|The Mammals of Texas -
Cetacea : Family
Balaenopteridae : Megaptera novaeangliae (Borowski)
Description. Humpback whales typically
reach lengths of 14.6-15.2 m and weights of 31-41 metric
tons. Females are usually slightly larger than males and
an exceptional individual may be up to 18.9 m in length
and weigh 48 metric tons. For their length, humpbacks
tend to be greater in girth than the other balaenopterid
Coloration is black overall with
irregular white markings on the throat, sides, and
abdomen. In some individuals the belly may be entirely
white, or there may be white patterns dorsally. The
flippers are very long (up to 4.6 m) but are narrow. The
flippers typically are white below but range from black
to patterns of black and white dorsally, or even entirely
white. The tail flukes are broad, serrated on the free
edge, and black above with black and white coloration
ventrally. Distinctive tail flukes may serve to identify
individual humpback whales in many cases.
As with other balaenopterid whales,
humpbacks have a dorsal fin, which may be up to 31 cm in
height, and is falcate to rounded in profile. Although
the humpback does have throat pleats, they are fewer and
spaced wider apart than is typical for balaenopterids.
Humpbacks, therefore, are not usually classed as
rorquals. Other differences of the humpback whale include
lack of a median head ridge, enormous flippers , and the
presence of numerous knobby structures, or "dermal
tubercles," about the dorsal surface of the snout,
chin, and mandible. The number and location of these head
tubercles vary between individuals. Each tubercle
contains a sensory hair.
Humpbacks typically submerge for 6-7
minutes at a time with occasional dives of 15-30 minutes.
The blow may be up to 3 m high and is not a slender plume
but rather bushy. When diving, humpbacks arch the back
steeply, thus the common name. The flukes rarely show in
shallow dives but when a deep dive is accomplished the
flukes may be lifted well above the waters surface.
Distribution in Texas. Humpback
whales occur in all oceans of the world. In the western
North Atlantic these whales are distributed from north of
Iceland, Disko Bay and west of Greenland south to
Venezuela and around the tropical islands of the West
Indies. Population estimates indicate that the worldwide,
prewhaling population of humpbacks was approximately
100,000. The present stock numbers 5,200-5,600 with about
800-1,000 occurring in the western North Atlantic.
Humpback whales are listed as endangered by the U.S. Fish
and Wildlife Service.
In the Gulf of Mexico humpback whales
have been captured in the Florida Keys and northern Cuba.
Sightings have occurred off the west coast of Florida and
Alabama. The only known occurrence along the Texas Coast
is of a young, immature animal observed by Victor
Cockraft and David Weller at the inshore side of Bolivar
Jetty near Galveston on 19 February 1992. No population
estimates are available for Gulf humpbacks.
Humpbacks are highly migratory. In the
western North Atlantic these whales occupy high latitude
feeding grounds from Cape Cod to Iceland during spring,
summer, and fall. In late autumn and winter the whales
then move into Caribbean waters for mating and calving.
Habits. Humpbacks often
congregate in groups of 20-30 to perhaps 100-200. These
are among the most acrobatic and visible of whales and
breach completely out of water in spectacular displays of
strength. Humpbacks commonly slap their tail flukes or
flippers on the waters surface and occasionally
lift their huge heads above water to peer about, a
behavior known as "spyhopping." Tail slapping,
breaching, and other such behaviors may serve in
communication between the whales, possibly as warnings or
a means of indicating location.
Humpbacks also produce a number of
unusual sounds described variously as moans, groans,
cries, squeals, chirps, and clicks. Sounds may be
arranged into complex and predictable patterns known as
"songs." Humpback songs may be repeated for
long periods of time and have been most often recorded on
low latitude breeding grounds. Although yet to be proven,
songs are thought to be broadcast by sexually mature,
lone males and may have some purpose in mating rituals.
Humpback whales eat krill, mackerel,
sand lance, capelin, herring, pollock, smelt, cod,
sardines, salmon, and anchovies. These whales are
lunge-feeders but use several different techniques to
concentrate their food before lunging. An especially
interesting technique is known as "bubble
netting." In bubble netting, one or more humpbacks
exhale while circling below a food source. The resulting
bubble column effectively forms a net to concentrate food
items through which the whales lunge with open mouths.
Females give birth to a single calf in
tropical or subtropical waters in winter. The gestation
period is approximately 11 months. Newborn humpbacks are
4.6 m in length and weigh about 1.3 metric tons. The
period of lactation lasts approximately 5 months. Sexual
maturity is reached at 2-5 years, at which time the young
whales measure about 12 m in length. Physical maturity
occurs at 12-15 years of age. Females breed every other
Illustration credit: Pieter