Niko Tinbergen

Niko Tinbergen appears as an experimental ethologist whose stickleback demonstration makes territorial behavior visible as a conditional strategy rather than an inexplicable instinct. By moving two fish between territories, Tinbergen changed which one attacked and which retreated, showing how the resident–intruder relationship could organize their behavior.

The Stickleback Experiment

Tinbergen placed two male sticklebacks in a fish tank. Each had built a nest at an opposite end and defended the territory around it. He then put each fish in a large glass test tube, held the tubes beside one another, and watched the males attempt to fight through the glass.

The decisive manipulation was a change of location. Near male A’s nest, A assumed an attacking posture while B tried to retreat. When Tinbergen moved the tubes into B’s territory, the pattern reversed: B attacked and A retreated. The fish responded not simply to one another, but to which male occupied the ground where the encounter took place.

Territoriality as a Conditional Strategy

The experiment revealed a straightforward rule: attack when resident, retreat when intruder. Because Tinbergen could reverse the roles merely by moving the test tubes from one end of the tank to the other, the behavior offered a neat demonstration of asymmetry based on prior occupation of a place.

The book connects this result to the evolutionary stability of territorial defense. Residents may have practical advantages, including better knowledge of local terrain, while intruders may be tired from entering the area. More generally, a strategy in which residents win and intruders retreat encourages individuals to remain in a particular place and defend it. A reverse arrangement would prompt individuals to avoid being residents by continually moving, tending to make the category of resident disappear.

Significance in the Argument

Tinbergen’s experiment supports the possibility that territorial defense can emerge as an evolutionarily stable strategy from the asymmetry of arrival, without requiring a separate explanation of the behavior’s biological advantages. In the book’s account, the value of the demonstration lies in how simply a change in location exposes the rule shaping the fish’s apparent aggression: who attacks is determined by who is resident.