Pheromones

The Down Low on Pheromones       

     Pheromones are molecules used for communication and interaction between animals, specifically, animals within the same species. More specifically, University of California Riverside entomologist defines pheromones as, “a chemical or a mixture of chemicals that is released to the exterior by an organism of the same species. Thus, if two or more chemicals are released together and cause a specific reaction, the chemical mixture must be regarded as a pheromone” (Shorey, 1976). 


     The term pheromone is originally derived from the Greek word, pherein, to carry or transfer, and, hormon, to excite or stimulate (Whatt, 2003). Since most animals cannot communicate through language as humans do, pheromones are widely used within the animal world and serve as a means of transmitting information from one member of the species to another (Shorey, 1976).

    
     Although the need is less obvious than for groups of animals, the need for pheromones is extremely important for solitary animals. These animals appear to live alone for the majority of the time except for crucial moments in their lives when they may use pheromones to find animals of the same species to mate with or to keep them from coming together with one another at inappropriate times (Shorey, 1976).  The way pheromones are released and transmitted can be broken into two main categories: releaser pheromones and primer pheromones, both of which are equally important to any animal. 


     Releaser pheromones elicit immediate responses by being mediated by the nervous system. The response to releaser pheromones cannot be seen, but may affect the reactivity of an animal to things such as danger or sound. On the other hand, primer pheromones go through the central nervous system after detection and cause direct and visible responses. One example of primer pheromones is the changing of hormonal levels of male and female animals causing them to mate (Shorey, 1976).

      

    A tiger is an example of a solitary animal. These animals come 

together to mate but part ways soon after. 

   
     Within these categories, pheromones are divided by function as well. Each set of pheromones triggers a function which in tern leads to a type of behavior. The way it works is pheromones from one animal cause another to show signs of behavior reactions about the animal releasing the pheromone. The different types of pheromones that cause these behaviors has been broken into three categories: recognition pheromones, identification pheromones, and appraisal pheromones. (Note that the naming of these categories often varies, but the behaviors they elicit are the same) (Wyatt, 2003).


     Recognition pheromones cause the receiving animal to perceive a pheromone as something that is previously known. For example, these pheromones can recognize the animal’s own home or other animals of the same species. Next, identification pheromones are used to recognize individuals and of prior recognition of these animals such as a mate or parent. For example, the tiger above uses his recognition pheromones to find other tigers, but once he find them he then uses his identification pheromones to determine which is his mother. The mixes of chemicals that produce these identification pheromones are unique in order for one animal to identify a specific other, thus the tiger can figure out which tiger is his mother (Shorey, 1976). Each species has different types of pheromones specific to that species that differentiates them from other species (all tigers) while each individual member of that species has exclusive pheromones that makes him or her recognizable to others within their species (the tiger above). The final category of pheromones is appraisal pheromones. Appraisal pheromones are used for animals within the same species as a stimulus for a specific action. Appraisal pheromones can lead to animals mating, dispersion, aggression, etc. (Shorey, 1976). The tiger above uses his appraisal pheromones to find a mate. 

Click the link below to see how animals use pheromones to find a mate:
Pheromones in Mating: What Women Want
http://www.evtv1.com/player.aspx?itemnum=12868#

By Cassie Kobrin 

Works Cited

Shorey, H. (1976). Animal communication by pheromones. Academic Press.

Wyatt, T. (2003). Pheromones and animal behavior: communication by smell and taste. Cambridge University Press.


Video retrieved from: EVTV1.com