Media Releases

Shark scientists at Dalhousie University, the Georgia Aquarium and the Scripps Institution of Oceanography at UC San Diego are challenging the status quo in shark and ray mating research with a new study that suggests females may be the ones who decide who fathers their offspring.

Many species of sharks and rays exhibit multiple paternity, where females give birth to a litter of pups that have different fathers. While widely documented in scientific literature, the reasons behind this phenomenon are not well understood.

Previous research has cited male aggression as the reason, claiming that the females are unable to avoid their advances during mating. This has led to an acceptance of the “convenience polyandry” theory -- the assumption that there is a greater cost for females when refusing male mating attempts.

The authors of a new study published today in the journal Molecular Ecology, argue that that diminish the role of females who invest significant energy into mating and may be physiologically capable of choosing which sperm they allow to fertilize their eggs.

Christopher Mull, a postdoctoral fellow at Dalhousie University, co-authored the study, which is the first to evaluate the phenomenon from the female point-of-view and notes that female mechanisms are often cryptic and challenging to identify. In addition, the study suggests previous literature may have an unconscious bias since much of it has been led by male authors.

The researchers developed models based on shark and ray biology and physiology to test whether multiple paternity could be in the best interest of females or males, or a combination of both. They found no conclusive evidence that multiple paternity is primarily a male-driven advantage. In most instances, the benefits for females and males were the same.

Dr. Mull is available to discuss the findings and how they may reshape our understanding of shark and ray mating rituals.

To view high-resolution photos, please visit this site. Credits provided with each photo.

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Media contact:
Alison Auld
Senior Research Reporter
Dalhousie University
Cell: 1-902-220-0491
Email: alison.auld@dal.ca