The long-finned pilot whale that died on Whanganui's South Beach last week was too weak to swim when refloating was attempted.
The whale was discovered on South Beach heading towards Whangaehu around midday last Thursday and died at 8.33pm that day.
Wildbase at Massey University performed a necropsy to determine the cause of death, with the Department of Conservation suspecting the pilot whale was an old individual.
"The whale had very worn teeth and some were missing," senior biodiversity ranger Sara Treadgold said.
"No squid beaks were found in its stomach, so it had not been fed for a while.