A releaser is a stimulus from one animal to another, which causes a particular response. The releaser, or sign stimulus triggers an innate releasing mechanism in the receiver. The receiver then does its response, the fixed action pattern (FAP).
This kind of system is inherited by both animals. Example: a fledgling bird does its releaser, say it squawks and opens its beak wide, showing bright red inside throat. This triggers the adult to cough up food stored in its gullet. Both 'partners' are behaving instinctually with inherited behaviours: these are not learnt during life. A FAP can truly be said to be 'hard-wired': a specific stimulus nearly always results in the same behavioral response.
Another behavious system is the 'dances' of water birds such as the Great Crested Grebe. They pair for life, and 'dance' whenever a pair meet up after an absence, and on other occasions. The dances are quite complex, and were first described fully by Julian Huxley. Here the meeting is the releaser, and both partners do the fixed action pattern. The function of the system is a little unclear, but it has something to do with reinforcing the pair's bond.
It is not necessary for both partners to benefit, nor to be of the same species. Some moths instantly fold their wings and drop to the ground if they encounter bat ultrasonic signals. This helps helps the moths, but obviously not the bats. In turn, some bats turn off the sound blips when they hear a moth, and glide in the last few feet. This also is an inherited behaviour. This example may be better described as a reflex action.
Questions and Answers
Q: What is a releaser?
A: A releaser is a stimulus from one animal to another which causes a particular response. It triggers an innate releasing mechanism in the receiver, resulting in the receiver doing its response, known as the fixed action pattern (FAP).
Q: How are these behaviours inherited?
A: These behaviours are inherited and not learnt during life. The FAP can be said to be 'hard-wired' because it results in the same behavioural response when triggered by a specific stimulus.
Q: What is an example of this behaviour?
A: An example of this kind of behaviour is when a fledgling bird squawks and opens its beak wide, showing bright red inside throat which triggers the adult to cough up food stored in its gullet.
Q: What do water birds such as Great Crested Grebes do?
A: Water birds such as Great Crested Grebes perform 'dances' whenever they meet up after an absence or on other occasions. The dances are quite complex and were first described fully by Julian Huxley. The meeting acts as the releaser for both partners who then perform their fixed action pattern.
Q: What is the purpose of this system?
A: It is believed that this system helps reinforce the pair's bond but it does not necessarily benefit both partners nor need them to be of same species.
Q: Can you give another example of an inherited behaviour?
A: Another example of an inherited behaviour is when moths instantly fold their wings and drop to ground if they encounter bat ultrasonic signals; helping them but obviously not benefiting bats who turn off sound blips when they hear moths and glide in last few feet - this may be better described as reflex action.
