First International Hedgehog Workshop European Hedgehog Research Group 25.-28.4.1996, in Arendal, Norway. ABSTRACTS OF PAPERS PRESENTED The first results of the hedgehog survey
in Latvia
Study of the distribution and ratio between
Erinaceus europaeus and Erinaceus concolor in Latvia is described. This
study was carried out as part of a Latvian mammal atlas project from 1992
to 1995. Questionnaires were the main source of information. Latvia lies
on the distribution edge of both hedgehogs species. The main distribution
area of E. europaeus is situated to the north, but E. concolor's to the
south. E. europaeus is found in northern, western, and central regions
of the country. In eastern region E. europaeus is not found. E. concolor
dominate; E. europaeus is rare in Latvia. Distribution map is based on
the standard European UTM-grid system.
How many hedgehogs are there, how can
we count them?
Hedgehogs live at a relatively low population
density, so conventional mark and recapture methods of estimating population
size over a large area would require considerable trapping effort. Hedgehogs
can easily be caught by hand, using a torch to find them but a study in
New Zealand indicates that overestimates result from sampling a study area
that is too small. We have attempted to use transect sampling to estimate
population density, but even 80 m of transects provided insufficient captures
to make a statistically reliable population estimate. However, the estimate
did more or less agree with capture-mark-recapture estimates made using
the same animals. Densities of around one animal per hectare are normally
found, but these are in study areas where there are plenty of hedgehogs
present and easily seen. It would be even more difficult to obtain reliable
estimates from habitats and areas where hedgehogs were harder to see the
possibility of using roadkills as an index of relative abundance has also
been investigated. A much higher incidence of roadkills was found in New
Zealand, compared to Britain. This suggests that traffic density is not
a complicating factor as there are far fewer vehicles on the roads in New
Zealand. Within Britain, regional differences were consistent from year
to year, with the north east having more kills per 100 miles of road than
the south east (where traffic densities are higher). However, there is
evidence that the method is fundamentally flawed. It appears that once
an observer has seen one hedgehog, he is more likely to notice another.
Thus the sampling intensity is not consistent.
Demographis variables of a hedgehog
(Erinaceus europaeus) population and road mortality
Demographic variables and road mortality
in a (sub)adult hedgehog population were studied in a small scale 150 ha
agricultural landscape located near Elburg, The Netherlands. Animals were
captured using traps after which they were individually marked with ear-
and spine marks. In 1994 6 trapping sessions took place, and an additional
4 in 1995. At the same time all roads in and around the study area were
intensively checked for traffic victims.
Variations among British Hedgehogs
The British hedgehog was described as a
distinct. subspecies earlier this century, but the features that distinguish
it are greatly affected by age changes. It is likely that 'our' hedgehog
is not significantly different from those elsewhere in north west Europe,
except perhaps in having a smaller average size. Within Britain, the animal
seems to vary little. Many have significant numbers of white spines, a
variation that has not been eliminated by natural selection, presumably
because the spines offer sufficient protection from predators that there
is no disadvantage in being different from normal. Albino hedgehogs are
reported fairly often in the popular press, from many parts of the country.
Leucistic hedgehogs are extremely rare on the mainland, but on the island
of Alderney, 25% of the population are of this type. Melanistic hedgehogs
have never been reported in Britain. A preserved spineless hedgehog exhibited
at a 19th century scientific meeting was probably a fake. However, two
recent examples of hedgehogs lacking spines were quite dissimilar. One
had an almost total failure of keratin production and an unpigmented skin.
This was probably a genetic abnormality. The other animal had a dark skin
and some hairs with a very few, distorted spines. It had been normal until
about 6 weeks old, then lost its spines. It is not clear why. It lived
to be six years old.
X-Ray measures of long bones as an aid
to the age-determination in hedgehogs
The determination of the age of wild animals
is an especially key component of demographic studies but it is also very
important in many other kinds of enquiry. In the present study the aim
was to find an expedient and accurate method of age determination for a
sample of 68 road-killed hedgehogs as part of an ecotoxicological investigation.
Various methods suitable for both live and dead animals were reviewed but
the study concentrated on determining the usefulness of ulna and dentary
length measures to aet as a cross-check against two age- determination
methods commonly used in hedgehogs: i) periosteal growth line counts from
stained sections of the dentary bone - a potentially absolute method; ii)
the categorisation of the stages of epiphyseal fusion in the manus - a
relative method. Inter-rater reliability in the determination of periosteal
growth line counts was also studied. X-ray radiographs were used for both
the categorisation of epiphyseal fusion stage and for the ulna length measures.
Dentary length was measured directly from the dissected out jaw.
Radio-tracking and home range studies
of hedgehogs
This paper provides a synthetic review
of radio-tracking and home range studies of
Juvenile dispersal and survival of sub-urban
hedgehogs in Trondheim, Norway
In Scandinavia there has been a very few
studies of juvenile hedgehogs. I wanted to study out what happened to the
juveniles from the moment they left the nest and five weeks forward and
to study dispersal and especially the mortality factors and rate. The mortality
among juvenile hedgehogs in Trondheim is especially interesting because
during the last 10 to 50 years the population has decreased. The reason
to this decrease would have been very interesting to find out.
Smallscale distribution and habitat
use as determined by food dispersal:
At a local scale the spatial distribution
and foraging behaviour of hedgehogs (Erinaceus europaeus) were analyzed
to investigate the influence of food availability and social organisation
on the pattern of distribution and abundance. The factors that can determine
the local distribution of foraging hedgehogs were studied, including prey
distribution, foraging success, food searching behaviour and size, age
and sex of hedgehogs. It was found that the relative increase in the density
of hedgehogs was directly proportional to the relative increase in the
density of earthworms and that the intake rate was systematically higher
in sites with high densities of worms than in poor sites. Heavy females
used more intensively the better sites and spent more time per night in
the habitat indicating a differential access to those sites by individual
hedgehogs.
Habitat use of hedgehogs (Erinaceus
europaeus) in a small scale agricultural landscape
Habitat use of five male and five female
adult hedgehogs was studied in a small scale 150 ha agricultural landscape
located near Elburg, The Netherlands. Animals were captured using traps
after which they were equipped with radio-transmitters. Individual animals
were tracked during 1-6 nights between July and November 1995. Every 10
minutes a location (N=774), obtained through actual sighting, was plotted
on a habitat map. Habitat selection was determined by comparing habitat
use with the relative area of the habitat types that were present, both
on the map as a whole, and within the home ranges of the individuals.
Some data about Eastern hedgehog (Erinaceus
concolor Martin, 1838) in Lithuania.
The data of two projects which had been
undertaken in 1959/61 and 1982/83 as well as other available information
on hedgehog in Lithuania were summarized.
Hedgehog Rehabilitation in Perspective
Several thousand British hedgehogs are
taken into care each year; mostly injured animals or small, late-born young
unlikely to survive hibernation. Those which survive are released back
into the wild, mostly in spring, but until recently there was little information
on their post-release welfare, behaviour and survival. A number of studies
have now been undertaken in different regions of Britain which show that
the majority, both adults and juveniles who had never experienced independent
life in the wild, survived surprisingly well. They found both food and
nest sites, made nests and very rapidly leamed their way about. All lost
weight intially but, after two to three weeks, they stabilised at a similar
weight to wild caught animals. Those which were heaviest at release lost
the greatest percentage of their weight. This suggests that they were heavier
than normal at the end of their captivity but this may facilitate their
survival during the intial period of life in the wild. Those hedgehogs
which did not survive (22%) included two road casualties and three eaten
by badgers; misfortunes which might happen to any hedgehog. It is possible
that their susceptibility to badger predation may be increased by tameness
acquired during captivity. Nevertheless, all these hedgehogs would have
died anyway had they not been taken into care. That so many survived, so
successfully, after release indicated that the work of carers is certainly
beneficial.
The survival and welfare of hedgehogs
(Erinaceus europaeus) after release back into the wild
The fate of rescued hedgehogs released
back into the wild after a period of captive care has now been the subject
of a few follow-up radio-tracking studies. Despite being subject to a number
of hazards, released hedgehogs clearly show essential 'life-skills'. However,
all studies have involved releases into hedgehog-rich areas and the observed
long-range dispersal movements shown by some subjects could be a consequence
of local intraspecific competition. The present study has reduced a number
of potentially confounding subject variables and provides follow-up data
on 12 age-matched female hedgehogs with similar histories. A main group
(n--10) was released into a rural woodland area (Surrey, UK) of low natural
hedgehog density and low badger activity, and were radio-tracked for up
to 108 days. A pilot release of 2 animals in an urban area with an established
hedgehog population also took place (tracked for 109-131 days). Most of
the main study group dispersed from the release site, those in the urban
site did not. This suggests that dispersal is not specifically the result
of intraspecifie competition. Observed behaviour and patterns of weight
change were similar to those previously reported. Overall survival at 8
weeks was 6 (50%) plus two lost animals; comparable with previous studies
but down to 3 (25%) plus 2 lost animals by week 15. Of 7 recorded deaths,
only one was the result of a failure to thrive and all other deaths (4
road deaths, 1 drowned in a pond, 1 badger predation) were accidental.
The study concludes that the hazards of the human environment seriously
threaten the welfare and survival of both released and wild hedgehogs in
the area. Further studies involving the release of similar groups with
concurrent monitoring of a matched cohort of wild hedgehogs are planned.
Heavy metals in the European hedgehog
Erinaceus europaeus
Many invertebrate species are good metal
accumulators. As a result, mammals which prey on invertebrates can ingest
a metal-rich diet in contaminated areas. Hedgehogs have a predominantly
invertebrate diet and can be relatively long-lived; some heavy metals,
such as cadmium, accumulate with age. Therefore, it is possible that hedgehogs
may accumulate large amounts of heavy metals. However, there do not appear
to be any published data on heavy metal residues in the Erinaceidae. In
the present study, we collected 67 dead hedgehogs from three sources, road
kills in the Cambridgeshire area (n=38), animals which died in rehabilitation
hospitals (n=19) and road-kills from the Avonmouth/Bristol area (n=10).
All animals were aged by assessing the degree of epiphyseal fusion in the
bones of the manus and forelimbs and counting the number of growth lines
in sections of the lower jaw. The concentrations of the pollutant metals
cadmium (Cd), lead (Pb), mercury (Hg), and the essential trace elements
copper (Cu) and zinc (Zn) were measured in the liver, kidney and femur
of each animal. Heavy metal residues in/on the prickles were also measured
to determine whether these were correlated with levels in the body organs.
Residues varied significantly in magnitude between the different tissues
analysed for all five elements. The highest median concentrations (m g
g-1 DW) were in the kidney for Cd (7.52) and Hg (4.2) and in the liver
for Cu (85.3) and Zn (281); median Pb concentrations were highest in the
femur (18.9) although they were similar in the liver (12.5). Although median
levels of the pollutant metals were generally low, some individual animals
had high kidney burdens, the maximum concentrations detected being 290,
100 and 780 m g g-1 DW for Cd, Pb and Hg respectively. These concentrations
are above those associated with adverse physiological effects in mammals.
There were no consistent differences between males and females in residue
magnitude. Cd and Hg increased significantly with age in the liver and
kidneys as did Pb in the kidney and femur. Cd concentrations also varied
significantly between animals from different locations and were highest
in males from the Avonmouth/Bristol area, an area of known Cd contamination.
Cu and Zn levels were significantly correlated with the levels of the pollutant
metals in both the liver and the kidney. Residue levels in unwashed prickles
were significantly correlated with concentrations in the body organs but
only for Pb (all three tissues) and for Cu (kidney only). The results of
this study demonstrate that hedgehogs are exposed to and accumulate heavy
metals, that Cd, Pb and Hg burdens increase with age (presumably because
of increased length of exposure) and that some animals are likely to suffer
adverse physiological effects as a result of their heavy metal burdens.
The study has also demonstrated that analysis of prickles may be of use
in predicting the body organ concentrations of Pb (but not Cd and Hg) and
so might potentially be a useful biomonitor of Pb pollution.
Does road mortality affect hedgehogs
(Erinaceus europaeus)?
Hedgehogs are one of the most common road
victims among mammals. Only a limited number of studies have focused on
quantifying road mortality in combination with population size and losses.
However, these studies do not address the question whether the size, presence
or structure of populations is affected by road mortality or not. There
are two basic strategies to answer this important question: 1. to build
a population model on which road mortality may be simulated (bottom-up),
and 2. to determine whether the size or presence of the populations is
affected to such an extend that we are able to measure it in the field
(top-down).
Some remarks for raising orphaned hedgehog
babies
In 1995 we got new facts about the composition
of hedgehog mother's milk by a dissertation of a German vet. This is essential
to find out the best substitute milk for orphaned hedgehog babies. Details
about the natural mother's milk and the substitute milk will be given in
that talk. The results of practical experiences of various nurses from
all over Germany and the difference between handraised babies and babies
raised by the natural mother will be shown and explained by overhead diagrams.
Tasks of the FG
The main task of the FG was originally
to clarify if hibernation in human care is useful, a contrivers question
among experts. Besides we wanted to find out how strong the conflict was
between protectors of species and protectors of animals in the former German
Democratic Republic.
Recapture rates
This report shows that safe markings make
it possible to obtain facts about essential biological datas. The observation
area is characterized and the difficulties working in settlement areas
are described. Feeding methods and the preparation of diet are explained.
How does hibernation vary with latitude?
Hedgehogs arouse during hibernation, even
in constant laboratory conditions. In the wild (at least in Britain) it
is unusual for them to remain in the same nest throughout the winter, again
suggesting that they awake normally, perhaps in response to warmer weather,
then resume hibernation. It is reported in the popular press that hedgehogs
are becoming active in February as a result of global warming, but this
is nothing new. Many books give dates for hibernation, but it is not clear
what is the scientific basis for such statements, when the animal's behaviour
seems to be quite variable. It is possible that the average dates of starting
and ending hibernation vary according to latitude (reflecting different
climatic conditions, particularly longer winters further north). An attempt
has been made to use roadkill data to investigate regional variations within
Britain. The results suggest that there may be small differences between
the north and south of Britain in hibernation behaviour, but these are
probably not statistically significant. However, a similar study across
Europe might yield more conclusive results. Longer hibernation means a
shorter breeding season. This has an impact on life strategies. Perhaps
shorter breeding seasons mean few litters can be raised and litters need
to have a higher mean size. Again, comparative data would be interesting.
There must be a limit to the way that increased litter size can compensate
for fewer litters. Perhaps the squeezing of the breeding season, and limited
maximum litter size are factors that control distribution in northern Europe?
Conversely, in New Zealand, hibernation is barely necessary at all in the
North Island. Two litters, perhaps even three may be raised in a year.
Perhaps as a result, the average hedgehog population density in New Zealand
is probably at least 5 times higher than in Britain.
Breeding biology of hedgehogs in Britain
In captivity, hedgehogs can produce three
litters in a year, especially if they lose an early litter. In the wild
it is unlikely that they ever do so, because the breeding season is not
long enough. In Britain, there are a significant number of litters born
late in the year (eg in September), but it is not clear whether these are
second litters or the first litters born to animals that were too young
to breed earlier that year. Anyway, these late born young must attain a
weight of at least 450g to be fat enough to survive the winter. Many fail
to do so and die. Thus, late litters probably do not add significantly
to the size of the breeding population in the following year. Mean litter
size is about 4.6 in Britain, based on embryo counts. Does it differ elsewhere
in Europe? A simple study was initiated, asking the public for observations
on the size of litters found in accidentally- discovered hedgehog nests.
The observations were divided into 'early' and 'late' young, based on appearance.
Family size was also noted where babies were seen with their mother. This
study suggests that nearly 20% of young hedgehogs die before weaning, with
the possibility that large litters may be lost entirely. Pre-weaning mortality
has rarely been studied in other mammals. However, this study could easily
be repeated in other European countries to obtain comparative information
about hedgehog reproductive success.
Breeding, mate selection & courtship
behaviour in the hedgehog (Erinaceus europaeus)
There remain serious gaps in our knowledge
of the breeding biology and sexual behaviour in hedgehogs and many ideas
and predictions remain to be tested with field data. In England, sexual
activity in hedgehogs occurs principally from May to mid-August, although
courtship or pregnancies may occur from March to October. It is widely
stated that hedgehogs in Britain may sometimes bear two litters in a season,
but no field studies have ever confirmed this. Preliminary studies have
shown that both sexes may court multiple partners but over M of 76 observed
courtships did not result in mating. Mate-guarding was never observed.
This, and other preliminary research has raised many questions about mate
selection, the possibility that females may accept multiple matings, the
likelihood of competitive exclusion of rivals by male suitors and many
other key issues. This paper discusses the limited information gathered
so far, and considers the requirement for further work. Previous captive
studies have indicated the apparent deployment of odour cues during courtship
but such behaviours have never been systematically observed in a natural
context. The possible role of self-anointing is also considered. There
is an urgent need for more rigorously collected physiological and behavioural
data that could improve our functional interpretation of breeding biology,
courtship behaviour and its adaptive consequences. Such data would improve
our ability to make population viability assessments of hedgehogs where
their populations are under threat from factors such as predation, road
mortality, or habitat degradation.
Urban hedgehogs in Zurich, Switzerland:
spatial distribution and habitat use.
An urban hedgehog population was studied
by means of radio tracking in the city of Zurich (360'000 inhabitants,
6500 ha urban area) in 1992. In order to get information on spatial distribution
and habitat use, 11 individuals were fitted with a transmitter and followed
during 35 complete nights. Additionally in a public inquiry of 20'000 inhabitants
interested in nature and animals 1383 observations of hedgehogs were collected.
These observations showed, that hedgehogs are distributed over a large
part of the city (69% of the total urban area). Estimations in two core
study areas showed, that hedgehogs can be quite abundant (0.5 - 1 hedgehog
/ ha). On the other hand in the city centre there are areas with very few
or no hedgehogs at all. The low abundance of hedgehogs in those areas is
correlated with a very high degree of build over space with lots of houses,
streets, places etc. and very little open space such as parks, gardens
etc.
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