A mystery over the growing number of animal deaths at America's prestigious national zoo in Washington has made its way to Congress.
Endangered in the wild, and allegedly in the zoo
Officials from the zoo are due to appear before a Congressional committee to explain why up to 70 animals - some of them endangered species - have died over the last three years.
Two rare red pandas have been among the casualties, along with a hippopotamus, giraffes, a lion, zebras, an orangutan and an elephant.
Animal rights groups have argued that many of the deaths were due to lack of care.
The zoo has admitted that the two pandas died after eating rat poison, but has refused to release post mortem reports on the causes of other deaths, saying the animals have a confidential doctor/patient relationship that protects their privacy.
Food cut back
Questions are being asked about the role played by the head of the zoo, Lucy Spellman, in the death of a zebra three years ago.
As chief vet at the time she ordered the food given to the zebras to be cut back.
An investigation into the death of the animal found that it had no body fat to ward off an especially severe winter.
Animal rights campaigners have also cited the case of a Persian onager, a relative of the horse, that died of salmonella at the zoo's conservation and research centre.
And further complaints have been made about a number of deer killed by dogs which got into their enclosure at the conservation centre.