New Delhi, May 18 -- A group of people watched three albino rats leap from small baskets into a big cage on Sunday as other rodents hid in makeshift tunnels or searched for applesauce offered by their keeper through the bars at an indoor hall in the Argentine capital.

It's Ratapalooza, an annual Buenos Aires event that promotes the adoption of rodents raised in animal facilities or used for research in science labs - once the animals are no longer useful, have outlived their purpose or are just surplus stock.

To attract adoptive families, Team Ratas, which is Spanish for rats, organizes events such as the Ratapalooza. In Argentina, keeping rats or mice as pets is perfectly legal - as long as they are not wild.

The whole thing turns int...