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Electronic Supplementary Material
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Environmental transmission of a personality trait: Foster parent exploration behaviour
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predicts offspring exploration behaviour in zebra finches
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Wiebke Schuett1,2, Sasha R. X. Dall1, Alastair J. Wilson1and Nick J. Royle1*
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TR109EZ, UK
Centre for Ecology and Conservation, University of Exeter, Cornwall Campus, Penryn,
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20146 Hamburg, Germany
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*author
Zoological Institute and Museum, University of Hamburg, Martin-Luther-King Platz 3,
for correspondence (N.J.Royle@exeter.ac.uk)
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Data associated with this paper have been deposited in Dryad (doi:10.5061/dryad.tf767)
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ADDITIONAL MATERIALS AND METHODS
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Zebra finches were maintained indoors on a 14.5:9.5 h full light:dark photoperiod under controlled conditions. They were
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kept in double-breeder cages (120 x 45 cm x 40 cm) in single-sex groups prior and post breeding and in pairs during
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breeding. Water and commercial seed mixture were available ad libitum and breeding pairs had access to nest-boxes and nest
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material. Size (wing length ±1 mm, head-bill length, HB, and tarsus length ±0.1 mm) and personality (exploratory tendency)
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of adults were assessed prior to breeding. Subsequently, males and females (>1 year old) were paired up at random in relation
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to their personality and were allowed to breed. We cross-fostered clutches just prior to hatching with clutches of similar age.
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Generally whole clutches were cross-fostered but because of simultaneous brood size manipulation (see below) this was not
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always possible. This meant some foster clutches consisted of chicks from more than one genetic clutch and individuals from
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one genetic clutch were not always all raised by the same foster parents (for details see below). When foster chicks were 3d
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old, we manipulated the rearing regime (as part of another experiment; for rationale see [1]): the foster father was removed in
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some breeding cages until the offspring reached independence (uniparental regime). In the remaining cages both parents
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raised their foster chicks together (biparental regime). Brood sizes were manipulated to two (uni-, biparental) or four to seven
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chicks (biparental care). When offspring reached independence at 35d, they were removed and housed in sibling groups
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before being transferred into single-sex peer groups at 65d. At adulthood, offspring were measured (HB, tarsus, wing; ca. 80d
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of age) and were tested for their exploratory tendency (ca. 90d of age). We assessed individual exploratory tendency of
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offspring and parents with novel environment tests. Tests were conducted indoors in two cages (120 cm x 20 cm and 38 cm
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high) that contained 10 features each and that were arranged as mirror images of each other. Each individual was tested twice
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for its exploration, once in each of the novel environments, with subsequent tests being one week apart. At the beginning of a
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trial, a bird was transferred into a box in the novel environment that was then opened remotely. We recorded how many
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features an individual visited during 5 min trials.
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We conducted the experiment in 2007 and repeated it in 2008, using only offspring from the first breeding round in 2007 as
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the new parental generation. The parental generation in 2007 had been raised by their genetic parents, contrary to the parental
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generation in 2008. 159 offspring were produced (N = 107 in 2007, N = 52 in 2008) of which 154 reached adulthood. We had
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a total of 51 genetic clutches (N = 31 in 2007, N = 20 in 2008; 102 genetic parents) and 53 foster clutches (N = 31 in 2007, N
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= 22 in 2008; N = 15 uniparental, N = 38 biparental treatment; 106 foster parents) in the experiment. Individuals from a
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genetic clutch were raised by one (N = 17 in 2007, N = 15 in 2008), two (N = 10 in 2007, N = 4 in 2008), three (N = 3 in
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2007, N = 1 in 2008) or four (N = 1 in 2007) foster pairs. Foster pairs obtained chicks from one (N = 16 in 2007, N = 19 in
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2008), two (N = 11 in 2007, N = 2 in 2008) or three (N = 4 in 2007, N = 1 in 2008) different genetic clutches. Of all clutches,
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data of 47 (HB) and 48 (exploratory behaviour), clutches respectively, were analysed in the mid-parent-mid-offspring
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regressions. The experiment was approved by the Ethical Committee of the University of Exeter.
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A risk of inflation/deflation of non-genetic and genetic behavioural transmission, due to (dis-)assortative mating was not
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present (cf. [2]) since pairs were not (dis-)assortatively mated for size or exploration (Pearson correlations; HB: R = -0.055, p
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= 0.706; tarsus: R = -0.173, p = 0.228; wing: R = -0.172, p = 0.233; mean of square rooted number of features visited: R =
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0.011, p = 0.940; N = 50 pairs).
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ADDITIONAL RESULTS
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Table S1. Parameter estimates from animal model analyses of tarsus and wing length. Statistical
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inference was based on conditional F-statistics for fixed effects and likelihood ratio tests for random
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effects (see main manuscript for details). Significant p-values in bold.
χ²
Response Explanatory
Effect
Estimate (SE)
Tarsus
Additive genetic
Permanent
environment
0.122 (0.044)
0.391 (0.121)
14.68
<0.0001
0.056 (0.042)
0.181 (0.139)
1.54
0.215
0.000 (-)
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1
Random effects
Foster environment
Fixed effects
Mean
Year (effect of 2008)ª
Status at test
Wing
Random effects
Fixed effects
(juv.)b
0.000
(-)c
Prop. of VP (SE) (DF=1)
F(DF)
p
14.3 (0.065)
644869 (1,45)
<0.001
-0.394 (0.070)
32.25 (1,21.8)
<0.001
-0.240 (0.060)
16.12 (1,172)
<0.001
Additive genetic
Permanent
environment
1.74 (0.534)
0.597 (0.125)
15.67
<0.001
0.183 (0.398)
0.063 (0.139)
0.166
0.684
Foster environment
0.055 (0.185)
0.019 (0.064)
0.086
0.769
Mean
Year (effect of 2008)ª
Status at test
(juv.)b
60.3 (0.204)
99597 (1,48.4)
<0.001
-0.412 (0.197)
4.36 (1,138.8)
0.040
-1.43 (0.164)
75.73 (1,109.7)
<0.001
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Prop. of VP, proportion of total variance explained; Status at test, age at personality test (factor with
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two levels: offspring (juv.) tested at ca. 90d of age, parents tested at >1 year of age); ªeffect of being
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tested in 2008 relative to the mean of being tested in 2007 (Mean); beffect of being tested at an age of
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ca. 90d relative to the mean of being tested at an age >1year (Mean); cparameter estimate bound at
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zero, therefore no SE estimated.
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Table S2. Test statistics from a mixed model with normal errors and individual exploration scores as
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response (N = 154 offspring measured at adulthood, in the year they were born) and foster and genetic
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clutch ID as random terms. Exploration scores were the square root of the number of features visited
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by an individual in a novel environment test, and averaged within individuals across the two trials
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(mean √(feat)). The mixed model was stepwise simplified using likelihood ratio tests. Test statistics
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stem from the time a non-significant variable dropped out of a model. Qualitatively the same results
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were obtained when using non-transformed parental behavioural data (not shown). Significant p-value
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in bold. Fost., foster.
Explanatory variable
Mean √(feat. fost. mother) *ͨ mean √(feat. fost. father) *ͨ care regime
Mean √(feat. fost. mother) *ͨ mean √(feat. fost. father) * offspring sex
Mean √(feat. fost. mother) *ͨ mean √(feat. fost. father) * year
Mean √(feat. fost. mother) *ͨ mean √(feat. fost. father)
Mean √(feat. fost. mother) * care regime
Mean √(feat. fost. father) * care regime
Mean √(feat. fost. mother)* offspring sex
Mean √(feat. fost. father) * offspring sex
Mean √(feat. fost. mother) * year
Mean √(feat. fost. father) * year
Mean √(feat. fost. mother)
Mean √(feat. fost. father)
Care regime
Offspring sex
Year
Manipulated foster brood size
Hatching position
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0.70
0.24
0.27
0.30
0.72
0.18
0.13
0.04
0.35
0.61
39.34
1.32
0.41
1.43
3.69
<0.01
1.12
p
0.401
0.625
0.605
0.587
0.397
0.671
0.716
0.833
0.552
0.433
<0.0001
0.251
0.522
0.232
0.055
0.986
0.291
ADDITIONAL REFERENCES
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χ2 (DF=1)
Schuett, W., Dall, S. R. X. & Royle, N. J. 2011 Pairs of zebra finches with similar
'personalities' make better parents. Anim. Behav. 81, 609-618.
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Lynch, M. & Walsh, B. 1998 Genetics and Analysis of Quantitative Traits. Sunderland:
Sinauer Associates.