SURABAYA, INDONESIA (Reuters) - Smiling visitors file into the Surabaya Zoo in East Java Province to catch a glimpse of its residents. But for some of the animals contained here, their lives are anything but happy.

The establishment is nicknamed the 'zoo of death' due to the high number of animals who perish while in captivity.

The latest victim, a Sumatran tiger named Rama who died unexpectedly in April.

"The zoo needs to thin out the over population," said Petrus Riski, a wildlife activist. "They can exchange animals, or send them to conservation institutes, but it's important to improve the animal welfare here."

Over population isn't the only problem.

This giraffe was found dead with some 40 pounds (18.1kg) of plastic in its stomach, trash thrown into its cage by visitors. An 18-month-old lion named Michael was found hanged to death by a steel wire in the roof of his cage.

Activists say a lack of proper food, untrained staff and general neglect have all contributed to the zoo's abhorrent conditions.

The zoo director says it's political.

"There are many people who have an interest in the zoo with their own agendas," she said. "That's what's been complicating our efforts."

After the hanging death of the lion in 2014, government officials said other zoos in the region had offered to take in some of the animals.