Forskning - Dr Hedgehog Communications

Here is an overview of some of the different research projects which Dr Hedgehog is conducting

Credits: Louise Marie Jønsson

The Danish Hedgehog Project

The Danish Hedgehog Project uses dead hedgehogs to understand the living, aiming to describe the causes behind the massive decline we witness in the hedgehog populations all over Europe. This enables us to optimise the efforts to conserve hedgehogs in the wild. In 2016, through extensive media coverage, Dr Hedgehog persuaded the Danes to collect dead hedgehogs, especially roadkills, and transport them to the nearest of 26 collection stations spread across the country. The Danish Hedgehog Project ended up with a remarkable 697 dead hedgehogs from all over Denmark, available for research. It's a completely unique dataset, both in terms of its scope and the geographic representation of the entire country. The investigations in the Danish Hedgehog Project are based on extensive interdisciplinary collaborations with specialists from Danish and international research institutions, who contribute with expertise and facilities to the numerous research projects. So far, we have conducted genetic investigations of the Danish hedgehog population and tested, which endoparasites the hedgehogs carry, and which factors determine the prevalence of endoparasites in hedgehogs. We have determined the age of the dead hedgehogs, examined their dental health, and have tested them for antibiotic resistant bacteria (MRSA), and this is only the beginning. Our investigations have led to important knowledge, which is not only ground breaking for the conservation of hedgehogs.

Age determinations of hedgehogs

Out of the total of 697 dead hedgehogs collected in the Danish Hedgehog Project, 388 of them still had intact jawbones that we could use to determine their age! You can count growth rings in hedgehogs' jawbones, just like in trees. Each time a hedgehog goes into hibernation, a ring forms in the bone because the hedgehog does not grow during that period. We found hedgehogs ranging from 0 to 16 years of age. Thorvald, reaching an amazing 16 years, unfortunately died in care due to a dog bite that became infected, and he is the world's oldest documented hedgehog!You can read the scientific publication here.

Kidney disease in hedgehogs

I have established a collaboration with the Royal Veterinary College in London, where specialists examine the kidneys of the hedgehogs collected in the Danish Hedgehog Project to describe kidney diseases in hedgehogs. The research is generously funded by the British Hedgehog Preservation Society.

The food choice of hedgehogs

Once I have successfully raised funds for the project, we will examine DNA from hedgehog faeces to describe the hedgehogs' dietary choices and determine whether hedgehogs are omnivorous or not. These studies will also indicate whether the survival of the hedgehog population is depending on supplementary feeding with cat food in residential gardens.The findings can also be used as an alternative measure of biodiversity, because if hedgehogs have eaten the species, then it was there. Our dataset will tell us precisely where in the country, as well as on what date, the hedgehogs had their last meal. We are very excited to see if we find DNA from rare or endangered species in the hedgehog faecal samples.

The microbiomes of hedgehogs

Due to generous support from the British Hedgehog Preservation Society we are currently screening hedgehog faecal samples collected both in Denmark and England to describe all the bacteria (both beneficial and pathogenic) and fungi that hedgehogs carry. This will enable us to better advise hedgehog carers and thus also target the treatment of sick hedgehogs if we know which bacteria most commonly infect them. However, it is also a method of monitoring bacteria that hedgehogs may risk spreading to other animals and humans. It is relevant to keep an eye on this because we share habitats with hedgehogs and come into close contact with them when we feed them. However, this potential transmission can be avoided if we ensure good hygiene around feeding.

Hedgehog genetics

Our genetic investigations showed that Danish hedgehogs are highly inbred, especially when comparing the results with studies from hedgehogs in other European countries. This is likely due to Denmark being comprised of many islands that are isolated from each other by the sea. Although hedgehogs are good swimmers, we do not expect them to freely move from one island to another. Another possible explanation for inbreeding could be landscape fragmentation, where the landscape is divided by roads, fences, and other barriers, isolating hedgehogs into small populations. This makes it harder for the hedgehogs to find mates, leading them to mate with each other locally. Surprisingly, our analysis showed that inbreeding is lower in rural areas compared to urban, despite studies concluding that hedgehog populations in rural areas are declining the most. Perhaps the lower inbreeding in rural areas is due to fewer roads or less traffic. Or perhaps hedgehogs are able to move more freely when seeking mates because there are fewer obstacles such as impassable fences and settlements in the rural landscape in general. We could divide the Danish population into three main genetic groups: Jutland, Bornholm, and a group consisting of Funen, Zealand, Lolland, and Falster. And these groups could be divided into six genetically different populations in Funen, Zealand, Lolland, and Falster combined, Bornholm, in Jutland north of the Limfjord, and Jutland south of the Limfjord. Our knowledge of hedgehog inbreeding will be a very important factor for further investigations of the dead hedgehogs collected in the Danish Hedgehog Project. There is a lack of solid, scientific data on the effect of inbreeding in wild animals. Therefore, the Danish Hedgehog Project will contribute significantly to this knowledge, as we investigate whether inbreeding affects hedgehog lifespan, parasites, bacterial flora, cancer risk, and dental health, among other factors.

Coronavirus in hedgehogs

We have tested hedgehog faecal samples from Danish and English hedgehogs to describe which coronaviruses they carry, with a particular focus on understanding whether they can become infected with SARS-CoV-2, the virus that caused COVID-19. The results will be published soon.

Endoparasites in hedgehogs

We have tested the dead hedgehogs collected in the Danish Hedgehog Project for endoparasites and found that up to 2/3 of the hedgehogs have endoparasites in their bodies! This means it is completely natural for them to carry endoparasites, and therefore we could conclude that they should only be treated for endoparasites if the burden becomes so significant that it leads to physical symptoms such as weight loss and respiratory problems. I explain the results here, and you can read the scientific publication here.

MRSA and ringworm in hedgehogs

Our hedgehog research led to a groundbreaking discovery. 188 of the collected dead hedgehogs from the Danish Hedgehog Project were swabbed for the bacterium methicillin-resistant Staphylococcus aureus (MRSA) in their snouts, and it turned out that up to two-thirds of the hedgehogs carried this antibiotic resistant bacterium, without getting sick from it. Such a high occurrence of MRSA, i.e., Staphylococcus aureus bacteria resistant to a particular type of antibiotic (methicillin), had never been seen before in wild animal species. We also tested hedgehog carers to investigate whether the bacterium was transmitted to humans with close contact to hedgehogs, and found that none of the carers tested positive for MRSA. To understand why hedgehogs often carry mecC-MRSA, we decided to conduct further investigations, which showed that the mecC gene, which provides resistance in mecC-MRSA, has arisen entirely naturally in hedgehogs for up to 200 years ago. You can read more on this ground breaking discovery here and here. However, it should be added that when hedgehogs have carried this resistant bacterium for 200 years without causing epidemics in the population, there is no need to worry about having hedgehogs visiting your garden.

Eco-toxicology and hedgehogs

We have screened liver samples from dead hedgehog collected in the Danish Hedgehog Project to describe the prevalence of pesticides and other xenobiotics in the hedgehog population. We detected pesticides in 9 out of 10 individuals. here.

Dental health in hedgehogs

We have performed dental investigations of almost 100 of the dead hedgehogs collected in the Danish Hedgehog Project to describe which dental diseases the hedgehog suffer from. The results will soon be published.

Hedgehogs and robotic lawn mowers

Hedgehog friendly robotic lawn mowers

In 2020, I initiated my research on robotic lawn mowers and hedgehogs, as there had been stories in the media for some years about robotic lawn mowers harming hedgehogs. I decided to investigate the matter scientifically, by testing whether robotic lawnmowers could harm dead hedgehogs (dying in care). It turned out that some models of robotic lawn mowers did harm the dead hedgehogs, while others did not. You can read more about it here. Subsequently, I decided that it was important to address this issue since it is possible to make a difference for hedgehog survival in residential gardens by creating hedgehog-friendly robotic lawn mowers. Therefore, I initiated a strong collaboration with the industry, the robotic lawn mower manufacturers STIHL and Husqvarna, and we are using the research results produced by my research team, to develop more hedgehog-friendly robotic lawn mowers. Here is a video describing the workOur research team also created a safety test, which can assess whether a robotic lawn mower is hedgehog friendly. The goal is for this safety test to be incorporated into the official testing procedure that approves robotic lawn mowers for sale on the European market. Additionally, we have also created a hedgehog crash test dummy that can be 3D-printed and used in future tests, including manufacturers, in their process of designing hedgehog-friendly robotic lawn mowers. My aim is for these tests to lead to a labelling scheme indicating whether a robotic lawn mower is hedgehog friendly, so consumers are guided to purchase the right products. This way we can reduce the risk that hedgehogs are harmed by robotic lawn mowers in the future. That is truly applied research.

Hedgehog hearing

What can hedgehogs hear?

Shortly, we will conduct tests on hedgehog hearing for the first time. We hope that the insight gained from these studies can be used to improve hedgehog conservation efforts.

Stress, personality and survival in hedgehogs

Stress in rehabilitated hedgehogs

In this research project, we examined the personality of hedgehogs, their survival after rehabilitation, and their levels of stress hormones to understand if hedgehogs became stressed from being in care, and if their personality affected their survival. We found that personality (shy or bold) did not affect survival, but hedgehogs in care generally had higher levels of stress hormones. This is not surprising, as hedgehogs are wild animals. But it clearly shows the importance of not keeping hedgehogs in care longer than necessary, as prolonged stress can be very harmful. In this video I explain the results. The scientific publication can be read here.

The survival of juvenile hedgehogs in the Danish gardens

How are the hedgehogs surviving in the Danish gardens?

I have investigated the survival of hedgehog juveniles through their first year of life in Danish suburban gardens to understand the challenges they face and what we as garden owners can do to improve the hedgehogs' chances of survival. I found that approximately 70% of hedgehog juveniles survived the first year, and unfortunately, attacks from dogs and foxes, drowning, poisoning, infectious diseases, and injuries caused deaths among hedgehogs. Hedgehogs typically lived in areas consisting of 10-14 suburban gardens, and the fatter they were before hibernation, the more weight they lost. They typically changed nests once during hibernation, but some changed nests up to 8 times. They particularly liked living in leaf piles, compost heaps, hedgehog houses, under woodpiles, and in dense vegetation under bushes and in ivy beds, but also under playhouses and wooden decks. They were very adaptable in their choice of nests. Some even lived in rubbish piles. You can read the scientific publication here.

Genetic syndromes in hedgehogs

Pug-nosed dwarf hedgehogs?

Over the past few years, hedgehog juveniles have emerged in care that do not resemble typical hedgehogs. They have flatter noses, shorter legs, and do not thrive. Therefore, in collaboration with colleagues at the Royal Veterinary College, I have initiated a research project where we ask hedgehog carers from across Europe to collect these "syndrome hedgehogs" for us if they pass away in care, so we can describe the condition and investigate it genetically to understand what causes it. We also ask hedgehog carers to report to us when they receive such hedgehogs in care by filling out this questionnaire.

Madras hedgehogs

Madras hedgehogs (Paraechinus nudiventris)

I have also initiated collaborations with Indian and Pakistani researchers where we will describe the biology and distribution of the Madras hedgehog. There is almost no research done on this species, and we suspect it is endangered, so it is extremely important to research the Madras hedgehog so we can help conserve it in the wild.

The hedgehogs on Uist

I am conducting research on the hedgehogs inhabiting the islands of Benbecula and South Uist to discover their diets and microbiomes (which bacteria they carry) and endoparasites. This is because the hedgehogs were introduced to the Uists in 1974. Due to the absence of predators of hedgehogs on these islands, the hedgehogs thrived a little too much, and started to pose a threat to the ground nesting birds on the islands, as the hedgehogs eat their eggs and nestlings. This is why a translocation programme is being planned, where the hedgehogs will be caught and released in mainland Scotland. We just want to do our best to avoid that the hedgehogs from the Uists introduce new parasites or diseases into the local, Scottish population once they are released. By sampling hedgehog faeces and using eDNA methods, we will describe the endoparasites, diet and microbiomes of the Uist hedgehogs.