Hello Bioacoustics-l,
Here are the bioacoustics articles in the recent issues of Journal of
Mammalogy. As usual, the articles can be downloaded from my web site at
http://www.uvm.edu/~bmitchel/Bioacoustics.html.
Murray, K. L. and T. H. Fleming. 2008. Social structure and mating
system of the buffy flower bat, Erophylla sezekorni (Chiroptera,
Phyllostomidae). Journal of Mammalogy 89(6):1391-1400.
Abstract: Polygyny and promiscuity are the 2 most common mammalian
mating systems, whereas monogamy and lek mating are rare. Mammalian
mating systems are thought to be influenced by the amount of paternal
investment required, defensibility of females, and the stability and
size of female groups. With some notable exceptions, male bats typically
make no paternal investment and, because of high mobility and broad
foraging areas of females, ranges of females often are not defensible.
Thus, we would expect most bats to be polygynous or promiscuous;
however, mating systems of only about 6% of bat species have been
studied. Mating systems of leaf-nosed bats in the family Phyllostomidae
have not been well studied, and no species in subfamilies Glossophaginae
and Phyllonycterinae, a major radiation of nectar-feeding phyllostomids,
have been studied. The buffy flower bat (Erophylla sezekorni) is a
phyllonycterine bat endemic to islands of the Greater Antilles. We
describe the social structure and mating system of E. sezekorni on
Exuma, Bahamas, using capture data, roost observations, and paternity
analysis. E. sezekorni roosts in multimale–multifemale groups and female
groups are large (50–350 bats) and labile. Males of E. sezekorni
aggregate at display areas where they exhibit wing displays and hold
territories throughout the 2-month mating season. Mature males also
produce garlic-scented supraorbital secretions and ultrasonic display
calls. Paternity analysis revealed that females do not mate exclusively
with displaying males and that there is limited polygyny and
reproductive skew. We also found sexual dimorphism in body mass and
condition, with males being both heavier and in better condition than
females. Based on large female group size, female group lability, and
existence of male mating territories, we hypothesize that E. sezekorni
employs a form of promiscuous mating system. More data about female
mating behavior are required to test this hypothesis.
Voigt, C. C., O. Behr, B. Caspers, O. von Helversen, M. Knornschild, F.
Mayer, and M. Nagy. 2008. Songs, scents, and senses: Sexual selection in
the greater sac-winged bat, Saccopteryx bilineata. Journal of Mammalogy
89(6):1401-1410.
Abstract: Like many other mammals, Saccopteryx bilineata exhibits a
polygynous mating system, in which each male defends a group of females
called a harem. Colonies consist of several harems, and nonharem males
roost adjacent to harems. Unlike most other mammals, females disperse
from their natal colony and most juvenile males remain in it. Thus,
colonies consist of patrilines, which promotes intense local mate
competition. Females are in estrus during a few weeks at the end of the
rainy season. Mating is most likely initiated by females and preceded by
intense courtship displays of males. Forty percent of colony males do
not sire any offspring during their tenure in the colony, whereas a few
males can sire up to 6 offspring in a single year. Males use olfactory,
visual, and acoustic signals for courtship, and they demonstrate
territory ownership by scent marks, lowfrequency calls, and visual
displays. Harem males sire on average more offspring than do nonharem
males but produce only 30% of the offspring within their own harem
territory, with 70% being sired by other harem males or nonharem males.
Reproductive success of males increases with decreasing size,
fluctuating asymmetry, and fundamental frequency of territorial calls.
In addition, females that are closely related to the harem holder are
more likely to mate with other males than with the harem holder. Sexual
selection in S. bilineata is most likely influenced by intense local
mate competition caused by scarce roosts and the patrilineal
organization of colonies.
Esser, D., S. Schehka, and E. Zimmerman. 2008. Species-specificity in
communication calls of tree shrews (Tupaia: Scandentia). Journal of
Mammalogy 89(6)1456-1463.
Abstract: Tree shrews are small mammals living in the tropical forest of
Southeast Asia. The habitus of species within the genus Tupaia is often
quite similar, so that it is difficult to differentiate the species
based on their morphology. We applied comparative bioacoustics, a tool
successfully used to discriminate cryptic species of nocturnal mammals,
to investigate whether species in the diurnal genus Tupaia can be
recognized noninvasively on the basis of a conspicuous loud call, the
chatter. We studied to what extent the chatter call of 2 tree shrew
species, Tupaia glis and T. belangeri, differed in acoustic structure.
We also acoustically analyzed the chatter call of T. chinensis, a
subspecies or closely related parapatric species of T. belangeri.
Analyzed acoustic features allowed assigning chatter calls with a
probability of more than 73% to the species that produced them.
Bioacoustical differences are in line with subtle morphological
differences, supporting species status for all 3 studied tree shrew
species and corroborating immunodiffusion and genetic data that
differentiate T. glis and T. belangeri. Loud calls may offer a reliable
noninvasive tool for species diagnosis and discrimination in cryptic
species of this diurnal mammalian group.
Matrosova, V. A., I. A. Volodin, and E. V. Volodina. 2009. Short-term
and long-term individuality in speckled ground squirrel alarm calls.
Journal of Mammalogy 90(1):158-166.
Abstract: Apart from the alerting function of alarm calls, selection may
favor cues that help individuals to distinguish between reliable and
unreliable callers. However, this mechanism for selective response to
real and false alarms may act only if the individual characteristics of
the call are stable at least for some time. Here we test this implicit
assumption for the caller’s reliability hypothesis, studying
individuality of alarm calls in a colony of free-living, individually
marked speckled ground squirrels (Spermophilus suslicus). We recorded
each of 20 study animals 4 times during repeated captures when calling
from a live trap toward a human, with spans of 1 day, 2 weeks, and 1
year from the 1st capture. Ten alarm call notes per animal per capture
were analyzed. Individual alarm call notes showed high similarity within
captures but differed strongly between captures. Both multivariate
analysis of variance and discriminant function analysis showed that
vocal individuality decreased rapidly with an increase of the time span
between recordings. However, vocal individuality always remained higher
than expected random value. Examination of our data suggests that alarm
calls are unstable, which contradicts the caller reliability hypothesis,
because its implicit assumption of stable individual identity is not
fulfilled. However, short-term stability still may be sufficient to
ensure short-term individual recognition between kin and neighbors.
Also, even if the alarm calls change structurally, because group members
meet up daily, they can update their knowledge of the call structure of
individuals, and this would likely allow them to distinguish between
reliable and unreliable individuals.
Grilliot, M. E., S. C. Burnett, and M. T. Mendonca. 2009. Sexual
dimorphism in big brown bat (Eptesicus fuscus) ultrasonic vocalizations
is context dependent. Journal of Mammalogy 90(1):203-209.
Abstract: Although bats are well known for their use of ultrasound for
echolocation, there is limited evidence for its use in a social context.
We tested whether ultrasonic vocalizations in bats were contextually
(roosting or flying) sexually dimorphic. During the reproductive season,
we recorded ultrasonic signals of captive adult male and female big
brown bats while the bats were flying on tether lines in the field, and
compared these signals to ultrasonic vocalizations made while roosting
in an anechoic chamber. Principal component analysis reduced 7
ultrasonic call descriptors to 2 components that related to frequency
(PC1) and time or shape (PC2). While bats were roosting, ultrasonic call
components related to time or shape and frequency were both sexually
dimorphic, being increased in males in each instance. However, when bats
were recorded while flying, these same call components were no longer
sexually dimorphic. This finding suggests that bats are changing their
ultrasonic calls in relation to functional context, making them
monomorphic and utilitarian for activities such as foraging and
navigation, but dimorphic in a situation when mating activity is likely.
