HUMPBACK WHALES IN THE HAWAIIAN BREEDINGWATERS: POPULATION AND POD CHARACTERISTICSLOUIS M. HERMAN AND RONALD C. ANTINOJA
Department of Psychology, University of Hawaii

ABSTRACT

Aerial, shipboard, and underwater observations were made during Spring 1976 of the population of humpback whales, Megaptera no1•aeangliae, breeding in Hawaiian waters. Animals were found around all of the major islands,
almost always within the 100 fathom contour, with the bulk of the population
concentrated in regions having the greatest contiguous extent of such water.
Breeding and calf rearing were not confined to any given area. Survey results yielded estimates of from 200 to 250 animals. The birth rate was estimatedas less than 10 %, a low figure of some concern. Coloration characteristics of the
Hawaii population differed considerably from the easten1 North Pacific population of humpback whales, suggesting little genetic exchange with that group.
Differences from the western North Pacific group were less clear, in part because of sparsity of data. Approximately 18% ofthe animals were alone whenobserved ; the remainder were in pods of 2 to 9 animals. Overall there wereconsiderably fewer singletons and considerably larger-sized pods than has been
observed in feeding ground aggregations. A calf was typically found in a multiple-animal pod, consisting of the mother and, most frequently, one other adult" escort " whale. The escort seemed to serve a protective function. The large
majority of the pods were swimming in fairly regular formations in apparent
local migratory movements. Milling pods, with animals contacting one another, or engaging in other behaviors seemingly consistent with sexual courtship or advertisement, was observed in 16 % of the cases. The possibly adverse
effects of increasing public and commercial on-water and in-water whale-watching activites on the reproductive success of the whales was noted.

INTRODUCTION
Each year, during the winter breeding/calving season, a population of humpwhales (Megaptera novaeangliae) migrates into waters adjoining the major Hawaiian
islands. The first arrivals may appear as early as November; peak numbers
occur during February and March, and the last stragglers depart as late as May
or June. From Hawaii, the animals return to summer feeding grounds along the
Alaskan peninsula or elsewhere in the high-latitude regions of the North Pacific.
This report focuses on the description of this population while in Hawaiian waters,
based principally on observations carried out during the Spring of 1976. The
study goals included the determination of areas of principal aggregation and theirfunction, the estimation of population abundance and of the rate at which calves
Sci. Rep. Whales Res. Inst.,
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HERMAN AND ANTINOJA

were recruited into the population, the description of some of the principal demographic and phenotypical characteristics of the population, the analysis of the organization of pods of whales, and the documentation of behaviors of the animals.
The study was carried out using aerial, shipboard, and underwater visual observations, and included extensive photographic documentation. The analysis of behaviors is reserved for a separate paper.
The humpback whale is part of the family of Balaenopterid whales, or rorquals,
which principally include the blue (Balaenoptera musculus), fin (B. physalus), sei (B.
borealis), Bryde's whale (B. edeni), and piked whale (B. acutorostrata). Rorquals
are cosmopolitan species, generally found in all oceans of the world. They are
distinguished from other mysticete whales by multiple longitudinal ventral grooves
extending from the throat to as far as the navel. These grooves can distend greatly,
like the lower jaw of a pelican, when feeding on the small marine crustacea or small,schooling fish that are their main diet. Additional rorqual characteristics are asmall, posteriorly-placed dorsal fin, and a generally slim, tapered body well adapted
for rapid swimming. Unlike the other rorquals, Megaptera has extremely long(e.g., 3.5 to 4.5 m), highly mobile, pectoral fins; rounded knobby tubercles on theupper jaw and portions of the lower jaw, possibly sensory in function; irregular
protruberances along the leading edges of the pectoral fins; moderately fine serrations or scalloping along the trailing edge of the caudal fin (tail flukes); and an
irregularly shaped dorsal fin. It has been described as stouter of body than otherrorquals, but those seen in Hawaiian waters seem generally slim and graceful inform. The slender form apparently reflects the reduced or even absent food intake,characterizing breeding migrations of humpback whales and other rorquals (Dawbin, 1966; Tomilin, 1967). We occasionally observed some Hawaiian humpback
whales engaging in what appeared to be feeding behaviors.
According to Rice's (1963) data on eastern North Pacific stocks, physicallymature female Megaptera average slightly longer in body length (14.8 m) than domales (13.6 m), though Tomilin (1967) reports somewhat smaller differences. Sexual maturity occurs when the animals are 2-3 m shorter. Newborn calves may
range from 4 to 5 m in length (Nishiwaki, 1972), but in Hawaii some appear to besmaller than the minimum stated. Following sexual maturity at 6-12 years, females
calve generally only every other year, giving birth almost always to a single young.
The gestation period is close to 12 months and the lactation period lasts from 10 to
11 months. Some additional aspects of reproductive biology of humpback whales
are discussed later in this paper. More detailed discussions of general and reproductive biology of Megaptera are available in a number of sources (e.g., Chittleborough,1959, 1965; Mackintosh, 1972; Matthews, 1937; Nishiwaki, 1959; Omura,
1953; Rice, 1963; Symons & Weston, 1958; Tomilin, 1967; Wolman, 1972).
Megaptera, like most other rorquals, engages in long-distance annual migrations
between higher-latitude summer feeding grounds and lower-latitude winter breeding
grounds. Dawbin (1966) described sexual and maturational temporal segregation
during migration and discussed some of the physical and ecological conditions possibly triggering and guiding migration of Southern Hemisphere humpback whales
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

HUMPBACK WHALES OF HAWAII(also see Chittleborough, 1965;

Nishiwaki, 1959, 1960).

61

Unlike other rorquals,

Megaptera prefers breeding grounds in the nearshore, shallow waters around continents or islands at approximately 10° to 20° latitude. In many cases, near-shore
preference increased the vulnerability of Megaptera to whaling.
DISTRIBUTION AND ABUNDANCE OF THE NORTH PACIFIC STOCKThe Hawaiian population is part of the highly-exploited stock of North Pacifichumpback whales. The distribution of this stock has been discussed, directly or
indirectly, in a number of sources (e.g., Kellogg, 1929; Mackintosh, 1947;
Nishiwaki, 1966; Omura, 1955; Rice, 1974; Tomilin, 1967; Townsend,1935). Charts prepared by Omura (1955) and Nishiwaki (1966) and material
provided by Tomilin (1967) reveal the orginal feeding range as extending from the
Sea of Okhotsk on the far western rim of the upper North Pacific to the Gulf of Alaska
on the eastern rim. Within this broad range, the whales were concentrated along
the Kuril Islands and on both sides of Kamchatka Peninsula in the western North
Pacific, within the Bering Sea and northward to the Bering Straits and the Chukchi
Sea, and along the northern and southern shores of the Aleutian chain and the Alaska
Peninsula down through S.E. Alaska.
Three breeding populations are generally recognized according to their separate
migration loci each winter in the tropical zones of the North Pacific. An eastern
Pacific, or American group, migrates southward past the west coasts of Canada andthe United States to calving/breeding grounds in the bays and outlying islands
along the west coasts of Baja California and the Mexican mainland (Kellogg, 1929;
Rice, 1974). A western Pacific, or Asiatic group, seemingly follows a southwesterlyroute along the east coasts of Japan to calving/breeding areas near Taiwan, or further east in the Bonin Islands, the Mariana Islands, and reportedly, the MarshallIslands. According to Kellogg (1929) and Tomilin (1967) some whales may penetrate into the Sea of Japan on their way to the Yellow Sea. Finally, the central
Pacific, or Hawaiian group, migrates into the Hawaiian waters by a route which isstill unknown. Also unknown is the degree to which the three populations disperse
and comingle in their summer feeding grounds, and whether there is any significant
genetic exchange across breeding populations. Ivashin and Rovnin (1967) believe that dispersed groups return to their original breeding grounds and that genetic
exchange is negligible. Coloration data for the different groups, discussed in alater section of this paper, tends to support this contention.
Historically, the humpback whale was hunted in the North Pacific as early as
the l 7th century by Japanese shore whalers using spears and arrows and, later,
nets (Omura et al., 1953). However, major exploitation did not occur until
the 19th and 20th centuries when the stock of North Pacific humpback whales
was extensively hunted throughout its summer feeding grounds by Japanese andRussian pelagic whalers (20th century); along its migratory routes in the eastern and western North Pacific by American and Japanese shore whaling stations;and in many of its tropical calving/breeding areas, principally by American andSci. Rep. Whales Res. Inst ..
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HERMAN AND ANTINQJA

Japanese whalers (Omura, 1955; Tomilin, 1967; Townsend, 1935). Its hunting
was finally banned in 1966. At that time there may have been 200-300 animals
remaining in the American population, based on extensive surveys in 1965 of thewinter breeding grounds of this population (Rice, 1974). There were probably
similar numbers remaining in the Hawaiian population, judging from the recent
survey reported in this paper. There appear to have been no formal surveys of the
Asiatic population since 1966. However, the rarity of sightings even before 1966,
as noted by Tomilin (1967) and the fact that western North Pacific concentrations
were always smaller than eastern North Pacific concentrations (Omura, 1955, Appendix 17) suggests that very few animals remained in the Asiatic population by
1966. Optimistically, it would seem that the North Pacific stock in 1966 numberedat most 1000 animals. Stock assessments by Wada (1972) suggested only 1200
animals. Thus, there are no indications of any substantial recovery of the North
Pacific stock since 1966.
Wolman's (1972) brief review of humpback whales included an estimate oforiginal abundance of the North Pacific stock as 4000 animals and Nishiwaki (1959)
suggested 5000-6000 animals. These estimates seem low given the 3037 humpback
whales caught in the North Pacific in the three-year period 1925-27 (International
Whaling Statistics, 1931) and the 3455 caught by Russian pelagic whalers in the
two-year period 1962-63 (International Whaling ·statistics, 1966). Also, the catch
statistics for 1925-27 apparently did not include the take off Kamchatka Peninsulain the western North Pacific (Omura, 1955). Ifwe assume the estimates of Wolman
and Nishiwaki are reasonable, then current abundance may be no more than 1525% of the original stock. Worldwide figures for humpback whale populations
are correspondingly low. The original abundance of the Antarctic stock may
have been as much as 90,000-100,000 animals, but census data between 1965-70
revealed, on the average, a maximum of 2800 animals, or roughly 3% of the original
stock (Chapman, 1974). The Antarctic stock has been protected since 1964. The
eastern North Atlantic stock was decimated before the end of the 19th century andis extremely rare today (Tomilin, 1967). The western North Atlantic groupcurrently numbers roughly 1200 animals (Winn et al., 1975). It has been protected
since 1955, and according to Winn et al. (1975) may not be much below its
numbers at the end of the nineteenth century just before major exploitation began.
Based on the slow recovery rates in other areas (Myers, 1975) and the small catchin the North Atlantic of only 22 whales in 1969/70 under a special permit to take
40, as compared with the total catch of 729 humpback whales in that area in 1903/
04/05 (Mitchell, 1974), it seems more likely that full recovery of the Atlantic grouplies considerably in the future. Chittleborough (1965), for example, estimated thatrecovery of portions of the Antarctic stock to original levels could take more than
65 years, while increases of world stocks to " significant " levels could take 50 years(Anon., 1975). The worldwide protection currently given the humpback whaleby member nations of the International Whaling Commission hopefully will someday enable its reclassification upwards from an endangered species.
Sci. Rep. Whales Res. Inst.,
No. 29, !977.

63

HUMPBACK WHALES OF HAWAIIBACKGROUND OF THE HAWAIIAN POPULATIONThe Hawaiian Island region nicely meets the preferred ecological requisites
for breeding grounds of Megaptera. The eight main Hawaiian Islands (Fig. 1),
around which the whales predominately aggregate, comprise the southeastern portion (Leeward chain) of a linearly arranged archipelago extending some 1300 nm
from Kure atoll in the northwest (178° 30' W, 28° 25' N) to the island of Hawaii
in the southeast. Figure 1 shows some extensive areas surrounding the main islands
160° w

159'

158°

156'

157°

w 155°HAWAIIAN ISLANDS
22°

21°

157°

156°
156°

w 155°

Fig. I. The main islands of the Hawaiian Archipelago. The inset expands thefour-island region of Molokai, Lanai, Maui and Kahoolawe. The dotted lines
are the JOO-fathom contours. Penguin Bank is the entire region within the 100fathom contour extending southwesterly from Laau and Ilio Points, Molokai.

in which the water depth is 100 fathoms or less, especially within the four-island
region of Molokai, Lanai, Maui, and Kahoolawe, and within Penguin Bank extending some 25 nm southwest of Molokai. Between November and March, surface water temperatures remain close to 25° C (77° F), with a near-isothermal layer
extending downward to 50-80 m (Gosline, 1965). Zooplankton is fairly uniformly
distributed throughout the coastal waters, though in markedly lesser concentrations
than in equatorial waters or in waters further to the north and northeast of the islands (King and Demond, 1954; King and Hida, 1954). The relatively low zooplankton abundance and that runoffs from land have little permanent effect on thenearshore environment make for clear waters. The water clarity and the concentration of the whales near shore make for ideal surface and underwater study conditions. Strong northeast trade winds or southern storms occasionally restrict viewing
opportunities, but the majority of the time the whales may be readily observed
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HERMAN AND ANTINOJA

from a number of key shore points or easily accessed by ship or light aircraft.
Prior to the 1976 season, the Hawaiian population had not been studied inany detail. In fact, it seems to have gone almost unnoticed in the scientific literature until relatively recently, as illustrated by a number of compendia on the zoogeography of cetacea that failed to record the population (e.g., Marcuzzi and Pilleri,
1971; Tomilin, 1967). Bryan (1915), in his review of Hawaiian ethnology,. geology, and natural history, seems to be the first to give mention of the population,
but as noted by Tomich (1969) Bryan's documentation is sparse. Unfortunately,
the situation improved little thereafter, being limited mainly to occasional newspaper reports of sightings (see summary in Tomich, 1969). This historical neglect
seem paradoxical given that Hawaii was the commercial hub of North Pacific whaling·in the early and mid-nineteenth century, offering rest, recuperation and reprovisioning to the hundreds of vessels hunting sperm whales in equatorial waters or in
the seas adjacent to Japan, or else searching for right whales in the Bering Sea, theSea of Okhotsk, and in adjacent waters. Apparently, the whalers had little interest in catching or even logging the presence of the seasonally resident humpback
whales in Hawaii, which were of lesser economic importance at the time than were
sperm or right whales. Minor exploitation of the Hawaiian humpback whale
population (and of a few sperm whales) did occur from the late 1840's through to
the late 1860's by shore whaling stations operating mainly from the island of Maui
(Anon. 1848, 1856, 1866; Baldwin, 1958; also see Jones, 1938), but the records
seem too fragmentary to allow for any estimates of nineteenth century abundanceof the humpback whale in Hawaii. The 19th century exploitation by shore stations appears to have begun just about the time when whales, in general, were diminishing in economic importance worldwide. Combined with the apparent
difficulty encountered by the Hawaiian shore stations in capturing the animals,
each operation seems to have petered out only a few years after it began. Exploitation of the at-large North Pacific humpback whale stock in its higher latitude summer
feeding grounds, which certainly must have included portions of the Hawaiian
population was, as noted, a continuing process from the latter part of the nineteenth
century, whenJapanese and, apparently, Russian pelagic whaling began (H. Omura,personal communication), through to the end of 1965.
There is no evidence of any exploitation of the humpback whale by native
Hawaiians prior to the nineteenth century. The antiquities of the Hawaiians,
including their petroglyphs, contain no record of humpback whales, or indeed ofwhales of any type, and there are no Hawaiian whale legends other than a very few
obviously imported from the South Pacific, where native whaling did occur (Beckwith, 1970; Kirtley, 1971; Malo, 1951). The Hawaiian language seems tocontain no special word for humpback whale, though a general word for whale,
kohola, exists, as does a special term, palaoa, for sperm whale teeth or products derived
from the teeth, such as whale-tooth pendants (Malo, 1951; Pukui and Elbert, 1971).
Sperm whales and other toothed whales were apparently washed ashore on occasion,and their teeth became the valued property of the royalty. No similar names forderivatives from baleen whales (such as baleen plates) appear in recorded Hawaiian
Sci. Rep. Whales Res. Inst.,
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HUMPBACK WHALES OF HAWAII

65

history or in the language. The sum of the evidence thus suggests that the humpback whale was either of little interest to the pre-nineteenth century Hawaiian natives, or else that the whales were inhabiting different breeding grounds than thoseused today, grounds which were not observable from the island shores or the nearby
waters. The resolution of those two hypotheses poses an interesting challenge tomarine mammalogists and archaeologists.
CURRENT OBSERVATIONS: FIELD METHODSWe began the study at the end of February 1976, while the migratory season
was in progress, and concentrated our efforts principally in the regions of suspected
highest whale density, the waters within the four-island region and on Penguin
Bank (Fig. 1). Other areas were also surveyed, but in less detail. Table 1 summarizes dates, times, and whale spotting conditions for the various aerial and ship
surveys. Aircraft surveys used a high-winged Cessna 172, flying at 152-m (500 ft.)altitude at air speeds of approximately 100-120 knots. During an aerial survey, apredetermined transect over an area of interest was flown untill sighting of a whaleor pod of whales. The aircraft then diverted from its path and orbited the pod at
152-m altitude for close-range visual observation and photography. We used
TABLE !.

AERIAL AND SHIPBOARD SURVEYS OF HUMPBACK WHALE
POPULATION IN HAWAII (1976)

Date

Time

Region

Method a>

29 Feb.
29 Feb.
I Mar.
I Mar.
13 Mar.
14 Mar.
14 Mar.
14 Mar.
15 Mar.
16 Mar.
19 Mar.
19 Mar.
9 Apr.
9 Apr.
9 Apr.
15 Apr.

1130-1454
1617-18330926-1222
1456-1737
0840-1801
0910-1810
1110-1420
1600-1735
0800-1640

Hnl to W. Maui
W. Maui to Hnl
Hnl to W. Maui
W. Maui to Hnl
Hnl to Molokai
Kalohi Channel
Hnl, Lanai, to W. Maui
W. Maui to Hnl
Kalohi Channel
Molokai to Hnl
S. coast Oahu to W. Kauai
Circle Kauai, Niihau, Oahu
Hnl to W. Maui
N. & E. Maui, circle Hawaii
N. Hawaii to E. Maui
Circle Oahu

A
A
A
A

0730~1615

1000-1056
1231-1627
0853-1137
1333-1651
1745-1840
1353-1517

s
s
A
A

s
s
A
A
A
A
A
A

Spotting
Conditionsb>
E
E (F after 1745)
G
G
E
E
E
G to FG
G (P after I OOO)E
G to FFFF
E to Ga> A =aircraft. S =ship
bl E =Excellent; weather fair and seas calm to slight; no whitecapping (Beaufort Scale No. 0-2).
G =Good; weather fair or cloudy and seas moderate with minor whitecapping (Beaufort Scale No. 3).
F =Fair; weather fair or cloudy and seas moderate with more frequent whitecapping (Beaufort
Scale No. 4); or reduced visibility due to poor light but sea state 3 or less.
P =Poor; reduced visibility and sea state 4 or more; or greatly reduced visibility in any sea state;or sea state 6 or greater.

Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

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HERMAN AND ANTINOJA

Nikon F2 and Canon FTB cameras equipped with 105, 200, and 300 mm lenses.
Visual observations were recorded in real-time on audio cassettes. The positionof the aircraft over whales was obtained by reference to land-based VORTAC radio
stations, if in range, or to landmarks using USCG navigational charts. The swimming direction of the whales was determined through use of the aircraft's onboard
compass. Three personnel in addition to the pilot accompanied each flight.
Shipboard surveys between Oahu and Molokai were made on March 13th and16th. The boat followed approximately the same path as the aircraft within asurveyed region, but did not divert from its path following a spotting. Three observers were positioned along the port side, and another three along the starboard
side. Whales observed beyond the stern of the boat were not counted unlessobviously not a previously-seen spot. The swimming direction of the whales wasestimated by handheld compass and their distance from the boat gauged by visual
estimation. The position of the boat was determined by reference to visibly charted
landmarks or by dead-reckoning using time and distance data.
The ship remained in the Kalohi Channel area between Molokai and Lanai
on March 14th and 15th for close-range observation of the whales and for launchingof underwater observations. Divers equipped with Nikonos II 35-mm underwater
cameras dropped off the stern of the moving ship at positions which hopefully wouldintercept the path of whales observed swimming astern. Scuba gear was not usedbecause it was felt that bubble emissions might prove aversive to the whales. A
surfboard was thrown into the water for the diver's use immediately after his departure, while the ship continued on its path. The diver was recovered by theship after completing observations or on failing to contact the whales. Divers madetape recorded notes of their visual observations immediately after returning to thevessel.
The aerial, shipboard, and underwater photographs obtained, in conjunction
with notes on visual observations, were used to refine the numerical counts of pod
size, to describe pod composition and organization, to identify morphometric characteristics of individual animals and to categorize behaviors.
RESULTS AND DISCUSSION

Population Parameters
Distribution and Concentrations:

Four Island Region.

Figures 2-4 show representative data, giving the locations of pods and numbers of whales per pod during
aerial surveys between Honolulu and W. Maui on February 29th and March 14thand during a ship survey between Honolulu and Molokai on March l 3th. Each
pod is numbered serially, in the order seen, and the movement characteristics of thepod, if obtainable, are shown. Calves are noted as cross symbols. The remaining
animals were almost always classified as adults, though a few of seemingly juvenile
status were also seen, but are not identified separately in this report. Table 2 summarizes pod and whale counts for all surveys within the four-island region. Figures
2-4 show that whales were principally found within the 100-fathom contour. AirSci. Rep. Whales Res. Inst.,
No. 29, 1977.

HUMPBACK WHALES OF HAWAII67

TABLE 2. FOUR-ISLAND REGION: NUMBERS OF PODS, WHALES PLUS CALVES,AND CALVES OBSERVED DURING AIRCRAFT AND SHIP SURVEYS

AircraftFeb. 29
Mar.
Mar. 14
Apr.

9

Ship
Mar.
Mar.
Mar.
Mar.

13
14
15
16

RegionPods

All Whales

CalvesWhales/Pod

Hnl-Maui
Maui-Rn!
Hnl-Maui
Maui-Rn!
Hnl-Maui
Maui-Hnl
Hnl-Maui
Totals:

22
20
23
22
22
15
6
130

43
52
56
54
55
27
15
302

4
5
0
4
5
3
22

1.96
2.60
2.43
2.45
2.50
1.80
2.50
2.32

Hnl-Mlk
Kalohi Ch.
Kalohi Ch.
Mlk-Hnl
Totals:

38
10
18
16
84

48
31
30
18
127

0
3
3
0
6

1.25
3.10
1.67
1.13
1.51

22·~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

N

30'

21·

AERIAL SURVEY
30'

Honolulu to Maui
February 29, 1976
1130-1454 hours
158°W

30'

157°

30'

156°

Fig. 2. Aerial survey results, showing path of aircraft (solid line), pod numbers in
the order seen, and the number of whales per pod. Adults are shown as open
circles and calves as cross symbols, Straight arrows show movement direction ofswimming pods; arrows with a cross-hatch indicate a re5ting pod oriented in the
direction shown; curved arrows. indicate milling pods. Not all pods were classifiable because of observation difficulty. The 100-fathom contour is shown as adashed line.
Sci, Rep. Whales Res. Inst.,
No. 29, 1977.

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HERMAN AND ANTINOJA
22·~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

N

30'

21'

30'

AERIAL SURVEY
Honolulu to Maui
March 14,1976
1110-1420 hours
158' w

Fig. 3.

KAHOOLAWE
30'

157'

30'

156'

Aerial survey results keyed as in Figure 2.

30'

21'

30'

SHIP SURVEY
Honolulu to Molokai
March 13,1976
0840-1801 hours
158' w

30'

157'

30'

156'

Fig. 4. Ship survey results keyed as in Figure 2. The Kalohi Channel area is expanded in the upper right of the chart to show details of the pods.

craft data gave the relatively greatest numbers of whales, on the average, in Kalohi
Channel (13. 7 whales/flight). This was followed by Penguin Bank (11. 7 whales/
flight), the Auau channel area southeast of Kalohi Channel (9.6 whales/flight) andthe south coast of Molokai from Laau Point to Kaunakakai (6.3 whales/flight).
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

HUMPBACK WHALES OF HAWAII

69

Other regions yielded much smaller numbers. The relative numbers of whales
seen in the various regions remained reasonably consistent across successive flights,
although some anomalies were evident. On the flight of February 29th from Mauito Honolulu, especially heavy concentrations were seen along the south coast of
Molokai, and on April 9th no whales at all were seen in Kalohi Channel. Thoughspotting conditions were only fair on April 9th (Table 1), possibly accounting forsome reduction in the counts, as on the return flight of March l 4th from Maui to
Honolulu, it is more likely that by this date many whales had already left on theirreturn migration to the summer feeding grounds. Kalohi Channel, especially thesouth and southeast portions, seems to be an important breeding area and as these
activities diminish over the season it would be one of the earliest areas expected toshow a population decline. With respect to the south coast of Molokai, ten of thetwenty-two whales seen on February 29th were actually located near the beginning of Penguin Bank. Though moving towards southwest Molokai, a survey
perhaps an hour earlier might have placed them within the usually more densely
populated Penguin Bank.
The ship survey of March 13th verified the aircraft data showing 'large concentrations of whales in Penguin Bank and Kalohi Channel. The fewer numbersof whales per pod, as compared with aircraft data reflects the difficulty in estimating the numbers of whales without approaching pods closely. On March 13th
(and on March 16), with but one exception, the ship did not divert from the planned transect to inspect pods. In contrast, on March l 4th in Kalohi Channel, theship frequently diverted from its transect for the close-range inspection of pods,
yielding an elevated count of 3.1 whales per pod (as compared with the overall
estimate of 2. 7 whales per pod from aircraft data in Kalohi Channel). It is significant that calves were seen from the ship only during close-range inspection. On
March 15th, less time was spent on close-range inspection from the ship than on the
14th and more on general survey, resulting in an elevated pod count, but less whales
per pod. Three of the pods approached on the 15th had calves, as was thecase on the 14th. In general, it seems that pods with calves are easier to approachthan those without, in part because the latter are capable of more rapid locomotion and prolonged diving.
On March 16th, during the ship survey, large swells and considerable whitecapping were encountered in the Penguin Bank region. Nevertheless, the pod
count in that area (9 pods) was not much reduced over that found on March 13th
(13 pods) under better weather conditions. Spotting of the pods on March 16th
was almost entirely through seeing the large splash resulting from the breachingof an animal, whereas on the 13th blows and the animals themselves could be
spotted in the absence of breaching. It may be, as has been suggested by others,
that breaching is more common in rough water, perhaps serving to maintain acoustic
and/or visual contact between whales.
Distributions and Concentrations: Other Regions and Islands. We cannot draw
strong conclusions about concentrations of whales in the areas outside of the fourisland complex or Penguin Bank, since the outlying areas were surveyed less freSci. Rep. Whales Res. Inst.,
No. 29, 1977.

HERMAN AND ANTINOJA

70

quently and sometimes beyond the peak of the migratory period. Nevertheless, it
seems apparent from the available data that outlying concentrations in no way approached those observed within the four-island region and Penguin Bank. Table
3 shows that on March 19th, presumably still at or near the peak period of concentration of whales in the four-island complex and Penguin Bank, a total of only
ten whales (four pods) was seen around the entire island of Oahu, along the northand northeast coasts; six whales (three pods) around the entire island of Kauai,
between Nawiliwili Bay and Makaha Point; and no whales at all around the islandof Niihau or nearby Kaula Rock. The island of Hawaii was not surveyed until
April 9th, and judging from our results on that same date in the four-island region(Table 2), this was already past the peak migratory period. The two pods ofwhales seen near Hawaii on April 9th were at or just south of Upolu Point. The
pod of six whales seen in Alenuihaha Channel was approximately 8-10 nm NWof Upolu Point heading north-northeasterly. It was one of the few pods foundconsiderably outside of the 100-fathom contour and possibly was on the beginningof a return migration to higher latitudes.
TABLE 3. OUTLYING REGIONS: NUMBERS OF PODS (P), WHALES PLUS
CALVES (W), AND CALVES (C) OBSERVED DURING AIRCRAFT SURVEYS
Mar. 19

Oahu
Kauai Ch.a>
Kauai
NiihauKaula RockE. Maui
Alenuihaha Ch.bl
Hawaii

Apr. 9

p

w

c

4

10
0
6
0
0

0
0
0
0
0

0
3
0
0

p

w

Apr. 15

c

p

c

w
3

2

1
6
4

0
0
0

al Survey path was a straight line between Kaena Pt. Oahu and Nawiliwili Bay, Kauai.
bl Survey path was a straight line between Kipahulu Gulch, Maui and Upolu Pt., Hawaii.

The survey around the island of Oahu on April lSth revealed only a single
pod of three whales, including a calf. No further surveys were conducted afterthat date, though as late as mid-May the authors observed several pods from peaks
overlooking the south coast of Oahu. Also, reports were received of a few whales
lingering around the island of Oahu in June.
The last departures on the northward migration seemingly would tend to bepods with calves, judging by the relatively high proportion of such pods (three ofsix) seen on April 9th and lSth. The delayed departure of calves would allow
for attainment of sufficient growth and blubber deposit before encountering the
rigors of migration and the colder waters of the higher latitudes, and typifies migratory characteristics of Southern Hemisphere populations of humpback whales(Dawbin, 1966).
Our data showing that concentrations of whales outside of the four-island reSci. Rep. Whales Res. Inst.,

No. 29, 1977.

HUMPBACK WHALES OF HAWAII

71

gion and Penguin Bank are relatively small are consistent with sighting reports
from commercial hydrofoil craft during the 1976 season (Shallenberger, 1976).
Population Estimates. The combined data from the ship and aircraft surveys
can be used to estimate population numbers in selected areas. Gulland (1972)
suggested that counting all whales for two miles on each side of a ship's paththrough an area yields accurate estimates of whale density (whales/nm 2 ) in thefour-mile wide strip covered, which may then be extrapolated to the entire regionof interest. Gulland's model assumes that nearly all whales in the strip will beseen. Our data suggest, however, that it is simpler to estimate pod density (pod/nm 2 ) than whale density by ship survey. Our ship, transecting an area at ten
knots, probably missed very few of the pods actually present within the 4-nm widesighting strip. But, our aircraft surveys over the same region revealed that the
number of whales per pod was underestimated, unless the ship approached thepods closely. Aircraft, from their favorable vantage point, count whales per pod
with great accuracy, but unless surveying a region in fine detail, miss some proportion of the pods actually present. It would seem, then, that nearly all whales
present in a region could be accounted for by using ship data to estimate pod
density in the region, and aircraft data to estimate mean whales per pod. Multiplying the two estimates should yield highly accurate population counts. This
simple model was used to estimate the number of whales present in the three main
regions surveyed by ship on March 13th. The results were 63 whales for Penguin
Bank (.22 whales/nm2 ), 9 for the south coast of west Molokai within the 100-fathom
contour (.2 whales/nm2 ), and 47 for Kalohi Channel (.57 whales/nm 2 ), for a totalof 119 whales. To this we can add seven more in the small region just north of
the NW tip of Penguin Bank, where the ship encountered three pods, and aircraft
data yielded an average of 2.5 whales per pod. Other than this small region, thenumber of whales in the area between Honolulu and Penguin Bank appears negligible. The estimates given suggest that aircraft surveys sampled from one-third
to two-thirds of the population present. The larger sample size was obtained when
the region was well covered by the aircraft, such as the restricted coast-line areas of
Molokai.
The remaining major concentration of whales present on March 13th in thefour-island region would have been in the Auau Channel region east of Kalohi
Channel between Maui, Lanai, and Kahoolawe, and within the I 00-fathom contour. This region was not surveyed by ship. If we assume the whale distribution
on March l 4th was not significantly different from that on the l 3th, we can use
the aircraft flights of the 14th to add to our population estimates. Five pods werespotted by the aircraft in the Auau Channel region on March l 4th, but all dove
before they could be approached closely. We can, however, use the mean valueof 2.0 whales per pod, based on all aircraft flights over that region, to estimate thenumber of whales in those pods as ten. Applying the sampling ratio for aircraft,
previously discussed, of from one-third to two-thirds of the population, gives a final
estimate of from 15 to 30 whales actually present in Auau Channel. The assumptions made in these calculations should be treated with caution but appear reasonSci. Rep. Whales Res. Inst.,
No. 29, 1977.

72

HERMAN AND ANTINOJA

able in view of our overall data.
In summary, the overall estimate of population size on March 13th in thefour-island region, and including Penguin Bank and the area immediately adjacent to its NW tip is thus 141-156 whales (119+ 7+15 to 30). There were undoubtedly whales in other regions, but likely in considerably smaller numbers thanin the four-island region and Penguin Bank. On March l 4th, for example, only
six whales were seen along the northeast coast of Molokai and the south and west
coasts of Lanai, and on March 19th, only 16 whales were found around all of
Oahu, Kauai, Niihau and Kaula Rock (Table 3). East Maui and the island of
Hawaii, surveyed on April 9th, yielded only 11 whales (Table 3). Concentrationsin these latter two regions were likely greater three weeks earlier, and our uncertainty in estimates for the period near March 13th is, accordingly, greatest for theseregions. For the present, it seems best to bracket our estimates for all combined
outlying regions and islands as perhaps 50 animals as a lower bound and 100 as an
upper bound. The total population on or about March 13th might then havenumbered from close to 200 animals to as many as 250 animals. The March 13th
period was apparently within the peak of the migratory cycle, judging by our aircraft data (Table 2). However, we do not know how long individual whales
remain in the islands, and it is possible that some animals might have already departed the Hawaiian waters and that others were still in-migrating, which would
add to our population counts somewhat. It would be desirable to extend thecensus work in the future, so that all major areas within the islands could be surveyed in parallel on given dates, and in- and out-migration studied in detail.
Nursery Grounds and Numbers of Calves. Tables 2 and 3 gave data for the number of calves seen during each aerial survey. Calves were typically accompanied
by more than one adult, as discussed more fully in a later section, but in no casewas there more than one calf in a pod. With the one exception of a pod of two
adults and calf observed off north Oahu on April 15th, all pods with calves were
found within the four""island region and on Penguin Bank. For all flights combined, the areas of greatest concentration were Kalohi Channel (9 calves), especially along the north coast of Lanai, and Penguin Bank (8 calves). Additionally,
two calves were seen south and southwesterly of Lahaina, Maui. No other area
yielded more than a single calf. Though the north coast of Lanai is clearly themost densely concentrated nursery region and should be protected, there is considerable dispersion of nursery areas throughout the regions surveyed.
The numbers of calves seen relative to total whales provides a basis for estimating gross recruitment rate (Seber, 1973). As a first approximation we can assume that the Hawaiian population is similar demographically to populations of
humpback whales elsewhere having characteristics known through whaling operations. Normal sexual maturity for humpback whales, as for some other baleen
whales, occurs from 6-12 years (Anon, 1975) for both males and females. Earlier
average onset may be recorded in highly exploited stocks due to the more rapid
growth rates in such cases, or the selective depletion of larger (older) animals(Chittleborough, 1965). Mackintosh (1972) states that given the two-year reSci. Rep. Whales Res. Inst.,
No. 29, 1977.

HUMPBACK WHALES OF HAWAII

73

productive cycle of female baleen whales, and that 99% of the births are single
calves with the sex ratio approximately equal, the expected birth rate would be 50%of the sexually mature female population. Rice (1963) calculated a pregnancy
rate of 43% based on examination of 168 humpback whales caught by shore stations near San Francisco. The number of females was not specified. Nishiwaki's(1959) data on humpback whales caught in Ryukyuan waters in the western North
Pacific gives the annual percentage of ovulating females as 60% and pregnancy
rates as 40%. Chittleborough (1965), using catch-effort statistics from the whaling station of Albany in southwest Australia, estimated that 37% of the female
humpback whales were pregnant. Of a small sample of 13 female humpback
whales collected in the northwest Atlantic in 1969 and 1970, 7 (54%) were pregnant (Mitchell, 1974). The collective data from these sources suggest that thenormal birth rate could be somewhat lower than 50% of the mature females; 43%
may be a reasonable best estimate.
According to Nishiwaki (1959) approximately half of a normal humpback
whale population are sexually mature animals, with half of these males and half
females. This places the normal limit on calf recruitment rate as .5x .5X .43=
.108 or 10.8% of the entire population. Applying this recruitment rate to the
Hawaii population, conservatively estimated as 200 animals, would yield an expected calf population of 22.
Across all of our aerial surveys, there were some obvious vagaries in our calf
counts (Table 2). Low counts can generally be attributed to unfavorable spotting conditions or to the abbreviated nature of a survey, though in the ca~e of themorning flight of March lst, the reasons for the zero count were unclear. The
largest number of calves seen on any flight was five, on the second flight of February 29th and then again on the first flight of March 14th. In each case, spotting conditions were excellent for all or nearly all of the survey. The most optimistic estimates of recruitment rates are obtained by considering the calf to adultratios on these two flights. (Calf to adult ratios obtained after the peak migratory
period, such as that of April 9th, are biased because mothers with calves remain
longest in the breeding grounds, cf. Dawbin, 1966). On the second flight of February 29th, 9.6% of the total of 52 whales seen were calves, and on the first flightof March l 4th 9 .1 % of the 55 whales were calves. These percentages can be considered the upper limits of the current calf recruitment rate for the Hawaiian population, but both are somewhat below the discussed expected rate of 10.8%. More
importantly, since the four-island region and Penguin Bank appear to contain the
major nursery grounds, birth rate samples from these areas may not be representaative of other areas, and would overestimate rates for the population at large.
Hence, the rates of 9.1 % and 9.6% should be regarded as optimistic.
The apparent low birth rate is disturbing and calls for additional assessment.
The reasons for the apparent low rate are unclear. In a small unexploited population, presumably below the carrying capacity of the environment, one would, infact, expect higher than normal rates of birth (Wilson, 1975). It seems doubtfulthat our sampling of the calves was disproportionately low, since pods with calves
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

74

HERMAN AND ANTINOJA

are typically slow moving or even resting, seldom diving deep or for long periods,
and hence are relatively easy to spot from aircraft. It may be that a demographic
analysis of the Hawaiian population would show, for reasons unknown, a smaller
than usual number of mature whales, explaining the low recruitment rate. Or, it
may be that the low rate reflects unfavorable biological or ecological conditions, ora response to continued harassment from the ships, aircraft, and divers passing
close to the whales, intentionally or otherwise. Whatever the cause, the apparent
low recruitment rate underscores the potential fragility of the population and thepressing need for its careful protection and management.

Pod Characteristics
Pod Si,ze. Table 4 summarizes the findings on sizes of pods for all aerial surveys combined. There is generally an orderly decrease in the frequency of occurence of successivCly larger pod sizes, though the majority (59%) of the pods
were comprised of two or more animals. The largest pod size, nine, was observedon February 29th in Kalohi Channel and on March lst near Laau Point, Molokai.
The percentage of singletons is very probably an overestimate, since we conservatively estimated one whale for all spots for which a single blow, breach, or bodypart was seen at a distance but the animal could not be relocated on closer approach. There were 23 such cases out of the total of 59 singletons.
TABLE 4.

SIZE COMPOSITION OF PODS FOR ALL AERIAL SURVEYS
Pod Size2
No. of Pods
% Total
Note:

59
41.5

37
26.1

3
18
12.7

4
11
7.8

5
8
5.6

6
6
4.2

7
1
0.7

8
0
0.0

9
2
1.4

Totals142
100.0

Pod size includes both adults and calves.

The data of Table 4 may be contrasted with that of Nemoto (1964) who reported on pod sizes for the humpback whales in their summer feeding grounds inthe upper North Pacific. Of 92 pods encountered by Nemoto, 50% were singletons, 43% pairs, 3% threesomes, 2% foursomes, and 1% fivesomes. There wasalso a single group of seven (1 %). The largest difference between our data andthat of Nemoto occurs for groups of three or more: 32% of our groups were threeor more animals but only 7% of Nemoto's. Dispersal in the feeding ground andclustering in the breeding ground appear obviously adaptive. Grouping in baleen
whales may stimulate and facilitate reproductive activities as it does for other species (Wilson, 1975) and is consistent with the presumed promiscuous mating behaviors of female baleen whales in which multiple males appear to attend a single
female (e.g., see Payne, 1976). Apparent polyandrous mating bouts were observed in a number of our aerial surveys, but we cannot be sure of the sex of theparticipants. The counts by Winn et al. (1975) of the humpback whales in
the West Indies breeding grounds seem discrepant in that only 23% of their sightings were groups of two or more as compared with 49% for Nemoto and 59% forSci. Rep. Whales Res. Inst.,
No. 29, 1977.

HUMPBACK WHALES OF HAWAII

75

our data. The Winn et al. counts were based on shipboard transects whichapparently did not approach the whales closely. Their data may thus underestimate whales per pod, as did similar ship surveys we conducted on March 13thand 16th. The data of Nemoto (1964), though based on shipboard observation,
relied on catch statistics in which boats necessarily pursued and approached whales
very closely, allowing for highly accurate counts of pod size.
Pods With Calves. Table 5 shows that calves are typically found in pods withmultiple adults, most often two adults, the mother and an " escort " whale. This
is in contrast to other Balaenopterid whales in which the mother and calf often
travel unescorted (Nemoto, 1964). The Southern Hemisphere mother-calf humpback whale pairs, like the Hawaiian group, do tend to school with other whales.
TABLE 5.
FlightFeb. 29 (1)Feb. 29 (2)Mar. 1 (1)Mar. 1 (2)Mar. 14 (1)Mar. 14 (2)Mar. 19
Apr. 9Apr. 15
TotalsNUMBER OF PODS WITH CALF(C) AND THE NUMBER
OF ACCOMPANYING ADULTS (A)
lA-lC

2A-1C

3A-1C

2
5

2

4A-1C

5A-1C

4
5
0

4

3
2

4

Totals

11

2

4

2

5

2

0
3
1
23

Chittleborough (1953) reported that all nine mother-calf humpback whale pairs
seen in Antarctic waters were accompanied by other whales. Four of the nine
were accompanied by a single additional whale. In some contrast only two of ninemother-calf humpback whale pairs seen in North Pacific waters by Nemoto (1964)
were accompanied by other whales. It may be that schooling with other whales
occurs principally in the terminal breeding and feeding areas rather than enroute.
Thus, Chittleborough (1953), observing migrating Southern Hemisphere humpback whales near the western Australia coast, reported that the calf was usually accompanied only by the mother. Also, in Exmouth Gulf, on the Australian west
coast, all seventeen calves seen by Chittleborough were accompanied only by themother. Exmouth Gulf does not seem to be a terminal point, since migrations
north and south of the Gulf were observed. Since mother-calf pairs do departthe breeding grounds last, there are few other whales for them to school with on
the return migration, except for other cow-calf pairs. But, as noted for the
Hawaiian population, multiple calves in a pod were never seen, and may indicate
a self-imposed segregation of mothers from calves which are not their own.
The escort whale or whales may serve a protective function, as discussed in alater section. Here we may note that Southern Hemisphere humpback whale trios·with calf have been observed defending themselves against killer whales. In one
Sci. Rep. Whales Res. Inst.,

No. 29, 1977.

76

HERMAN AND ANTINOJA

case cited by Chittleborough (1953), one adult of the two present kept the calf very
close while the second charged the pack of 4-5 killer whales, successfully beatingthem off with its flukes.
Gross Activiry ef Pods. The gross activity of a pod was classified as swimming,
milling, or resting (Table 6). Swimming behavior was defined as movement in a
fixed direction during the aircraft's approach. Milling was defined as spatially
undirected activity occurring within a small area. Milling animals might be lolling about, rolling on their backs, or contacting one another in the case of multiple
animal pods. For singletons, the animal was classified as milling using a similar
criterion of area-restricted activity, though contactual behavior was of course
absent. Resting animals were lying quietly in the water, dorsal surface up, barely
moving at best, usually stationary. Gross activity data was available for 97(68.3%) of the total of 142 pods seen on all flights. The remaining pods either
dove when closely approached and before they could be classified or else we could
not locate the animal on close approach.
TABLE 6.

GROSS ACTIVITIES OF PODS CLASSIFIED BY TYPE AND SIZE

Activity/Size

Singleton

Swimming
Milling
Resting(Subtotal)
No Data(Total)20(83.3)
4(16.7)0 ( 0. 0)24
35
59

Pods with Calfal

Multiple-Adult Pods
2

3

4

s+

19
3
2
24
9
33

5
0
1
6

4
4

10 38(76.0)
1 8(16.0)0
4 ( 8. 0)
11 50
0 JO
II 60

I

7

I

9
0
9

All

Totals

2

3

4

s+

1 6
0
2
3
3
4 11
0
0
4 II

2
0
0
2
0
2

2
2
0
4
0
4

2 13(56.5)
0 4(17.4)
0 6(26.1)
2 23
0 0
2 23

All

71 (73.2)
16(16.5)
10(10.3)
97
45
142

Note: Percentages, given in parentheses, are based on subtotals.
al pod size refers to number of adults accompanying calf.

It is clear from Table 6 that for multiple-adult pods, and for single adults aswell, active swimming was the most common gross activity, with milling considerably less common but still more frequent than resting. It is the milling multipleadult pods that are engaging in mating behaviors. There are no obvious relations
between pod size and pod activity.
For pods with calves, swimming was relatively less frequent though still themost common behavior, while resting was more common than milling. It is probable that the young calf tires easily and tends to require that the mother be stationary while nursing. Whalers in the past have taken advantage of the lesser
stamina of the calf to catch and kill the mother who remains nearby the tiririg calf
throughout the pursuit.
The breakdown of activity by size of pod having calves reveals a tendency forswimming and milling activities to be associated with larger-sized pods, while resting seems common when the calf is accompanied only by the mother. The database is very small so these trends must be interpreted with caution. If they are
indicative of the population at large, it may be that calves accompanied only by
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

77

HUMPBACK WHALES OF HAWAII

the mother are quite young, and that as they mature the pair either joins otherwhales, who tend to be active, or else are attractive to other whales who join them.
Spatial Organization of Pods. The spatial formation of swimming pods, whenobservable, was classified into eight different categories as described in Table 7:line astern (file); diagonal; line abreast (rank); wedge-shaped with animals spreadout symmetrically behind a leading animal or animals (simplified echelon); veeshaped with multiple leading animals abreast and one or more additional animals
centered and behind; T-shaped; diamond shaped; and x-shaped. In many cases,
the formation was clean-cut, as in the case of a pod of five whales observed line
astern, each animal nearly touching the flukes of the one ahead, or the neatly staggered diagonal array of a pod of four whales observed on another occasion. Moreoften, the formation was broken by one or two animals, so that three might betightly astern while a fourth swam off to one side. In such cases, the formationof the majority of the animals was used to categorize the pod's organization.
Only formations actually seen are listed. There are obviously other possibilities.
TABLE 7.

SPATIAL ORGANIZATION OF SWIMMING PODS GROUPED BY POD SIZE

Formation/Pod Size
AsternDiagonal
Abreast
Wedge
Vee
Tee
Diamond

All-Adult Pods

Totals
2

3

4

5+

All

2

3

4

5+

All

2
2
5

1
0
0
0
2

5
2
0
2
0
0
0

2

2
3

1
0
0
1
0

0
0
0
0
0
0
0

0

0
0
0
1
0

9
9
18

3
3
6

9
0
9

5
0
5

10(38.5)
5(19.2)5(19.2)2 (7. 7)2 (7. 7)
1 (3.8)0 (0.0)1 (3.8)
26
12
38

2
0
2

0
0
0

0
3

3 (27 .3)
4(36.4)2(18.2)
1(18.2)0 (0. 0)0 (0.0)1 (2. 7)0 (0.0)
11

4

12

x
(Subtotal)
No information(Total)Pods With Calvesal

6
0
6

1
0
0
0

13(35.1)
9(24.3)7(18.9)4(10.8)2 (5 .4)(2. 7)(2. 7)(2. 7)
37
13
50

Dashes in columns mean that spatial organization of the type specified is not possible for the
given number of animals. Numbers in parentheses are percentages of subtotals.
a) Organization based on adults in pods only.
One swimming pod of the total of 13 in Table 6 wasa single adult with calf and hence is not classified here.

Note:

Among the all-adult pods, the line abreast formation was observed only forpaired animals, swimming side by side. For larger pods, the adults arranged
themselves most commonly in the line astern formation or what may be simply its
variant, the diagonal. The function of these "follow-the-leader" formations is
not apparent, nor is it clear whether specific animals maintain leadership positionsin the swimming pod. More protracted observations are necessary to answer thesequestions.
For pods with calf, only the spatial organization of the adults was classified,since the calf typically remained close to a given adult, presumably the mother.
The number of swimming pods having calves was small, so generalizations are difSci. Rep. Whales Res. Inst.,
No. 29, 1977.

78

HERMAN AND ANTINOJA

ficult. In pods with a single escort whale, the escort tended to remain behind themother-calf pair. If multiple escorts were present, one or more might remain aheadof the mother-calf pair while the others remained behind or abreast. Invariably,
we noted that when a pod with calf shifted its formation in response to the orbiting
aircraft, it was to tighten the formation and move the calf to a more central position between the adults, a clearly protective behavior. In contrast, for all-adultpods, shifts of formation occurring in response to overhead aircraft were predominantly dispersals of the pod, the animals moving further apart or temporarily
going in different directions. Another defensive response of a pod to the aircraft
was deep diving (sounding). This tended to occur more commonly for singletonsand for pods of two but rarely for larger groups.
Underwater observations of milling or stationary pods revealed that verticaldispersion was often greater than horizontal dispersion. In pods with calf, theescort would typically appear from well beneath the near-surface mother-calf pair,
presumbably in response to the presence of the diver. The pod would then departfrom the area of the diver.

Coloration: A Clue to Population Identification
Most humpback whales are predominantly black on their dorsal surface, excluding the pectoral fins and tail flukes which may have extensive white coloration.
White coloration is common on the ventral surface of the pectoral fins, flukes, andportions of the body from the throat region to the navel. In earlier whaling days
when humpback carcasses could be examined, investigators studying coloration
focused on the description of ventral surfaces as these seemed to show the mostvariability. Lillie (1915), working with carcasses of Southern Hemisphere humpback whales, devised a seven category classification scheme for ventral surface coloration, ranging from extensive white to all or nearly-all black. Later invesigators
generally continued to use Lillie's categories (Chittleborough, 1965; Matthews,
1937; Omura, 1953; Nishiwaki, 1959; Symons and Weston, 1958). The major interest was in whether coloration differences could predict demographic characteristics of the population, in particular sex and body length (age). No stable, clearcut relationships were found within or across studies, but a by-product of the research was the observation that geographically isolated groups often demonstrated
different coloration characteristics. In the Southern Hemisphere, Matthews(1937) found that humpbacks from the South Georgia and South Africa regions
were on the average darker in color (84.8% of 53 animals fell in the darkest twoof Lillie's categories and 1.8% in the lightest two) than humpbacks from the New
Zealand area (26% of 30 animals were in the darkest two categories and 26. 7%in the lightest two). Symons and Weston (1958) reported that 24.1 % of 58 animals captured in the Bellinghausen Sea adjoining Antarctica fell in the darkest twocolor categories while 36.2% were in the lightest two. Omura (1953) provides
an excellent summary of differences among all five Antarctic groups and Chittleborough (1965) gives additional data on coloration differences between east andwest coast Australian populations.
Sci. Rep. Whales Res. Inst.,
No. 29, 1977.

HUMPBACK WHALES OF HAWAII79

In the North Pacific, Pike's (1953) data for 184 British Columbia humpback
whales reveal that all fell into the darkest two coloration categories. Nishiwaki(1959), examining 237 western North Pacific whales captured in Ryukyuan waters,
classified 92.2% as being black or mostly black and none as being predominantly
white. These results were very similar to another 164 animals subsequently captured in the same waters (Nishiwaki, 1962), leading Nishiwaki (1965) to conclude
that North Pacific humpback whales are darker in coloration, having only a few
small white areas, than Southern Hemisphere humpback whales, which often havelarge white areas.
Our coloration data for the Hawaiian population, based principally on aerial
observations, must rely on coloration of dorsal, not ventral surfaces. We havefound considerable variation in dorsal surface coloration of the pectoral fins. Past
literature on humpback whale coloration has in a few cases reported dorsal surface coloration of the pectoral fins. These data suggest considerable color variation in the dorsal surfaces of the pectoral fins between geographically isolated breeding groups.
In Table 8 dorsal surface coloration of the pectoral fins for the Hawaii population is classified into four categories: all black; slight white (leading or trailing
TABLE 8.

COLORATION OF DORSAL SURFACE OF PECTORAL FINS:COMBINED AERIAL TRANSECTS
Mother

Adult a>

Calf

Total

ColorationN
All Black
Slight White
Moderate White
Extensive White
Subtotal
Undetermined
Grand Total
al

7
3
3
8
21
2
23

%
33.3
14.3
14.3
38.1
100.0

N
6
3
3
7
19
4
23

%
31.6
15.8
15.8
36.8
100.0

N

%

N

%

53
27
14
55
149
137
286

35.6
18.1
9.4
36.9
100.0

66
33
20
70
189
143
332

34.9
17.5
10.6
37.0
100.0

Includes six animals classified as juveniles, two with all black coloration, one with slight whitecoloration and three undetermined.

edges white, or a few small spots of white seen elsewhere on the surface); moderate
white (mottled, piebald, speckled, or patchy areas of white); and extensive white(solid white or mostly white). Classification was based on detailed examinationof aerial photographs and on supplemental notes made while circling a pod. Coloration data were available for 189 of the total of 332 whales spotted during thevarious aerial transects. Many of these whales were undoubtedly the same animal seen on different occasions, but assuming that whales are sampled on a random basis (with replacement in the population) the percentages should estimate
population parameters closely. Table 8 shqws that 37% of the whales were classified in the extensive white category and 35% in the all black category. The
data reveal very close correspondence in percentages for mothers, calves, and adults, suggesting that phenotypical color characteristics are stable in the population.
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These characteristics could prove useful in identification of the Hawaiian population in its summer feeding grounds, if dispersal and intermingling of populations is
minimal.
From the limited data available on Southern Hemisphere stocks, it appears
that white coloration on the dorsal surface of the pectoral fins was rare. Lillie(1915) made no mention of all-white pectoral fins; neither did Omura (1953) orSymons and Weston (1958). Matthews (1937) stated that of the groups in thedarkest two categories, 7% had white pectoral fins. Unfortunately, data for othercoloration categories was not given. In the eastern North Pacific, Pike (1953) reported that only 14. 7% of the British Columbia whales had predominantly whitecoloration on the dorsal surface of the pectorals. This is considerably below the
37.0% value we find for the Hawaiian group. Scammon (1874) described theeastern North Pacific population as all black above, or nearly so. Very recent observations of humpback whales in the southeast Alaska region describe them as
having all black pectoral fins above and as numbering 60-61 animals (M. Tillman,personal communication). From these combined data, we can infer that the
Hawaiian population is reproductively isolated from the eastern North Pacific stockand that it does not summer in the feeding grounds of that region.
Tomilin (1957) provided only qualitative data on coloration of the western
North Pacific stock, presumably in the area of the Kamchatka Peninsula. He described the dorsal surface of the pectorals as ranging from black to piebald or evencompletely white. He also described a group from the Chukchi Sea and the Bering Sea as having dusky flippers with an exceptionally white border. This was
not a characteristic observed in the Hawaiian group, suggesting reproductive isolation of the Hawaiian group from at least portions of the Asiatic population. It isdifficult to say whether significant intermingling of the populations occurs in common feeding grounds in the Aleutian Island regions or further to the west andnorth.
Chittleborough (1953), using aerial surveys to study the New Zealand humpback whale population, reported that calves were born light and darken rapidly
with age. How rapidly was not specified. All of the calves we saw in Hawaii
were dark above, except for pectoral fin coloration as noted and, occasionally, somewhite coloration on the dorsal surface of the tail flukes. We cannot say whether
the calves we saw had already darkened, or whether the light color of the newborn
does not occur in the Hawaiian population. Other than Chittleborough's observations on newborns, investigators seem to agree that coloration and age are notrelated.
The extensive color variation among individuals within the Hawaiian population, and here we include ventral as well as dorsal surfaces, may function in individual recognition among conspecifics. Colar patterns may also serve as signals
communicating movement intention or direction, as in the exposure underwater ofthe white surface of a raised pectoral or caudal fin to a school-mate swimming
nearby. Additionally, light ventral surfaces and darker dorsal surfaces provide forcryptic coloration important for predators, such as Mageptera, which at least in partSci. Rep. Whales Res. Inst.,
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81

feed on schooling fish (A.V. Yablokov, in Sokolov, 1971).
SUMMARY AND CONCLUSIONSThe Hawaiian population of humpback whales may number between 200 and 250
animals, though more detailed surveys of outlying islands and study of migratory
patterns is necessary to refine the bounds of these estimates. Our estimates concurwith Shallenberger's (1976) data on peak population size, peak population periods,
and that the population numbers are much reduced by or after the first to second
week of April. A ship survey from Kauai to Hawaii from 23 February to 7 March
1976 by the National Marine Fisheries Service counted 373 whales (M. Tillman,personal communication). The bases for this somewhat larger count have notyet been clarified.
Almost all of the whales were found within the 100-fathom contour surrounding the islands, a trait noted also for other breeding groups of humpback whales(Chittleborough, 1953; Winn et al., 1975). The principal areas of aggregation
were within the four-island region of Molokai, Lanai, Maui, and Kahoolawe, andwithin Penguin Bank extending 25-nm southwesterly from Molokai.
No unique nursery area was found, though the greatest numbers of calves werein two areas: Kalohi Channel between Molokai and Lanai, particularly on the
Lanai side, and on Penguin Bank. Since these two areas are also regions of maximum whale density, it is not clear whether the greater number of calves simply
reflects that fact. The number of calves recruited into the population was numerically small, and the recruitment rate, at its most optimistic, appeared to be
somewhat below normal expectations. Given the small population size, this seems
an unusual occurrence and leads to concern for the recovery of the stock. Highpriorities should be given to further investigations of recruitment rate.
Calves were typically found with multiple adults, most usually two (including
the mother). The additional adults seemed to serve a protective function as notedfrom the tightening of calf groups versus the dispersal of all-adult groups on approach of aircraft. Over the entire population, pod size was on the average larger
than that noted by investigators of humpback whale populations in other waters,either in breeding or feeding areas. Accurate determination of pod size seems
heavily dependent on close approach by ship or aircraft, and unless this is done thenumber of animals in a pod may be underestimated. Also, calves are often difficult to detect without close approach. Our data were in most cases based on
close-range observations.
The amount of migration between subregions within the island waters is unclear, though the 76% of the all-adult pods seen swimming on "determined"
courses suggested considerable local migration, but without any obvious pattern.
The remainder of the all-adult pods were milling about within some small area
often in great activity (16%), or else simply stationary or nearly so (8%). Milling
pods appeared to be engaged in courtship and mating activities, though actual
mating was not seen. Pods with calves were more frequently resting (26%) thanSci. Rep. Whales Res. Inst.,

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HERMAN AND ANTINOJA

were all-adult pods, possibly reflecting the lesser stamina of the calf (or mother)
and/or a requirement for nursing.
The most common formation for swimming pods was line astern (file), noted
in 38% of the cases. Diagonal arrays and line abreast (rank) each typified 19%of the swimming pods. The functions of the various formations were not clear.
Most of our data were obtained within the peak period of the migratory cycle,
from the end of February through to the third week of March. Therefore, wehave no information on changes in local aggregations over time. Data collectedby E. Shallenberger (1976), particularly those based on daily observations madeby the crews of hydrofoil craft transiting between the various islands of Hawaii,suggest that the earliest immigrants may arrive in the four-island region. As theseason progresses, the population appears to extend itself easterly and westerly, incomparatively small numbers, from the four-island region.
The routes by which the whales arrive at or leave the islands are unknown, as
is their migratory loci in northern waters. A survey we made in November 1976of the Northwest Hawaiian Islands, the small atolls and islands extending 1,200 nm
northwesterly to Midway and Kure from the main Hawaiian Islands, revealed nowhales. Coast Guard flights over this region by others in November 1975 andMarch 1976 (Shallenberger, 1976) also found no whales. However, in late
December 1976, a report was received of two pods of whales in the eastern portionof the Northwest chain, moving southeasterly. It may be that the Northwest
Hawaiian Islands are used as a migratory route by only a few whales, or only during portions of a season. Further studies of this area are necessary. Currently,
there seems to be no evidence that any humpback whales breed in this chain. Our
discussions with personnel based on the Midway Islands indicate that no humpback whales are ever seen there, nor heard there by underwater listening stations.
Nishiwaki's (1972) statement that humpback whales are frequently seen aroundthe Midway Islands in winter is therefore puzzling.
Based on their early arrivals in the four-island area, it may be that the principal migratory route to the main Hawaiian Islands is due south, south-southeasterly, or south-southwesterly from the higher-latitude feeding grounds along thenorthern rim of the North Pacific. The major return migration may simply be in
the reverse direction, as suggested for example, by the northerly heading of a podof six adult whales we observed in deep water on April 9th 10 nm off the west
coast of Hawaii. Direct observations of these possible migratory routes needs tobe implemented.
Coloration characteristics of the dorsal surfaces of the pectoral fins of the
Hawaiian whales strongly suggest that the population is not that observed in thefeeding areas near southeast Alaska. The coloration also appears to differ fromsome subpopulations observed near Kamchatka in the upper western Pacific,
though this is less certain. The degree to which there may be dispersal of the
Hawaiian population in the feeding grounds should be studied, and its degree ofintermingling with other populations ascertained. If the three North Pacific populations are like the Southern Hemispere humpback whales, little migration beSci. Rep. Whales R.es. Inst.,

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HUMPBACK WHALES OF HA WAil83

tween populations would be expected (Ivashin and Rovnin, 1967; Mackintosh,1947). However, ecological conditions vary widely in the higher latitudes of thetwo hemispheres. In particular, feeding areas are more restricted in the North
Pacific, so generalizations are difficult to make.
It was also noted that color variations within the Hawaiian population anddisplays of coloration could function in individual identification among conspecifics and as signals for movement intention and direction. Additionally the ventraldorsal variations provide cryptic camouflage.
Finally, the potential fragility of the Hawaiian population, given its small
numbers and apparent low recruitment rate, should be stressed. The annual migration of the population into Hawaii has been receiving increasing popular attention, and the number of people observing or wanting to observe the whales seems
to be increasing annually at an exponential rate. The generally good weather in
Hawaii and the nearshore clear-water regions favored by the whales makes theirobservation easy. While this is a scientific boon, and vitally important to the description and understanding of the natural behaviors and dynamics of a breeding
population of mysticete whales, the rare spectacle of the whales is an attraction toall. Increasingly, commercial and pleasure ships and small boats are launched towatch the whales, divers enter the water to observe, photograph, and perhaps
touch the animals, planes and helicopters on tourist runs circle the animals. Allof this unregulated activity constitutes a potential source of major harrassment
to the whales, and some controls on this activity are needed which will, first, protect and conserve the whales and, secondly, allow the expression of their benefit
to humans as an educational and aesthetic experience.
Harmer (1928) long ago warned that whales may abandon their preferredgrounds under harrassment, a warning that has been realized too often in whaling
history. When driven from a given locality, whales rarely return to it, selecting
instead secondary and likely less favorable grounds. Harmer's warning should bewell heeded in the case of the Hawaiian humpback whale.
ACKNOWLEDGMENTS

This research was supported in part by a grant from the Office of the Dean for
Research of the University of Hawaii. Use of the vessel Noi'i was arranged by
the Office of the Dean for Marine Programs, University of Hawaii. Appreciation
is extended to G. Curtis, H. Herman, M. Palmgren, and M. Yunker for their help
in obtaining and processing the data. M. Tillman and P. Forestell provided helpful comments on an earlier version of this paper. This paper is contribution No.
527 from the Hawaii Institute of Marine Biology.
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