Sylvain Alem, Klemen Koselj, Björn M. Siemers & Michael D. Greenfield
(2011): Bat predation and the evolution of leks in acoustic moths. Behav.
Ecol. Sociobiol. 65 (11), 2105-2116.
Abstract: Theories of lek evolution generally invoke enhanced mating success
experienced by males signalling in aggregations. Reduced predation has also
been acknowledged as a potential factor driving lek formation, but its role
is more ambiguous. Although lekking is a complex behaviour, few empirical
studies have investigated the role of both claims. We studied the potential
pressures imposed by mating success and predation in an acoustic moth,
Achroia grisella, in which males gather in leks and broadcast a calling song
attractive to females. We exploited the ability to manipulate the
distribution of singing males in laboratory arenas to create different-sized
leks and tested female preferences for these aggregations. Because A.
grisella are vulnerable to predation by bats while in flight and on the
substrate, we also tested the responses of a potential predator, Rhinolophus
ferrumequinum, a bat species that feeds on moths, to the experimental leks.
We found that the per capita attractiveness of A. grisella males to females
rose with increasing lek size. R. ferrumequinum also oriented toward
experimental A. grisella leks, but this attraction did not increase at
larger leks. Thus, a male?s per capita exposure to predation risk declined
as more moths joined the lek. A. grisella males appear to benefit from
advertising in larger leks in terms of both increased mate attraction and
reduced predation risk. Our results support the idea that multiple factors
operating simultaneously may maintain lekking behaviour.
For reprints please contact S. Alem (email:
Janet M. Lapierre, Daniel J. Mennill & Elizabeth A. MacDougall-Shackleton
(2011): Spatial and age-related variation in use of locally common song
elements in dawn singing of song sparrows Melospiza melodia: old males sing
the hits. Behav. Ecol. Sociobiol. 65 (11), 2149-2160.
Abstract: In many songbirds, individuals have repertoires of multiple song
types, some of which may be shared with others in the local area. Hypotheses
about the evolution of song repertoires differ as to whether selection acts
primarily on repertoire size itself or the ability to match songs of
neighbours. We used a 16-channel acoustic location system to record
neighbourhoods of song sparrows (Melospiza melodia melodia) during the dawn
chorus. We asked whether males sing all songs with similar frequency as
predicted by the Repertoire Size Hypothesis, whether males preferentially
sing highly shared songs as predicted by the General Sharing Hypothesis, or
whether use of highly shared songs is associated with phenotype as predicted
by the Conditional Sharing Hypothesis. Contrary to the Repertoire Size
Hypothesis, most males did not sing all songs equally often. Contrary to the
General Sharing Hypothesis, we found no general tendency to overproduce
highly shared songs. The degree to which males overproduced highly shared
songs was repeatable across days, indicating consistent individual
differences, and varied across neighbourhoods. Moreover, and consistent with
the Conditional Sharing Hypothesis, older males were more likely to
overproduce highly shared songs. If highly shared song is a conventional
signal of aggression, with the threat of receiver retaliation maintaining
honesty, older males may be more willing or able to risk conflict.
Alternatively, males may learn which songs are effective signals for an
area. Finally, age-related variation in vocal performance may shape the
adaptive value of highly shared song.
For reprints please contact Elizabeth A. MacDougall-Shackleton (email:
Simon W. Townsend, Markus Zöttl & Marta B. Manser (2011): All clear?
Meerkats attend to contextual information in close calls to coordinate
vigilance. Behav. Ecol. Sociobiol. 65 (10), 1927-1934.
Abstract: Socio-demographic factors, such as group size and their effect on
predation vulnerability, have, in addition to intrinsic factors, dominated
as explanations when attempting to understand animal vigilance behaviour. It
is generally assumed that animals evaluate these external factors visually;
however, many socially foraging species adopt a foraging technique that
directly compromises the visual system. In these instances, such species may
instead rely more on the acoustical medium to assess their relative risk and
guide their subsequent anti-predator behaviour. We addressed this question
in the socially foraging meerkat (Suricata suricatta). Meerkats forage with
their head down, but at the same time frequently produce close calls
(?Foraging? close calls). Close calls are also produced just after an
individual has briefly scanned the surrounding environment for predators
(?Guarding? close calls). Here, we firstly show that these Guarding and
Foraging close call variants are in fact acoustically distinct and secondly
subjects are less vigilant (in terms of frequency and time) when exposed to
Guarding close call playbacks than when they hear Foraging close calls. We
argue that this is the first evidence for socially foraging animals using
the information encoded within calls, the main adaptive function of which is
unrelated to immediate predator encounters, to coordinate their vigilance
behaviour. In addition, these results provide new insights into the
potential cognitive mechanisms underlying anti-predator behaviour and
suggest meerkats may be capable of signalling to group members the ?absence?
of predatory threat. If we are to fully understand the complexities
underlying the coordination of animal anti-predator behaviour, we encourage
future studies to take these additional auditory and cognitive dimensions
For reprints please contact S. W. Townsend (email:
Michael S. Reichert (2011): Effects of multiple-speaker playbacks on
aggressive calling behavior in the treefrog Dendropsophus ebraccatus. Ecol.
Behav. Sociobiol. 65 (9), 1739-1751.
Abstract: In addition to producing signals, males of chorusing species also
act as receivers by adjusting properties of their vocalizations in response
to those of other nearby individuals. Although it is likely that males are
responsive to more than one other individual, most playback studies
investigating male response have involved dyads in which vocal responses are
measured to stimuli presented from a single speaker. In this study, I
explored changes in both the propensity to give aggressive calls and the
temporal properties of those calls in response to the playback of multiple
aggressive call stimuli in the treefrog Dendropsophus ebraccatus. I found
that males were sensitive to both the number of simulated aggressive callers
and their specific call characteristics. Males generally gave a highly
aggressive response to the first stimulus presented, but their response to
the modification of this stimulus by the addition or subtraction of a
simulated competitor depended on the degree of aggressiveness of the
stimuli. Males tended to decrease their aggressive responses when either a
more aggressive call was silenced or a less aggressive call was added and to
increase their aggressive responses in the opposite situation. Aggressive
calling in this species is clearly affected by complex changes in the social
environment and I suggest that future studies explore these issues in other
species to improve the understanding of communication interactions.
For reprints please contact Michael Reichert (email:
Kensuke Okada, William R. Pitchers, Manmohan D. Sharma, John Hunt & David J.
Hosken (2011): Longevity, calling effort, and metabolic rate in two
populations of cricket. Behav. Ecol. Sociobiol. 65 (9), 1773-1778.
Abstract: Intraspecific variation in a resting metabolic rate (RMR) is
likely to be an important determinant of energetic-resource use and may
influence the resources subsequently available for allocation to traits not
directly associated with somatic maintenance. The influence of RMR on
resource availability could be especially important for condition-dependent
sexual traits, such as cricket calls, that are themselves energetically
costly to produce. RMR may also be associated with longevity, either
negatively because individuals with a high RMR burn resources faster and die
young, or positively as individuals with high RMR are more able to accrue
resources to fuel survival. Additionally, the associations between RMR and
other characters may vary across populations if differential selection or
drift shapes these traits. Here we tested for differences in RMR, body mass,
calling effort, and longevity in two populations of cricket Gryllodes
sigillatus and then evaluated the potential influence of RMR on calling and
longevity. We find that RMR, calling effort, and longevity varied across
populations, but mass did not. Controlling for population and mass, RMR was
not significantly associated with calling effort, but was negatively
associated with longevity. These findings suggest that male crickets that
live fast die young.
For reprints please contact D. J. Hosken (email:
Dr. Sonja Amoser