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Rasmussenetal. BMC Ecol Evo (2021) 21:96
https://doi.org/10.1186/s12862-021-01816-7
RESEARCH ARTICLE
An exploratory investigation
ofglucocorticoids, personality andsurvival rates
inwild andrehabilitated hedgehogs (Erinaceus
europaeus) inDenmark
Sophie Lund Rasmussen1,2,3* , Otto Kalliokoski4 , Torben Dabelsteen3 and Klas Abelson4
Abstract
Background: The European population of hedgehogs (Erinaceus europaeus) is declining. It is therefore essential to optimise
conservation initiatives such as the rehabilitation of sick, injured and orphaned hedgehogs. Wild animals placed in captiv-
ity may be prone to chronic stress, potentially causing negative health effects. Therefore, the effects of these rehabilita-
tion efforts should consequently be evaluated. Furthermore, hand-raising orphaned hedgehogs is a laborious and costly
task, and it is therefore relevant to document whether they have equal post release survival rates compared to their wild
conspecifics.
The objectives of this research were therefore to conduct an exploratory study of glucocorticoid levels in hedgehogs from
different backgrounds and compare the post release survival of translocated, rehabilitated and wild, juvenile hedgehogs as
well as the possible effect on survival of differences in shy or bold behaviour (personality) exhibited by individuals.
Results: We measured glucocorticoid levels in 43 wild-caught (n = 18) and rehabilitated (n = 25) hedgehogs and com-
pared the post release survival and spatial behaviour of 18 translocated juvenile hedgehogs (eight hand-raised and ten wild)
until hibernation. The possible effect on survival of differences in shy or bold behaviour (personality) exhibited by 17 juvenile
individuals (seven hand-raised and ten wild) was also examined.
Rehabilitated individuals and females had higher levels of faecal corticosterone metabolites compared to wild individuals
and males, respectively. Rehabilitated individuals showed higher levels of saliva corticosterone than wild. The personality
tests labelled 13 individuals as shy and 11 as bold. Post release survival was 57% for rehabilitated and 50% for wild individu-
als. Neither background nor personality affected post release survival. Home range measures were 3.54 and 4.85 ha. Mean
dispersal length from the release sites was 217 ± 100 m.
Conclusion: The higher levels of corticosterone observed in rehabilitated compared to wild hedgehogs calls for considera-
tion of the duration of admission to wildlife rehabilitation centres to reduce stress levels in the patients.
Hand-raised juveniles appear to have the same prospects as wild, and personality does not seem to affect post release sur-
vival in hedgehogs, indicating that hand-raising of orphaned juvenile hedgehogs is a relevant contribution to the conserva-
tion of this species.
Keywords: Cortisol, Corticosterone, Stress, Wildlife rehabilitation, Wildlife conservation, Behaviour
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Open Access
BMC Ecology and Evolution
*Correspondence: sophielundrasmussen@gmail.com
1 Wildlife Conservation Research Unit, Department of Zoology, The
Recanati-Kaplan Centre, University of Oxford, Tubney House, Abingdon
Road, Tubney, Abingdon OX13 5QL, UK
Full list of author information is available at the end of the article
Page 2 of 16
Rasmussenetal. BMC Ecol Evo (2021) 21:96
Background
Conservation andstatus oftheEuropean hedgehog
e western European hedgehog (Erinaceus europaeus)
is found on the British Isles and Continental Europe,
from Iberia and Italy in the south to Scandinavia in the
north, as well as on New Zealand. It is widely distributed
and can survive across a wide range of habitat types [1,
2]. However, investigations on both national and local
scales have documented declines, or expressed concerns
about decline, of the hedgehog populations in several
western European countries [3–10]. e suspected rea-
sons for the decline include habitat loss and fragmenta-
tion, intensified agricultural practices, inbreeding, road
traffic accidents, lack of biodiversity and suitable nest
sites in residential gardens, molluscicide and rodenticide
poisoning, and badger predation [4, 11–23]. In Denmark,
where this study occurred, hedgehogs become active
after hibernation in mid-April to mid-May [22, 24, 25].
e juveniles are typically born from late July onwards
and become independent around mid-September [26].
During mild autumns, second litters have been observed
[22]. Hibernation is usually initiated from late September
for adult males, late October for adult females and mid-
November for young of the year [27]. However, hiber-
nation may be postponed if the conditions are mild and
food is available [22].
During the past 30 years, the rehabilitation of sick,
orphaned, or injured wild hedgehogs has become an
established practice in many western European coun-
tries. Denmark has several working hedgehog reha-
bilitation centres, where volunteers care for hedgehogs
and release them back into the wild after recovery. e
extent of hedgehog rehabilitation in Denmark is quite
comprehensive, with the three largest organisations
taking approximately 3200 hedgehogs into care during
a year (pers. comm. Dyrenes Beskyttelse, Pindsvineven-
nerne i Danmark and Pindsvine Plejerne). Yet, Danish
authorities have only recently established legal frame-
works and monitoring programs for the practice of
wildlife rehabilitation [28].
ere are currently no monitoring programmes in
Denmark tracking population numbers, however the
data from other European countries is concerning.
Conservation actions to preserve the species in the wild
should thus be optimised and initiated across Europe.
Wildlife rehabilitation andtheeect ofstress
e rehabilitation of orphaned, sick or injured wildlife
followed by their release back into the wild is an impor-
tant aspect of the conservation of threatened wildlife [29,
30]. However, when wild animals are placed in captiv-
ity, e.g. at a wildlife rehabilitation centre, they encoun-
ter a novel, confined and unpredictable environment,
which often includes handling and close proximity to
humans [31]. ese conditions cause physiological stress
responses in a range of species [32–36], which can have
severe effects on their health [37–40]. Previous research
has documented that chronic physiological stress can
have detrimental consequences that may affect the recov-
ery process [41], such as reduction in immuno-respon-
siveness [42] and body mass [43, 44]. Physiological stress
may even cause death from e.g. capture myopathy, which
can occur in several different forms with the more acute
being capture shock syndrome (sudden death at capture
or a few hours after capture) or acute/ataxic myoglobi-
nuric syndrome (death a few hours to a few days after
capture) [45]. It is therefore essential to understand the
causes, risks and effects of physiological stress in the
wildlife species one wishes to rehabilitate to improve ani-
mal welfare and survival during the care and captivity,
and thereby eventually enhance the conservation success.
is is especially important when handling a species such
as the European hedgehog, which is undergoing a docu-
mented decline.
Measuring stress inanimals
Glucocorticoid (GC) levels, measured in a number of
matrices (blood, saliva, urine, faeces, milk, etc.) can
be used as a proxy measure of stress [46] since physi-
ological and psychological stress are known to reliably
increase circulating GC concentrations. Although, not a
perfect measure of stress (there are numerous situations
known to increase GC levels, but which are not consid-
ered stressful, e.g., sexual behaviour [47]), there is a con-
siderable body of literature demonstrating the usefulness
of assessing GC levels in captive and wild populations of
wildlife. In the present investigation, corticosterone lev-
els were measured in both saliva (as has previously been
done for many species ranging from guineas pigs [48] to
elephants and rhinoceros [49]) and (as corticosterone
metabolites) in faeces (as has previously been done in a
range of species from rats [50] to elephants [51]).
When analysing corticosterone or cortisol in faeces, it
is not merely the steroids themselves that are quantified,
but instead a plethora of immunoreactive metabolites
produced in the liver during glucocorticoid metabolism,
including cortisone/dehydrocorticosterone [52]. In saliva
on the other hand, intact corticosterone and cortisol is
measured. us, for the faecal samples, the term faecal
corticosterone (or cortisol) metabolites (FCM) is used,
and for saliva samples corticosterone and cortisol.
Measuring personality inanimals
Personality affects how individuals react to challenging
situations [53] and may influence the post release sur-
vival of captive-reared mammals, as shown in a study
Page 3 of 16
Rasmussenetal. BMC Ecol Evo (2021) 21:96
by Bremner-Harrison etal. [54]. e personality of juve-
nile, captive-bred swift foxes was assessed and its influ-
ence on post release survival was scrutinised. e study
revealed that bolder individuals were less suited for
release if success was measured as post release survival,
and it was suggested by the authors that the future selec-
tion of release-candidates based on personality should
enhance the success on reintroduction programmes [54].
It is posited that the shyness/boldness of individuals
can be estimated by analysing how they explore a novel
environment or arena, and by measuring their latency to
approach a novel object in a familiar environment [54–
57]. Previous studies have demonstrated the existence
of a shy–bold gradient in natural populations, and some
have furthermore quantified the fitness consequences
of personality [54, 58–60]. Personality can affect fitness
through reproductive success and survival [54, 61, 62].
Population levels of boldness are subject to natural selec-
tion [63], which is why released individuals with inap-
propriate levels of boldness may suffer reduced fitness
in the wild [54]. erefore, when using rehabilitation of
orphaned hedgehogs as a conservation effort for the spe-
cies in general, it may be relevant to consider the per-
sonality of the individuals when deciding which release
sites to use, since it may affect post release survival. is
is particularly important with juveniles as their expected
survival rate is low in general [60]. Previous studies have
estimated survival probabilities for juvenile, Scandina-
vian hedgehogs ranging between 0.31 and 1.00 depend-
ing on the age and period of time in which they were
studied [22, 25, 26, 64–66].
Post release monitoring ofrehabilitated hedgehogs
Previous research has investigated the post release sur-
vival and spatial behaviour of rehabilitated hedgehogs
[30, 67–73], and some have included wild individuals for
comparison [30, 70, 73] or described the survival of wild,
translocated individuals [74]. However, few studies have
directly compared the survival of rehabilitated and wild
individuals, where both groups had been translocated
[30].
Post release survival of rehabilitated hedgehogs have
been found to range between 25 and 82% depending on
the sample size (n = 4–34), age of the individuals (juve-
niles < 1 year or adults), time of year and duration of
the studies (n = 3–22 weeks) [30, 67–74]. In two studies
of rehabilitated, juvenile hedgehogs in the UK released
during spring, the post release survival was 58% (n = 12,
age = approximately 20 weeks, duration = 5–8 weeks
from April) [69] and 77% (n = 13, age = approximately
20 weeks, duration = 6 weeks from April to June)[67].
e post release survival of rehabilitated, juvenile hedge-
hogs released in the UK during summer was 83% after 2
weeks, 75% after 4 weeks, 42% after 8 weeks and down
to 25% 15 weeks post release (n = 12, age = autumn juve-
niles < 1year released in June, duration = 15weeks) [71].
In a study comparing five different groups of adult
hedgehogs (local wild, local translocated wild, translo-
cated rehabilitated, directly translocated wild from the
Uist Islands (< 6days in captivity) and translocated wild
from the Uist Islands (> 1month in captivity)), Molony
etal. (2006) [30] discovered that the local wild hedgehogs
had a significantly higher survival rate (94.7 ± 0.2%) than
individuals in the rehabilitated translocated (73.1 ± 1.1%),
directly translocated (40.9 ± 1.2%) and local translocated
wild groups (63.6 ± 0.9%), and that the survival probabil-
ity of translocated hedgehogs (having spent > 1month in
captivity) (81.8 ± 0.7%) was significantly greater than that
for directly translocated individuals. Yarnell etal. (2019)
[73] found no significant difference between the sur-
vival of wild and rehabilitated hedgehogs during the first
150days after release of the rehabilitated individuals.
Morris and Warwick (1994) [69] recorded that three
out of twelve rehabilitated, juvenile individuals dis-
persed up to 2 km away from the release site during
the study period. e rest remained in the release area.
Morris (1997) [67] described how all thirteen reha-
bilitated, juvenile hedgehogs remained within 400 m of
the release point for at least a month post release, after
which five hedgehogs dispersed, travelling at least 400m
and up to 5.2km from the release point. Reeve (1998)
[71] found that all surviving rehabilitated, juvenile indi-
viduals released in a rural woodland area dispersed
from the release site during the 15weeks of study, with
a mean distance of 3km, and the nearest animal found
1476 m from the release point. All individuals moved
to areas of human habitation. In contrast, two individu-
als released into an urban area did not disperse far from
the release site [71]. Molony etal. (2006) [30] found that
there was a significant difference in the mean distance
from the release site to the last known location after
8 weeks between the directly translocated wild group
(directly translocated from the Uist Islands (< 6days in
captivity)), which travelled the largest mean distance
(0.69 ± 0.82km) compared to the rehabilitated translo-
cated group (0.31 ± 0.33 km) and the translocated wild
group (translocated from the Uist Islands (> 1month in
captivity)) (0.56 ± 0.45km). e dispersal distance of the
local wild group was 0.15 ± 0.14km and 0.22 ± 0.18 km
for the local, translocated wild group of hedgehogs.
Aims
e objectives of the present study were:
1. To conduct an exploratory study of glucocorticoid
levels in European hedgehogs from different loca-
Page 4 of 16
Rasmussenetal. BMC Ecol Evo (2021) 21:96
tions, with different health status and backgrounds
(wild and rehabilitated).
2. To quantify personality in European hedgehogs,
measured as shyness-boldness, and to estimate the
possible effects of personality on post release sur-
vival.
3. To measure and compare the post release survival of
translocated, rehabilitated and wild, juvenile Euro-
pean hedgehogs.
Results
Salivary corticosterone levels
e measured saliva corticosterone levels from indi-
viduals in cohort 2 ranged between 0.41 and 59.96
(mean = 7.69 ± 9.83ng/mL, n = 57). Only the background
(wild/rehabilitated) of the subjects appeared to have an
effect on saliva corticosterone levels in the present study
(χ2(1) = 5.58, p = 0.018, n = 55), with wild individuals
having significantly lower levels of saliva corticosterone
compared to rehabilitated individuals (Fig.1).
Faecal corticosterone metabolite levels
e detected faecal corticosterone metabolite levels
ranged between 15.33 and 369.5ng/g (n = 86). However,
only 43 samples from 29 individuals with representation
from all three cohorts were included in the data analysis,
as the remaining samples were collected from enclosures
with more than one individual (cohort 2) or randomly in
the wild (cohort 3), and could therefore not be allocated
to a specific individual, which was a necessary informa-
tion for the type of data analysis chosen. e faecal cor-
ticosterone metabolite levels for samples included in the
data analysis still ranged between 15.33 and 369.5 ng/g
(n = 43) with a mean of 53.3 ± 58.2ng/g.
We failed to find an effect of health status (dying from
Salmonella or not) on faecal corticosterone metabolite
(FCM) concentrations. However, both sex and back-
ground appeared to influence FCM levels: rehabilitated
hedgehogs had significantly higher FCM levels than wild
hedgehogs, and females had significantly higher levels
than males in the present study (χ2(1) = 6.98, p = 0.008).
Cortisol levels
Faecal cortisol metabolite levels of 19.85–79.30 ng/g,
with a mean of 41.29 ± 21.67 ng/g, were detected in 7
faecal samples from six different individuals from cohort
3. Cortisol levels of 2.16–15.34 ng/mL, with a mean of
10.14 ± 6.15ng/mL, were measured in four saliva sam-
ples from individuals belonging to cohort 3. Due to the
low sample size, we refrained from further data analysis.
Novel arena test
e data obtained in the novel arena test was condensed
using PCA. Two components, explaining 84% of the vari-
ance in data, were extracted, based on scree plot analy-
sis. Moreover, due to the small sample size in relation
to the number of dependent variables, extracting more
than two latent trends was deemed excessive. e two
components were tentatively interpreted as a measure of
fearfulness (shyness/boldness) (PC1) and general activity
level (PC2), respectively, based on their factor loadings
(Additional file 5). PC1 correlated strongly (positively)
with the time individuals spent lingering in, or near, the
carrier, but also correlated strongly (negatively) with
the time spent in the distant zones. is suggests a shy/
bold axis. e second component correlated (positively)
with the total number of zone transitions and frequency
of entries into the distant zones. is suggests an axis of
general activity level. No clear trends could be found with
respect to any of the two latent trends on a group level.
Neither sex, health status, nor background appeared to
have an effect on either boldness or general activity as
trends were investigated using analysis of variance.
Fig. 1 Salivary corticosterone and faecal corticosterone metabolite
(FCM) levels in wild and rehabilitated individuals of both sexes.
Markers denote individuals. Where multiple samples were analysed,
an average is presented for the single individual. Bars represent the
geometric mean for each group, as glucocorticoid data is known to
conform to log-normal distributions
Page 5 of 16
Rasmussenetal. BMC Ecol Evo (2021) 21:96
Novel object tests
Similar to the novel arena test, data were subjected to
condensation using PCA and two components were
extracted based on scree plot analysis, explaining 88%
of the variance in the dataset. e two components split
neatly between the two tests, PC1 describing the fearful-
ness shown in the ball test and PC2 describing the fear-
fulness in the badger test (Additional file4). is suggests
that the responses in the two tests were somewhat inde-
pendent of one another.
Whereas we expected to see an effect of testing order
caused by habituation (whether individuals were sub-
jected to the ball or badger setup for the first novel arena
test), this was not evident from the limited data (Addi-
tional file6). Consequently, testing order was excluded
as an explanatory variable in further testing. On a group
level, two trends could be discerned. Subjects with a
“rehabilitated” background appeared to present with a
higher average PC2 score (F1,14 = 5.49, p = 0.034), sug-
gesting a more timid behavioural response in the badger
test. Sick individuals presented with a slightly lower PC1
score (F1,14 = 4.68, p = 0.048), suggesting a less timid
response in the ball test (Additional file7).
Personality
A total of 24 individuals from cohort 2 were tested for
personality measured as shyness-boldness. 13 individu-
als were labelled as shy and 11 individuals as bold. e
distribution of shy and bold individuals based on back-
ground were five shy and five bold for wild individuals;
eight shy and six bold for hand-reared, rehabilitated indi-
viduals. See Additional files 8, 9, 10 and 11 for personality
test results and an overview of the distribution of shyness
and boldness per individual.
Post release survival, personality andhibernation
behaviour ofcohort 2
Post release survival from release during the autumn and
until initiation of hibernation was 53% (n = 9 out of 17). A
total of four out of seven hand-reared, rehabilitated indi-
viduals survived (57%) and five out of ten wild individuals
survived (50%). Originally, eight hand-reared, rehabili-
tated individuals were released, but the radio signal was
lost from one, which was consequently excluded from
the survival analyses. Causes of death were predation by
badgers (n = 3, two wild, one rehabilitated individual),
Salmonella infections (n = 4, two wild, two rehabilitated),
and one wild individual was stepped on by a cow. e dif-
ference between post release survival rates of wild and
hand-raised individuals was not statistically significant
(Fisher’s Exact Test, two-tailed P value = 1.00). Personal-
ity, measured as shyness–boldness, did not influence post
release survival in the present study (Fisher’s Exact Test,
two-tailed P value = 1.00), with 4 shy individuals dying, 5
shy individuals surviving, 4 bold individuals dying and 4
bold individuals surviving, post release, until hibernation.
Individuals dying post release (n = 8) did so within 9
days after release (range 2–9days). Hibernation was initi-
ated between 31st of October and 17th of November, the
majority (n = 6) around mid-November. e hedgehogs
began hibernating 6–38days post release (n = 9) de pend-
ing on the release date, as individuals released late in the
season initiated hibernation quite promptly.
Post release spatial behaviour ofindividuals fromcohort 2
Based on the GPS coordinates obtained from the post
release radio tracking, home range estimates were made
for individuals W7 (n = 35) and W8 (n = 28) in cohort
2, being the only individuals with sufficient data points
(> 30) for calculating representative home range estimates
[75]. 95% minimum convex polygons: W7 (4.85ha) and
W8 (3.54ha). Kernel density estimates: W7 (95%: 7.07ha,
50%: 0.12ha) and W8 (95%: 5.58ha, 50%: 0.06ha),
For comparison, home ranges for individuals from
cohort 3 can be found in Rasmussen et al. (2019)
[22]. Mean dispersal length from the release sites was
217 ± 100m (range 100–408m), measured as the great-
est distance from the release sites recorded per indi-
vidual, for 11 individuals in cohort 2 released back into
the wild. e dispersal lengths were measured during
the period post release until initiation of hibernation,
ranging from 6 to 38days. e remaining six individuals
(range 5–45m) were excluded from the analysis because
they died shortly after release and never got to explore
the new habitats. Dispersal length was equal for rehabili-
tated (212 ± 102m, range: 100–322, n = 4) and wild indi-
viduals (219 ± 106m, range: 101–408, n = 7).
Discussion
During our tests of glucocorticoids in hedgehogs we dis-
covered that rehabilitated individuals and females had
higher levels of faecal corticosterone metabolites com-
pared to wild individuals and males, respectively. Fur-
thermore, rehabilitated individuals showed higher levels
of saliva corticosterone than wild.
e difference detected in faecal corticosterone
metabolite levels between males and females is most
likely a general sex difference, which has previously been
detected in a range of species (e.g., [76–80]) and was pre-
viously hinted at by Fowler (1988) [81].
Rehabilitated individuals had significantly higher lev-
els of corticosterone and corticosterone metabolites in
both saliva and faeces, respectively, compared to the wild
individuals in the study, and the high occurrence of Sal-
monella infections (category labelled as “health” in the
Page 6 of 16
Rasmussenetal. BMC Ecol Evo (2021) 21:96
statistical models) among the rehabilitated individuals
did not affect the results. Taking into consideration that
ten of the wild individuals included in the analyses were
kept in captivity for a week under the same conditions as
14 of the rehabilitated individuals tested (cohort 2), the
results could indicate that the rehabilitated individuals
were in general more stressed, having been kept in cap-
tivity for a longer period of time and having been moved
from one enclosure to another. It is therefore relevant to
consider the length of the rehabilitation process and the
potential negative consequences of a long admission to a
wildlife rehabilitation centre, as well as whether the ben-
efits of moving individuals to new enclosures for a soft
release will outweigh the potential increase in stress lev-
els caused by this act. However, further studies on the
effects of translocation to new enclosures are needed to
confirm this.
Previous studies have investigated different aspects of
adrenal function and adrenal hormone levels in hedge-
hogs [81–88]. ese studies have principally focused on
glucocorticoid-involvement in relation to/in preparation
for hibernation. Both corticosterone [84] and cortisol
[81] have been measured in this context in hedgehogs,
however, to our knowledge, there are no studies of either
glucocorticoid’s involvement in stress. Similar to, for
example, hamsters [89], hedgehogs appear to secrete
considerable levels of both cortisol and corticosterone
(as opposed to most mammalian species where there is
a considerable skew toward one of the two). Comparing
the faecal samples from cohort 3, where we could obtain
reliable measurements of both faecal corticosterone- and
cortisol metabolite levels, we found the average level
of corticosterone metabolites (48.4 ± 24.92 ng/g) to be
higher than that of cortisol metabolites (41.3 ± 21.7ng/g).
However, the mean saliva cortisol level in general
(10.1 ± 6.1 ng/ml) was higher than that of corticoster-
one (7.7 ± 9.8 ng/ml) detected in the saliva samples.
is supports the findings by Werner and Wünnenberg
(1980) [88] who found 3–4 times higher levels of cortisol
in hedgehog plasma. It is, therefore, tempting to suggest
that cortisol should be focused on as the primary stress-
associated glucocorticoid. But we would argue that this
would be a premature conclusion since it has been sug-
gested that cortisol and corticosterone may take on dif-
ferent roles [90] in species where both hormones are
found in appreciable concentrations (e.g., hamsters [91]
or bats [92]). To move forward, there is, instead, a need
for validating cortisol and corticosterone concentrations
in European hedgehogs in relation to controlled stress-
ors; for example, ACTH challenges. As the European
hedgehog is protected by law in Denmark, such experi-
ments would require specific permits which are not easily
obtainable.
Unfortunately, we had to exclude a number of faecal
samples (n = 43) from the data analysis of faecal corti-
costerone metabolite levels, because they could not be
assigned to a specific individual.
Seven out of 15 rehabilitated individuals from cohort 2
died from Salmonella infections before release back into
the wild. Four individuals (two wild and two rehabili-
tated) died of Salmonella infections post release, showing
no symptoms before release. One could anticipate that
sick individuals would not behave as they would have
done under normal conditions, which could influence the
results of the personality tests. Surprisingly, we observed
that individuals dying from Salmonella infections were
among the most active (bold) individuals during the per-
sonality tests, even though apathetic behaviour could
have been expected. e detected levels of corticosterone
may also have been affected by disease, but this could not
be confirmed by the statistical analyses, as health sta-
tus did not significantly influence corticosterone levels.
However, the Salmonella infections did reduce our post
release sample size (cohort 2) considerably, which should
be taken into consideration when interpreting the results.
e majority of personality studies have been carried
out on captive-bred individuals [93]. Archard and Braith-
waite [93] stated that there is a need for personality tests
of wild populations in order to discover the selection
pressures that affect personality in natural environments.
e stress associated with the capture, handling and cap-
tivity of wildlife should be considered [93] as well as a
potential bias in trapping wild animals for research, since
“trappability” of wild animals has been used as a meas-
ure of boldness in previous studies [59, 94]. However, five
out of ten wild individuals were categorised as bold in the
present study, which does not indicate any “trappability”
bias. Yet, given the small sample size, it could also just be
caused by coincidence. Additionally, it is relevant to men-
tion that some individuals may have personalities that
allow them to thrive in rehabilitation, which could give
them an advantage upon release.
Fucikova etal. [95] describe how handling stress can
potentially influence the behaviour in personality tests,
and how this should be taken into consideration when
interpreting the results. As the rehabilitated, hand-raised
individuals of cohort 2 should be more habituated to
handling by humans, the wild individuals would then be
expected to show more shy behaviour compared to the
rehabilitated individuals in the personality test, if they
were influenced by handling stress. is was not the case,
as only five out of ten wild individuals were labelled as
shy, compared to eight out of 14 rehabilitated individuals.
However, some individuals may also appear to be bold
whilst masking very high stress levels [96]. is did not
Page 7 of 16
Rasmussenetal. BMC Ecol Evo (2021) 21:96
seem to be the case in the present study, as personality
did not affect stress levels.
Post release survival did not appear to be affected by
background or personality in the present study. However,
it is important to consider the potential biases caused by
the rather small sample size (n = 17). All individuals dying
post release did so within 9 days after release, which is
remarkable, and may indicate that if an individual is able
to survive after approximately the first week post release,
there is a good chance that it will survive until hiberna-
tion. Post release survival of rehabilitated hedgehogs has
previously been found to range between 25 and 83% [30,
67–73]. Yarnell etal. (2019) [73] detected no significant
difference between the survival of wild and rehabilitated
hedgehogs (n = 42, overall survival rate = 83%) during the
first 150days after release of the rehabilitated individuals.
Rasmussen etal. (2019) [22] found a survival rate of 78%
(n = 23) for wild, juvenile hedgehogs during the autumn
until initiation of hibernation. e post release survival
rate of 53% observed in the present study is remarkably
lower and is likely due to the presence of the Salmonella
infection, which killed four individuals post release.
However, the survival rate of 53% in the present study is
still average compared to the range of 25–83% found in
previous studies of post release survival of rehabilitated
individuals.
e post release home range sizes measured for indi-
viduals of cohort 2 were almost equal to the levels found
in Rasmussen et al. (2019) [22], where wild juvenile
hedgehogs were radio tracked in the same area as used in
the present study. Combined with the small post release
dispersal length of 217 ± 100m we detected, especially
compared to previous studies on translocated hedgehogs
[30, 67, 69, 71], it seems translocated, juvenile hedgehogs
do not travel far from their release site and stay in a small
area, if the habitat is of suitable quality. is suggests that
future post release monitoring of hand-raised orphans
should be possible for hedgehog carers even without the
use of tracking equipment.
Conclusions
In conclusion, we determined the personality measured
as shyness-boldness of 24 independent, juvenile hedge-
hogs with different backgrounds. Afterwards, they were
radio tagged and released into a novel habitat. We found
no difference in the post release survival of hand-reared
rehabilitated and wild, juvenile European hedgehogs, and
survival did not seem to be affected by personality. ese
results show that hand-raised, rehabilitated juveniles
have the same prospects post release as wild individu-
als brought up naturally, and that chances of post release
survival are seemingly not influenced by personality
(shyness-boldness).
We measured glucocorticoid levels in 43 European
hedgehogs from different backgrounds, age groups and
locations using commercially available assays for corti-
costerone and cortisol to quantitate (an unknown mix
of) the native glucocorticoids and their metabolites. We
found that rehabilitated individuals had higher levels
of corticosterone metabolites (faeces) and corticoster-
one (saliva) compared to wild individuals. Additionally,
females had higher levels of saliva corticosterone than
males, but this was most likely a general sex difference.
e results indicate that rehabilitated individuals show
higher levels of saliva corticosterone and faecal corticos-
terone metabolites than wild individuals, likely due to a
longer stay in captivity. Based on these observations we
suggest that the duration of admission to hedgehog reha-
bilitation centres should be considered. However, more
research on the subject is needed, particularly a valida-
tion of the detected levels of cortisol and corticosterone
in European hedgehogs through ACTH tests, before we
can draw any definitive conclusions on the stress levels of
the individuals studied.
Methods
e samples in the study came from 43 individual hedge-
hogs (25 rehabilitated and 18 wild) collected over the
course of three different research projects. In addition
to sex, individuals were defined either as wild or reha-
bilitated (ten sick/injured adults being treated at a wild-
life rehabilitation centre (cohort 1) and 15 hand-reared
orphans (part of cohort 2)). Table1 provides a flow chart
of the entire research setup.
Subject characteristics
Cohort 1
Cohort 1 consisted of ten adult hedgehogs in care due to
either injuries or sickness at a hedgehog rehabilitation
centre near Copenhagen. Samples, one saliva and one
faecal sample per individual, were collected on the 2nd of
July 2012. See Additional file1 for information on weight,
sex and conditions of the individuals.
Cohort 2
Cohort 2 consisted of ten wild juvenile hedgehogs (esti-
mated age > 6 weeks) and 15 hand-reared orphans
(7–8weeks old). All were from Zealand, Denmark; born
between July and the beginning of September 2012. See
Additional file 2 for further information. e orphans
were resident at two wildlife rehabilitation centres (oper-
ating under Dyrenes Beskyttelse) for at least 3 weeks
before entering the study. All animals were over the age
of independence [1, 97]. e wild individuals were hand
caught in the suburbs of Copenhagen using headlights
and night vision goggles. Wild-caught and hand-reared
Page 8 of 16
Rasmussenetal. BMC Ecol Evo (2021) 21:96
hedgehogs were separately housed in outdoor enclo-
sures under the same conditions to facilitate direct com-
parisons between the two groups. Each chicken-wire
enclosure (3m × 2m) had a chipboard roof and housed
2 individuals. Nest boxes (50cm × 50cm × 40 cm) were
provided with sawdust on a sheet of surgical base, hay, a
bowl of water and a bowl of kitten dry food. Additional
kitten wet food placed beside the box entrance. Food and
water was also present in the pen. Food and water were
changed daily, and the nest boxes were cleaned thor-
oughly every second to 3rd day.
Experimental design for cohort 2 Each individual was
colour coded for identification purposes using Hama
beads (www. hamab eads. com) glued to its spines. Hedge-
hogs were weighed and faecal samples collected daily. On
day 1 (arrival), the hedgehogs were tested in a novel arena
setting. On days 3 and 5 they were exposed to the novel
object test. On day 6, radio transmitters were attached,
and the individuals were released at night on day 7.
Cohort 3
is group consisted of four radio-tagged wild, juve-
nile hedgehogs, aged approximately 8 months at the
time when the faeces and saliva samples were obtained.
A more detailed description of the individuals and the
study in which they participated can be found in Ras-
mussen etal. (2019) [22]. Faecal samples from five wild,
unidentified individuals from Taastrup and Rødovre
were also included to increase the representation of wild
Table 1 A flow chart presenting the research setup for the three cohorts studied
Categories Cohort 1 Cohort 2 Cohort 3
Subject characteristics n = 10 rehabilitated, adult hedgehogs n = 15 rehabilitated, juvenile hedgehogs n = 8 wild hedgehogs (3
juveniles, 5 unidentified)
n = 10 wild, juvenile hedgehogs
Glucocorticoid analyses
Sampling Faecal samples (n = 10) Saliva samples (n = 57) Saliva samples (n = 4)
Faecal samples (n = 67) Faecal samples (n = 9)
Sampling before (wild) and during captivity
(both groups) and post release (both
groups)
Laboratory procedure Testing: Testing: Testing:
Faecal corticosterone metabolite levels
(n = 10) Faecal corticosterone metabolite levels
(n = 67) Faecal corticosterone
metabolite levels (n = 9)
Saliva corticosterone levels (n = 57) Faecal cortisol metabolite
levels (n = 7)
Saliva cortisol levels (n = 4)
Personality testing Not performed Novel arena test on day 1 in enclosures Not performed
Novel object tests on day 3 and 5 in
enclosures
Release into the wild Not performed After 7 days in enclosures (n = 18, 8 reha-
bilitated and 10 wild juveniles) Already free-living
Post release monitoring of survival
and spatial behaviour Not performed Radio tracking of 18 juveniles, out of
which 1 was unaccounted for Results not included in the
present study: Radio track-
ing of the 3 radio tagged
wild juveniles (Rasmussen
et al. (2019))
Data analyses
Faecal corticosterone metabolite
levels in relation to back-
ground, sex and health
Linear mixed effects model (LME) for
all cohorts Linear mixed effects model (LME) for all
cohorts Linear mixed effects model
(LME) for all cohorts
Saliva corticosterone levels in
relation to background, sex
and health
Linear mixed effects model (LME)
Personality (novel arena and
novel object tests) Principal component analyses (PCA)
Effects of personality (shy/bold)
and background (wild/rehabili-
tated) on post release survival
Fisher’s exact test
Page 9 of 16
Rasmussenetal. BMC Ecol Evo (2021) 21:96
individuals in the study. All samples were collected in
May 2015.
Sampling methods
Faecal samples were collected and frozen (− 20°C) as
soon as possible, at the latest within 30 min after the
samples were collected, awaiting analysis.
e saliva samples were collected with a single-use
pipette (model LW4273 Alphalabs UK), kept in cooler
bags directly after sampling, and stored frozen (− 20°C).
e saliva samples were collected by gently placing the
long and narrow tip of the single-use pipette in the cor-
ner of the mouth of the hedgehog. Saliva was aspirated
from the inside of the individual’s cheek, after which
the pipette was gently extracted from the mouth of the
hedgehog. During the procedure, the hedgehog was
placed in the hands of the person extracting the sample
and was not restrained. Each procedure lasted < 20s. e
saliva sampling took place at the first given opportunity
during their activity period at night, when handling the
hedgehogs, in an attempt to avoid detecting the stress
from handling in the samples. e first saliva sample for
individuals belonging to cohort 2 was taken upon arrival
to the pens, 15min before the novel arena test. In some
instances further samples were obtained before the novel
object tests. e last samples were collected upon tagging
and release into the wild, and in some cases, when it was
possible to catch the individual, post release.
Laboratory procedure
A total of 57 saliva samples and 86 faecal samples were
analysed for glucocorticoids. Corticosterone and cor-
ticosterone metabolites in saliva, as well as faecal corti-
costerone metabolites (FCM) were quantitated using a
commercially available corticosterone assay. Similarly,
faecal cortisol metabolite levels were assessed in seven
faecal samples and an additional four saliva samples were
analysed for cortisol levels using a commercially avail-
able cortisol assay. Saliva samples (n = 61) were analysed
neat or diluted in PBS where needed. Faecal samples
(n = 93) were extracted in ethanol (96%) overnight. e
supernatant was recovered by centrifugation, evapo-
rated, and the extracted material was resuspended in PBS
prior to analysis. Both cortisol and corticosterone con-
centrations were measured in the samples, but due to a
highly pronounced matrix effect in the initially chosen
assay for cortisol quantification (“Cortisol ELISA”, EIA-
1887; DRG Instruments GmbH, Germany), combined
with limited sample material (faeces and saliva samples
from cohort 1), the results from a number of cortisol
analyses had to be discarded. Corticosterone concen-
trations were determined using commercially available
ELISA kits (“Corticosterone ELISA”, REF EIA-4164; DRG
Instruments GmbH, Germany). Known cross-reactivities
are with progesterone (7.4%), deoxycorticosterone (3.4%),
11-deoxycorticosterone (1.6%), cortisol (0.3%), and preg-
nenolone (0.3%), with other steroids cross-reacting at less
than 0.1%. Sensitivity of the kit (detection limit) is listed
at 1.6nM and typical intra- and inter-assay CVs are listed
at 3% and 6%, respectively. A small subset of saliva (n = 4
from cohort 3) and faecal (n = 9 from cohort 3) samples
that had not been exhausted were analysed for cortisol
concentrations using an assay which was deemed reliable,
and did not show signs of matrix effects (“Parameter cor-
tisol assay”, KGE008, R&D Systems Parameter Cortisol).
Known cross-reactivities are with prednisolone (4.4%),
11-deoxycortisol (3.4%), progesterone (1.7%), and corti-
sone (0.2%), with other steroids, including corticosterone
cross-reacting at less than 0.1%. Sensitivity (detection
limit) of the kit is listed at 0.071ng/ml and typical intra-
and inter-assay CVs are listed at 5% and 9%, respectively.
Despite the need for validating cortisol and corticoster-
one concentrations in European hedgehogs in relation to
controlled stressors with for example ACTH challenges
[98], it was unfortunately not possible to provide such a
validation in the present study, as the European hedge-
hog is protected by law in Denmark, and such experi-
ments would require specific permits which are not easily
obtainable.
Personality testing
Individuals from cohort 2 were tested in the novel arena
test and the novel object test before being released into
the wild.
Novel arena test
When released into the enclosure for the first time, the
hedgehogs were tested in a novel arena paradigm. e
enclosures were divided, lengthwise, into zones of 50cm
(numbered 0–5) by use of strings which were woven into
the chicken-wire netting placed in the ground-level of the
enclosures. e nest box was placed in zone 5 extending
into zone 4, but was kept shut during the test. e out-
door water and food bowls were placed in zone 3 (Fig.2).
Each individual was brought to the arena in a cat trans-
port carrier with bedding and left near the enclosure for
15min prior to the experiment. e transport box was
gently placed in the entrance corner of the enclosure
(zone 0) and opened. During the next 15min, the hedge-
hog’s latency to exit the carrier (tout), latency to enter the
different zones (t1–5) and the total time spent in each zone
(Σ0–Σ5), was recorded, as well as the total number of vis-
its to each zone (visits1–5) and the total number of bor-
ders crossed (total visits). Entering a zone was defined as
having moved the entire body into the zone. e record-
ing of the novel arena tests was made by the same, single
Page 10 of 16
Rasmussenetal. BMC Ecol Evo (2021) 21:96
observer, with the exception of two occasions, where a
second person was also present alongside the observer.
e observer wore a headlight pointing downwards to
light up the registration sheet, and made the observations
from a distance of 2m from the enclosure staying silently
in place for the duration of the experiment. e transport
box was cleaned between each test.
Novel object tests
On day 3 and day 5 the response of the hedgehogs in
cohort 2 to a novel object was tested. e objects were
a pink football (25cm in diameter) and a badger setup
consisting of a small paper box with badger faeces and a
stuffed animal toy with white and black colours, mimick-
ing a badger pup (around 40cm in length). New samples
of badger faeces were provided for each test night. e
badger setup was chosen as badgers are natural predators
of hedgehogs [15, 97, 99] and the football was chosen as
a neutral item, with the two novel object tests reflecting
personality in a relatively neutral and a more threaten-
ing environment [100, 101]. e novel items were placed
in the centre of the enclosure next to the outdoor food
and water bowls. e hedgehog was gently placed in an
open carrier next to the closed nest box at a distance of
90cm from the novel object (Fig.3). Each test was filmed
with a Prostalk PC3000IR wildlife trail camera, which
was set to record for 90s after each detected movement
in the enclosure, with a time lag of two minutes between
recordings. e placement of the wildlife camera in the
right corner of the enclosure ensured a full view of the
arena and therefore accurate measurements of distances.
All novel object tests lasted 90min and were carried out
at night (the active period of hedgehogs). Each hedge-
hog was tested individually, whilst the other individual
housed in the same enclosure was confined to the nest
box. e latency to exit the carrier (tout), the latency to
approach the novel object, tapp (defined as coming within
50cm of the object), and the smallest distance from the
object were recorded. e distance from the object was
measured to the tip of the hedgehog’s snout. All videos
were coded by a single observer.
e testing order (ball/badger) was randomized and
took place on day 3 and 5. Each testing session ideally
consisted of two wild and two rehabilitated individuals
in separate enclosures, one housing the wild individuals
and the other the rehabilitated. With a few exceptions,
each individual was tested once in each of the two setups.
21 individuals were tested in the ball setup and 18 in the
badger setup (the uneven number of tests was caused by
deaths among the test individuals).
Salmonella detection
Seven out of 15 hand-raised, rehabilitated individuals
from cohort 2 died from Salmonella infections before
release back into the wild. ey had contracted the infec-
tions during care at a wildlife rehabilitation centre due to
the lack of necessary hygienic precautions and diagno-
sis/treatment. Four individuals from cohort 2 (two wild
and two rehabilitated) died of Salmonella infections post
release, showing no symptoms before release. All cases
were confirmed through PCR validation and categorised
as causes of death during the necropsies conducted at
Wildlifehealth.dk.
Spatial behaviour andsurvival postrelease
After staying in the enclosures for 7 days, the surviving
hedgehogs of cohort 2 (eight hand-raised and ten wild
individuals) were released back into the wild wearing
radio transmitters (Biotrack PIP transmitters of 3–4g).
e purpose was to compare the post release success of
Fig. 2 The novel arena test setup. The test was made when the
individual entered the arena (enclosure) for the first time, on day 1.
The arena was divided into zones. The individual was placed in the
carrier in zone 0, and the carrier was opened when the test started.
Test duration was 15 min. A researcher monitored the events from
outside the enclosure and recorded the test results
Page 11 of 16
Rasmussenetal. BMC Ecol Evo (2021) 21:96
wild and hand-raised, rehabilitated individuals. A total
of seven groups, each consisting of both hand-raised and
wild individuals, were released at six different locations
between 14th of September and 8th of November 2012,
after spending 6 days in the enclosures during the per-
sonality testing (Additional file2).
e hedgehogs were transported to the release site in
two carriers, wild and rehabilitated housed separately.
e hedgehogs were allowed to exit the carriers at their
own speed. Dry cat food and water was offered for a week
post release, and the two carriers were not removed until
a week post release, providing the individuals with an
alternative nest site during the first week after translo-
cation into the foreign area. e first two releases were
made in the area of Gribskov in a forest edge habitat sur-
rounded by grassland and containing a single house and
garden which was evaluated as suitable based on a previ-
ous study on the habitat types of Danish hedgehogs [102]
(Latitude, longitude: 55.975983, 12.266367; 55.974898,
12.264987). Afterwards new release sites were found in
Taastrup in a large recreational area suitable for release
due to the presence of a large hedgehog population, adja-
cent to residential areas, and with the presence of foxes
(Latitude, longitude: 55.642388, 12.328723; 55.643445,
12.331849; 55.649443, 12.333854; 55.651115, 12.328648).
e change of release site was prompted by a surprisingly
high predator (badger and fox) density in Gribskov, likely
causing multiple deaths (n = 3) among the hedgehogs
during the first days post release. All wild-caught hedge-
hogs were released at least 3km from their capture site to
avoid a possible bias of advantages due to acquaintance
with local conditions. e measure of 3km was based on
previous studies of adult hedgehogs, wherein the larg-
est observed distance travelled in a night was 2km, and
adult home ranges were < 40ha [1].
Post release, the hedgehogs were radio tracked with a
Sika receiver and Yagi antenna and found every one-two
nights post release. eir locations were recorded with
a Garmin eTrex 20 GPS. e radio tracking was carried
out in the activity periods of the hedgehogs, between 8
p.m. and 3 a.m., in order to cover the two possible peaks
of activity, 21:00–24:00 and around 3:00 o’clock, as sug-
gested by Campbell [103] and Wroot [104]. Only one
position was recorded each night (in different hours
of the night) as an attempt to obtain independent data
for the calculation of home ranges [105]. e surviving
hedgehogs were followed until initiation of hibernation.
Post release survival and home ranges were measured
and compared between treatment groups (wild and reha-
bilitated juveniles). A total of 18 individuals were radio
tagged and released back into the wild, but the signal
was lost from one rehabilitated individual shortly after
release, which means we excluded this individual from
the different post release data analyses.
Data analysis
All measures of dispersion in the manuscript are listed as
standard deviation (SD).
e linear mixed effects models (LME) were prepared
and tested using the software R [106]. e principal com-
ponent analyses were performed in SPSS v. 25 [107].
Saliva corticosterone samples
A linear mixed effects model (LME) was used for analys-
ing the corticosterone levels found in saliva. e model
included the subjects as a random effect as some individ-
uals contributed with multiple saliva samples. e corti-
costerone levels were log-transformed prior to analysis
to obtain a normal distribution (Shapiro–Wilk normality
Fig. 3 The novel object test setup. Individuals were tested in the
novel object test setup on day 3 and 5 in the enclosure. The novel
objects were a ball and a badger setup. Trying to avoid habituation
bias, some individuals were tested with the ball as the first novel
object test, and some were tested with the badger as the first novel
object test. Test duration was 90 min. A wildlife camera in the lower
right corner of the enclosure recorded the test situations
Page 12 of 16
Rasmussenetal. BMC Ecol Evo (2021) 21:96
test, post transformation: W = 0.9893, p = 0.9051). An
initial model included the background (wild/rehabili-
tated), sex and health (dying from Salmonella infection
or not) as fixed effects.
Stepwise reduction of the model’s explanatory val-
ues was subsequently employed, using ANOVA tests to
compare the models, gradually removing non-significant
terms from the models indicated by the results of the
ANOVA tests. e best fit model only included the back-
ground of the subjects in addition to the random effect
of subject identity (lmer (log-corticosterone ~ Back-
ground + (1|Individual), data = Corticosterone_Data).
Faecal corticosterone metabolite levels
We prepared a linear mixed effects model (LME) for the
statistical analyses of the faecal corticosterone metabolite
levels detected. e model included the subjects as a ran-
dom effect as some individuals contributed with multiple
samples. e faecal corticosterone metabolite levels were
log-transformed prior to analysis to obtain normal distri-
bution. An initial model included the background (wild/
rehabilitated), sex and health (dying from Salmonella
infection or not) as fixed effects. As the data was analysed
with faecal corticosterone metabolite levels per individ-
ual as the response variable, we had to exclude a number
of faecal samples (n = 43) collected from enclosures with
more than one individual (cohort 2), or from unknown
wild individuals (cohort 3), unless we knew exactly which
individual the sample came from.
Stepwise reduction of the model’s explanatory val-
ues was subsequently employed, using ANOVA tests
to compare the models, gradually removing non-sig-
nificant terms from the models indicated by the results
of the ANOVA tests. e best fit model included
the background of the subjects, and sex, in addition
to the random effect of subject identity (lmer (log-
corticosterone ~ Background + Sex + (1|Individual),
data = Corticosterone_Data).
Personality tests
To facilitate analysis/interpretation, the data collected
from both the novel arena tests and the novel object tests
were dimensionally reduced using principal component
analysis (PCA). One analysis utilized the data collected
from the novel arena test, a separate analysis was car-
ried out for the novel object test (combining data from
both testing conditions—ball/badger). Varimax rota-
tion was employed, post-extraction, to facilitate easier
interpretation of data. Whereas the number of param-
eters used in both PCAs was high in relation to the num-
ber of subjects, this approach was still deemed preferable
over analysing the parameters individually in, for exam-
ple, ANOVA models.
The eects ofpersonality andbackground onsurvival
Shyness or boldness was established for each of 24 indi-
viduals in cohort 2 based on the three personality tests
(novel arena, novel object ball, novel object badger). Each
individual therefore received three shyness/boldness
labels and were registered as either shy or bold on the
basis of these. In cases where both shyness and boldness
labels were allocated to the same individual, the majority
determined the final personality label (e.g. shy, bold, shy
was labelled shy). Due to challenges during the initiation
phase of the personality tests, two of the individuals sur-
viving to be released back into the wild did not take part
in the novel object tests, and were consequently labelled
shy or bold based on their performance in the novel arena
test. A further four rehabilitated individuals who did not
survive to be released, were additionally categorised as
shy or bold based on their results from the novel arena
test. e division of individuals into a shyness-boldness
spectrum was based on the clustering in the PCA space
by visually distinguishing and ordering the individuals
into the binary categories of shy and bold (See Additional
files 3 and 4). Half of the individuals were categorised as
shy and half as bold based on each of the three PCs repre-
senting the tests (PCA plot for novel arena = PC1, n = 24;
PCA plot for novel object tests: PC1 and PC2, n = 18).
Fisher’s Exact test was employed to test for an effect
of background (wild/rehabilitated) and personality (shy/
bold) in the post release survival of the 17 released indi-
viduals from cohort 2.
Post release spatial behaviour ofindividuals fromcohort 2
e calculations of home ranges, measured as minimum
convex polygons, and kernel density estimates were made
in ArcGIS 10.0 by application of the extension program
Geospatial Modelling Environment. For the kernel den-
sity calculations, bandwidth was set to 500m and cell size
to 1m, as these settings created the smoothest kernels.
We measured the maximum distance from the release
point in Google Maps for the 17 individuals surviving to
be released back into the wild.
Page 13 of 16
Rasmussenetal. BMC Ecol Evo (2021) 21:96
Supplementary Information
The online version contains supplementary material available at https:// doi.
org/ 10. 1186/ s12862- 021- 01816-7.
Additional le1. Overview of individuals from cohort 1. The individuals
of cohort 1 were all in care at a local hedgehog rehabilitation centre.
Additional le2. Overview of individuals in cohort 2. The column weight
indicates the weight in grams of an individual when entering the study.
Additional le3. Novel arena tests: Distribution of individuals in PCA
space. Note that the labelling of the axes is speculative.
Additional le4. Novel object tests: Distribution of individuals in PCA
space. Note that the labelling of the axes is speculative.
Additional le5. PC scores for the novel arena test data.
Additional le6. Novel object tests: Distribution of subjects in PCA space,
labelled by order of test. No obvious effect of testing order can be seen.
Additional le7. PC scores for the novel object tests’ data.
Additional le8. Personality. A table presenting the division of individu-
als into shy or bold based on their behaviour in the three personality tests.
Shy behaviour is indicated by S and bold by B.
Additional le9. Results from the novel object test with a badger setup.
A table presenting the results from the novel object test with the badger.
Total duration: 90 min. “Type” indicates whether the individual was tested
in the novel object test scenario with the badger as the first test (NO1) or
the second test (NO2). ∆t out is the latency time before the individual left
the carrier and entered the arena.
Additional le10. Results from the novel object test with a ball setup. A
table presenting the results from the novel object test with the ball. Total
duration: 90 min. “Type” indicates whether the individual was tested in
the novel object test scenario with the ball as the first test (NO1) or the
second test (NO2). ∆t out is the latency time before the individual left the
carrier and entered the arena.
Additional le11. Results from the novel arena test. A table presenting
the results from the novel arena test. Total duration 900 s/15 min. ∆t out
is the latency time before the individual left the carrier and entered the
arena. ∆t X describes the latency time before the individual reached the
respective zone. ∑ X describes the time spent in the respective zone. V
X is the number of visits to the zone. Background is labelled R for hand-
reared, rehabilitated, and W for wild.
Acknowledgements
The authors would like to thank Helle Runchel Porsdal and Trine Marie Ahlman
Glahder for their technical assistance in the laboratory. We would also like to
thank Dyrenes Beskyttelse (Animal Protection Denmark), Pindsvinevennerne
i Danmark and Pindsvine Plejerne for sharing their hedgehog rehabilitation
data with us, and Pindsvinevennerne i Danmark and Dyrenes Beskyttelse for
allowing us to take samples from hedgehogs in their care.
Authors’ contributions
SLR conceived and led the research projects from which the samples derived.
SLR collected the samples. TD supervised the research projects. KA was
responsible for the laboratory work. SLR, OK and KA analysed the data. SLR
wrote the manuscript with considerable contributions and input from the
other authors. All authors read and approved the final manuscript.
Funding
This work was supported by Dyrenes Beskyttelse (Animal Protection
Denmark), British Hedgehog Preservation Society, Department of Experi-
mental Medicine at the University of Copenhagen, Otto Bruun Foundation,
Lars Eduard Troelstrup and wife Else Troelstrup Foundation, Christen Møller
Sørensen and wife Marie Christine Sørensen Foundation and Headmistress
Sigrid Hansen’s Scholarship.
Availability of data and materials
The datasets supporting the conclusions of this article are included within the
article and its additional files.
Declarations
Ethics approval and consent to participate
The research was performed in accordance with Danish Law (The Adminis-
trative Order on the Protection of Species, Artsfredningsbekendtgørelsen).
Permission to carry out the procedures described in the article was given by
the Danish Nature Agency (J. Nr. SNS-41500-00210).
Consent for publication
Not applicable.
Competing interests
The authors declare that they have no competing interests.
Author details
1 Wildlife Conservation Research Unit, Department of Zoology, The Recanati-
Kaplan Centre, University of Oxford, Tubney House, Abingdon Road, Tubney,
Abingdon OX13 5QL, UK. 2 Department of Chemistry and Bioscience, Aalborg
University, Fredrik Bajers Vej, 7H, 9220 Aaborg, Denmark. 3 Department
of Biology, Section for Ecology and Evolution, University of Copenhagen,
Universitetsparken 15, Building 12, 2100 Copenhagen Ø, Denmark. 4 Depart-
ment of Experimental Medicine, University of Copenhagen, Blegdamsvej 3,
2200 Copenhagen N, Denmark.
Received: 27 September 2020 Accepted: 6 May 2021
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