12. PREDATORS AND PARASITES
353
whales. The populations of whales in the North Atlantic were exploited
to such an extent in the eighteenth and nineteenth centuries that they
became over fished and scarce so that about the only major work on
whale biology in this region is that of Hjort and Ruud (1929). No
recent work is available because of the continuing scarcity of whales.
The Antarctic populations have now been reduced to such an extent
that they also are becoming uneconomic to catch, but much information
on their biology has been obtained.
There are about ten species of baleen whales (Table XXXVII) but
several races of a species may exist. Mackintosh (1965) has given a
recent authoritative account of the biology and distribution of whales
and reference to this book should be made for further information. He
provides a brief description, derived principally from the descriptions
of Ingebrigtsen (1929), Tomilin (1954) and Nemoto (1959)) of the
methods of feeding used by the various whales. Apparently, most
whales eat by swallowing food in mouthfuls but the right whales and
sometimes the sei whales, which have baleen plates of finer texture than
others, feed by “ skimming ”. These whales often feed on copepods,
which are much smaller than euphausiids, and swim along with the
mouth open, the water flowing presumably more continuously through
the baleen plates so that more efficient gathering of a dispersed food is
effected than would be by taking a mouthful of water, expressing it
through the plates and swallowing the strained organisms. As
Mackintosh points out, the details of the feeding methods of the whales
are mostly conjectural because of the difficulty of making direct
observations on the living animals.
The type of food eaten by the whales is indicated in Table XXXVII.
The items on each list are presented in order of importance to the whale
concerned. Nothing appears to be known about the food of the pigmy
right and very little about that of the Greenland right whales. The black
right whale feeds probably more frequently on copepods than on
euphausiids. The Pacific grey whale is reported to feed on bottomliving organisms and Mizue (1951a) records Nephrops thomsoni, a
bottom-living decapod crustacean, as present in the stomach contents
along with “smaller Crustacea” in whales caught in the northern
Yellow Sea. The blue whale seems to feed almost exclusively on
euphausiids as does the humpback except that the latter is known to
feed on fish in certain sea areas. The fin and sei whales have much more
variable diets, euphausiids usually being more important to fin whales,
copepods to sei whales. Bryde’s whale feeds predominantly on fish,
secondarily on euphausiids while the minke whale shows a preference
for euphausiids but also eats fish in large quantities.
353
whales. The populations of whales in the North Atlantic were exploited
to such an extent in the eighteenth and nineteenth centuries that they
became over fished and scarce so that about the only major work on
whale biology in this region is that of Hjort and Ruud (1929). No
recent work is available because of the continuing scarcity of whales.
The Antarctic populations have now been reduced to such an extent
that they also are becoming uneconomic to catch, but much information
on their biology has been obtained.
There are about ten species of baleen whales (Table XXXVII) but
several races of a species may exist. Mackintosh (1965) has given a
recent authoritative account of the biology and distribution of whales
and reference to this book should be made for further information. He
provides a brief description, derived principally from the descriptions
of Ingebrigtsen (1929), Tomilin (1954) and Nemoto (1959)) of the
methods of feeding used by the various whales. Apparently, most
whales eat by swallowing food in mouthfuls but the right whales and
sometimes the sei whales, which have baleen plates of finer texture than
others, feed by “ skimming ”. These whales often feed on copepods,
which are much smaller than euphausiids, and swim along with the
mouth open, the water flowing presumably more continuously through
the baleen plates so that more efficient gathering of a dispersed food is
effected than would be by taking a mouthful of water, expressing it
through the plates and swallowing the strained organisms. As
Mackintosh points out, the details of the feeding methods of the whales
are mostly conjectural because of the difficulty of making direct
observations on the living animals.
The type of food eaten by the whales is indicated in Table XXXVII.
The items on each list are presented in order of importance to the whale
concerned. Nothing appears to be known about the food of the pigmy
right and very little about that of the Greenland right whales. The black
right whale feeds probably more frequently on copepods than on
euphausiids. The Pacific grey whale is reported to feed on bottomliving organisms and Mizue (1951a) records Nephrops thomsoni, a
bottom-living decapod crustacean, as present in the stomach contents
along with “smaller Crustacea” in whales caught in the northern
Yellow Sea. The blue whale seems to feed almost exclusively on
euphausiids as does the humpback except that the latter is known to
feed on fish in certain sea areas. The fin and sei whales have much more
variable diets, euphausiids usually being more important to fin whales,
copepods to sei whales. Bryde’s whale feeds predominantly on fish,
secondarily on euphausiids while the minke whale shows a preference
for euphausiids but also eats fish in large quantities.