No. 4 (8) 2005

Common noctule bats noctule Common dexterous are not very and so most in flight, over hunt frequently and treetops clearings Hans–Peter Stutz/8. European Night Bat European Stutz/8. Hans–Peter - - - There There are more than 1,100 bat species Despite the considerable ecological Despite diver the ecological considerable of of people’s homes, church towers, breeding in cracks inside bats, or birds for up set boxes shutters. window under or bridges in the world, 22 of which occur in Poland. sity present among bat species, a vast major a vast species, bat among present sity and shelters own their build to unable are ity have to make use sites. roosting of available these that therefore, It as comes no surprise, popu to keen most are sociable very late areas that offer plenty of feeding sites winter Their kinds. various of hideaways and roosts all include sorts of cosy subterranean nooks: most frequently caves, bats underground although basements, and mines, shelters, can in also as places such hibernate strange snakes, hibernating alongside or holes rodent roosts summer Their surface. the under 0.7m can be located in hollows bark of and trees, inside rock the fissures, attics under the sturdily built, warm warm built, sturdily live to places safe and many of their customs remain remain customs their of many has research Yet understudied. criteria their that uncovered similar very are homes choosing in dry, prefer they humans: of those to IRENEUSZ RUCZYŃSKI Białowieża Research Institute, Academy of Polish Sciences [email protected] lives, clandestine live bats Because WIESŁAW BOGDANOWICZ WIESŁAW Museum Warsaw and Institute of Zoology, Academy of Polish Sciences [email protected] Bats Come Home to Roost to Home Come Bats Where do nighttime prowlers go in the day?

evolution, evolution, No. 4 (8) 2005 (8) 4 No. 4 behavior of bats bats of behavior Prof. Bogdanowicz Prof. and genetics of bats Dr Ireneusz Ruczyński Ruczyński Ireneusz Dr functional morphology, functional morphology, studies the ecology and and ecology the studies

in natural-growth forests natural-growth in

specializes in the ecology, specializes in the ecology, Focus on on Focus Chiropterology

ACADEMIA No. 4 (8) 2005 5

Distribution of roost trees trees of roost Distribution by colonies occupied in bats of Leisler’s located Forest, Białowieża telemetry radio using Even though echolocation echolocation though Even main bats’ constitutes of information source surroundings, their about they not lost have to see the ability Ruczyński I. (2004) I. Ruczyński - ). ). These two ) ) and the or Nyctalus leisleri Nyctalus Nyctalus noctula of of two bat species: the bat ( Leisler’s bat ( types were chosen because they have much in common: they are closely related, inhabit the forests of Eurasia and North , and usually choose tree hollows as their repro duction sites. They form their reproductive colonies in May, with the young being born area of the Polish- 2 The The research we carried out in both the In search of a good home fully-protected and fully-protected portions managed-use of behavior the compared Forest Białowieża the other hand, was carried out in the Białowieża Białowieża the in out carried was hand, other Forest - a 1,500km Belarusian borderland that has long and been deciduous famous as the best-preserved lowland. European the in forest mixed environment over environment the past several thousand years. But most of the existing research on has forests European in roosts of choice bats’ been carried out in forested areas that have been greatly affected by man, are young, or exhibit low diversity. Our research, on the almost almost exclusively inhabit natural predominantly (which bats roosts) synanthropic and live in man-made terms, in scientific is interesting more group shelters). The test litmus of kind a as former seen be can it because for the that taken place have in changes our Simplifying things in Simplifying considerably, terms of the type of roosts they inhabit bats can be into classified two types: sylvan bats (which Krzysztof Skrok ACADEMIA

Where do nighttime prowlers go in the day? Chiropterology Ireneusz Ruczyński Focus on

Nets set up over rivers and ponds are the best way to catch bats

in mid-June. They are migratory species that their energy expenditure. Bats then lower winter outside the Białowieża Forest. Of their body temperature, and thereby the pace course, aside from their similarities they also of their life processes. show some differences: the smaller Leisler’s bat (8-20g in body mass) is considered to be Outwitting predators closely associated with old-growth forests, The hollow occupied by a bat colony has while the larger common noctule (17-44g) to protect them not only from unfavorable also lives in considerable numbers in rela- weather conditions, but also from the numer- tively young forest stands. ous predators present in the Białowieża One might imagine that one tree hollow Forest, such as the pine marten and perhaps differs little from the next, and that when also such nest-robbers as woodpeckers and choosing where to dwell bats are more con- dormice. To protect themselves bats choose cerned with a hollow’s “floor-space” than the hollows with small exit holes, usually less conditions inside. It turns out, however, that than 4.5cm in radius - i.e. smaller than the many factors have an influence over which head of the pine martin, thereby minimizing of the available hollows are indeed chosen. A the risk of the hollow being ravaged by at dominant role here is played by weather con- least this one very dangerous type of intrud- ditions. Relatively low ambient temperatures er. At the same time, the preferred hollows and large diurnal fluctuations cause bats are located deep enough from the entrance- to choose warmer roosts, with smaller exit way that predators do not stand much chance holes. Bat homes also have to be dry and have of dragging bats out with their paws. sturdy walls. These flying clearly There are also interesting differences prefer oak and ash trees, more rarely making between the two species in terms of how the use of hollows in alder, linden, hornbeam, hollows they choose were created. Common maple, and pine trees. Interestingly, these noctules most frequently employ hollows preferences varied depending on the bats’ carved out by woodpeckers, while Leisler’s physiological state: the females of both spe- bats most eagerly inhabit what are called nat- cies most frequently occupied warmer oaks ural hollows, formed by decomposition proc- when pregnant or feeding their young, yet esses in the wood. Ornithological research, in eagerly chose hollows in colder ash trees at turn, shows that the risk of losing a roost is the end of July, when their young had already greater in hollows carved out by woodpeck- taken wing. There is a logical explanation for ers than in the case of natural hollows - this this - bat pregnancy and growth proceed is probably because of the woodpeckers more rapidly in higher temperatures, but themselves, who recognize “their” hollows moving into colder hollows after the rearing and revisit them in successive years. They period allows them to significantly reduce then destroy the roosts of other species: birds

6 No. 4 (8) No. 2005 ACADEMIA Focus on on Focus Chiropterology

Lesser noctules or Leisler’s bats are small and weigh some 15 grams Robert Mysłajek

and bats. We surmise that common noctules, the pied flycatcher (Ficedula hypoleuca) build being a larger and more aggressive species, no more than 10 meters above ground. So are able to defend themselves from wood- why do birds choose the upper portions of peckers, while the small Leisler’s bats may trees, while birds prefer hollows lower down? be vulnerable to direct attack. For the latter, Research in the Białowieża Forest has shown the best strategy is to avoid encountering a that the higher portions of tree trunks are potential enemy in the first place. warmed by the sun more strongly, and thus the hollows there are warmer. Birds protect Higher means warmer? their chicks from heat-loss by lining their For their reproductive sites, bats choose nests with down - the temperature of the hol- hollows situated an average of 19 meters low itself is thus not as crucial as it is for bats, above the ground. This is much higher than for whom the degree of sunlight and height of birds that nest in tree hollows. By way of a hollow are of key significance. comparison, the marsh tit (Parus palustris) builds its nests at somewhat above 5 meters On the hunt on average, while the great tit (P. major) and We installed miniature transmitters (weigh- ing 0.5g) on more than 50 bats and monitored In order to take their location night after night for at least measurements of treetop several days. All of them chose roosts within hollows, researchers 6km of their hunting grounds. Nevertheless, have to employ climbing bats moved from one place to another every techniques. This gives 2.5 days on average, switching to new homes them a chance to take a across a distance of some 700m. The factors “bat’s-eye” glimpse usually seen as underlying such behavior of the Białowieża Forest include the lower risk of being discovered by predators, fewer parasites in the roosts, and greater opportunities to find roosts with a bet- ter microclimate. As long as we are talking about the hunt- ing grounds of the bats we studied, we can mention that the diets of the two species chiefly include , small flies and , although the proportion of beetles is some- what smaller for Leisler’s bats than for com- mon noctules. A more interesting European representative of the Nyctalus genus in terms Claire Duriez

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No. 4 (8) 2005 occur hs pce’ it esnly nlds small includes seasonally diet species’ this that showSpain and Italyscientists) in(bat central Poland). Research by chiropterologists were found among the pellets specimen of a barn one owl in of remains (the sporadically erus ( noctule giant the is diet of day?the goin prowlers nighttime do Where uzńk I (04. ooick z ónc pięter górnych z Borowiaczki (2004). I. Ruczyński (2003).eds. M.B.,Fenton T.H., Kunz P.T. Agirre-Mendi J.L., Garcia-Mudarra J., Juste C., Ibáňez reading Further theysay, is adifferent story. asbranches.that,tree sleepingButbirdson Australia,Africa,andAsia,uponpreywhich tropicssubtropicstheandSouthAmerica, of victimsflight,in unlike thepredatory batsin routetoAfrica. This bat probably captures its en Mediterranean Sea the across way their 500million small passerine birds are making theautumn migration (August-November), as during increases particularly diet bat’s this in birds proportion of The warbler. wood or robin, copper, the as such birds,passerine ),which also occurs in our country, albeit au Lilrs as n pe frs lyr] I: B. In: layers]. forest upper in bats [Leisler’s lasu UniversityofChicago Press. UnitedStates ofAmerica ProceedingstheNationalof Academy Sciencesof theof (2001).predationBatnocturnally on migrating birds. , 17:, 9700-9702.

Bat ecology Bat Nyctalus lasiopt . Chicago: .  - Higher than birds than Higher Ruczyński I., Bogdanowicz W. (2005). Roost cavity selection Poland. Eastern Forest, Primeval Białowieża in Chiroptera) leisleri(,NyctalusN.noctula andby Białowieża,pp. 121-128. Mammals Białowieskiej Puszczy (eds.): Wójcik J.M. Jędrzejewska, JournalofMammalogy , A Mma Rsac Institute, Research Mammal PAN ], [ sas n iłwea Forest Białowieża on Essays , 86(5),, inprint. sj o ssakach o Eseje

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