Helping Hedgehogs Without the Common Mistakes: Robot Mowers and Slug Pellets Are the Real Danger

When October shortens the days and the first frost settles on the lawn, he turns up again: the hedgehog, rustling through the beds in the evening. Most gardeners want to help him, and many build a hedgehog house for that. It is well meant, yet a missing hedgehog house is almost never the problem. The real dangers are less obvious: a robot mower that keeps running after dark, a handful of slug pellets in the bed, a light shaft with no way out. This article shows you how to really help during the window from CW 40 to CW 46, and which well-meant mistakes are better left undone.

Auf einen Blick

The three biggest avoidable hedgehog killers in the garden are robot mowers, slug pellets and open shafts. A missing hedgehog house is not on the list.
Switch your robot mower off from sunset to sunrise. Hedgehogs are nocturnal, curl up when threatened and do not flee.
From CW 40, leave a pile of leaves lying in a quiet corner. It is the best winter quarters you can build, and it costs nothing.
Skip the slug pellets and poison. The hedgehog eats the poisoned slugs and slowly dies with them.
A hedgehog staggering about in daylight or weighing clearly under 500 grams needs help: weigh it and call a hedgehog rescue.

Why the hedgehog house is almost never the problem

Hedgehog houses are popular because they feel good: you build something, put it out and have the sense that you have helped. But the hedgehog by no means moves into every house, and an empty house protects nothing at all. A hedgehog overwinters wherever it finds a dry, frost-free, undisturbed shelter: under a hedge, in a brushwood pile, beneath the garden shed. What kills him is not a lack of comfort, but injury, poisoning and hunger. So deal with the dangers first, then with the comfort.

The robot mower: danger number one

The robot mower is the most underestimated danger. It runs quietly, often on a schedule, and many models prefer to mow during the cool evening hours. That is exactly when the hedgehog is out and about. And here comes the fatal misunderstanding: a hedgehog does not flee from danger, he curls up and stays put. Against a predator that is perfect; against a rotating blade it is a death sentence. Every autumn, hedgehog rescues see the same severe cutting injuries.

Ein Mähroboter zieht seine Bahnen über einen kurz geschorenen Rasen. — Der Mähroboter ist die größte vermeidbare Gefahr für Igel. Nachts abgeschaltet, wird er harmlos.· Foto: W.carter, Wikimedia Commons

The solution is simple and costs you nothing but a setting in the app.

Set a night curfew
Set your robot mower to run only between sunrise and sunset. Hedgehogs are active almost exclusively at dusk and at night.
Check the lawn before mowing
In autumn especially, it pays to glance across the lawn before you mow by hand. A hedgehog in tall grass is easy to miss.
Mow the edges higher
Leave the transitions to hedge and bed a little taller. That is where the hedgehog runs, and there he finds cover.

A robot mower running at night is no theoretical danger. The typical injuries are deep cuts that end fatally without veterinary care. The night curfew is the single most important measure in this article.

Danger 2: slug pellets and poison

The second big mistake is chemical slug control. The logic is understandable: slugs eat the lettuce, so you scatter slug pellets. But the hedgehog loves to eat slugs, and he does not tell healthy from poisoned. He eats the sluggish, dying slugs first, because they are easy prey, and so takes in the poison in a concentrated dose. Metaldehyde, the classic active ingredient, leads to convulsions and a slow death. Rat poison works the same way.

In fact the hedgehog is your best ally against slugs: a single animal devours dozens of slugs in one night. Whoever scatters slug pellets poisons exactly the helper who would have cleared them for free.

Slug collars instead of poisonA metal collar or a raised bed edge keeps slugs out mechanically, entirely without any active ingredient.
Collect them at duskIn damp weather, do a round in the evening and gather up the slugs. Tedious, but effective and non-toxic.
Encourage beneficial creaturesGround beetles, hedgehogs and toads keep slugs in check if you leave them habitat. Iron(III) phosphate is also considered gentler than metaldehyde, but still belongs in sparing use.

Danger 3: garden traps you overlook

Besides the mower and poison, there are quiet traps that cost hedgehogs their lives every year. They are defused with just a few steps.

Cover light shafts and pits
A light shaft without a grille is a deadly trap: the hedgehog falls in and cannot get out again. Cover it with a close-meshed grille.
Give the pond edge an exit
Hedgehogs can swim, but they drown at a smooth, steep pond edge. A shallow bank or a board laid down as a ramp saves lives.
Do not shred leaves blindly
Before you move a leaf pile or start the shredder, poke through it carefully. A hedgehog might already be sleeping in there.
Create a fence gap
A hole about 10 by 10 centimetres in the fence to the neighbour lets the hedgehog roam. He covers up to two kilometres a night and needs several gardens.

The first night frost arrives in many regions from mid-October · CW 42. No reason to panic: a healthy hedgehog with enough weight survives frost easily in its nest. More important than the cold is that its quarters stay dry and undisturbed.

What the hedgehog really needs now: winter quarters

From CW 40, the hedgehog fattens up for winter and builds a nest. He hibernates from roughly November to March, during which his body temperature drops to a few degrees and his heartbeat slows dramatically. In this time he must not be disturbed, because every waking costs him precious fat reserves. You build the best quarters by doing less.

Eine dicke Schicht bunter Herbstblätter bedeckt den Boden unter einem Strauch. — Ein liegen gelassener Laubhaufen in einer stillen Ecke ist das beste Winterquartier, das du bauen kannst.· Foto: Sheba_Also, Wikimedia Commons

Leave a leaf pile lyingLoosely pile up leaves in a sheltered, quiet corner, ideally under a shrub or along a hedge. Half a cubic metre is enough.
Stack brushwood and deadwoodA pile of branches and cuttings gives structure and shelter. Brushwood below, leaves on top is ideal.
Leave perennials standingCut perennials back only in spring. The dry stems provide cover and harbour insects as food.

This pairs well with a deadwood corner or Benjes hedge, which gives the hedgehog both shelter and insects as food. You will find the rest of this season's tasks compactly in the gardening calendar for October.

Feeding: when yes, when no

In autumn the question almost always comes up whether one should feed hedgehogs. The short answer: in a near-natural garden with enough insects, a healthy hedgehog needs no supplementary feeding. A feeding spot can, however, help underweight animals through the last weeks before hibernation.

If you feed, do it properly: wet cat food or special hedgehog food, plus a shallow dish of water. Put it out sheltered and in the evening, and clear away leftovers in the morning so no rats come.

Never give hedgehogs milk. Hedgehogs cannot tolerate lactose; milk causes severe diarrhoea and can be fatal. Bread, fruit and kitchen scraps are unsuitable too. Water is the only right drink.

When a hedgehog really needs help

Most hedgehogs manage on their own, but sometimes an animal depends on help. A hedgehog that weighs clearly under 500 grams by the onset of winter has too few reserves. An animal that wanders about disoriented in daylight, staggers or lies apathetic is almost always sick or hypothermic.

Observe and weigh
If the hedgehog looks healthy and trots briskly through the garden at night, leave him be. Only step in with conspicuous behaviour. A weight under 500 grams in November is a warning sign.
Secure it warm and calm
Put a hedgehog in need into a tall box with a towel, place it in a quiet, moderately warm spot and slip a lukewarm hot-water bottle under the towel.
Call the experts
Call a hedgehog rescue or a wildlife vet before you feed or overwinter the animal yourself. Hedgehogs are specially protected, and taking one in is bound by rules.

Hedgehogs are under special protection of the German Federal Nature Conservation Act. You may not simply take a healthy animal from the wild and overwinter it at home. When in doubt, a call to the local hedgehog rescue clarifies whether and how you are allowed to help.

Helping hedgehogs is, in the end, not an autumn project but an attitude across the whole year. Whoever clears the leaf piles late in spring, switches the mower off at night in summer and leaves a wild corner in autumn has done more than anyone who sets out a ready-made house. The garden does not become untidy that way, but alive.

Häufige Fragen

From when should I switch off my robot mower for the hedgehogs?

Ideally all year round at night, because hedgehogs are nocturnal from spring to autumn. The time from late summer to November is especially critical, when the young hedgehogs are out too. Set the mower to run only between sunrise and sunset. A hedgehog does not flee but curls up and stays put, which is why only the night curfew protects him.

Why are slug pellets dangerous for hedgehogs?

The hedgehog loves to eat slugs, and poisoned, sluggish slugs are especially easy prey for him. So he takes in the poison, usually the active ingredient metaldehyde, in a concentrated dose through the food chain. The result is convulsions and a slow death. Instead, rely on slug collars, collecting at dusk or the gentler iron(III) phosphate, and use the hedgehog as a natural slug hunter.

Do I really need a hedgehog house in the garden?

No, a bought hedgehog house is rarely necessary. More important is a natural, undisturbed shelter: a leaf pile in a quiet corner, a brushwood pile, a dense hedge or the space under the shed. Hedgehogs often take to such quarters more readily than to a ready-made house. Deal with the dangers and a wild corner first; that helps him more than any bought house.

How heavy does a hedgehog have to be for hibernation?

As a rough rule of thumb, a hedgehog should weigh clearly over 500 grams by the onset of winter, that is from about late October into November. Young animals that are still noticeably lighter in late autumn often do not make it through the winter on their own. Weigh a conspicuously small animal with a kitchen scale and, when in doubt, call a hedgehog rescue before you intervene yourself.

May I give hedgehogs milk or fruit to eat?

No. Hedgehogs cannot tolerate lactose; milk causes severe diarrhoea and can be fatal. Bread, fruit and kitchen scraps are unsuitable too. If you want to feed, give wet cat food or special hedgehog food and put a shallow dish of water beside it.

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Rechtlicher Hinweis

This article replaces no veterinary or professional advice. Hedgehogs are specially protected under the German Federal Nature Conservation Act. When in doubt, consult a hedgehog rescue, a wildlife rescue centre or a vet before you take in or feed an animal.