Hedgehogs are small, spiny mammals belonging to the order Eulipotyphla. Today there are around 16 species spread across Europe, Africa and Asia, and they’ve also been introduced by humans to places like New Zealand. Beyond their cute appearance, they have some very unusual behaviours and adaptations.
Below you’ll find 10 curiosities about hedgehogs: where they come from, how their “armor” works, what they eat, why they cover their spines with foam, and even why they’re restricted as pets in some countries.
1. Hedgehogs are part of an ancient mammal lineage
Hedgehogs belong to an early branch of placental mammals (eutherians).
Fossils with spines similar to those of modern hedgehogs suggest that their basic body plan has been around for millions of years.
Today we recognise about 16 species in five genera.
They occur naturally in Europe, Africa and Asia, with introduced populations on some islands.
The European hedgehog (Erinaceus europaeus), for example, is widespread across much of Europe and adapts well to gardens, farmland and other human-modified landscapes.
2. Their spines act like a flexible suit of armor
One of the most famous hedgehog facts: those spines aren’t just for show.
An adult can have 5,000–7,000 spines, which are modified hairs made of keratin, about 2–3 cm long.
Under the skin they have a ring of powerful muscles that can raise or flatten the spines and pull the skin tight, allowing the hedgehog to curl into a ball.
When fully rolled up, it protects its belly, legs and face, exposing only a dense, prickly surface.
Unlike porcupines, hedgehogs don’t shoot their spines and they don’t fall out easily. They’re replaced gradually, like hair. This defensive “armor” discourages predators such as foxes, badgers and dogs, and can absorb bites long enough for the hedgehog to escape.
3. They have excellent senses (even if they don’t see well)
Hedgehogs don’t rely on good eyesight. Instead, they depend on:
Poor but functional vision mainly for close objects
A highly developed sense of smell
Very sensitive hearing, capable of detecting high-frequency sounds (including some ultrasound)
Their long snout constantly explores the ground by smell and touch, guiding them on night-time foraging walks that can cover 1–3 km in a single night.
Strong claws help them dig shelters and search for prey in the soil and leaf litter. All these abilities together compensate for their short-sightedness and allow them to move efficiently through hedgerows, gardens and fields, even in cold or windy nights.
4. Their diet is flexible and more varied than many people think
Hedgehogs are often described simply as insect-eaters, but in reality they are opportunistic omnivores with an insectivorous base.
In the wild they commonly eat:
Beetles, caterpillars and other insects
Earthworms, slugs and snails
Occasionally eggs, frogs and small mammals when they can catch them
This flexible diet helps reduce competition with other species and keeps their energy levels stable throughout the year.
In captivity, responsible diets use:
High-quality, low-fat cat food or specific insectivore diets as a base
Supplementation with insects (e.g. crickets, mealworms) and small amounts of vegetables
Milk and dairy products are not suitable: most hedgehogs are lactose intolerant and can suffer digestive problems if they consume them.
Their mouth holds 36–44 sharp teeth, and a relatively short digestive tract, both adapted to processing chitin (insect exoskeletons) and animal protein efficiently.
5. They perform a strange behaviour called “self-anointing”
One of the weirdest hedgehog behaviours is self-anointing (or self-anointing).
When a hedgehog encounters a new or strong smell, it may:
Lick or chew the source of the smell.
Produce a frothy, foamy saliva.
Twist and contort its body to spread this foam over its spines.
Scientists still don’t fully agree what this behaviour is for, but the main hypotheses include:
Scent camouflage: blending its own smell with that of the environment.
Chemical defence: if the substance is bitter or irritating, spreading it on the spines could make the hedgehog less attractive to predators.
Learning and exploration: a way of “processing” new sensory information.
Social signalling: possibly carrying odours that convey information to other hedgehogs.
The hedgehog itself doesn’t produce poison during this process – it mainly uses external substances it finds.
6. They save energy through hibernation and torpor
In cold climates, hedgehogs use extreme energy-saving strategies:
In autumn they eat a lot to build up fat reserves.
When winter arrives, they can enter hibernation:
Body temperature drops considerably.
Heart rate and breathing slow down dramatically.
Metabolism is reduced to a minimum.
During hibernation they may wake up briefly, change position, move to another nest or drink water, and then return to a torpid state.
In very hot and dry conditions some species can also enter aestivation (summer torpor), reducing activity to cope with heat and lack of food.
In captivity, sudden drops in temperature can trigger dangerous, uncontrolled torpor, so pet hedgehogs need a stable, suitable thermal environment.
7. They are solitary and not monogamous
Hedgehogs are not social pets and they are not monogamous.
In nature they are solitary and usually meet only to mate.
Males don’t form long-term pairs or help raise the young.
Breeding facts:
Litters typically contain 2–6 babies.
Newborns have soft, white spines under the skin that harden within a few days.
At 6–8 weeks the young are already independent and weigh about 250 g.
In the wild, many hedgehogs die from predation, traffic, or disease, so their average lifespan is only about 3–5 years. Under good care in captivity, some individuals can live up to 8–10 years, which shows how strongly environment influences their true life expectancy.
8. Some hedgehogs can tolerate certain venoms
Hedgehogs are not venomous, but some species show partial resistance to certain snake toxins.
They have modifications in nicotinic acetylcholine receptors, which reduce the effect of some α-neurotoxins found in snake venom.
This is similar to what happens in mongooses and opossums, which also show some resistance.
This does not mean hedgehogs are immune to snakebites, but it may reduce the impact of certain bites and broaden the situations they can survive. They also tolerate some bitter plant compounds, which may be relevant during self-anointing when they cover their spines with substances from the environment.
9. Keeping hedgehogs as pets is restricted in several places
Because of concerns about invasive species and diseases, hedgehog ownership is:
Restricted or banned in some countries and regions, such as Spain and U.S. states including California, Georgia and Arizona (regulations can change, so always check local laws).
Reasons include:
Risk of hedgehogs becoming invasive if released or escaped.
Possible transmission of salmonella, skin fungi and external parasites.
Negative impacts on local wildlife: wild hedgehogs play an important ecological role as invertebrate controllers in their native habitats.
For these reasons, conservationists often recommend enjoying wild hedgehogs responsibly, creating hedgehog-friendly gardens (with shelter, safe access and no toxic pesticides) instead of capturing animals from the wild.
10. Hedgehogs are surprisingly diverse
Although many people picture the classic brown European hedgehog, the group is actually quite varied:
Some populations, especially on islands, show cream or “blonde” colour morphs, caused by rare recessive genes.
Desert species tend to have larger ears, which help with heat regulation.
There are differences in:
Number of toes
Tooth structure
Nesting habits and preferred habitats
Most hedgehogs are terrestrial, but many are capable swimmers and can climb low obstacles or banks when necessary.
All of this diversity reflects their ability to adapt to temperate, Mediterranean and semi-desert environments, explaining why they have been so successful in rural mosaics, farmland edges, parks and even some urban green spaces.
If you’re interested in hedgehogs, it’s always worth combining this kind of general knowledge with local information about the species in your region and the best ways to protect them in the wild.
Bibliografía
Animalia. https://animalia.bio/
Kowalski K, Rychlik L. Venom Use in Eulipotyphlans: An Evolutionary and Ecological Approach. Toxins (Basel). 2021 Mar 22;13(3):231. doi: 10.3390/toxins13030231. PMID: 33810196; PMCID: PMC8004749.
Scholtz, Gerhard (2008). Scarab beetles at the interface of wheel invention in nature and culture?». Contributions to Zoology (National Museum of Natural History Naturalis) 77 (3). ISSN 1875-9866.
University of London. (2022). AFRICAN PYGMY HEDGEHOG CARE. https://www.rvc.ac.uk/Media/Default/Beaumont%20Sainsbury%20Animal%20Hospital/EXOTICS/Animal%20Care%20Factsheets/African-pygmy-hedgehog-care-and-advice-Dec-2022-NS-1.pdf#:~:text=solitary%20life%2C%20mainly%20sleeping%20during,handled%20from%20a%20young%20age
