Table 4.
Structure of the generalized linear mixed models developed for each experimental test to contrast the behaviour of wolves and admixed wolves in captivity, with estimates, standard deviation (SD), 95% confidence intervals (CIs) and P values
| Predictors | Estimate | SD | 95% CIs | P value |
|---|---|---|---|---|
| M1—probability of being vigilant in the first ten seconds of the trial (human task) | ||||
| Intercept | 0.54 | 0.62 | − 0.68 to 1.76 | – |
| Admixture (wolves) | 1.34 | 0.64 | 0.09 to 2.60 | 0.048* |
| Rank | 0.82 | 0.22 | 0.38 to 1.25 | 0.001 |
| Trial number | − 0.33 | 0.20 | − 0.72 to 0.07 | 0.099 |
| Sex (male) | − 0.39 | 0.50 | − 1.37 to 0.59 | 0.419 |
| Age | − 0.22 | 0.30 | − 0.81 to 0.37 | 0.474 |
| M2—probability of being in proximity to unfamiliar humans in the first ten seconds of the trial (human task) | ||||
| Intercept | − 0.86 | 0.84 | − 2.51 to 0.79 | – |
| Admixture (wolves) | 5.67 | 1.24 | 3.23 to 8.10 | < 0.001* |
| Rank | − 0.28 | 0.24 | − 0.76 to 0.20 | 0.246 |
| Trial number | − 1.17 | 0.45 | − 2.05 to − 0.29 | 0.009 |
| Sex (male) | 2.30 | 1.09 | 0.17 to 4.43 | 0.034 |
| M3—probability of being vigilant in the first ten seconds of the trial (object task) | ||||
| Intercept | 4.99 | 2.43 | 0.22 to 9.77 | – |
| Admixture (wolves) | − 4.24 | 1.60 | − 7.38 to − 1.10 | < 0.001* |
| Rank | − 0.45 | 0.60 | − 1.64 to 0.73 | 0.446 |
| Trial number | − 1.23 | 0.74 | − 2.69 to 0.23 | 0.062 |
| Kind of object (kb) | 1.33 | 1.01 | − 0.65 to 3.31 | 0.168 |
| Sex (male) | − 2.34 | 1.51 | − 5.31 to 0.63 | 0.071 |
| M4—probability of fearful behaviour during the trial (object task) | ||||
| Intercept | − 4.97 | 1.33 | − 7.57 to − 2.37 | – |
| Admixture (wolves) | − 1.51 | 1.35 | − 4.15 to 1.13 | 0.305 |
| Rank | 0.42 | 0.47 | − 0.50 to 1.34 | 0.369 |
| Trial number | 0.73 | 0.40 | − 0.04 to 1.51 | 0.050 |
| Kind of object (kb) | − 5.62 | 1.17 | − 7.91 to − 3.33 | < 0.001 |
| Sex (male) | − 1.51 | 0.80 | − 3.07 to 0.06 | 0.052 |
| Age | 0.08 | 0.74 | − 1.38 to 1.54 | 0.915 |
| M5—proportion of time in proximity to novel objects during the trial (object task) | ||||
| Intercept | 2.75 | 0.55 | 1.68 to 3.83 | – |
| Admixture (wolves) | − 2.38 | 0.51 | − 3.38 to − 1.39 | < 0.001* |
| Rank | − 0.01 | 0.17 | − 0.33 to 0.32 | 0.957 |
| Trial number | − 0.16 | 0.12 | − 0.40 to 0.08 | 0.187 |
| Kind of object (kb) | 0.70 | 0.40 | − 0.08 to 1.49 | 0.084 |
| Sex (male) | − 0.46 | 0.28 | − 1.01 to 0.08 | 0.094 |
| Age | 0.21 | 0.25 | − 0.29 to 0.70 | 0.418 |
| Initial distance from object | 1.26 | 0.21 | 0.85 to 1.68 | < 0.001 |
| M6—probability of exploring novel objects during the trial (object task) | ||||
| Intercept | − 10.65 | 1.90 | − 14.38 to − 6.92 | – |
| Admixture (wolves) | 4.52 | 2.26 | 0.08 to 8.95 | 0.015* |
| Rank | 1.11 | 0.73 | − 0.31 to 2.54 | 0.097 |
| Trial number | − 1.43 | 0.47 | − 2.34 to − 0.51 | < 0.001 |
| Kind of object (kb) | 4.21 | 1.21 | 1.85 to 6.57 | < 0.001 |
| Sex (male) | − 1.14 | 1.04 | − 3.17 to 0.89 | 0.248 |
| Age | 1.01 | 0.86 | − 0.67 to 2.68 | 0.224 |
For each model, controls are in italics and reference categories are in parentheses; kb stands for kettlebell, and the asterisks denote a significant P value for test predictors. Rank, trial number and age were previously z-transformed. Variation in the probability of fearful, aggressive and exploratory reactions in the human task, as well as in the probability of aggressive reactions in the object task, could not be tested as these behaviours were observed only in wolves or only in admixed wolves (see text)