228 
PACIFIC SCIENCE, VoL XIII, July 1959 
TRAILS: The shade of Scaevola shrubs is 
attractive to seals (see Fig. 4). In order to 
reach the thickets, the seals must often crawl 
up the sloping sand beach, then up an em- 
bankment of solidly packed coral rubble a 
foot or two high. Certain favorite routes are 
habitually used and grooves, or trails, are 
worn in the sand and hard steep banks. These 
are visible from the air and during aerial 
counting help to locate seals lying partially 
hidden beyond the beach line (Fig. 5). On 
Rocky Island, the only small islet in Midway 
Atoll with vegetation, a number of seals use 
the same trails and resting places. Whether 
certain trails and resting places along less 
frequented beaches are used by certain indi- 
viduals or by a number of seals was not 
ascertained. 
WALLOWS: While resting on coral sand 
beaches, monk seals roll and root to form 
depressions about 6 inches deep. When dig- 
ging such a depression, the nostrils are closed 
and the muzzle is pushed into the sand as the 
seal forces itself forward with its foreflippers 
(Fig. 6). In this way, the head becomes par- 
Fig. 4. Large adult female. Monk seals often retreat 
to the shade of Scaevola shrubs above the beach line. 
Kure Atoll, June 5, 1957 (KWK 57-16-34). 
dally buried and a ridge of sand is pushed up, 
rising to eye level or above. During such 
rooting and rolling, the eyes often become 
caked with sand and mucus. The eyes of one 
seal, seen sleeping, were so caked with sand 
that the lids could be only partially closed. 
This animal and others, seen sleeping with 
lesser amounts of sand sticking to the cornea, 
appear oblivious of any discomfort. When 
seen from the air, sand wallows are quite evi- 
dent on beaches frequented by monk seals. 
Daily Cycle of Activity 
Very few seals may be seen on land early 
in the morning. Generally, as the day ad- 
vances, an increasing number of seals haul 
out. About noon, or throughout the after- 
noon, the number on land reaches a maxi- 
mum. Just before sunset, there is a drop in 
number on land. This is partially illustrated by 
the number of seals observed on the regular 
boat runs between Sand and Eastern islands. 
Table 8 presents the average number observed 
during 57 trips. We were unable to make com- 
parable counts at sunset or shortly thereafter 
when seals were leaving the hauling grounds. 
For this and other reasons (see food habits), 
it may be presumed that monk seals are noc- 
turnal, or at least crepuscular, feeders. Never- 
theless, swimming and feeding seals may be 
seen in the water all during the day. 
Seasonal Movements 
At Midway we have noticed a marked sea- 
sonal variation in the number of seals hauled 
out on the islets and sandspits between Sand 
and Eastern islands. In November and early 
December few seals hauled out. In late De- 
cember, coincident with the beginning of the 
winter storm period, they increased markedly. 
About March, when calm summer weather 
began to prevail, the number dropped and by 
June very few were seen. Figure 7 shows the 
seasonal variation in six aerial counts, in six 
ground counts made when we landed on all 
of the islets and sandspits, and in the highest 
