By . Olivia Williams . PUBLISHED: . 12:04 EST, 22 June 2013 . | . UPDATED: . 05:56 EST, 23 June 2013 . With their eyes tightly shut and clinging to their mother's chest, these rare gorilla twins were born only yesterday. Gorilla mothers usually only give birth to one baby every four years, so N'Gayla was particularly over the moon with her twins. The 20-year-old mother, who already has three offspring, gave birth to them at Burgers' Zoo in the Netherlands. Scroll down for video . Vulnerable: The newborn gorilla twins took a nap on their mother's chest at Burgers' Zoo . Zookeepers were delighted when the boy and girl twins arrived, as gorilla twins born in captivity are extremely rare. 'Twins are very rare because in the last fifty years, there have only been ten births in zoos,' Wilco Limpers, head keeper of the great apes at the zoo, told RTV. The zookeepers knew N'Gayla was pregnant but they had no idea that she was having twins. They said that although N'Gayla will have her hands full with the two of them, she will make a caring mother. Gorilla mothers often invest huge amounts of time and love in their offspring as they do not breed often. The babies with their eyes tightly shut and very vulnerable. For the first three to four months, they cling to their mother’s chest 24 hours a day. Cute: The boy and girl twins will be hanging onto mother N'Gayla's chest for the first few months of their lives . Bonding: The twins will live with their mother for at least eight years, before heading to a different zoo . To protect the twins from too much rough . and tumble, they will not be allowed to play with their father until . they have grown stronger. Mr Limpers explained that their father will protect them from other gorillas but their mother will be the one to bring them up. He said: 'When the youngsters are one and a half years old, they want to play and then he will play with them.' For at least eight years the pair will live with their family, before being sent to another zoo to prevent any possible incest within the group.
Gorilla twins are very rare, particularly in captivity .
The boy and girl were born yesterday at Burgers' Zoo in the Netherlands .
By . Olivia Williams . PUBLISHED: . 12:04 EST, 22 June 2013 . | . UPDATED: . 05:56 EST, 23 June 2013 . With their eyes tightly shut and clinging to their mother's chest, these rare gorilla twins were born only yesterday. Gorilla mothers usually only give birth to one baby every four years, so N'Gayla was particularly over the moon with her twins. The 20-year-old mother, who already has three offspring, gave birth to them at Burgers' Zoo in the Netherlands. Scroll down for video . Vulnerable: The newborn gorilla twins took a nap on their mother's chest at Burgers' Zoo . Zookeepers were delighted when the boy and girl twins arrived, as gorilla twins born in captivity are extremely rare. 'Twins are very rare because in the last fifty years, there have only been ten births in zoos,' Wilco Limpers, head keeper of the great apes at the zoo, told RTV. The zookeepers knew N'Gayla was pregnant but they had no idea that she was having twins. They said that although N'Gayla will have her hands full with the two of them, she will make a caring mother. Gorilla mothers often invest huge amounts of time and love in their offspring as they do not breed often. The babies with their eyes tightly shut and very vulnerable. For the first three to four months, they cling to their mother’s chest 24 hours a day. Cute: The boy and girl twins will be hanging onto mother N'Gayla's chest for the first few months of their lives . Bonding: The twins will live with their mother for at least eight years, before heading to a different zoo . To protect the twins from too much rough . and tumble, they will not be allowed to play with their father until . they have grown stronger. Mr Limpers explained that their father will protect them from other gorillas but their mother will be the one to bring them up. He said: 'When the youngsters are one and a half years old, they want to play and then he will play with them.' For at least eight years the pair will live with their family, before being sent to another zoo to prevent any possible incest within the group.
were born only yesterday. Gorilla mothers usually Zoo in the Netherlands. Scroll down for video . are extremely rare. 'Twins are very rare because hours a day. Cute: The boy and girl twins will be