When I was in middle school I wrote a report about bubble rings but I don’t remember if I had the same problem I do now of trying to sound serious, I was probably less concerned about that at the time. That paper was about individual ring-shaped bubbles, like the kind dolphins (or humans like me) blow underwater. This blog is about the bubble nets that humpback whales create to corral their prey underwater (I have yet to master this skill).
I have just finished auditing about 7.5 hours of video footage that we obtained from the suction cup tag we deployed on a Humpback whale earlier this month. My objective was to create a detailed log of underwater foraging behavior. We were especially interested in recording video footage and collecting fine-scale movement data from the whale during coordinated bubble net feeding events. This video footage is the first of its kind documenting this type of feeding behavior in Antarctic Humpback whales.
I found many occurrences of both bubble net and lunge feeding events, and in some cases the underwater visibility was good enough to observe other whales in the video frames. Throughout most of the 7.5 hours the tagged whale was travelling and foraging with at least one other whale, but at one point up to three other individuals were present. Other notable behavior included vocalizations and pectoral fin slapping on the surface of the water. Krill were frequently observed rushing by the forward facing camera just after lunge events.
Watching these videos over the course of a few days I became kind of committed to this whale’s story, and where each video ended and another began I found a narration running through my head that went something like, “next time on the life of the whale… will he find more food?” When the final video ended I even felt a little sad that I wouldn’t be able to keep following him on his journey.
I’ve included some screen shots below to give you a better idea of what I observed while watching the videos.
P.S. I named this whale Mr. Opihi man, since the barnacles and the suction cups stuck to his back reminded me of the way Opihi (the Hawaiian word for limpet) stick to the rocks.
Yesterday someone said to me, “I don’t know if it was sunrise or sunset, but it was beautiful” So it goes on the LMG, the surrounding scenery is incredible but the general work schedule on this research ship makes it difficult to remember what time of day it is.
Here on the Antarctic Peninsula, the sun never really sets and our daily schedules are dependent on things like the diel vertical migration of krill, the current wind speed and the amount of sea ice in between us and our study species, the humpback whale. For these reasons, we sometimes find ourselves starting our workday at odd hours, like 11:45 pm (or 4:00 am).
We are about one week into our journey and so far, so good! We have spent the last four days transiting between various sampling stations around Palmer deep, which is an underwater canyon just south of our home base at Palmer station. When conditions allowed, we loaded up our tagging and biopsy gear into a small boat and went to look for humpback whales. We’ve been incredibly successful with the limited amount of time we’ve had on the water and this morning we finished deploying our sixth tag.
We brought a few different types of satellite tags with us to deploy on humpback whales. One type is an implantable satellite tag that transmits location data over a long period of time. These data allow us to gain a better understanding of the large-scale movement and distribution patterns of these animals. The other tag we deploy is a suction cup tag, named for the four small suction cups that attach the tag to the whale. These multi-sensor tags measure location as well as fine scale underwater movement (e.g. pitch, roll, and heading). They are also equipped with forward and backward facing cameras and most importantly, radio transmitters! This allows us to recover the tags once they fall off the animal and float to the surface (after about 24 hours). The data we get from these tags will allow us to quantify fine-scale foraging behavior in terms of underwater maneuverability, prey type and the frequency, depth and time of day that feeding occurs.
When we deployed each of these tags we also obtained a biopsy sample and fluke photos. Fluke photos and biopsy samples allow us to distinguish between individual animals, and the biopsy samples will also be used to study the demographics of this population through genetic analysis.
Now that we’ve deployed all of our satellite tags and have recovered the suction cup tag just in the nick of time (!), we are starting our first major transect line toward the continental shelf. We will be continuing south along these grid lines for the next week.
Right now we don’t have a good enough internet connection on the ship to post photos, but I’m hoping to get around that and have a few up for you soon!