525.83 | 2.93 | 832.21 | 11.50 |
| 12 | ELF(3): Age + Age | 5522.35 | −0.54 | 832.89 | 12.18 |
| 13 | ELF(3): Age + Age2 | 5523.86 | 0.96 | 833.31 | 12.60 |
| 14 | ELF(3): Age + Age3 | 5525.47 | 2.57 | 823.73 | 3.02 |
| 15 | ELF(2): Age + Age | 5522.97 | 0.07 | 843.28 | 22.57 |
| 16 | ELF(2): Age + Age2 | 5524.52 | 1.62 | 841.90 | 21.19 |
| 17 | ELF(2): Age + Age3 | 5526.16 | 3.26 | 834.18 | 13.47 |
ELF, early life fecundity.