Aisha O’ Connor wrote this post as part of Dr. Stacy Krueger-Hadfield’s Principles of Scientific Investigation course at the University of Alabama at Birmingham. Aisha is a non-thesis Masters student in the Krueger-Hadfield lab, and is interested in marine conservation and sustainable management of marine resources. Aisha tweets @Aisha_MOC.
Imagine swimming 1000’s of kilometers just to get some food.
Humpback whales (Megaptera novaeangliae) do just this. In the summer, theytravel in excess of 2000 km to higher latitudes to feed, returning to lower latitudes in the winter to breed (Fig. 1).
Richard et al. (2018) analyzed humpback mitochondrial DNA (mtDNA) between two Russian sites where previous work had documented a difference in feeding behaviors. At the Karaginsky Gulf, humpbacks predominantly fed on fish while those around the Commander Islands fed on zooplankton. Considering these sites are separated by a mere 500km, is this feeding behavior a result of traditional practices of a population or were the whales at each site simply seizing the day, eating whatever was on the menu?
Whales from the Commanders were similar to those whales for which mtDNA sequences were available from the Gulf of Alaska and feeding grounds in the Aleutians. By contrast, the whales that were at the Karaginsky feeding grounds differed from all other whales (Richard et al. 2018). However, based on microsatellites, there was no genetic differentiation among the North Pacific humpbacks. Richard et al. (2018) concluded it was likely that two different maternal lineages gave rise to the populations at Karaginsky Gulf and the Commanders.
The significant differentiation in mtDNA sequences between the two feeding sites led the authors to question if this could be an example of gene-culture coevolution. Whale cultural practices may have an influence on adaptations to specific environments, such as foraging sites. Both Russian feeding sites host whales that come from different breeding sites. Due to little or no mtDNA differentiation, it appears whales from the Philippines and Okinawa breeding sites feed at Karaginsky. Whales from the Mexican breeding grounds likely feed at the Commanders. This also demonstrates that whales at breeding sites don’t necessarily travel to the most geographically proximal feeding site.
These results have conservation and management implications. Humpback whales within the grounds of Karaginsky Gulf and the Commanders should be treated as separate entities rather than combining them together as one feeding ground. The uniqueness of Karaginsky Gulf as a feeding site may justify it being designated as a marine protected area. Without genetic work, the conservation needs of Karaginsky may have slipped under the radar. Leaving Karaginsky unprotected could lead to a loss of genetic and cultural heritage among the whales that frequent these feeding grounds, particularly those travelling from the Philippines breeding grounds that do not feed around the Commanders.
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