The reproductive cycle and determination of sexual maturity in male brown long‐eared bats, Plecotus auritus (Chiroptera: Vespertilionidae)

Abstract

Observations of the external morphology of wild-caught and captive male brown long-eared bats (Plecotus auritus) revealed a marked seasonal pattern of spermatogenesis, similar to that established by histological examination of other temperate-zone vespertilionids, with a peak in testes size in August and a lag between testicular growth and epididymal distension. This was followed by complete cessation of spermatogenesis and shrinkage of the testes to prepubertal size. The period of peak spermatogenesis coincided with a reduction in the incidence of torpor and also a decline in body mass. This suggests that torpor and spermatogenesis may be incompatible in this species. Outside the season of testicular growth and epididymal distension, sexual maturity could not be con®dently determined in P. auritus by the pigmentation of the tunica vaginalis surrounding the epididymis, a characteristic which has become established in other species. Instead, the size and shape of the caudae epididymides appeared to be a better criterion for de®ning sexual maturity in this species. Most males underwent testicular growth and epididymal distension, and were assumed to have reached sexual maturity, at an age of 15 months. However, some individuals (29%), particularly those in good condition (relatively heavy individuals), showed a degree of testicular and epididymal development in their ®rst autumn, i.e. at 3 months of age, indicating that the onset of puberty may be dependent on body condition. Poor body condition was associated with delayed spermatogenesis in adult males.

The role of swarming sites for maintaining gene flow in the brown long-eared bat (Plecotus auritus)

“…In Lennebergwald, female philopatry is strong, and is comparable to that found in Scottish populations (Entwistle et al, 1998). The maximum distance between two colonies of Lennebergwald was only 2250 m, a distance well within the range of foraging female brown long-eared bats (Entwistle et al, 1996).…”

“…They assumed that, as in most other European bat species, males and females mate during the autumn and winter. Although brown long-eared bats usually roost singly in winter, this mating schedule is supported by the fact that spermatogenesis is completed around the end of August followed by a gradual shrinkage of caudae epididymides, in which sperm can be stored throughout hibernation (Entwistle et al, 1998). In addition, the number of inseminated females steadily increases during the winter (Strelkov, 1962).…”

“…Age was classified into two categories: juveniles (pre-reproductive individuals with unfused phalangeal epiphyses) and adults (reproductive individuals with fused epiphyses and brown pelage colour) (Racey, 1974;Entwistle et al, 1998).…”

“…However, genetically detected panmixia in Scottish P. auritus populations is in contrast with direct observation. Adults of both sexes show high fidelity to the roost at which they were captured first, with less than 1% of recaptured bats having moved among colonies (Entwistle et al, 1998(Entwistle et al, , 2000pers.obs.). Since the range of P. auritus during foraging is high (2.8 km in Scotland and 3.3 km in Germany; Fuhrmann and Seitz, 1992;Entwistle et al, 1996), roost philopatry and social cohesion must prevent individuals from joining new colonies.…”

Activity pattern and fat accumulation strategy of the Natterer’s bat (Vespertilionidae, Chiroptera) swarming population indicate the exact time of male mating effort

“…In M. daubentonii, the lowest body mass of adult males in swarming season overlaps with the swarming activity peak of adult females as well (Encarnação et al 2004;Šuba et al 2008;Rughetti and Toffoli 2014). Similarly, the short period of lowering the body mass of males of Plecotus auritus in autumn was interpreted as their mating effort (Entwistle et al 1998). The compilation of results of studies relating to the swarming populations of M. daubentonii and M. mystacinus or Myotis brandtii indicates that adult males of these species seem to spend on foraging only the nights with low proportion of adult females (Piksa 2008;Šuba et al 2008.…”