8 November 2004
Honeybee Survival Puts Question Mark Over Chicxulub Asteroid
by Kate Melville

The tropical honeybee may challenge the idea that a post-asteroid impact "nuclear winter" was a big player in the decimation of dinosaurs 65 million years ago. The tropical honeybee, Cretotrigona prisca, survived the end-Cretaceous extinction event, despite what many researchers believe was a years-long period of darkness and frigid temperatures caused by sunlight-blocking dust and smoke from the asteroid impact at Chicxulub.

Modern tropical honeybees have an optimal temperature range of 31 - 34 °C in order to maintain vital metabolic activities. That's also the range that's best for their food source: nectar-rich flowering plants. Based on what is known about the Cretaceous climate and modern tropical honeybees, Jacqueline M. Kozisek, of the University of New Orleans, estimates that any post-impact winter event could not have dropped temperatures more than 2 - 7 °C without wiping out the bees. Current nuclear winter theories from the Chicxulub impact estimate drops of 7 - 12 °C - too cold for tropical honeybees.

Amber-preserved specimens of the oldest tropical honey bee, Cretotrigona prisca, are almost indistinguishable from - and are probably the ancestors of - some modern tropical honeybees like Dactylurina, according to other studies cited by Kozisek.

The survival of C. prisca is problematic and telling, asserts Kozisek. Late Cretaceous tropical honeybees preserved in amber are almost identical to their modern relatives, she says. If no modern tropical honeybee could have survived years in the dark and cold without the flowering plants they lived off of, Kozisek reasoned, something must be amiss with the nuclear winter theory. "It couldn't have been that huge," says Kozisek of the Chicxulub-related temperature drops asserted by other researchers.