Variation in morphometric parameters of the sacrum (<i>os sacrum</i>) in farmed and feral American mink—An effect of domestication?

The sacrum, which is the only element of the spine formed by the fusion of vertebrae, exhibits considerable variability among taxa in terms of the number of vertebrae, their shape, and size. Along with the lumbar vertebrae, it contributes to the variation in the number of vertebrae of the spine within a species. The literature suggests that the shape and size of the sacrum are influenced by both the animal's lifestyle and sex. The aim of this study was to compare the morphometric parameters of the sacrum in farmed and feral American mink in Poland. Analysis of dissected sacra revealed the presence of bones composed of two and three vertebrae in both populations, with statistically significant differences observed in most analyzed measurements. Examination of seven measurements for each bone showed statistically significant differences between farm and feral mink in all measurements, except for the width of the last vertebra measured at the transverse processes (BT). Significant differences were also found between the sexes and populations, with feral females exhibiting the lowest values and farmed males showing the highest values in the analyzed measurements. Additionally, females from both populations displayed lower variability in sacrum measurements compared to males. Correlation analysis revealed statistically significant high positive correlations between all analyzed sacrum parameters, ranging from 0.53 to 0.88. The observed differences in sacrum structure between farmed and feral American mink are likely attributed to the domestication process. Varied living conditions such as space limitation, lack of access to water, nutrition, and controlled breeding can significantly impact the biology of animals. Further research is needed, including continued analysis in the field of geometric morphometry, to precisely identify differences and explore their relationship with factors such as movement and lifestyle.