Revista Chilena de Historia Natural 78 (4): 687-700, 2005
RESEARCH ARTICLE
Breeding patterns in southern sea lions, Otaria flavescens
(Shaw 1800), in south-central Chile
The latitudinal effect of reproductive patterns for Otaria flavescens
suggests the existence of behavioral and physiological adaptation to local environmental conditions. The identification of
intraspecific behavioral pattern changes due to these environmental conditions suggest a relation among them. We pretend here to
determine reproductive synchronization and reproductive stability of O. flavescens in the Punta Lobería colony during two
breeding seasons 1996-1997 and 1997-1998. Direct observations of groups and breeding behavior were watched with binoculars
backed by video and photography. Results evidenced modification in (a) the number of harems (decreased from 28 to 19 during first to
the second seasons), (b) the spatial distribution of harems (70 % of these were located in northern part of the reproductive beach
during the 1997-1998 season whereas they occupied the whole beach rather uniformly during the previous season), (c) age structure
(one male: 12 females: one juvenile and seven pups decreased to one male: nine females: two juveniles and six pups), (d) the
polygyny index (decreased from 12.4 to 7.8 HPMT and from 11 to 9 HP), and (e) the reproductive population organized in harems
(decreased of up to 10.3 %). These variations would be related to optimum space reduction for harem establishment after an
earth/rock slide over the area. Behavioral reproductive patterns remaining stable during both seasons were (a) seasonality of harems
(harem formation during the fourth week in December, dissolution during the fourth week of February), (b) birth period (beginning during
the second week of January and ending during the fourth week of January), and (c) mating period (beginning during the third week of
January, ending during the second week in February). Otaria flavescens exhibited modifiable and stable behavioral
patterns according to environmental conditions. Modified breeding behavior potentially would mitigate loss of reproductive output, and
stable breeding behavior would be related to physiological and behavioral processes according to environmental conditions. Thus,
reproductive patterns when compared to other known reproductive localities in Chile are consistent with a latitudinal effect due to
variations registered by their seasonality, as well as its duration (e.g., mating and birth periods).
Key words:
Otaria
flavescens, reproductive patterns, reproductive synchronization, polygyny index
