Can Cats Recognize Poisonous Plants?

The common belief that cats have bitter taste receptors to protect them from ingesting poisonous plants may not be true, according to new research from the Monell Center.

The research showed that there doesn’t appear to be a strong relationship between the number of bitter receptors and the extent to which a species consumed plants in its diet.

“Alternate physiological roles for bitter receptors may be an important driving force molding bitter receptor number and function. For example, recent Monell-related findings show that bitter receptors also are involved in protecting us against internal toxins, including bacteria related to respiratory diseases,” said study author Gary Beauchamp, PhD, a behavioral biologist at Monell.

Scientists speculate that the sense of taste evolved so animals could make the critical decision of whether a potential food is nutritionally advantageous or possibly harmful. For example, sweet taste is believed to signal the presence of sugars, an important source of energy. Similarly, scientists have long assumed that bitter taste evolved as a defense mechanism to detect potentially harmful toxins commonly found in plants.

In support of the sweet taste hypothesis, Monell scientists previously found that both domestic and wild cats are unable to taste sweet compounds. This inability reflects damage to an underlying gene for the sweet taste receptor. The researchers theorized that the strictly meat-eating cats lost their ability to taste sweetness because they have no need to detect sugars.

Additional findings from Monell revealed that other exclusively carnivorous mammals, including sea lions and spotted hyenas, also have lost the ability to detect sweet taste.

The current study, published in the open access journal PLOS ONE, used a similar rationale to ask whether cats, which typically do not eat plants, have maintained the ability to detect bitter taste.

Unlike sweet taste, which has only one or perhaps two different receptor types, the number of functional bitter taste receptor types – those that are able to respond to bitter compounds – varies greatly across species.

If bitter detection evolved to detect plant toxins, the scientists expected to find fewer functional bitter receptors in strictly carnivorous animals like cats and more functional bitter receptors in related species that eat more plants.

In the study, the researchers, from the Monell Chemical Senses Center, in Philadelphia, first examined DNA from domestic cats and identified 12 different genes for cat bitter receptors.

The Monell scientists next evaluated whether these genes encode functional bitter receptors. To do this, they incorporated the gene sequence of each receptor into cultured cells and then probed the cells to determine if they were activated by one or more of 25 different bitter-tasting chemicals.