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First quantitative evidence of territorial behavior in squid near spawning substrates
Shun Tokioka1, Jun Yamamoto2, John R Bower3
1Shiogama Field Station, Fisheries Resources Institute, Japan Fisheries Research and Education Agency, 3-27-5 Shinhama, Shiogama, 985- 0001, Miyagi, Japan. stokioka@aori.u-tokyo.ac.jp.
Scientific Reports
|August 8, 2025
Summary
Large male spear squid (Heterololigo bleekeri) establish territories near spawning sites. This territorial behavior, observed quantitatively for the first time in squid, may relate to complex fertilization patterns.
Area of Science:
- Marine Biology
- Cephalopod Behavior
- Reproductive Strategies
Background:
- Solitary large males are observed near spawning grounds in some loliginid squids.
- Reproductive behaviors of these males are not well understood.
- Spear squid (Heterololigo bleekeri) are a species within the loliginid family.
Purpose of the Study:
- To describe the reproductive behavior of spear squid (Heterololigo bleekeri) in a controlled environment.
- To investigate territoriality in male spear squid near spawning substrates.
- To analyze the relationship between territorial behavior and mating opportunities.
Main Methods:
- Observations of spear squid behavior in a 300 m³ tank.
- Recording proximity to spawning substrates.
- Quantifying agonistic and mating behaviors of individual males.
Main Results:
- Individual males consistently remained near spawning substrates in both experiments.
- Territorial males exhibited more frequent agonistic behavior than non-territorial males.
- Territorial males did not monopolize females or mating opportunities.
Conclusions:
- This study provides the first quantitative data on territorial behavior in squid.
- Territorial tactics in spear squid may be linked to their complex fertilization patterns.
- Further research is needed to fully understand the evolutionary advantages of this behavior.
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