Columbia's rat population has been halved
NASA has revealed that 45 - nearly half - of the baby rats launched earlier this month aboard Columbia have died as a result of maternal neglect.
NASA's chief veterinarian, Joseph Bielitzki said the surrogate mother rats were not drinking enough water, and either shunned the young animals or simply did not produce enough milk for nursing.
"We did not anticipate a problem with maternal care," he said. "This was really an unexpected result."
Most of the rats, which are about two-and-a-half weeks old, died naturally. At least five animals, however, were so sick that the crew had to kill them.
They would have been killed in any case - the rodents were to have been dissected and their brains analysed to measure the effect of weightlessness.
NASA scientists admitted there would be an impact on the brain development studies, but expect the primary objectives to be met.
Rats get TLC
Columbia's astronauts managed to nurse some of the sick rodents back to health, feeding the young rats by hand and giving them water as though they were newborn kittens.
But others were still ailing and were excused from a dexterity experiment by astronaut Rick Linnehan, Columbia's veterinarian.
"They appear somewhat depressed and dehydrated. There is no meaningful data to be gained with these animals at this point," he said.
Columbia's menagerie includes also includes four oyster toad fish, 229 swordtail fish, 60 snails and about 1,500 crickets.
Nasa says the experiments may provide an insight into earthbound ailments such as insomnia, blood pressure trouble, balance problems and motion sickness.