[MARMAM] New publication:Sex-specific variation in conspecific-acquired marking prevalence among dusky dolphins (Lagenorhynchus obscurus)

Dara Orbach dnorbach at gmail.com
Thu Apr 30 21:24:42 PDT 2015

Dear colleagues,

My co-authors and I are pleased to announce the publication of a new paper:

Orbach, D.N., Packard, J.M., Piwetz, S.,  and Würsig, B. 2015. Sex-specific
variation in conspecific-acquired marking prevalence among dusky
dolphins (*Lagenorhynchus
obscurus*). *Canadian Journal of Zoology* 93: 383–390. doi:

Despite logistical challenges that limit direct observations of behavior
for some species, physical scars can provide indirect evidence of
aggression. Dusky dolphins (*Lagenorhynchus obscurus *(Gray, 1828)) off
Kaikoura, New Zealand, derive most of the notches and scars on their dorsal
fins from conspecifics. However, aggressive encounters have rarely been
observed in this sexually monomorphic species. If injurious interactions
are associated with intrasexual competition among males but not females, we
predicted males would have more conspecific-acquired markings than females.
High-quality dorsal fin photographs of dolphins of known sex (*n* = 79)
were collected during boat-based surveys off Kaikoura. We measured three
quantitative variables (notch height ratio, notch depth ratio, and dorsal
fin rake direction) and one qualitative variable that scored the overall
prevalence of markings (notches and scars). All four measures yielded
consistent results. Males had significantly more conspecific-acquired
markings than females. We reject the hypothesis that there is no difference
between the sexes in marking prevalence. We propose that brief events of
direct competition are missed by observers but recorded in accumulated
patterns of conspecific-acquired markings that differ between the sexes.

A PDF version of the paper is available online at:

or via e-mail request to: dnorbach at gmail.com

Dara Orbach

Ph.D. candidate
Marine Mammal Behavioral Ecology Group
Department of Marine Biology- IDP
Texas A&M University at Galveston
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