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(Find abstracts below.)
Robert L. Robbins & E. Kim McCreery 2003. African wild dog pup vocalizations
with special reference to Morton's model. Behaviour 140 (3): 333-351.
Karen L. Bayly & Christopher S. Evans 2003. Dynamic changes in alarm call
structure: a strategy for reducing conspicuousness to avian predators?
Behaviour 140 (3): 353-369.
Sonja Wolters & Klaus Zuberbühler 2003. Mixed-species associations of Diana
and Campbell's monkeys: the costs and benefits of a forest phenomenon.
Behaviour 140 (3): 371-385.
Robert J. Thomas, Innes C. Cuthill, Arthur R. Goldsmith, Delia F. Cosgrove,
Helena C. Lidgate & Selene L. Burdett Proctor 2003. The trade-off between
singing and mass gain in a daytime-singing bird, the European robin.
Behaviour 140 (3): 387-404.
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Abstracts
Robert L. Robbins & E. Kim McCreery 2003. African wild dog pup vocalizations
with special reference to Morton's model. Behaviour 140 (3): 333-351.
African wild dog (Lycaon pictus) pup vocalizations were studied in Hwange
National Park, Zimbabwe for weeks 3 through 7 of the socialization period.
Here we present the vocal repertoire, including the use of repetitive and
mixed sounds, and investigate the extent to which the emerging sound system
of Lycaon conforms to predicted design features of Morton's (MS)
motivation-structural rules. Features of the pup sound system are
highlighted by comparison with adults and other social canids.
Data were collected at three den sites (litter sizes: 8, 8, and 9) of two
study packs. A total of 1903 vocalizations were classified, and eight vocal
classes and seven subclasses were identified. Although all sounds identified
persist into adulthood, observations indicate a delayed onset in some vocal
classes, including both the lowest (i.e. rumbles) and highest (i.e.
twitters) frequency sounds. As predicted by the (MS) model, pups invested
heavily in high frequency, harmonic care/social soliciting sounds (91%, N =
1586 unmixed vocalizations), however, no clear association between acoustic
structure and sound repetition was found. Significantly more repetition was
heard in all vocal classes with the exception of moans and barks. Intra-pack
aggression is generally muted in this obligate social carnivore suggesting
that repetition may be a low cost strategy to induce social outcomes and
obtain food. The patterning of mixed vocalizations (N = 317) was consistent
with the (MS) model. Given the high degree of cooperation necessary for
individual survival, the predominant use of cross-mixed sounds may serve to
minimize conflict as pups begin to form relationships with littermates and
adults. Noisy/noisy sounds were exceptionally rare. Comparative data suggest
a relationship between the early patterning of mixed sounds and
species-specific social organization in canids.
Karen L. Bayly & Christopher S. Evans 2003. Dynamic changes in alarm call
structure: a strategy for reducing conspicuousness to avian predators?
Behaviour 140 (3): 353-369.
The design of many animal signals reflects the need to maximize signal
efficacy while minimizing conspicuousness to eavesdroppers. The aerial alarm
calls of birds have been a useful model system for exploring such
evolutionary tradeoffs at the level of general call structure, but much less
is known about changes in fine-scale signal characteristics over the course
of an encounter with a potential predator. We analyzed variation in the
alarm calls that male fowl, Gallus gallus, produced in response to raptor
silhouettes moving overhead. Spectrogram cross-correlation was used to test
for changes in structure over the course of a call bout. This analysis
revealed that aerial alarm calls are individually distinctive and that they
vary significantly from the first call to the second. We then measured
single acoustic parameters, including the duration, dominant frequency and
frequency bandwidth of each component in successive calls. Males almost
invariably began the first call in a bout with a high amplitude broad-band
pulse, which was followed by a much longer and highly variable sustained
element. They then selectively reduced or eliminated the introductory pulse,
while leaving other aspects of alarm structure unchanged. Recent work has
shown that the introductory pulse is potentially costly because it has
attributes that are readily localized by raptors. We suggest that male fowl
have adaptive plasticity in alarm call structure, allowing them to manage
short-term predation risk while continuing to signal to companions.
Sonja Wolters & Klaus Zuberbühler 2003. Mixed-species associations of Diana
and Campbell's monkeys: the costs and benefits of a forest phenomenon.
Behaviour 140 (3): 371-385.
One of the most striking behavioural patterns of many forest primates
concerns their tendency to live in semi-permanent mixed-species groups.
Functional investigations have ascertained that individuals obtain some
antipredator benefits without paying the costs of intra-species resource
competition. Despite these advances, very little is known about the subtle
mechanisms that keep mixed species groups together on a daily basis. Our
results showed that in the Diana-Campbell's monkey association both species
benefited from each other in diverse and idiosyncratic ways. In the presence
of Campbell's monkeys the conspicuous Diana monkeys were more likely to
descend into the lower forest strata, increased their foraging behaviour,
and individuals became less vigilant. The cryptic Campbell's monkeys, in
turn, were able to use the higher forest strata and exposed areas more
often, spread out over larger areas, were more likely to travel, and engaged
in more conspicuous vocal behaviour when associated with Diana monkeys.
These data suggested that both species benefited from each other in ways
that went beyond passive group-size related antipredator benefits, such as a
dilution effect and increased chances of predator detection. Instead, the
increased safety of the mixed species group allowed individuals to exploit
their ecological niche more broadly, to forage more efficiently, and to
engage in more social behaviour, suggesting that the benefits of mixed
species groups are much more varied and diverse than currently thought.
Robert J. Thomas, Innes C. Cuthill, Arthur R. Goldsmith, Delia F. Cosgrove,
Helena C. Lidgate & Selene L. Burdett Proctor 2003. The trade-off between
singing and mass gain in a daytime-singing bird, the European robin.
Behaviour 140 (3): 387-404.
The functions of bird song are well described, but empirical studies
examining the costs of singing are scarce. Two potential costs are a
metabolic cost of singing, and lost feeding opportunities, but such
energetic costs will only be biologically important if they have a
significant effect on the bird's body reserves. Overnight loss of reserves
has previously been found to increase with increasing song rates in
nocturnally singing common nightingales Luscinia megarhynchos. However, it
is not clear how such costs compare with those incurred by daytime-singing
birds, which may forfeit foraging opportunities when they sing. In this
paper we investigated the effect of variation in song rate on the body
reserves of a typical daytimesinging bird, the European robin Erithacus
rubecula, singing at different rates in three different circumstances: (i)
Natural variation in song rate of free-living robins. (ii) Manipulations of
the song rate of free-living robins using playbacks of conspecific song.
(iii) Manipulations of the song rate of aviary-housed robins using playbacks
of conspecific song. In all three parts of our study, birds gained less mass
when they sang more. Our analyses suggested that this might have been due
primarily to a reduction in food intake rate, rather than to the metabolic
cost of the singing itself or a concurrent increase in locomotor costs.
These results together demonstrate that the costs of singing, as measured by
their overall net effects on body reserves, can have a significant impact on
the energetic state of daytime-singing birds.
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Frank Veit
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