ACS Research Committee Report

Humpback Calf Vocalizations in Hawaii
Source: Zoidis, A.M., Smultea, M.A., Frankel, A.S., Hopkins, J.L., Day, A., McFarland, A.S., Whitt, A.D., and Fertl, D. 2008. Vocalizations produced by humpback whale (Megaptera novaeangliae) calves recorded in Hawaii. J. Acoust. Soc. Am 123 (3): 1737-1746.

Underwater humpback vocalizations and behavior were recorded in their wintering grounds near Maui and Kauai, Hawaii between 2001 and 2006.

Data were collected by snorkelers using digital underwater video cameras with a dual hydrophone array mounted on either side of the camera that were used to determine bearing to sound sources.

Vocalizing whales were identified by repeated measurements of signals within a 10 degree angle of the plane bisecting the two hydrophones and the whales centered in the center of the video frame.

Underwater video recordings of 170 groups containing a humpback mother/calf pair were filmed, producing a total of 1007 minutes of video footage.

Non-song vocalizations were recorded in 110 (65%) of the 170 mother/calf groups; 34 of 39 (87%) lone mother/calf pairs, 76 or 111 (68%) of mother/calf escorts, and no groups with two or more escorts.

One group that produced non-song vocalizations was recorded with the dual hydrophone array and the remaining 109 groups were recorded using the single hydrophone with the video camera.

Directional bearings from the dual hydrophone array were identified for 21 sound signals from one male calf. The majority of sounds were pulsed signals (71%), followed by frequency modulated (19%) and then amplitude modulated (10%) sounds. All sounds were relatively short (less than 1 sec) in duration and low in frequency (mean lowest frequency was 220 Hz and mean highest frequency was 2221 Hz). “Grunts” were the most commonly heard signal from this calf. During these recordings, the calf made four close (1-5 m) approaches to a diver, while the group rested near the bottom.

In the recordings using the single hydrophone, non-song vocalizations were detected more often when the calf was at or near its closest point of approach to the hydrophone and the mother and escort were resting in deeper water. Most of the signals were short in duration (less than 1.1 sec) and low in frequency (mean low frequency was 306 Hz). Frequency modulated signals were most common (50%), followed by pulsed (30%), and then amplitude modulated (20%).

The function and biological significance of calf vocalizations are unknown.

Several hypotheses are that vocalizations may elicit the mother’s approach. In three cases, calf grunt vocalizations, sometimes accompanied by bubbles or a jaw clap, was followed quickly by the mother surfacing and "herding" the calf away from the diver. Other hypotheses are that the calf vocalizes in response to novel stimuli or as a means of unidirectional contact communication between mother and calf. 

Video-imaging Tags on Blue Whales
Source: Calambokidis, J., Schorr, G.S., Steiger, G.H., Francis, J., Bakhtiar, M., Marshall, G., Oleson, E.M., Gendron, D., Robertson, K. 2008. Insights into the underwater diving, feeding, and calling behavior of blue whales from a suction-cup-attached video-imaging tag (Crittercam). Mar Tech Soc J 41(4): 19-29.

"Crittercam," suction-cup-attached video-imaging tags, were deployed on blue whales primarily off of California. Attachments were made from July through September 1999 to 2003.

The Crittercams provide underwater video, sound, depth, and temperature.

Supporting data, including photographs, skin samples for genetics, positional, and behavioral data were collected from tagged animals.

Individuals were identified using natural markings on the dorsal fin and side of the whale compared against the catalog held by Cascadia Research.

In addition, prey was identified using an echosounder.

There were 35 deployments; 13 were successfully recovered with at least 15 minutes of dive and/or video data. Of these 13 deployments, nine were determined to be male and two female using genetic analyses.

Males were either alone or the trailing animal in a pair or trio.

The two females were the lead animals in the pair.

The Critercam provided information on positioning and association of animals while beneath the surface.

Sightings of other individuals were typically just brief glimpses, none of which showed cooperative feeding; however, poor water visibility and low light resulted in limited ability to detect other whales.

Positioning of other whales during Crittercam sightings indicate that associations and orientations observed at the surface continue during dives.

Krill, the primary prey of blue whales, was observed in eight of 11 deployments with available footage. Two deployments gave evidence of lunge feeding during dives; these whales dove below the krill layer and lunged during ascent up through the prey. One whale dove to nearly 300m and lunged in depths of 200 to 290m.

Fluke beats could be identified by watching the positioning of the back during dives. Fluking occurred at the beginning of a descent and strongly during ascents and lunges, but mostly ceased during the majority of the descent.

Crittercam deployments, in spite of limited light and visibility at depth, can provide insights into foraging behavior at depth. 

Mother/calf Association in Humpback Whales
Source: Szabo, A. and Duffus, D. 2008. Mother-offspring association in the humpback whale, Megaptera novaeangliae: following behaviour in an aquatic mammal. Anim. Beh. 75: 1085-1092.

Studies involving maternal strategies in mysticetes have concluded that they have a follower approach, similar to ungulates. However, mysticetes must deal with the constraint of separation between ventilation at the surface and foraging at depth. Long dives are typical of foraging mysticetes, but calves have a reduced physiological capacity for dives relative to adults.

Social cetaceans, such as sperm whales, deal with this separation through cooperative care of offspring. There is no evidence of this strategy in mysticetes.

This study examined mother/calf association and dive behavior of humpback whales in southeast Alaska. Observations were made in the months of June through September in 2001 and 2002.

During each surfacing of a mother/calf pair, the identity of each animal (mother, calf, and associates) were noted, as well as the distance between the mother and calf in relation to the mother’s body length (BL).

Encounters continued up to eight hours, or until weather, nightfall or other factors interfered with observations. Forty-two mother/calf pairs were observed for a total of 154 hours.

As expected, mother and calf maintained continuous proximity; they were within 50m of one another an average of almost 94% of all surface observations. Proximity decreased as the mother/calf association lengthened.

At the beginning of the feeding season, calves’ dive duration was an average of 82% that of their mothers, but the ratio of calf to mother dive durations increased as the season progressed.

By the end of the feeding season, their dives were similar in duration. Mothers dove for shorter durations when their calf remained at the surface then when it followed her on a dive. This reduction in dive duration was less dramatic as the season progressed, potentially due to the increased energetic demands on the mother through lactation or due to the calf’s increased ability to dive with the mother and avoid separation.

These results support the hypothesis that humpback whales and their offspring share an association that is similar to terrestrial followers 

Geographic Variation in Killer Whale Attacks on Humpback Whales
Source: Steiger, G.H., Calambokidis, J., Straley, J.M., Herman, L.M., Cerchio, S., Salden, D.R., Urban-R, J., Jacobsen, J.K., von Ziegesar, O., Balcomb, K.C., Gabriele, C.M., Dahlheim, M.E., Uchida, S., Ford, J.K.B., de Guevara-P, P.L., Yamaguchi, M., and Barlow, J. 2008. Geographic variation of killer whale attacks on humpback whales in the North Pacific: implications for predation pressure. Endang Species Res 4: 247-256.

A total of 3650 good-quality humpback whale fluke photographs were taken between 1990 and 1993 on the feeding and breeding grounds in the North Pacific.

The photos were coded for the presence of killer whale rake marks. Rake marks were defined as a set of three or more parallel lines in close proximity.

The photographs were put into five categories: 1) rake marks associated with serious injuries to the fluke, 2) severe scarring- three or more sets of rake marks, 3) one to two sets of rake marks present, 4) scratches that were probably caused by killer whales, and 5) no rake marks.

Overall, 15% of photographs from all North Pacific regions had unambiguous rake marks. Of those, 20% had serious injury or missing pieces of the fluke associated with the rake marks.

Humpback whales on the three primary breeding grounds, Mexico, Hawaii, and Japan, had significantly more rake marks than whales on the feeding grounds.

The incidence of rake marks for whales off California- Washington was at least twice as high as other feeding areas. There was no significant difference between the other feeding areas when California- Washington was removed.

Rake marks were most prevalent in Mexico than in other breeding grounds. The presence of rake marks on humpback whales indicates that killer whales must make predation attempts on this species.

Killer whales risk physical injury by attacking such large species, so they must receive a significant benefit from assuming this risk. The population with the highest proportion of rake marks most likely has the greatest number of killer whale attacks.

Humpback whales off California- Washington most often migrate to Mexico for the breeding season, which explains the high proportion of rake marks seen in these two areas. Whales in all three Mexican wintering areas had high prevalence of rake marks, in spite of the fact that these areas have different migratory destinations.

These results suggest that attacks occur most often on the Mexican breeding grounds.

There is a low density of killer whales in both California and Mexico compared with higher latitudes.

The high incidence of killer whale attacks on humpback whales in California and Mexico may be due to the high number of both humpback and gray whale calves in these areas.

A recent debate amongst whale researchers is the reason for large whale migration; one hypothesis is that migrating whales avoid predation at high latitudes. The results found here that predation risk seems to be higher in the wintering grounds contradicts this hypothesis. 

Historical weapon fragments help estimate bowhead whale longevity
Source: George, J.C. and Bockstoce, J.R. 2008. Two historical weapon fragments as an aid to estimating the longevity and movements of bowhead whales. Polar Biol 31: 751-754.

During nineteenth century whaling in the Bering-Chukchi-Beaufort seas, whales were sometimes struck and lost, carrying pieces of whaling equipment in their bodies for the rest of their lives.

In 1890, a whaling iron that bore the mark of a ship from New London, CT was recovered from a bowhead whale in the Bering Sea. The last cruise of that particular ship to the Bering Sea was 1853; therefore, the whale carried that iron for 37 years.

In 1880, an Eskimo in Alaska recovered an iron made in London that had been used by whalers on the Greenland coast. That whale must have been struck and lost near Greenland and carried the iron in his body all the way to the Pacific Ocean.

Traditional ivory and metal blades were used until the 1880s and were recovered from whales in 1992 and 1993, meaning that those whales were 100 years old or more.

Similarly, scientists have used an aging technique on whale eyes that indicate bowheads live over 100 years.

In 2007, fragments from a bomb lance were discovered in the shoulder of a bowhead whale caught in Alaska. Bomb lances were introduced in the early 1850s and were used widely in the Bering-Chukchi-Beaufort seas. This lance was a model that was patented in 1879 by Ebenezer Pierce. Pierce modified his patent in 1885 because the earlier model was found to have safety concerns. Knowing of these safety issues, whalers would have stopped using the first model soon after the new model came out and manufacturers would have ceased production on the first model by 1885. Bomb lances were expensive and whalers were not likely to purchase very many at one time. Considering this, it seems likely that this bomb lance was fired prior to 1890. This evidence indicates that bowhead whale carried these lance fragments for at least 117 years.

This finding supports the longevity estimates of bowhead whales made using different techniques. 

Efficacy of voluntary whale watching guidelines
Source: Wiley, D.N., Moller, J.C., Pace, R.M., and Carlson, C. 2008. Effectiveness of voluntary conservation agreements: case study of endangered whales and commercial whale watching. Conserv Biol 22(2): 450-457.

This study evaluates the efficacy of voluntary guidelines for commercial whale watching vessels.

The guidelines were created by the U.S. National Oceanic and Atmospheric Administration (NOAA) and are in effect throughout the northeast Unites States from Maine to Virginia.

The guidelines were created to reduce boat strike risk and harassment for endangered whales.

Whales are legally protected from injury and harassment by the Marine Mammal Protection Act and the Endangered Species Act.

The northeast guidelines involve speed reductions when boats come within 3.7km of a whale, posting dedicated observers, avoiding head-on boat approach to whales, and a minimum watching distance of 30.48m. Speed zones around whales consist of several concentric rings, or zones, within which there are specified speed limits.

The research for this study was conducted in the Stellwagen Bank National Marine Sanctuary in Massachusetts Bay. Data were collected by observers on board commercial whale watching vessels; the observers did not identify themselves to the crew or captain of the vessel.

Observers recorded the track and speed of the vessel using a GPS (global positioning system) that recorded time, location, and speed every five seconds.

When a whale was sighted, observers recorded its range and bearing, using rangefinder binoculars, and the time of the sighting.

The ratio of noncompliance was calculated as the ratio of distance not in compliance with the guidelines to the total distance traveled in each speed zone.

Estimated noncompliance was significantly higher in the outer zones (94% noncompliance) than in the zone closest to the whales (61% noncompliance), but it was over 50% in all zones.

Noncompliance differed between companies but was high throughout. The low level of compliance with the guidelines was unlikely to have accomplished their goal of substantially reducing vessel speed, and therefore boat strike risk, near endangered whales.

Noncompliance occurred throughout the industry and there were many cases of operators reaching the maximum speeds of their vessels even in the zone closest to whales.

Not knowing that whales were in the area was not likely to be a valid excuse in most cases, because there was extensive radio communication between whale watching vessels.

Whale abundance was low during this study, which may have increased noncompliance as each company was under significant time pressure to locate whales.

However, whales in the area during seasons of low abundance need protection just as much as at any other time.

In addition, during seasons of high abundance, whale watching vessels are likely to be within 3.7km of a whale for a higher proportion of their trip, which may put additional strain on their schedules. Therefore, one could make an argument to ignore the guidelines in almost any circumstance, which is the significant negative of having voluntary guidelines.

The conclusion from this study is that voluntary guidelines are not effective in conservation of endangered whales. 

   

Support ACS's public education programs - Join Today