Salim bin Abdullah narrates from his father (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) used to pray on his riding animal in whichever direction it faced, and would also pray witr on the riding animal, except for the obligatory prayer. In the hadith of Abu Dawud the word 'qibala' (towards) does not occur.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4594
Nafi' (may Allah have mercy on him) said that Abdullah bin Umar (may Allah be pleased with them both) used to pray voluntary prayer on his camel in whichever direction it faced, and he told them that he (peace and blessings be upon him) used to do so, and Abdullah bin Umar (may Allah be pleased with them both) used to pray witr on his camel.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4595