Bat Calendar

We will list the activities that we have observed bats follow per month, We decided to make this colander after making our bats in the house page. I organized that page by seasons, it was at this time i realized that we should have a page that is dedicated to explaining the actions of bats on a monthly bases.

Remember, this page is written to be educational and differences may exist from area to area in terms of timing and bat behavior.


January is a time of year that bats are typically at rest, It is usually cold at this time and most bats are in torpor (Hibernation or Very Deep Sleep). Sometimes the bats will emerge in the warmer spells of the month, often it will need to be warm many days in a row for a bat to emerge from torpor. Male bats will also be in the breeding process during this month. He will often breed the female bat while she is hibernating.


February is much the same as January in many areas of the country. The weather is cold and the bats are still in their hibernation state. The male bats are still in the breeding process and you still may see a bat in the warmer stretches of the month. The bats are still burning stored energy from the fat reserves that they built up in the fall time of the year. Their fat supply is getting low and around the end of the month they may become more active inside their den.


March is a strange month in many parts of the United States, Some years you will have an excessive warm month and the bats will start to emerge early in the month, other years when the weather is colder, the bats will stay in the hibernation stage a little longer, because it is important that as soon as the bats come out of torpor, they need a immediate food source, which is flying insects. The male bats will also finish up breeding all the rest of the available females in the colony


April is the month that the bats will start to officially come out of torpor for the year. The weather is now nice and the days are getting longer and warmer, the flying insects that the bats feed off of are now present on consistent bases and the bats will start the rebuilding process of the fat that was used during their time of torpor. The male bats are starting to gather together in order to form a bachelor colony. This will usually happen near the end of the month and towards the beginning of May. All the female bats have been bred and depending on the weather, let their body accept the sperm from the male. Bats have a delayed fertilization process that lets the female bats environment dictate when baby bats will be born.


May is the month will the males and female bats will separate. The males form the bachelor colony and the females will form what is called a maternal colony. This is a colony of female bats that have formed a large colony together in order to have babies; typically they will use the same places over and over. They will continue to use the spots until they are torn down or destroyed by man. If this is area is located in your attic, you may have large piles of bat guano to cleanup. Some of the birthing areas have been used for 100’s of years. This month the bats will also continue to add to their body fat by very aggressively eating insects. Around the end of the month, you may see bat babies, but not usually until late June or early July.


June is the month when the males and females have been separated; the males have found the roosting spot for their smaller bachelor colony. The females have settled into their maternal colony and the female bats are eating large amounts of insects in order to build up fat for the up and coming birthing season. Bats are considered mammals and they nurse their young. This takes up a lot of energy and the only way a bat can gain energy is to eat more bugs!
You may see some baby bats in the latter half of the month, depending on how the weather was in the spring. A bat gestation period varies between species but is between 40 to 6 days. Some of the larger varieties of bat will have a gestation period of 6 months, but these are usually found in South America.


July is the month when most all females will have their babies, most females will have released the male sperm from their delayed fertilization process in early may, now 40 to 60 days later, they have babies. the baby bats are born naked, meaning they have no fur at all, so the mother bat will depend on the internal temperature of their maternal colony to keep the baby bats warm. Baby bats require a average temp between 90 and 100 degrees to be successfully weaned. The mother bat will nurse the baby bat for approximately 4 weeks. At this time the baby bats will start to fly and will start to be self dependant. The male bats are still in their bachelor colony living away from the females and babies.


August is another transition month, this is the month that some baby will start to fly and other baby bats will just have been born. All maternal bat colonies will have baby bats in different stages of growth all summer long. This is done for several reasons by mother nature. It keeps the “nursery” from having to many baby bats at once. It also assures that if something would happen to the nursery, (Temp drop) or something else, it doesn’t kill the entire litter of baby bats. The male bats are still in their bachelor colony and continue to be separated from the females and babies.


September is a month when the weather will start to take its first turns towards winter, many areas of the eastern part of the united states will experience their first frosts of the year. The bats are by now all flying, including the last of the babies that were born in at the end of birthing season. The males and females are now starting to regroup and start feeding excessively in order to gain fat reserves for the up and coming winter. The bats will now start their push towards their wintering location, often in a secluded building or cave deep in the ground. This is also the month that you can remove the bats from your attic without a special permit. This is also the time you should do do your bat guano cleanups.


The bats are now almost sure to be in the winter fat building mode, eating everything possible, moths, mesquites and any other flying insects, all in order to gain valuable fat reserves to make it thru the winter, food and eating is the only thing the bats are thinking about this month, as the winter weather is starting to creep in, their bodies are signaling them to fatten’ up as much as possible because their food sources are starting to dwindle. Most flying insects are now gone for the winter. In some colder areas of the US, bats will start their torpor session, only flying on warmer nights when the possibilities of catching food are greater. Bat will not fly on colder nights because the lack of food, they would exert more energy than they would gain in food caught. So they just stay put inside.


Bats will only make themselves present in November on the warmer days of the month, as they have all settled into their winter dens and have started their torpor process. Most bats have lots of fats stored on their body by now, so sleep this month should be easy.


December is typically a cold month, Bats are in their state of Torpor and are relatively inactive, however you will see bats in December in the warmer periods. Most of the bats that you see during this month will be males and they are only flying because they are restless in the den site. Bugs are almost nonexistent during this month, so they are not flying for food. Males will almost certainly breed some females this month, starting to entire process over again!

My disclaimer!

This was a brief snapshot in the life of the bat as stated before, this information is accurate for the eastern part of the US and the process may differ by several weeks to several months in your area. This is only to be used as a guideline. If you have any questions about bats or their removal, just click on the contact us link above, we will be more than happy to assist you anyway we can.
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We have many pages on several different species of bats, please use our main bat removal page for specific species of bats needing controlled..

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