Snail Smarts

Some friends are book smart, others are street smart. It’s very difficult, if not impossible, to be both. Turns out the same holds true for snails.

“It’s widely assumed that there are intelligent individuals in all species, but this has been very difficult to demonstrate,” says the Aberystwyth University’s Sarah Dalesman. “Our research suggests that rather than ‘smart’ and ‘dumb’ animals, all individuals are smart at some things but not everything. This is not really surprising if we think of things our friends are good at. Not everyone I know is good at everything, but everyone I know has some things they are very good at.”

Dalesman and her colleagues tested pond snails (Lymnaea stagnalis) to see what they might be good at—remembering food or remembering predators—and if their skills depended on their habitat. The scientists studied populations of snails that lived in the lab all of their lives with plenty of food and no predators, and then compared the well-off snails to other groups living in the wild, with predator risks and varying food availability.

To test the snails’ memory, certain behaviors were either encouraged or discouraged, and scientists assessed the animals’ ability to remember according to the behavioral response to the training. The snails were trained in three different ways. First, they were taught to associate food taste (in this case carrot, yum) with a bad chemical taste. Then they associated the neutral smell of pear drops with a good food taste. Finally, they were taught to associate breathing at the water’s surface with being poked—considered by snails to be a predator threat.

Snails that were good at one type of food memory were also good at the other type of food memory. If they were good at forming food memories, however, they were very bad at remembering about predator threat. They exceled at one or the other, but not both.

And their habitat made no difference at all, says Exeter University’s Sasha Dall. “What was very striking was the consistency in the relationship between different memories across different populations. We tested eight different populations and they all showed the same pattern irrespective of the type of habitat they came from.

“There is no such thing as a universally smart snail,” he says.

“Demonstrating general intelligence in wild animals has so far proved elusive, but our research has revealed why this may be,” Dalesman adds. “We tested memory ability in individual pond snails across a range of tasks including memory of what is good or bad to eat, and predator avoidance. This revealed that individuals who are good at one type of memory are generally very poor at other types of memory.”

The study is published this week in Scientific Reports.