Little is known about the role that communication plays among humpback whales. With this in mind, AWF analyzed hundreds of humpback vocalizations recorded at the lighthouse. Humans are champion acoustic discriminators, so AWF worked with student volunteers to detect subtle differences among vocalizations and classify them into different ‘call types’. The classification scheme was then corroborated with statistical analysis techniques. As a result, AWF created the first comprehensive catalog of vocalizations produced by humpback whales on their foraging grounds.
With the catalog complete, the next step is to investigate the role that these vocalizations play among foraging whales. This will involve correlating the various vocalizations with specific whale behavioral and social patterns observed from the lighthouse tower. Ultimately, we hope to use this information to anticipate some of the consequences humpbacks will face as ocean noise continues to rise.
RESEARCH ON THE BUBBLE-NETTING WHALES OF ALASKA
RESEARCH ON THE BUBBLE-NETTING WHALES OF ALASKA
Dr. Fred Sharpe has been following bubble-netting humpbacks for more than two decades. By identifying individuals through their unique fluke patterns, he has come to know many of them quite well. There’s Captain Hook, leader-apparent in the bubble-netting pod that frequents Chatham Strait. And Melancholy, well-known for his haunting, melancholic ‘feeding call’ used to drive the prey – always herring for these animals – into the waiting net. In fact, Dr. Sharpe has identified about 60 regular bubble-netting participants among the 4000 or so whales that frequent Southeast Alaska during the summer foraging season
So why such social and behavioral complexity, which is unknown for other baleen whales? Herring are surprisingly quick and evasive prey. Presumably, by working together in this elaborate way bubble-netting humpbacks are able to capture far more fish than they could on their own. And just as human workers can operate more efficiently when we have established roles and enduring partnerships, it is likely humpback whales can as well!
There's no way around it, surveying whale prey can be tedious work. For several field seasons, volunteers piloted rigid-hull inflatable boats (RIBs) along thousands of miles of predetermined transects at a slow 5 knots for 12 hours each day. The boats were outfitted with a sonar - a high tech fish finder that uses echolocation to shed light on what is happening below the waves - and a plankton net to collect krill samples. There weren’t always whales around. In fact, sometimes there weren’t even prey. But in science, the absence of something is often important data (so goes the aphorism: 'absence of evidence is not evidence of absence'), so the volunteers pressed on regardless.
So what can be done with all these prey data? For one, they can tell us a lot about prey dynamics in this comparatively unstudied region: How much does prey availability vary within or across years? Are there consistent prey ‘hot-spots’? Do different prey species vary in their reproductive and/or life history strategies? They can also provide the foundation for understanding whale abundance, distribution and behavioral patterns, and perhaps most importantly, how these patterns might change as our oceans succumb to rising temperatures, acidification and the overexploitation of marine resources.
Citizen-science programs encourage volunteers to participate in research by providing simple means for them to record important field data. Oregon State University graduate student and AWF biologist Courtney Hann is developing an application for a mobile platform that will allow boaters to record marine mammal sightings, while simultaneously raising their awareness of important conservation issues. Developing such an application is a collaborative process that will rely on the efforts of many volunteers. Hann hopes to engage boaters, including commercial fishermen, pleasure boaters, and charter vessel operators, through a targeted outreach program at AWF's Center for Coastal Conservation on Baranof Island .
Dr. Szabo spent several field seasons observing humpback whale mother-offspring pairs in Southeast Alaska. These pairs tend to remain close to one another so mom can both nurse her calf and drive away hungry killer whales that might be looking for a meal. But young calves can’t dive as often or as long as their foraging mothers, so sometimes the two must separate. Dr. Szabo revealed that early on females sacrifice their own foraging needs by returning to the surface often to attend to their calves. But as the season progresses and the demands of lactation grow, calves are increasingly left to fend for themselves. Not wanting to be left behind and undoubtedly wanting to continue to nurse, the hungry calf soon begins to follow and is forced to begin supplementing its milk diet with food, such as krill, that it must catch itself.
Dr. Szabo cast these observations of changing priorities in light of a broad evolutionary theory called parent-offspring conflict. This theory suggests that at some point mothers should stop allocating energy to their present offspring and start conserving energy for their next one. Although the timing differs among different species, it always occurs at an age where juveniles can fend for themselves and mortality risk is low. However, this comes sooner than the offspring, who is more concerned with its own survival than its future siblings, might like. In some animals, the ensuing “conflict” is obvious; many hooved mammals can be seen forcibly driving their young away from their teats or actively avoiding their them. But until now, no instance of conflict has been observed among baleen whales.