Analysis of Lunge Feeding Movements in Alaskan Humpback Whales

By Eman F. Khwaja and Andy Rogan, Ocean Alliance science manager

During research expeditions to South East Alaska in 2016 and 2017, Ocean Alliance used their SnotBot drone to remotely collect exhaled breath samples from humpback whales (Megaptera novaeangliae) in the area. While collecting these samples, SnotBot continually recording video footage of the whales and their surrounding environment using a high-definition camera. Subsequent viewing of this video showed that the drone had recorded a great variety of behaviors, which can then be analyzed for ethological studies.

In this study, we analyze the lunge-feeding behaviors of humpback whales recorded by SnotBot. This study demonstrates the potential use of this tool for incidentally collecting valuable behavioral data on whales, which can later be analyzed for ethological studies, while focusing on the collection of other data streams such as exhaled air samples.

Lunge feeding is a behavior during which a whale consumes a large quantity of prey and water after a high-speed horizontal or vertical propulsion, followed then by the removal of water through closed-mouth filtration (Goldbogen et al 2013). This specific behavior is unique to rorquals, a distinct group of baleen whales belonging to the family Balaenopteridae. For this report, a series of distinct movements in each lunge were analyzed, with particular focus on the type of lunge (horizontal or vertical), the use of pectoral fins during lunge, lateralization of the behavior (lunged on left side or right side), and the time length of the lunge. The intention of this analysis was to determine parallels and variation between lunges recorded in both individual and group feeding events.

The whales congregated in this area of South East Alaska are comprised of two distinct populations: the Hawai’i population, and the Mexico population. It is unclear which of these two populations the individuals analyzed in this report are part of.

Lunge Direction

Lunge-feeding, as previously mentioned, involves a high-speed horizontal or vertical movement to engulf a large quantity of prey. For the analysis of the footage, each lunge was characterized as either vertical or horizontal (Figure 1). Thirty-eight lunges in group feedings and thirty-five lunges in individual feedings were analyzed. Of the total seventy-three lunges, only eight were recorded as vertical lunges. Seven of the eight recorded vertical lunges occurred during group feeding events. Thirty-four of the sixty-five horizontal lunges occurred during individual feeding events.

There appeared to be a strong preference for horizontal lunging, in both group and individual feeding with only 18% of group lunges and 2% of individual lunges being vertical. Little research exists on this particular topic, but further studies can be conducted to determine the potential energy and consumption trade-off that occurs with each type of lunge. Additionally, in group feeding, it was recorded if the whales lunged in the same direction or opposite directions (Figure 2). Of the videos analyzed, 95% of the lunges showed uni-directional lunging.

Figure 1: Image (left) of horizontal lunge feeding on right side. Image (right) of vertical lunge.

Figure 2: Image (left) of lunge in opposite directions. Image (right) of lunge in the same direction.

Pectoral Fin

In 2019, a group of researchers used drones to record and officially documented a behavior called “pectoral herding”. Based on these records, humpback whales use their pectoral fins to corral fish into tighter schools prior to the whale lunging, allowing for more effective foraging and feeding (Kosma et al 2019). This behavior was seen in the same populations of humpback whales recorded during Ocean Alliance’s study. Unfortunately, despite eager investigation, there was only one lunge of the seventy-three lunges analyzed that showed evidence of pectoral fin use (Figure 3). The single event that included pectoral fin use was during a group feeding event, however only one whale in the group was seen using pectoral herding during its lunge.

Figure 3: Sequence of pectoral fin movements during vertical lunge using pectoral herding.

Lateralization

Lateralization refers to an overall preference for using a particular side of the body or direction of movement consistently in specific behaviors (Canning et al. 2011). Studies conducted on the North Atlantic humpback Whale population in the Gulf of Maine have shown that the population are more strongly lateralized towards their right side in a manner that is almost consistent with the 90/10 handedness seen in humans. Each humpback whale lunge was recorded as either lateralized on the left or right side (Figure 3). Analysis of the horizontal lunging behavior in the Alaskan population showed that of the sixty-five horizontal lunges recorded, all were executed on the right side. Unfortunately, no conclusions can be made from this limited behavior data set, but the potential for future studies to understand the extent of the right-side bias would be beneficial.

Figure 4: Image of humpback whale lunging on its right side.

Length of Lunge 

The length of lunges was compared between group feeding events and individual feeding events. It was defined as the time between when the whale broke the surface with its mouth open to the time that the whale closed its mouth or descended beneath the surface. Individual lunge feeding events averaged at 3.45 seconds per lunge, with a range of 2-5 seconds. Group feeding events averaged at 4.65 seconds per lunge, with a range of 3-7 seconds. An unpaired T-test produced a p-value of .000024*, suggesting that the difference in time between the individual and group feeding events are significant. A previous study completed in 2012 explored the metabolic expenditures of lunge feeding behavior and suggested correlations between the energy expended, the product gained, and the time and cooperation of the lunge between humpback whales (Potvin et al 2012). Further studies should be conducted to fully understand the time and energy difference between lunges in group and individual feeding events.

*Result is significance at p<.05

 About the author: Eman Khwaja is a Biological and Environmental Science Master’s student with a specialization in Evolution and Marine Biology at the University of Rhode Island. Her aim is to investigate the dynamic behavioral adaptations of marine organisms in their changing marine environments. Most of Eman’s undergraduate research focused on behavior in marine organisms, particularly on feeding and reproductive behavior in Humpback Whales. In addition to her Master’s work, she engages with Ocean Alliance as a volunteer to analyze and communicate research focused on cetaceans.

 References: 

  1. Canning, C., Crain, D., Eaton, T., Nuessly, K. (2011) Population-level lateralized feeding behavior in North Atlantic humpback whales, Megaptera novaeangliae. Journal of Animal Behavior
  2. Goldbogen, J., Friedlaender, A., Calambokidis, J., McKenna, M., Simon, M., Nowacek, D. (2013) Integrative Approaches to the Study of Baleen Whale Diving Behavior, Feeding Performance, and Foraging Ecology. BioScience.
  3. Kosma, M., Werd. A., Szabo, A., Staley, J. (2019) Pectoral Herding: an innovative tactic for humpback whale foraging. The Royal Society.
  4. Potvin, J., Golbogen, J., Sahdwick, R. (2012) Metabolic Expenditures of Lunge Feeding Rorquals Across Scale: Implications for the Evolution of Filter Feeding and the Limits to Msximum Body Size. PLOSOne.

 

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