Contingency Plan for Hawaiian Monk Seal Unusual Mortality Events

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30N
Kure Atoll
Midway Atoll
Pearl and Hermes Reef
Lisianski I.
Laysan I.
25N
French Frigate Shoals
Necker I.
Nihoa I.
20N
Northwestern Hawaiian Islands
Main Hawaiian Islands
Johnston Atoll
15N
180° 175W 170W 165W 160W 155W
Fig. 1. The Hawaiian Archipelago, with the six main monk seal breeding and pupping
sites identified (French Frigate Shoals, Laysan I., Lisianski I., Pearl and Hermes Reef,
Midway Atoll, Kure Atoll).
Females give birth on beaches with adjoining shallow waters, which provide
protection from sharks. Most pups are born between February and August, with a peak
from late March to May (Johnson and Johnson, 1980; Johanos et al., 1994). Females give
birth for the first time at ages 5 to 10, and typically 50%-70% of all adult-size females
give birth each year (Johanos et al., 1994). Gestation is approximately 1 year, with a
mean interval between births (for those females that pup in consecutive years) of 381
days (Johanos et al., 1994). Females fast during the 5 or 6-week nursing period, and
nursing pups are sometimes exchanged between females (Kenyon and Rice, 1959; Alcorn
and Henderson, 1984; Boness, 1990; Gerrodette et al., 1992). Mating occurs 3 or 4 weeks
after pups are weaned. Although mating takes place in the water and is rarely observed, a
mating peak in May and June is inferred from the occurrence of fresh mounting injuries
and association patterns of males and females (Johanos et al., 1994). Unlike other
gregarious pinnipeds, monk seals are typically solitary and do not form large, seasonal
breeding aggregations. They have a serially monogamous social system with males
forming a dominance hierarchy.
Pups are born with a black coat, which is shed gradually at the end of the nursing
period and replaced by pelage that is silver gray on the dorsum and sides and beige on the
venter. Juveniles and adults undergo a “catastrophic” annual molt, in which the epidermis