Survey
The survey received 14 responses, comprising of 12 zoos and 2 breeding centres. The average response rates for questions in each sections of the survey is displayed in Table 3. The size of European mink population per centre compared to breeding success is shown in Table 4.
Centres with a large European mink population (10 or more mink) had significantly more breeding success than centres with a small population (less than 10 mink) (p < 0.05) as seen in Table 4. Population size also had a significant effect on the most common nest box count per enclosure, with centres with a large population having more nest boxes than small population centres (p < 0.05). Performing a Bonferroni correction on all the p-values collected from the individual Fisher’s exact tests, the significant values were adjusted to only stay significant for next box count against population size.
All other factors in the survey had no significant effect (p > 0.05) on breeding success and abnormal repetitive behaviours in the European mink at the respective centres. The analysis for the effect of the most common abnormal repetitive behaviour, route tracing, to breeding success is seen in Figure 1.
Table 3 Average percentage of questions answered by participants per survey section
| Survey section | Number of questions | Average percentage answered by participants |
| General | 6 | 91% |
| Outdoor holding type design | 11 | 95% |
| Indoor holding type design | 13 | 13% |
| Diet | 18 | 83% |
| Enrichment | 5 | 74% |
| Training | 7 | 53% |
| Behaviour | 2 | 75% |
| Abnormal repetitive behaviours | 10 | 40% |
| Breeding management | 26 | 68% |
| Transport and restraint | 5 | 89% |
Table 4 The size of the population of European mink at a centre compared with whether the centre are successfully breeding mink
| Centre number | Population size (number of individuals) | Successfully breeding |
| 1 | Large (19) | Yes |
| 2 | Small (7) | No |
| 3 | Large (115) | Yes |
| 4 | Large (60) | Yes |
| 5 | Small (2) | No |
| 6 | Small (1) | No |
| 7 | Small (2) | No |
| 8 | Small (1) | No |
| 9 | Large (38) | Yes |
| 10 | Small (3) | No |
| 11 | Small (1) | No |
| 12 | Large (39) | Yes |
| 13 | Small (3) | No |
| 14 | Small (2) | No |
Video
The male European mink in group A successfully reproduced, while the ones in group B did not. The total time that mink interacted with enrichment was 5394 seconds for group A (n = 4) and 1982 for group B (n = 6). On average the breeding group (A) interacted with enrichment for 58.63 seconds per hour (SE = 10.48), while the non-breeding group (B) interacted for 14.36 seconds per hour (SE = 2.71). The mean of frequently observed key behaviours is summarised in Table 5.
Table 5 Average count and standard error of stereotypic and enrichment interaction behaviours per hour by group
| Group A – Breeders | Group A – Breeders | Group B – Non-breeders | Group B – Non-breeders | |
| Mean | Standard Error | Mean | Standard Error | |
| Investigate enrichment | 5.23 | 0.83 | 1.82 | 0.32 |
| Climb on enrichment | 14.55 | 2.70 | 4.42 | 0.55 |
| Inside enrichment | 1.92 | 0.34 | 0.51 | 0.13 |
| Manipulate enrichment | 1.52 | 0.31 | 0.29 | 0.13 |
| Pacing stereotypic behaviour | 0.02 | 0.015 | 20.35 | 1.92 |
| Stationary stereotypic behaviour | 1.85 | 0.63 | 0.123 | 0.052 |
Rubbing and shaking behaviours were significantly affected by enrichment quantity, the more enrichment there was in an enclosure the fewer counts of these behaviours were observed. Mink with additional enrichment (categorical variable) were observed to manipulate enrichment significantly more than mink with the standard two types of enrichment. No other behaviours were significantly affected by enrichment type or quantity (p > 0.05).
Pacing stereotypic behaviour was significantly affected by group, with non-breeding males pacing significantly more than breeding males. The breeding group was observed climbing on enrichment significantly more than the non-breeding group. While the breeding group was observed inside enrichment significantly less than the on-breeding group. No other behaviour was significantly affected by group. The total duration mink interacted with enrichment was not significantly affected by the enrichment quantity or group (p > 0.05).
The group and breeding success was significantly affected by enrichment quantity, with breeding males having significantly more enrichment than non-breeding males as seen in Figure 2.
Conducting a binary logistic regression, enrichment quantity (numerical) was found to significantly predict the breeding group. As enrichment quantity increases, the probability of males being in the non-breeding group decreases as displayed in Figure 3. The total enrichment interaction duration was also able to significantly predict the breeding group, with increased interaction duration leading to lower probability of being in the non-breeding group, see Figure 4.
Some videos to show the enclosure design and examples of behaviours recorded
The left video is an example of a mink interacting with enrichment. They are first seen on a plastic bag, they then they go inside, later re-appearing to walk on a tube/tunnel and run out of sight.
On the right is an example of a mink displaying abnormal repetitive behaviour. This mink is route tracing/pacing in a circular patterned partly out of sight.