Novel pre-copulatory behavior in basking sharks observed by drone

Area of Science:

• Marine Biology
• Animal Behavior
• Elasmobranch Research

Background:

• Basking sharks (Cetorhinus maximus) are large filter-feeding sharks that seasonally aggregate in coastal areas.
• While basking sharks are frequently observed, their reproductive behaviors, particularly copulation, remain undocumented.
• Previous observations have suggested potential courtship displays, but concrete evidence is lacking.

Purpose of the Study:

• To document and analyze novel behavioral interactions of basking sharks in their natural habitat.
• To investigate behaviors potentially related to mating in Cetorhinus maximus.
• To provide new insights into the reproductive ethology of basking sharks.

Main Methods:

• Utilized high-definition video footage captured by an unmanned aerial vehicle (UAV) deployed in Cape Cod Bay, Massachusetts.
• Recorded and analyzed specific behavioral sequences between basking sharks during May 2021.
• Compared observed behaviors with known pre-copulatory and courtship patterns in other shark species.

Main Results:

• Observed previously undocumented close-following behaviors between basking sharks.
• Documented tight, concentric circling patterns among interacting individuals.
• These behaviors align with established pre-copulatory sequences observed in related shark species.

Conclusions:

• The observed behaviors provide the first visual evidence consistent with pre-copulatory activities in basking sharks.
• These findings enhance our understanding of Cetorhinus maximus reproductive strategies.
• Further research using advanced observational techniques is warranted to confirm copulation and detail reproductive behaviors.