2012 COURSE DATES: AUGUST 4 – 17, 2012 - Sirenian International

Captive Female Manatee Social Behavior 141
dispersion (CD) at the three facilities with at least three manatees was always greater
than one, indicating clumping of the distribution (HSWSP ¼ 3.9, SeaWorld ¼ 6.2,
Lowry Park Zoo ¼ 1.9). The distribution of contacts was significantly different from
a Poisson distribution for HSWSP (Gadj ¼ 9.24w 2 0.05[1] ¼ 3.84) and for SeaWorld
(Gadj ¼ 13.74w 2 0.05[1] ¼ 3.84). We could not perform the analysis for Lowry Park
Zoo because of the low number of manatees, resulting in single frequencies per cell.
DISCUSSION
Manatees in captivity associated and interacted with certain individuals. The
occurrence of regular, non-aggressive contacts by manatees in captivity and the
relative rarity of aggressive contacts support the contention that manatees may be
more social than previously considered [Koelsch, 1997]. Hence, we reject our first
hypothesis that manatees will rarely interact. The number of non-aggressive contacts
increased with density (Fig. 1), supporting our second hypothesis. Aggression was
rare and only occurred at the facilities with the greatest densities (Lowry Park Zoo
and SeaWorld) but these facilities had one or two juvenile males in with the females.
Of the ten total aggressive encounters observed, nine were recorded at Lowry Park
Zoo. These aggressive contacts were directed mainly toward the 9-month-old male
Lowry by the adult females, possibly to prevent the formation of a mother–calf
bond. Lowry was born in captivity but his mother Ionia died from her injuries
during rehabilitation when Lowry was introduced to the two resident adult females,
BB and Cinco. Because aggression was rare and not related to feeding, we reject our
third hypothesis and show support for our fourth hypothesis that most interactions
will be non-aggressive and occur outside of feeding periods. A concurrent study
showed that time in captivity or differences in facilities did not affect manatee
activity patterns [Young, 2001].
The density-dependent nature of non-aggressive interactions suggests that
contacts were random and not selective. Interactions were not equally distributed,
however, among manatees at least at the two facilities with more than three
manatees. At HSWSP, greater association was apparent within two social
subgroups. One subgroup consisted of Amanda and her two adult daughters, Ariel
and Betsy. This observation in captivity fits nicely with field studies, where mother
and offspring form the most apparent long-term bonds during calf dependency in the
wild [Hartman, 1979; Bengtson, 1981; Reynolds, 1981]. All three animals were adults
(Betsy is the youngest, born in captivity in 1990). This long-term close association
may be common in the wild or an artifact of captivity. These three individuals
contacted the other subgroup composed of six unrelated manatees only once. In
contrast, this subgroup exhibited 12 contacts within the group and no contacts to
Amanda, Ariel, or Betsy. Random interactions would predict more contacts between
the two subgroups and the analysis supported a clumped distribution of contacts.
This segregation of manatees is especially interesting at HSWSP, which represented
the site with the lowest density of manatees.
At Sea World of Florida, Charlotte and Sara associated regularly with Rita on
the periphery of this pair. The two young males (Brooks and Pistachio) initiated a
majority of the contacts, mostly as play mounting contacts with the females. Between
the females, the overall distribution of contacts was clumped, not random. At Lowry
Park Zoo, the two adult females, BB and Cinco initiated non-aggressive contacts to