Roost selection and roost switching of female Bechstein's bats ( Myotis bechsteinii ) as a strategy of parasite avoidance

Ectoparasites of vertebrates often spend part of their life cycle in their hosts' home. Consequently, hosts should take into account the parasite infestation of a site when selecting where to live. In a field study, we investigated whether colonial female Bechstein's bats (Myotis bechsteinii) adapt their roosting behaviour to the life cycle of the bat fly Basilia nana in order to decrease their contact with infective stages of this parasite. B. nana imagoes live permanently on the bat's body but deposit puparia in the bat's roosts. The flies metamorphose independently in the roosts, but after metamorphosis emerge only in the presence of a potential host. In a field experiment, the bats preferred non-contagious to contagious day-roosts and hence were able to detect either the parasite load of roosts or some correlate with infestation, such as bat droppings. In addition, 9 years of observational data on the natural roosting behaviour of female Bechstein's bats indicate that the bats largely avoid re-occupying roosts when highly contagious puparia are likely to be present as a result of previous occupations of the roosts by the bat colony. Our results indicate that the females adapted their roosting behaviour to the age-dependent contagiousness (emergence probability) of the puparia. However, some infested roosts were re-occupied, which we assume was because these roosts provided advantages to the bats (e.g. a beneficial microclimate) that outweighed the negative effects associated with bat fly infestation. We suggest that roost selection in Bechstein's bats is the outcome of a trade-off between the costs of parasite infestation and beneficial roost qualitie

The reproductive success of the parasitic bat fly Basilia nana (Diptera: Nycteribiidae) is affected by the low roost fidelity of its host, the Bechstein's bat ( Myotis bechsteinii )

We studied the reproductive ecology of the bat fly Basilia nana on free-ranging colonial female and solitary male Bechstein's bats (Myotis bechsteinii) during one reproductive season. The reproduction of B. nana took place from April to September, and the production of puparia in bat roosts was high. The metamorphosis of the flies took a minimum of 30days, and at least 86% of the puparia metamorphosed successfully. However, only about 30% of flies from puparia deposited in female roosts and 57% of flies from puparia deposited in male roosts emerged in the presence of Bechstein's bats and were thus able to survive. The significantly higher emergence success of bat flies in male roosts was caused by the higher roost fidelity of the solitary males compared with the social females. Our results indicate that bats can control the reproductive success of bat flies by switching and selecting roost

Roost selection and roost switching of female Bechstein's bats (Myotis bechsteinii) as a strategy of parasite avoidance.

Ectoparasites of vertebrates often spend part of their life cycle in their hosts' home. Consequently, hosts should take into account the parasite infestation of a site when selecting where to live. In a field study, we investigated whether colonial female Bechstein's bats (Myotis bechsteinii) adapt their roosting behaviour to the life cycle of the bat fly Basilia nana in order to decrease their contact with infective stages of this parasite. B. nana imagoes live permanently on the bat's body but deposit puparia in the bat's roosts. The flies metamorphose independently in the roosts, but after metamorphosis emerge only in the presence of a potential host. In a field experiment, the bats preferred non-contagious to contagious day-roosts and hence were able to detect either the parasite load of roosts or some correlate with infestation, such as bat droppings. In addition, 9 years of observational data on the natural roosting behaviour of female Bechstein's bats indicate that the bats largely avoid re-occupying roosts when highly contagious puparia are likely to be present as a result of previous occupations of the roosts by the bat colony. Our results indicate that the females adapted their roosting behaviour to the age-dependent contagiousness (emergence probability) of the puparia. However, some infested roosts were re-occupied, which we assume was because these roosts provided advantages to the bats (e.g. a beneficial microclimate) that outweighed the negative effects associated with bat fly infestation. We suggest that roost selection in Bechstein's bats is the outcome of a trade-off between the costs of parasite infestation and beneficial roost qualities

The reproductive success of the parasitic bat fly Basilia nana (Diptera: Nycteribiidae) is affected by the low roost fidelity of its host, the Bechstein's bat (Myotis bechsteinii).

We studied the reproductive ecology of the bat fly Basilia nana on free-ranging colonial female and solitary male Bechstein's bats (Myotis bechsteinii) during one reproductive season. The reproduction of B. nana took place from April to September, and the production of puparia in bat roosts was high. The metamorphosis of the flies took a minimum of 30 days, and at least 86% of the puparia metamorphosed successfully. However, only about 30% of flies from puparia deposited in female roosts and 57% of flies from puparia deposited in male roosts emerged in the presence of Bechstein's bats and were thus able to survive. The significantly higher emergence success of bat flies in male roosts was caused by the higher roost fidelity of the solitary males compared with the social females. Our results indicate that bats can control the reproductive success of bat flies by switching and selecting roosts

Information transfer about roosts in female Bechstein's bats: an experimental field study.

Information transfer among group members is believed to play an important part in the evolution of coloniality in both birds and bats. Although information transfer has received much scientific interest, field studies using experiments to test the underlying hypotheses are rare. We used a field experiment to test if communally breeding female Bechstein's bats (Myotis bechsteinii) exchange information regarding novel roosts. We supplied a wild colony, comprising 17 adult females of known relatedness, with pairs of suitable and unsuitable roosts and monitored the arrival of individuals marked with transponders (PIT-tags) over 2 years. As expected with information transfer, significantly more naive females were recruited towards suitable than towards unsuitable roosts. We conclude that information transfer about roosts has two functions: (i) it generates communal knowledge of a large set of roosts; and (ii) it aids avoidance of colony fission during roost switching. Both functions seem important in Bechstein's bats, in which colonies depend on many day roosts and where colony members live together for many years

Host and parasite life history interplay to yield divergent population genetic structures in two ectoparasites living on the same bat species

Host–parasite interactions are ubiquitous in nature. However, how parasite population genetic structure is shaped by the interaction between host and parasite life history remains understudied. Studies comparing multiple parasites infecting a single host can be used to investigate how different parasite life history traits interplay with host behaviour and life history. In this study, we used 10 newly developed microsatellite loci to investigate the genetic structure of a parasitic bat fly (Basilia nana). Its host, the Bechstein’s bat (Myotis bechsteinii), has a social system and roosting behaviour that restrict opportunities for parasite transmission. We compared fly genetic structure to that of the host and another parasite, the wing-mite, Spinturnix bechsteini. We found little spatial or temporal genetic structure in B. nana, suggesting a large, stable popula- tion with frequent genetic exchange between fly populations from different bat colo- nies. This contrasts sharply with the genetic structure of the wing-mite, which is highly substructured between the same bat colonies as well as temporally unstable. Our results suggest that although host and parasite life history interact to yield similar transmission patterns in both parasite species, the level of gene flow and eventual spa- tiotemporal genetic stability is differentially affected. This can be explained by the dif- ferences in generation time and winter survival between the flies and wing-mites. Our study thus exemplifies that the population genetic structure of parasites on a single host can vary strongly as a result of how their individual life history characteristics interact with host behaviour and life history traits