A trio of rare sumatran tiger cubs, born at the Adelaide Zoo in December, are growing fast and feisty, according to their keepers.The unnamed three cubs, one male and two female, were born to mom Delilah on December 21.Footage from Zoos SA shows the cubs climbing all over Delilah, using her tail as a chew toy, and play-fighting with one another.“Delilah is such a doting mum,” senior keeper Arliah Hayward said. “She is very patient with them despite them using her as a kind of play equipment. Their little teeth and claws are getting pretty sharp now but she puts up with their biting and climbing."Hayward said the cubs are growing quickly, with each one developing their own personality.“The little boy is the most vocal of the threesome and is playful with keepers," Hayward said. “One of the girls, who has triangular markings on her head, has started to chuff to keepers and is very food obsessed. While the third cub, also a female, is extremely feisty!”Adelaide Zoo hopes that the tiger cubs will come out into their exhibit in April, after sticking close to their den for the first months of their life.The arrival of the three cubs is a significant addition to the population of the critically endangered tiger. Credit: Zoos SA via Storyful