The decomposing whale was found by 7-year-old Archie Dennis-Milne at a remote spot on the Omimi shoreline last Friday.
University of Otago marine scientist Dr Will Rayment said the washed up juvenile was not a normal find, but it was not entirely unexpected either.
The massive marine mammals had a fairly predictable migration cycle and there were populations in the northern and southern hemispheres which rarely crossed over.
Over the last few months, many of the southern hemisphere humpbacks had been travelling north past the coast of Otago.
Unlike species such as sperm whales, which preferred the open ocean, humpbacks tended to stick to coastal waters as they travelled.
"It’s almost like they’re using the coastline as a guide," Dr Rayment said.
It was hard to estimate exactly how many passed by Dunedin each year, but it was likely in the hundreds.
The migrating humpbacks were leaving the Antarctic, where they spend the summer feasting on krill and small fish, which in turn grazed on tiny phytoplankton.
While the waters might be cold, the long days made for a "seasonal boom in abundance", which the humpbacks made full use of.
"It's a really, really productive, rich foraging area for them," Dr Rayment said.
Between the end of summer and early winter, humpbacks migrated north to warmer waters in the tropics, where they sought more sheltered waters to have their calves.
In recent years, quite a few humpbacks had been seen off the coast of Fiordland during the springtime, possibly because they were stopping to feed on their way down the coast.
Humpbacks had not been particularly well studied in New Zealand, but one of Dr Rayment’s master’s students was hoping to change that with an upcoming research project focused on the Fiordland visitors.
The migrating whales usually travelled alone or in small temporary groups, as only mothers and calves usually had long term bonds.
All whale species had been affected by commercial whaling, which had continued as late as the 1960s in Antarctic waters, but humpbacks had recovered quite well as a species, although some sub populations were slower to recover than others.
