Ideally, phone the National Bat Helpline immediately. The helpline is run by the Bat Conservation Trust (BCT) in the UK-only and can be reached on (0345) 1300 228 at firstname.lastname@example.org. The helpline is, however, only staffed Monday to Friday from 9am to 5.30pm (GMT/BST).
Should you find a grounded bat, or if your cat brings one home, there are a few things you can do help while you contact the necessary authorities. The Bat Conservation Trust has a list of guidelines on their website regarding the caring for of grounded and/or injured bats. Alternatively, you can contact your local bat group, who can offer advice over the telephone or send a qualified bat handler out to you. There are upwards of 90 volunteer bat groups in the UK and most of the country is covered. Owing to the requirement for a licence to handle bats for anything other than immediate rescue, not all wildlife rescue centres will treat them, but many will and most will offer advice over the phone.
The following is a summary of the information provided by the BCT. The most important thing to remember is DO NOT pick the bat up with your bare hands, use decent gloves (gardening gloves are excellent) or a cloth/towel. This is for your and their protection.
Care for a grounded bat:
1. If the bat has injuries and you are going to be keeping the bat for longer than a couple of hours, prepare some suitable housing.
2. Housing should be something such as a shoebox or large margarine tub, with sufficient air holes (but no gaps larger than 5mm / one-quarter in.).
3. Line the housing with kitchen towel or soft cloth and place it in a warm spot – a dark airing cupboard is ideal.
4. Offer water regularly on a small clean paintbrush, cotton bud or in a teaspoon. It is best not to put a pot of water in with the bat, but if needs must it should be very shallow (e.g. a plastic milk bottle lid).
5. Bats may be enticed to feed on small meaty chunks of cat food.
It is very important that you do not harm the bat. The law protects all species of UK bat and, under the Wildlife and Countryside Act of 1981, causing injury to them (or their roosts) is a criminal offence.
Outside the UK?
Detailed instructions for releasing healthy bats caught indoors and rescuing injured bats in the USA can be found on the Bat World Sanctuary website. The article also contains a link to help find your local bat rescue centre and additional information is also provided by the Wildlife Rehabilitation website. In Australia, advice can be found on Bat Conservation & Rescue QLD's rescue website.