We tested whether pronounced morphological variability of horses caused by artificial selection was followed also by variation in their vocalization. We compared whinnies of 10 breeds representing horse varieties both in morphology and history using discrimination analyses (Wilks´ lambda = 0.070). Whinnies of Shetland pony were the most distinct from calls of other breeds (74.1% classification success). This result is in agreement with distinction based on morphological features. Whinnies of the primitive Hucul horse belonged among the most correctly classified ones (73.5%). Classification results of both Old Kladruby horse colour forms were very different: whinnies of the grey form revealed the least successful classification (18.9%) whilst calls of the black form showed one of the best classification outputs (72.4%). A surprising result was the extreme vocal distinction between the heaviest breeds, confirmed by discrimination analysis, the Czech-Moravian Belgian (55.5%), and Silesian Noriker (51.4%). This finding was contrary to their morphological similarity.
The relationship between morphological and acoustical variables revealed a significant correlation (r ˂ -0.57). Our results did not confirm the hypothesis of acoustic distinction in horse breeds based simply on their morphology. However, whinnies of an old breed, the Shetland pony, were the most distinct ones from all the others. The other old breeds, the Thoroughbred and the Old Kladruby horses, clustered together with the modern Czech warmblood. Our results seem to not confirm the second hypothesis of vocal distinction based on the length of time since establishment of the respective breed. Significant differences among horse breeds indicate the process of vocal distinction during the process of artificial selection.
Stepanka Holeckova, Richard Policht and Dominika Polichtova
We have used a discriminant function analysis to compare morphology of five Czech autochthonous breeds (including two colour varieties as independent breeds) to test whether a small number of basic morphological variables (wither height, thoracic, nose and shin perimeter, length of head) can discriminate them. The breeds included Czech Warmblood, black and grey colour variety of the Old Kladruby horse, Czech-Moravian Belgian horse and Silesian Noriker. The tested individuals were assigned with overall 81.9% classification success to correct breed. The best classification result reached Czech Warmblood 95.7%, the black Old Kladruby horse 87.5% and Silesian Noriker, respectively, 85.7%. Czech-Moravian Belgian horse showed a poorer success of classification (60%). Discrimination analysis identified the most important variables related to their head (nose perimeter and length of the head). Based on discrimination model both colour varieties of the Old Kladruby horse clustered more closely. Similarly both cold-blooded breeds (Czech-Moravian Belgian and Silesian Noriker) grouped more together and locations of the Czech warmbloods were more apart from all others. Such result is in concordance with the origin history of these horses.
Loud acoustic signals of mammals may contain information about their progenitors. There is a question whether such phenomenon is possible to expect in domestic animal breeds as well, since the time of breed establishment has been a rather long one. Therefore we tested whether a significant morphological distinction of a newly established horse breed and its important founding contributor differed in their vocalization. We analyzed 304 whinnies of 35 individual horses (197 whinnies of 23 individuals belonging to Czech Warmblood and 107 calls of 12 Thoroughbreds). Despite of the fact that the two breeds differed significantly in most of their morphological measurements (height at withers, thoracic perimeter, cannon bone perimeter, and body weight), they did not differ in any of the measured acoustic parameters (both frequency and temporal ones). Our results indicate that morphological distinction of Thoroughbred and Czech Warmblood was not accompanied by distinct vocalization.