The police say it was an offence under the Marine Mammals Protection Act to take the bone.
They urged anyone who recognised the man or his truck or anyone who witnessed this incident to contact Papamoa Police on 07 572 2440 or to call Crimestoppers anonymously on 0800 555 111.
The whale was found dead and decomposing at the Kaituna end of Pāpāmoa Beach. File photo
Members of the public were guarding the whale and authorities were in the process of arranging formal security when what witnesses described as two men in a ute turned up and hacked the jaw off with chainsaws.
The Department of Conservation, local iwi and a carver condemned the brutal and unceremonious removal of the jaw, considered the most spiritually - and financially - valuable bone of the whale.