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Because bats are widespread in the world, there are different characteristics that are related to mating. For species inwarm regions of the globe, between males and females of the same species there are differenceseasy to spot: the males are larger, there are differencesregarding the coat color, they have the ability to ripple their fur. Also, there may be other physiological adaptationssuch as the characteristic skin gland secretions smell.

For species in the temperate region(mostly in Europe, North America andAsia), gender recognition is more difficult, requiring observation of the external genitalia. Most times they are not easily visible. When they rest these are hidden in the fur on the abdomen, covered by membranefolds or wingswhile for the eared bats (Plecotus auritus and Plecotusaustriacus), testicles and scrotumare located on the sides of the abdominal cavity and they are out only during the mating .

Their Behaviour and The Periodicity of Reproduction

In warm areas of the globe, there are sufficient foodresources throughout the year, sothese allow reproduction, birth and rearing of their litters in any interval. Intemperate climates, the female bats make delivery in the year when it is the best time for babies to feedand when they can grow deep enough intohibernation until the coming winter. Inthese situations all stages of breeding (pregnancy,childbirth, lactation, learning techniques of flying and hunting) are shortened.
Mating time and frequency characteristics are determined by climate and food resources in increase. Thus, the chiroptera were classified into:

1. Monoestriene (they reproduce only once a year)

2. Poliestriene (they reproduce several times per year):

- Two reproductions per year, seasonal

- With continuous reproductive behavior (mating can occur at any time of year)

The species with tworeproductions, seasonalreproduction - This includes several species oftropical India (belonging to the genera Rousettus, Cynopterus, Pipistrellus)and Africa (Pteroptide). The two reproductive periods overlapperiod of transition from one season to another, and between the restoccurs in malesexual a significantregression of testisvolume.

The species withcontinuous reproduction – they are not dependent on environmental conditions of life. In thecolonies there were identified pregnant female who are breastfeeding (species of the genera Nycteris, Rousettus, Taphozous, Mollus,Carroll, Glossophaga).

The species with one breeding a year - Mating takes place during autumn and even winter, the birth of offspring having place from May to July.At birth the young should be suficient developed and to have the adequate time for growth and fataccumulation. A very important thingfor all holarctic species and also for all bats of our country, is that of the male sexual cycle (spermatogenesis) ending a few months earlier than that of the the female (ovogenesis).

Each species has its own strategy of mating, characterizedby: the type ofmale flight, courtshipflight, the ultrasound issue, the attendance to false shelters to confuse other males – the potential rivals, the shelter impregnation with odoriferous secretionsproduced by the glands of male facial. Mating is between individualsof the same species. Deviations from this rule were observed for the water bat(Myotis daubentonii) which seeks partner inmixed colonies withMyotis myotis and Plecotus auritus (the eared bat). Matingin this species is performed during theformation of the hibernationcolon or during hibernation. Coupling takes place withoutprior ritual becausefemales are addressed in sleep, bitten andscratched to wake up.

After studies by Ransom (1990), inhot summers, thepups which were born early and the adults havehad sufficient time to prepare for hibernation, in late October mating frequency is of 85%.Contrary to this situation, if babies were bornlater, in the short and cold summer, the adultindividuals haven’t accumulated enoughfat reserves and inthe early stages ofhibernation period the mating frequency isonly 20%.

Mating and pregnancy

Sexual maturity for the Chiroptera in the temperate zone is reached in the second year of life. The first mating takes place after 14 months. The only exceptionsare Rhinolophus hipposideros and the South American speciesthat can reproduce in the first year of life.

For European bats, mating begins with the collapse of maternitycolonies and with the weaning of pups (August-October). Individuals of both sexes do not show fidelity to one partner.The more intense is the spermatogenesis, the chance that at least a part ofthe sperm to survive until ovulation is greater.

After mating, sperm is stored inthe female genital tract, where it is storeduntil ovulation, which occurs usually in spring (March).Normally sperm should be destroyed by the immune systemof the female. On the contrary, however, they are fed by uterine fluidscontaining large amounts of glucose and fructose. Also, the high pressure of the dissolved carbondioxide and proteins in the uterus lumen, reduce to the minimum the requirementsof sperm consumption, conducting tp their immobilization.

In early spring, pregnant females are the first to leave the hibernation shelters lookingfor maternity roosts.During pregnancy and maternity, both mothers and babies are very sensitive to any activity disturbing (noise, light, temperature changes)

Females during pregnancy and lactation are in theintensive feeding to recover weight lost during hibernation and the lastperiod of pregnancy. The time spent feeding variesbetween 2.5 and 5 hours / night.

The gestation period varies between 45 and 60 days, depending on the climate featuresof the year and on the species. All holarctic species of bats have the ability to slow down or speed up the process of gestation. Because metabolismduring pregnancy is sustained and the energylosses are high, femalesare grouped together as much as possible in order to regulate the body temperature in the community.

The vampire bat female (Desmodus rotundus)have the longest period of gestation.

Life cycle of bats in temperate Europe (according to V. Decu, D Murariu, V. Gheorghiu)

Autumn Transit: males and females are regrouping, are movingtoward winter shelters.Females store spermin the genital tract.(Feature: the Miniopterusschreibersii after the ovulation occurs the mating, fertilization and early pregnancy).

Hibernation: in wintershelters continue the fertile matings for some species. (Feature: the pregnancyis interrupted for schreibersii Miniopterus)

Transit vernal: females begin to separate themales and to move toward summer shelters,fertilization occurs and pregnancy.

Maternity: females are regrouping in summer colonies in shelters,ending pregnancy, females give birth andraise their young until late August,early September, when they are separated from it.

Motherhood and the rearing of young

For birth and the rearing of young, single females form the maternitycolonies separated from males.
In some species the birth takes place in the normal position (upside down), and for others the females rotate180 degrees. Immediatelyafter birth the young slip in the foldsof the wings and tail membrane (uropatagiu),as in a pocket. After birth, youngsters remain about2 hours with their cord tied by the mother,to reduce the risk of fall. They cling with their clawson their mums’ fur looking for the breasts to feed immediately.

Most of the Chiroptera give birth to oneoffspring. However, some species of Vespertilionidae give birth to two oreven three babies.For example, in Western Europe, Pipistrellus pipistrellus creates a single offspring, while in the continentalregions with a focus on Eastern Europe, thereare often borntwins within the same species. The same is the result of more severe climatic conditions, a greater number of births ensure the perpetuation of the species.Usually, twins areborn to older females.

A very special social behavior has been reported in Pteropus rodricensis (the flying fox, a species in which young females are assistedat birth by other adult females. Mammaryglands are located on the abdomen. For some species (Nyctaride, Hipposideros) they are false, and are designed to provide offspring witha good grip area.

Intensive care of the offspring is typical of all species, because the birth rate is low and highly fluctuating over time andmortality rate is high.

At birth babies are deprived of fur, blind, weigh 1/3-1/5 of adult weight,but have a strong maternal instinct, clinging with the claws and teeth of their mothers’ fur. Their eyes open after 3-10 days, and after the first week the body is already covered by hair. After another 10 days, theinitial dentition falls and the final one forms. After3-4 weeks, the pups take the first flight lessons, initially clinging to mothers within the maternal shelter. On their first flying pups cannotavoid the obstacles, so they are landing on them. Tolaunch the newflight, they climb the walls with their claws.

Females of insectivorous species have highly nutritious milk. The offspring are breastfed for at least 2 times a day in between sleep by day and hunting. Lactationperiod lasts between 4 and 8 weeks, depending on the species and by the pups’ habit to hunt.

While mothers are left to hunt,youngsters are gatheredtogether to maintain body temperature. Both mother and baby have highly developed olfactory sense, looking toeach other without fail. If the young fall while they are too young to fly, they send signals tobe spotted by the mother and brought back to the colony. Otherwise they die of hypothermia and starvation.