Abstract : Males of the
sac-winged bat, Saccopteryx bilineata,
actively fill their propatagial sacs with
secretions from the genital region, the gular
gland, urine and saliva. From our observations
and those of Starck we deduce that propatagial
sacs in S. bilineata do not have a glandular
function, but are instead organs for the storage
and display of odours.
In addition to the already known "salting"
and hovering behaviour of male S. bilineata, we
describe in detail how odour is fanned to
roosting individuals during the complex,
stereotypic hovering displays. S. bilineata
males also coat the fur of their backs with
saliva using the wing tip and might scent-mark
"Yawning" may represent a visual as
well as an olfactory cue. Odour seems to play an
important role in the social communication of S.
bilineata and in other emballonurids, as
revealed by the broad distribution of wing sacs
in this family. S. bilineata males display odour
during energetically costly hovering flights in
front of females. We demonstrate that the number
of hovering displays increases with harem size.
The mating effort of S. bilineata males
comprises a multimodal signalling behaviour.
ALThough males defend harem territories in which
females gather, females seem to be able to
choose the father of their progeny freely among
the males of a colony. This may have led to the
evolution of the complex mating displays by male
S. bilineata. [....]
"Yawning" : Male Saccopteryx often
"yawn" after or before agonistic
interactions with other individuals. First
they lowered their head and opened their mouth
slowly, then both lips were lifted and turned up
so that both rows of white teeth and the moist
pale gum were exposed.