Franks VR, Marshall RC,
(2012) Animal Behaviour, doi:
10.1016/j.anbehav.2012.10.013
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"Mechanisms
and extent of information transfer in socially foraging
guppies Poecilia reticulata"
Many species in social groups
make use of readily available, socially provided information
for behaviours including predator avoidance, mate choice and
foraging. Not only are actions imitated, but they may also
be reapplied in variable future situations, suggesting an
explicit knowledge of the purpose of the behaviours. Social
learning thus enables animals to learn about their complex
environments rapidly and efficiently, aiding survival.
However, little is known of the processes underlying
information transmission and the complexity of information
that can be exchanged. We used shoals of guppies to
investigate how animals decide which individual to copy, and
the extent of information that can be transferred. Naďve
guppies followed the first fish to move. However, although
the speed and accuracy of foraging increased significantly
during training, the first fish to move was not always the
trained (knowledgeable) guppy. No significant difference was
found between the number of guppies entering areas of
varying food quality, supporting the hypothesis that these
fish learn foraging locations by following and suggesting
that leaders forage without considering the reduced personal
reward arising from sharing a low-quality patch with
followers. Animals that learn by copying thus appear limited
in the amount of information they can receive, highlighting
a selection pressure for more extensive means of
transmitting information in complex environments.
Mockford EJ, Marshall RC,
Dabelsteen T, (2011)
PLoS ONE, 6(12): e28242, doi:
10.1371/journal.pone.0028242
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"Degradation
of Rural and Urban Great Tit Song: Testing Transmission
Efficiency"
Acoustic signals
play a fundamental role in avian territory defence and mate
attraction. Several studies have now shown that spectral
properties of bird song differ between urban and rural
environments. Previously this has been attributed to
competition for acoustic space as a result of low-frequency
noise present in cities. However, the physical structure of
urban areas may have a contributory effect. Here we
investigate the sound degradation properties of woodland and
city environments using both urban and rural great tit song.
We show that although urban surroundings caused
significantly less degradation to both songs, the
transmission efficiency of rural song compared to urban song
was significantly lower in the city. While differences
between the two songs in woodland were generally minimal,
some measures of the transmission efficiency of rural song
were significantly lower than those of urban song,
suggesting additional benefits to singing rural songs in
this setting. In an attempt to create artificial urban song,
we mimicked the increase in minimum frequency found several
times previously in urban song. However, this did not
replicate the same transmission properties as true urban
song, suggesting changes in other song characteristics, such
as temporal adjustments, are needed to further increase
transmission of an avian signal in the city. We suggest that
the structure of the acoustic environment, in addition to
the background noise, plays an important role in signal
adaptation.
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Anderholm S, Waldeck P, van der Jeugd H, Marshall RC,
Larsson K, Andersson M, (2009) Molecular Ecology, 18,
p4955-4963
doi:10.1111/j.1365-294X.2009.04397.x
"Colony kin structure and
host-parasite relatedness in the barnacle goose"
Conspecific brood parasitism
(CBP), females laying eggs in the nest of other 'host'
females of the same species, is a common alternative
reproductive tactic among birds. For hosts there are likely
costs of incubating and rearing foreign offspring, but costs
may be low in species with precocial chicks such as
waterfowl, among which CBP is common. Waterfowl show strong
female natal philopatry, and spatial relatedness among
females may influence the evolution of CBP. Here we
investigate fine-scale kin structure in a Baltic colony of
barnacle geese, Branta leucopsis,
estimating female spatial relatedness using protein
fingerprints of egg albumen, and testing the performance of
this estimator in known mother-daughter pairs. Relatedness
was significantly higher between neighbour females (nesting
≤ 40 metres from each other) than between females nesting
farther apart, but there was no further distance trend in
relatedness. This pattern may be explained by earlier
observations of females nesting close to their mother or
brood sisters, even when far from the birth nest. Hosts and
parasites were on average not more closely related than
neighbour females. In 25 of 35 sampled parasitized nests,
parasitic eggs were laid after the host female finished
laying, too late to develop and hatch. Timely parasites,
laying eggs in the host's laying sequence, had similar
relatedness to hosts as that between neighbours. Females
laying late parasitic eggs tended to be less related to the
host, but not significantly so. Our results suggest that CBP
in barnacle geese might represent different tactical
life-history responses.
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Mockford EJ, Marshall RC (2009)
Proc. R. Soc. Lond. B.
doi:10.1098/rspb.2009.0586
"Effects of
urban noise on song and response behaviour in great tits"
Acoustic communication is
fundamental in avian territory defence and mate attraction.
In urban environments where sound transmissions are more
likely to be masked by low-frequency anthropogenic noise,
acoustic adaptations may be advantageous. However, minor
modifications to a signal could affect its efficacy. While
recent research has shown that there is divergence between
songs from noisy and quiet areas, it is unknown whether
these differences affect the response to the signal by its
receivers. Here, we show that there is a difference in
spectral aspects of rural and urban song in a common
passerine, the great tit Parus major, at 20 sites across the
UK. We also provide, to our knowledge, the first
demonstration that such environmentally induced differences
in song influence the response of male territory holders.
Males from quiet territories exhibited a significantly
stronger response when hearing song from another territory
holder with low background noise than from those with high
background noise. The opposite distinction in response
intensity to homotypic versus heterotypic song was observed
in males from noisy territories. This behavioural difference
may intensify further signal divergence between urban and
rural populations and raises important questions concerning
signal evolution.
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Anderholm S,
Marshall RC,
van der Jeugd H, Waldeck P, Larsson K, Andersson M, (2009)
Animal Behaviour
doi:10.1016/j.anbehav.2009.04.011
"Nest parasitism in the barnacle goose:
evidence from protein fingerprinting and microsatellites"
Geese are often
seen as one of nature's best examples of monogamous
relationships, and many social pairs stay together for life.
However, when parents and young are screened genetically,
some chicks do not match their social parents. Although this
has often been explained as adoption of foreign young after
hatching, conspecific nest parasitism is another
possibility. We used nondestructive egg albumen sampling and
protein fingerprinting to estimate the frequency and success
of nest parasitism in a Baltic Sea population of barnacle
geese, Branta leucopsis. Among the 86 nests for which we had
the most complete information, 36% were parasitized, and 12%
of the eggs were parasitic. Almost 80% of the parasitic eggs
were laid after the host began incubation. Hatching of these
eggs was limited to the few cases where the host female
incubated longer than normally because her own eggs failed
to hatch. Conspecific nest parasitism in this population
therefore seems mainly to be an alternative reproductive
tactic of lower fitness than normal nesting. Comparison with
DNA profiling of chicks (with 10–14 microsatellites) and
other evidence confirmed the suitability of protein
fingerprinting for analysis of nest parasitism. It can often
provide more data than microsatellites, if eggs are
albumen-sampled soon after being laid, before most losses
occur.
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Nicholson JS, Buchanan
KL, Marshall RC, Catchpole CK, (2007) Animal Behaviour
74 (5) p1585-1592
doi:10.1016/j.anbehav.2007.04.006
"Song
sharing and repertoire size in the sedge warbler,
Acrocephalus schoenobaenus: changes within and between
years"
The complex song of the male
sedge warbler functions mainly in sexual attraction and the
evolution of repertoire size is driven primarily by female
choice. As male song ceases upon pairing, male-male singing
interactions are relatively brief and have not been studied
to our knowledge. This study shows that young males in their
first breeding season shared significantly more syllables
with their nearest neighbour than with their fathers or more
distant males. Moreover, daily recordings revealed that
rapid learning and modification of syllable repertoires
occurred, resulting in a progressive increase in sharing
within just a few days. This does not lead to a gradual
increase in repertoire size as some syllables are dropped
and new ones are acquired. This turnover process allows
males to share syllables with their neighbours, whilst
repertoire size, known to be important in female choice,
remains relatively constant in any one year. Individual
males were followed for several years and also showed
considerable syllable turnover between years. However, in
this case, repertoire size was found to increase between
years, the largest increase occurring between the first and
second years. We obtained a significant positive correlation
between repertoire size and age, suggesting that females
choosing males with larger repertoires may gain indirect
(genetic) benefits for their offspring, such as good genes
for viability. Whilst these results reveal a more flexible
picture of repertoire turnover than previously suspected,
the relative stability of repertoire size within a season
and the increase with age suggests that repertoire size
remains a likely target for sexual selection by female
choice.
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Marshall RC,
Buchanan KL, Catchpole CK, (2007) Animal Behaviour 73 (4)
p629-635
doi:10.1016/j.anbehav.2006.06.011
“Song &
female choice for extra-pair copulations in the sedge
warbler Acrocephalus schoenobaenus”
Although 90% of passerine birds
live in socially monogamous pair bonds, molecular studies
have revealed that genetic polygamy occurs in 86% of
surveyed passerines, because individuals engage in
copulations outside the pair bond (extrapair copulations;
EPCs). Most explanations for the occurrence of EPCs involve
female gaining indirect benefits from the extrapair male.
The sedge warbler is a socially monogamous species in which
some offspring result from EPCs (8% in this study). Complex
song is a sexually selected male trait used by females which
select mates based on a variety of male qualities. We used
microsatellite DNA profiling to detect extrapair young and
assign paternity. 'Good genes' theory predicts that females
should engage in EPCs with males of higher quality than
their social mate, with resulting fitness benefits.
Extrapair males had smaller song repertoires and smaller
territories than the social mate. This apparent preference
for small-repertoire males as extrapair mates conflicts with
the predictions from previous studies of this species.
Sudden cessation of song after pairing may mean that song
cues are unavailable for later extrapair matings and females
may switch to other cues. Such behaviour may lead to
different patterns of female choice during social and
extrapair mating in the sedge warbler. We conclude that
multiple reasons underlie patterns of female choice in this
species.
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Leitner, S.,
Marshall, R.C., Leisler, B., Catchpole, C.K., (2006)
Ethology 112 (6) p554-563
doi:10.1111/j.1439-0310.2006.01195
“Male song quality, egg size and offspring
sex in captive canaries, Serinus canaria.”
Life history
theory predicts that females should vary their investment in
offspring according to the quality of their mate. In birds,
several studies have now shown that females do vary
investment according to perceived male quality, by producing
larger eggs, investing more in parental care or by
manipulating the sex of their offspring. In a captive
breeding colony of canaries, we first show that under normal
conditions larger eggs in a clutch are more likely to hatch
male offspring. In canaries, male song functions in female
attraction and females respond more to complex structures in
male song called sexy syllables. In a series of experiments,
we go on to show first, that females exposed to playback of
male song produce larger eggs than those who heard no song.
Next, using synthetic songs, we show that females exposed to
playback of more attractive songs containing sexy syllables,
produced larger eggs than those exposed to simpler songs
containing no sexy syllables. However, in a final analysis,
we found no evidence from our experiments that females
exposed to playback of more attractive songs also produced
more male offspring.
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Marshall R.C.
Leisler B, Catchpole CK, Schwabl H (2005) J Exp Bio. 209
p4593-98, (doi: 10.1242/jeb.01949)
doi:10.1242/jeb.01949
“Male song quality affects circulating but
not yolk steroid concentration in canaries”
Male song
complexity is a sexually selected trait found in many
songbirds, including strains of the domestic canary. Studies
on several species have shown that male song can affect the
hormonal state of females and may also influence
concentrations of maternal hormones in the yolk of their
eggs. In this study, we show that the level of circulating
androgens and oestrogens of female canaries, as measured in
faeces, varies with the quality of male song to which they
are exposed. The female-perceived quality of male canary
song depends on the production of special 'sexy syllables'
to which females respond with more sexual displays. Using
playback of synthetic song we show that females hearing
songs with sexy syllables have higher levels of faecal
testosterone than control females hearing songs without
them. However, unlike previous studies on the canary, we
found no evidence that such females laid eggs with more
testosterone (or other steroids) in their egg yolks. We
discuss these results in relation to the evolution of male
signalling and maternal investment strategies.
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Marshall R.C.,
Buchanan, K.L.., Catchpole, C.K (2003) Proc. R. Soc. Lond. B.
270 pS248-250
doi:10.1098/rsbl.2003.0081
“Sexual
selection & individual genetic diversity in a songbird”
Here, we report for the first
time, to our knowledge, a strong correlation between a
measure of individual genetic diversity and song complexity,
a sexually selected male trait in sedge warblers,
Acrocephalus schoenobaenus. We also find that females prefer
to mate with males who will maximize this diversity in
individual progeny. The genetic diversity of each offspring
is further increased by means of non-random fertilization,
as we also show that the fertilizing sperm contains a
haplotype more genetically distant to that of the egg than
expected by chance. These findings suggest that species'
mating preferences may be subject to fine tuning aimed at
increasing offspring viability through increased genetic
diversity. This includes external and internal mechanisms of
selection, even within the ejaculate of a single male.
Buckland PR,
Marshall R, Watkins P,
McGuffin P, (1997) Molecular Brain Research 49 (1-2) p266-70
doi:10.1016/S0169-328X(97)00160-5
"Does phenylethylamine have a role in schizophrenia?:
LSD and PCP up-regulate aromatic L-amino acid decarboxylase
mRNA levels"
Aromatic L-amino
acid decarboxylase (AADC) is rate limiting in the production
of 2-phenylethylamine (2PE). AADC activity and 2PE serum
concentrations have been found to be increased in
schizophrenic patients. Both antipsychotic and psychotogenic
drugs, including amphetamine, affect the activity and
encoding mRNA levels of AADC. Amphetamine is an analogue of
2PE and has a similar physiological effect. We have looked
at the effects of chronic (32 day) treatment of rats with
LSD (0.12 mu g/kg/day) and phencyclidine (PCP; 10 mg/kg/day)
on AADC mRNA levels. Both drugs up-regulated AADC mRNA
levels in striatum, nucleus accumbens, hippocampus and
cerebellum by between 50% and 150%. A splicing variant of
AADC, present in human brain, which lacks the 3rd exon does
not appear to be present in rat brain. These results are
consistent with the hypothesis that over activity of AADC
leading to increased production of 2PE is involved in
endogenous psychosis such as schizophrenia.
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