Pheromone Field Experiments

This aspect of the human pheromone problem was investigated. The water in an aquarium, where a pike (Esox lucius L.) lived, was tested for the presence of alarm substance before and after the pike had eaten a minnow (Phaxinus). These human pheromones studies showed clearly that the capture of a minnow by a pike created damage sufficient to initiate a fright reaction. Recently Verheijen and Reuter (1969) confirmed that enough alarm substance was given off when a pike swallowed a minnow. The odor of the pike, by itself, did not provoke a fright reaction in schools of minnows that had not had previous experiences with the predaceous activities of pike. However, G62 (1941) showed that minnows quickly learn the odor of pike and that pike odor alone will produce a marked reaction in fish which have experience with pheromone odor in combination with the alarm substance. Goz used blinded minnows which showed no initial response to pheromone odor. Learn more at and

After some of the blinded members had been attacked by a pike, the remainder showed alarm pheromone reactions to pike odor in absence of alarm substance. Recently Reed (1969) reports human pheromone odor capable of eliciting an alarm response in local prey species in the American pike and various Percifor- mes. Von Frisch(l941b) has shown that a school of minnows reacts more intensely to the alarm substance if the water also contains the odor of the pike. Immature individuals of the predaceous northern squawfish, Ptychocheilus oregonense (Richardson), showed a marked fright reaction after eating a smaller conspecific, and it was proven that alarm substance was released (passively, of course!) (Pfeiffer 1962d). lt is evident, however, that a pike with its sharp teeth injures its prey more than a toothless cyprinid does. Pheromone Field Experiments In field experiments, Von Frisch (l94lb) noted repeatedly that minnows which became alarmed in the region of the feeding tube would subsequently feed much less readily there than in nearby areas. The pheromone fright reaction changes the behavior of the fish fundamentally; they not only swim away, but their vigilance and readiness to flee are increased and they are particularly wary of the area where they were frightened. Twice Von Frisch observed the fright reaction under natural conditions: once when a perch captured a member of a school of minnows, and again when a bittern caught and dropped a member of a school of bleaks. Another aspect of the value of the reaction is seen in ontogenetic relationships. Very young minnows possess the alarm substance in their skins but fail to respond until they are about 4~6 weeks old. An older fish, after eating or injuring a very small individual, will be alarmed, swim away and avoid the schools of small fish. Consequently, the small juveniles may be protected from the cannibalistic attacks of the adults (Schutz 1956). Verheijen (1962), admitting that it is difficult to provide direct evidence pro or contra this supposed function of the alarm substance, was cautious about accepting the theory that alarm substance prevents intra-specific predation of pheromones. Learn more at