The bats were discovered in two wards at Ninewells Hospital in Dundee
Bats were discovered flying around wards at Ninewells Hospital in Dundee, it has emerged.
The animals were spotted on the general medical ward 6 and on the surgical ward of the infirmary last month.
A freedom of information request revealed NHS Tayside spent £11,173 dealing with pests at its hospitals between October 2008 and July 2009.
In addition to bats, pest controllers were called out 462 times to deal with pests like rats, mice and cockroaches.
The details, obtained by The Courier, also reveal that mice were found in the kitchen and main dining room at Stracathro Hospital, and in the main kitchen of Ashludie Hospital in Monifieth.
Rats were found in ward four at Little Cairnie Hospital in Arbroath.
Most incidents involved insects including cockroaches, ants, flies, silverfish, beetles, wasps and hornets.
Cockroaches were found in the dining room at Sunnyside in Montrose, and maggots in the corridor near the kitchen at the hospital.
Silverfish were discovered in the food preparation area at Perth Royal Infirmary.
Margaret Watt, chairwoman of the Scotland Patients Association, said: "This is totally unacceptable.
"We've got enough to contend with, with MRSA and Clostridium difficile, without having foreign bodies running around.
"Patients are frightened enough to go into hospital without knowing there are rats and mice and cockroaches.
"This health board has got to waken up and realise this cannot continue."
Public Health Minister Shona Robison said pest control was a common problem among health authorities and that she had been assured by NHS Tayside that appropriate measures were in place.
She added: "Patients should be reassured that NHS Tayside has robust procedures in place to tackle infestations, to ensure that they do not increase and that there is no deterioration in standards for patients.
"NHS budgets are at a record high and NHS Tayside is investing more in hospital cleaning, including in Ninewells.
"Extra cleaning staff have also been employed using the additional £400,000 Scottish Government funding provided earlier this year."
Marlyn Glen, Labour MSP for North East Scotland, said the revelations would be "concerning" for patients and their families.
She added: "When someone we love goes into hospital we have a right to expect that they will be treated in clean and safe conditions.
"The idea that our hospitals are infected with mice, cockroaches and even bats is utterly repellent.
"Nicola Sturgeon needs to get on top of this and support staff instead of cutting budgets and piling pressure on our doctors and nurses."