[MARMAM] New paper on sex segregation in bottlenose dolphins

Ali Galezo aligalezo at gmail.com
Thu Jan 4 11:55:36 PST 2018

We are pleased to announce the publication of our new article in Behavioral

*Sexual segregation in Indo-Pacific bottlenose dolphins is driven by female
avoidance of males*

Allison A. Galezo, Ewa Krzyszczyk, and Janet Mann

Sexual segregation is widespread in mammals, although the proximate causes
are poorly understood in monomorphic species. Indo-Pacific bottlenose
dolphins (*Tursiops aduncus*), which exhibit a high degree of
fission–fusion dynamics, offer a useful lens to examine the ecological and
social drivers of sexual segregation. While ecological hypotheses suggest
that sexual segregation is a by-product of sex-specific ecological
preferences (e.g., related to habitat, foraging, or predator avoidance),
the social hypothesis proffers that segregation results from same-sex
preferences (e.g., due to cooperative benefits) and/or opposite-sex
avoidance (e.g., due to competitive or exploitative interactions).
Indo-Pacific bottlenose dolphin females range from nearly solitary to
highly sociable. Males associate in alliances that cooperate to sequester
individual females and exclude competing males. Given evidence for allied
sexual coercion, our primary hypothesis was that sexual segregation is
driven by female avoidance of aggressive males. However, given robust
evidence for sex-biased foraging tactics, ecological factors likely also
contribute. Using the Sexual Segregation and Aggregation Statistic with
17,468 sighting records spanning 31 years, we found strong sexual
segregation. Unique to our work, we analyzed the direction of joins and
leaves between males and females from focal observations (N = 10,715
fission–fusion events, 87 females, 111 males) to determine which sex drives
sexual segregation. Females drove segregation by rarely joining and often
leaving males. Although ecological factors likely reinforce sexual
segregation, social factors predominate. This study demonstrates a sex-bias
in fission–fusion dynamics in a socially complex wild mammal population and
offers strong empirical support to the social hypothesis of sexual

The full article is available online at: https://doi.org/10.1093/

Feel free to email me at aag65 at georgetown.edu for a PDF of the article.


Allison Galezo
Research Associate
Georgetown University
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