No, not all donkeys have a cross on their back, but it is a common marking.
The "cross" marking on a donkey's back is formed by two dark stripes: a dorsal stripe running down the spine and a shoulder stripe crossing it. These stripes are a form of primitive marking. While frequently seen, especially in certain breeds like the European donkey, it's not a universal trait for all donkeys worldwide.
Here's a breakdown:
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Prevalence: The presence and prominence of the cross vary. Some donkeys have a very distinct and clear cross, while others have faint markings or lack them entirely.
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Genetics: The genetics determining the presence and intensity of these markings are complex and not fully understood. It's likely influenced by multiple genes.
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Breeds: Some donkey breeds are more likely to exhibit the cross than others.
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Other Markings: In addition to the cross, some donkeys may also have zebra-like stripes on their legs.
In summary, while the cross marking is a characteristic feature of many donkeys, it is not a definitive trait present in every individual.
