Rats Conquer New York City, Genome Study Reveals

Rats in New York are known to be adaptable. They eat practically what every New Yorker does and have conquered every corner of New York. A study on the genome of the Yankee rats identified several genes involved in its diet, behavior, and movement that helped them adapt and eventually conquer the Big Apple.

The study team, led by Arbel Harpack from Columbia University collected nearly 400 brown rats (Rattus norvegicus) across the city. The study team trapped rats, giving them bacon, peanut butter, and oats as baits. Genomes of the rats were sequenced and compared with the previously sequenced genome of rats from rural northeast China, the origin of brown rats in New York.

The study team studied variations on sections of the genome that may have aided the Yankee Rats to adapt to New York. The adaptation is linked to an evolutionary process known as selective sweep, the tendency of a particular trait that is beneficial for survival to be more prevalent in a population. It is the same evolutionary process that allowed some humans to digest milk as adults.

The genome analysis produced several genes that had the traits of the selective sweep in rats. The genes discovered were associated with diet, behavior, and mobility, reflecting the challenges and ways of life to survive Big Apple. Among the genes identified was CYP2D1, the gene that is responsible for detoxifying plant compounds which probably explains why Yankee Rats enjoy kale salads. However, scientists cannot conclude how these genes affect the animals' biology yet.

Results from the genome study opened a lot of questions and a new wish list for future research. The research team, for example, is curious: how did the change in the genes involved in the development of new neurons affect the behavior of the rats? Can the gene responsible for the metabolism of carbohydrates and sugar influence the rat's diet?

Andrés Bendesky, an evolutionary geneticist and neuroscientist at Columbia noted that some of the genes identified are also involved in brain wiring. Researchers believe that animals change their neural circuitry to adapt to a new environment. There is no evidence to prove this yet, Bendensky admits.

Harpack and his research team are also interested to know when the selective sweeps occurred by studying the DNA of rats from the nineteenth century. The teams also plan to trap rats from other cities to study if their genome has evolved in the same way as the New York rats.

Evolutionary biologist Hopi Hoekstra expects some differences in the genetic adaptations of rats from other cities. She related an experience where her baiting efforts at home in Cambridge had failed, despite trapping rats for 25 years. When she called the exterminator, she was told that she was using the wrong bait for Cambridge rats. Instead of peanut-butter laced traps, the exterminator recommended that she use Cambridge 'delicacies': Dunkin Donuts and Slim Jim's, a dried sausage snack. True enough, they were able to catch the rat which will be used for DNA analysis.