232 
PACIFIC SCIENCE, Vol. XIII, July 1959 
TABLE 9 
Food of Two Hawaiian Monk Seals 
FOOD SPECIES 
STOMACH 
CONTENTS 
BDM 490 
VOLUME 
100 CC. 
1 
SPEV 
VOL 
440 
nNG 
UME 
CC. 
Num- 
ber 
items 
Per 
cent 
vol- 
ume 
Num- 
ber 
items 
Per 
cent 
vol- 
ume 
Conger eel 
{Ariosoma botversi) .... 
2 
2 
9 
60 
Moray eel 
{Gymnothorax sp.) 
— 
— 
4 
35 
{Echidna sp.) 
5.? 
3 
— 
— 
Flatfish {Bothus mancus ) . 
— 
— 
2 
1 
{Bothus pantherinus ) .... 
— 
_ 
1 
1 
Scorpenid 
{Scorpaenopsis gibbosa?) 
— 
— 
1 
1 
Larval fish (Surgeon fish?) 
— 
— 
1 
1 
Squid or octopus 
(Cephalopod) 
3 
95 
2 
1 
the vertically held hind flippers obviously fur- 
nished the chief means of propulsion, the 
foreflippers were in almost continuous mo- 
tion. For only a few seconds, one seal was 
observed to hold the foreflippers motionless, 
when it trailed them back and down at an 
angle of about 45° from the body. 
Regular and energetic use of the foreflip- 
pers for swimming appears to be unusual 
among phocids. 
Progression by dorsoventral undulatory 
movements of monk seals on land is in every 
respect similar to other phocids (Fig. 18). 
Vocalization 
Sounds produced by monk seals fall into 
two categories: "bubbling” sounds and "bel- 
lowing” sounds. 
BUBBLING SOUNDS: When a sleeping seal is 
awakened, it usually utters a rapid series of 
soft bubbling sounds which originate deep in 
the throat: "bgg-bgg-bgg-bgg-bgg.” The 
sound is audible under usual circumstances 
to a distance of about 50 feet. It is similar to 
the sound made as water flows from an in- 
verted jug. To some observers, it sounds like 
a rapid series of belches. This sound appears 
to denote mild alarm. If the seal is not an- 
noyed but approached closely, the mouth is 
kept closed while the sound is made. If the 
seal is touched, it opens its mouth in threat 
attitude while continuing to utter this sound. 
Weddell seals apparently make a similar 
sound (Bertram, 1940). 
BELLOWING SOUNDS: When one seal is 
threatening another, when a mother is de- 
fending her pup, or when a seal’s route to the 
water is blocked, several basically similar 
sounds are uttered, perhaps best described as 
a grunting bawl. Sometimes a blast of air is 
expelled simultaneously, forming a snort or 
snorting bellow. A mother defending her 
young from an intruder utters a louder ver- 
sion, best described as a bellow — "mrrraugh.” 
The sound is very similar to that made by 
female northern sea lions {Eumetopias juhata). 
In general, the pup may be said to bleat— 
"mwaa-mwaa-mwaa.” Except for its lesser 
strength and volume, and higher pitch, the 
sound resembles the bellow of the adult. 
When the mother is displaying affection to- 
ward her pup, she utters a hoarse throaty 
growl or moan, a modification of the bellow, 
to which the pup responds by bleating. When 
disturbed, the pup utters a diminutive version 
of the grunting bawl, an explosive "aaah” 
or "gaah.” 
Escape Reactions \ 
The fearless nature of Hawaiian monk seals I 
is similar to that of other marine mammals i 
which have evolved and remained in remote i 
oceanic areas. Terrestrial predators are un- 
known. Human populations have invaded ji 
only in recent times, and permanent settle- | 
ments exist only on two of the six atolls ‘ 
where the seals breed. In some respects, the 
behavior of the monk seals is similar to that 
of the fur seals (Callorhinus and Arctocephalus) il 
and certain antarctic phocids which breed in 
isolated regions. It is quite unlike that of the 
