A Question of Whether Taste Aversion can be Learned

While vampire bats may have lost the systems associated with conditioned taste aversion on an evolutionary time-scale due to a lack of adaptive value in parasitic animals for taste aversion, there is the corallary question of whether vampire bats may not have conditioned taste aversion due to an inability to actually learn taste aversion in their immediate life-times.

As mentioned previously, Ratcliffe tested to see if vampire bats could in fact learn taste aversion by offering the bats both unflavored blood and blood flavored with citric acid.  Though vampire bats could discriminate between both types of blood in control groups as seen in a relative decrease of consumption of blood with citric acid as compared to unadulterated blood, they still ingested appreciable amounts of both unadulterated and adulterated blood in experimental groups over a period of time, even after injections of lithium chloride.  In comparison to the fructivirous bats tested, which showed profound aversions to food tainted with citric acid, vampire bats were unable to learn similar associations with a nonpreferred food sample over a short time period.  This suggests that different species of bats may or may not be able to retain the ability to learn taste aversions depending on the selective pressures allowing for the immediate learning of a pervasive behavioral trait such as taste aversion.  In short, it must be a cost-effective trait to maintain.  

         fruitbat @ http://www.abdn.ac.uk/~nhi708/classify/animalia/chordata/mammalia/chiroptera/chiroptera.html

        A fruitivirous bat is able to learn taste aversions to undesirable foods in comparison to vampire bats.

        Photo found at  http://www.abdn.ac.uk/~nhi708/classify/animalia/chordata/mammalia/chiroptera/chiroptera.html