We don't know much about pygmy right whales but two things biologists were sure of were that they are the smallest of all living whales and that they are restricted to the Southern Hemisphere. Now, however, we know that the latter is wrong, as pygmy right whale bones have been discovered in Italy and Japan. Since Caperea marginata was already considered an oddity among cetaceans, the find is particularly intriguing.
“This is like finding a fossil kangaroo in Scotland. It is a totally unexpected discovery,” said Dr Erich Fitzgerald of Museums Victoria in a statement. Granted the wild wallabies of Scotland may one day leave a fossil record, but the whales have had no human assistance. Fitzgerald's comment indicates just how surprised he was to realize that the 0.5 to 1 million-year-old section of a whale skull from Japan, and an Italian earbone dating back 1.7 to 1.9 million years, both came from pygmy right whales.
Today equatorial waters are far too warm for pygmy right whales, which are restricted to waters off New Zealand, and southern parts of Australia and South America. Fitzgerald concludes in Current Biology that the cooler temperatures associated with past ice ages must have shifted the whales' range north, allowing them to reach the Northern Hemisphere.
Subsequent warmer periods would have seen the right whales' habitat move towards the poles, and eventually, some force wiped them out in the north. The large time gap between the fossils indicates that they survived in the Northern Hemisphere for a long time, or that the crossing happened more than once. Fitzgerald hopes to discover if any other cold-adapted marine species made similar migrations. “Even southern walruses and northern penguins, should be anticipated,” the paper noted.
The findings “provide new insights into how climate change has profoundly impacted the distribution of whales throughout the Earth’s oceans over millennia,” Fitzgerald said. “[They] also point to how living species may be impacted by climate change, now with an added human dimension, in the future.”
Pygmy right whales' remote habitat and low numbers mean we know very little about their behavior, let alone their ancestry. Until now, our knowledge of their evolution came from three fossils from between 3 and 8 million years ago, all from locations similar to their current range.
Distinctive coloring, mitochondrial RNA, and unique anatomy suggest these whales' lifestyles differ from all other surviving species, but we know very little.
Despite both fossils making up only a small part of the whales from which they came, the ear bones of the pygmy right whale are so distinctive Fitzgerald is confident of the species identification.