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As a Professor of Psychology and Biology at Georgetown University, I teach courses in animal behavior, primatology,
development, and evolution. I received my Sc.B from Brown University and my Ph.D from The University of Michigan.
My dolphin research is primarily funded by the National Science Foundation, the National Geographic Society,
The Brach Foundation, The Eppley Foundation, and Georgetown University. In addition to my own research (below),
I manage the long-term project data at Georgetown with the help of a full-time research associate, Ewa Krzyszczyk
and database development from Dr. Lisa Singh in Computer Science. Our goal is to build an integrated relational
database for processing and analyzing information on the dolphins, including demographic, reproductive, genetic,
ecological, behavioral and acoustic data. Ewa Krzyszczyk will be joining my lab as a graduate student in August 2008,
along with three other students: Maggie Stanton, Eric Patterson and Jean Tsai. Approximately 4-6 undergraduates are
also involved in our lab in any given year.
My Shark Bay research is a longitudinal study, the Dolphin Mother-Infant Behavioral Ecology Project, initiated in 1988.
Since then, we have studied over 115 calves born to 81 mothers and are examining a number of questions concerning calf
development, female reproduction, ecology and behavior. I am generally interested in why bottlenose dolphins have such
slow life histories, why females invest substantially in each calf, and what factors predict female reproductive success.
These questions have both theoretical and applied (conservation and management) value. Some of this work is summarized
below.
Much of my work is collaborative, with graduate students taking the lead on a number of topics. Jana Watson-Capps
(PhD 2005) and I published a paper on the causes of calf mortality, testing whether predation risk or calf condition
are the primary causes. We don't tag or capture dolphins in Shark Bay, so we assess condition indirectly. Since most
calves that disappear show poor signs of health prior to their disappearance, and calves are not more likely to die
during the warm months, when sharks are present than when they are absent (June-August), calf condition seems to be
the primary cause of calf mortality. An interesting result from this study is that calves who were either in poor
condition or more likely to disappear before weaning (under age 3) sought additional contact with their mothers.
In contrast, the adventurous calves that separated from their mothers, socialized and foraged more often tended to
be the survivors (Mann & Watson-Capps 2005). We have published a number of papers on factors affecting female behavior
and calving success (e.g., Mann et al. 2000; Mann & Kemps 2003; Watson-Capps & Mann 2006) and are currently examining
how foraging type and habitat is related to calving success.
Weaning age in Shark Bay bottlenose dolphins is extremely variable, ranging from 2.7-8+ years of age
(Mann et al. 2000). These are some of the latest weaning ages reported for any mammal.
Currently, I am investigating why some females wean calves late (after the average time period of 4 years)
and others wean early. An analysis of 60 calves and their mothers suggests that the calf's sex plays a role.
Preliminary data also suggest that some females tend to wean early consistently and others late, suggesting
that maternal style and/or condition play a role. Approximately 35 mothers have been observed with more than
one surviving calf.
One of the great pleasures in behavioral research is observing individual differences in and how calves change
as they grow up. Quincy Gibson (PhD 2007) and I have two papers coming out this year (Gibson & Mann in press a,b)
pertaining to individual differences in calves and how-when sex-specific strategies emerge. Calves form distinct
social patterns while still dependent on their mothers. This is evident during temporary mother-calf separations,
where the calf typically joins others or forages alone. When mother and calf are together, they associate primarily
with females and male calves, but avoid juvenile and adult males. During separations, calves of both sexes
preferentially associated with immatures over adults, but male calves also preferred juvenile and adult males.
The sociability of the mother also influenced calves; daughters mirrored their mothers during separations,
whereas sons did the opposite, seeking more social contact if their mothers were solitary and less social contact
if their mothers were sociable. These sex-specific patterns foreshadow strategies that are likely to be successful
for males (alliance formation) and females (adoption of maternal social patterns) in the future.
Few behaviors are more thrilling to watch than calf play. Dolphins are known for their playfulness,
yet we understand little about the meaning and function of play. Most theories of play suggest that it strengthens
behavior patterns and social skills that young animals will need later in life, but it may also help foment bonds
that are important when they are young. I recently examined patterns of sociosexual behavior during development
published in Homosexuality in Animals (Mann 2006). Sociosexual play usually involves mounting, goosing
(beak to genital contact) and other types of close physical contact. Male calves engage in sociosexual play at much
higher rates than female calves, similar to patterns found in other mammals. However, unlike other mammals,
sociosexual play often involves multiple partners simultaneously and synchronous behavior, such as two young males
simultaneously attempting to mount a male or female. Males often exchange roles (actor and recipient) with each other.
Overall, the patterns of sociosexual behavior suggest that males and females are practicing for adult courtship behavior
and that males begin to develop close bonds during this period. This might be expected given the importance of male
alliances in adulthood.
Social experience is obviously important, but before a calf can be weaned, s/he must learn to hunt for themselves.
This is no easy task. Calves begin foraging in the first year, but must sometimes develop highly specialized skills
for finding, capturing and processing prey. In collaboration with Brooke Sargeant (PhD 2005), we have been investigating
the development of calf foraging tactics and whether these are primarily socially learned from the mother or other
individuals. More than 13 foraging types have been identified and each adult female has a distinct foraging profile.
For example, we are looking at the development of tool-use (sponge-carrying, described in the foraging section) in a
subset of our population. We have observed approximately 14 sponge-carriers and their offspring. Most of the calves
appear to adopt the sponge-carrying technique, although the behavior shows a distinct female bias (Mann & Sargeant 2003).
Vertical social transmission is strongly implicated in the development of most foraging tactics. If social influence is
a factor, some foraging behaviors might be considered traditions or cultures. This naturally depends on one's definition
of tradition or culture. Analysis of mitochondrial DNA haplotypes suggest that this tradition is spread exclusively
through matrilines (Krutzen et al. 2005). We have also found that social factors and habitat are important predictors
of many, but not all foraging behaviors (Sargeant et al. 2005; Sargeant et al. 2007; Sargeant & Mann 2007;
Mann et al. 2007). We are currently extending this work and examining the mechanisms of transmission and long-term
impacts of foraging behavior on survival and reproduction.
For more information see Dr Mann's publications.
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