1. How scientists learn what hedgehogs eat at night by examining their scat
Hedgehogs are nocturnal, so it is not easy to see them eating [1]. Therefore, researchers examine their scat, which contains visible food remnants and DNA. In an analysis of scat from 137 wild hedgehogs in England, introduced by the UK conservation group Butterfly Conservation, 74% contained beetles, 49% contained caterpillars, and 34% contained earthworms. Recently, 23% had eaten slugs [2].
Overall, invertebrates make up 80 to 90% of the volume, with beetles, earwigs, and earthworms being central [5]. Dictionaries note that hedgehogs also eat fruits and roots [1], but this explanation suggests that plants are often just accidentally ingested [5].
At first glance, slugs seem to be just one of many ordinary foods. However, when measured differently, the story changes.
2. Which foods many hedgehogs eat and which foods give them the most energy
A 2026 paper reports that in scat collected from 209 wild hedgehogs across Europe, slug and snail relatives appeared in the food of 177 out of 193 analyzed individuals (92%) [3]. On the other hand, the group introducing the England analysis explains that in terms of energy, slugs and snails do not reach 5% of the required amount, while caterpillars and beetles can each exceed one-third [2].
Think of it this way: even if everyone receives 1 yen a day, it is a tiny amount in the total money held. "How many individuals ate it" and "how much power it provided" are different measures. However, real surveys are not this simple. The 92% figure is the percentage of individuals that ate it, not the amount or energy. Also, the two analyses differ in location and method. The percentage of slugs appearing is 23% versus 92%, so they cannot be directly compared as the same trend. So, how are high-energy foods selected?
3. Why hedgehogs choose soft earthworms over hard beetles, and how rain changes this
A study conducted at one golf course in the UK during the summers of 1981 and 1982 examined how hedgehogs choose food. The study summary states that when able to choose, hedgehogs preferred softer foods like earthworms over hard ground beetles [4]. Earthworms and similar soft foods were said to contain about 9 times more energy on average than ground beetles.
Also, the percentage of earthworms eaten increased with the amount of rain. The proportion eaten depended on the amount of earthworms present and the rain [4]. It is well known that earthworms come to the surface after rain in gardens and parks at night. However, the study summary only supports the conclusion that the percentage of earthworms eaten changed according to the amount of earthworms and the rain.
Since this was a summer survey at one golf course, it is not a conclusion for all hedgehogs. Beetles are not always avoided; they appeared in 74% of scat in the England analysis [2].
4. How caterpillars supplied half of one hedgehog's energy before hibernation
From late summer to autumn, hedgehogs prepare for hibernation. Hedgehogs living in cold regions are said to hibernate [10]. One survey found an example where about 50% of energy intake during this period came from caterpillars. In one scat sample, remains equivalent to 56 caterpillars were found [2].
However, "about 50%" is a maximum-level example. This was from a survey at a golf course near Heathrow Airport, and it may not be the same in other places or years. It is best to read this as indicating there are times when caterpillars become the main food.
If you walk under fallen leaves or in grass in a garden, you might find caterpillars. Small animals like hedgehogs likely search for and eat these ground-level insects at night.
Note: You cannot connect these facts to say "the percentage of caterpillars increased by season." The only common point is that caterpillars can become a significant energy source.
5. Should you give milk and bread to hedgehogs that visit your garden?
Many people might think "milk is for hedgehogs." However, the UK conservation group Hedgehog Street calls on people not to give cow's milk because hedgehogs have difficulty breaking down lactose. They also state that bread has low energy and almost no value [6].
A poster from the British Hedgehog Preservation Society also states that "bread and milk harm hedgehogs." As supplements to natural food, they recommend meat-based cat, dog, or hedgehog food, and water as the only drink [7].
The same group writes that natural food for hedgehogs visiting gardens includes earthworms, ground beetles, caterpillars, earwigs, and millipedes [6]. This overlaps with the analysis in previous sections.
However, this is a call from UK groups. What do hedgehogs in the wild in Japan eat?
6. What hedgehogs living in the wild in Japan eat
Among hedgehogs established in the wild in Japan, those confirmed in Shizuoka and Kanagawa prefectures are Amur hedgehogs, which are designated as specific invasive alien species under the Invasive Alien Species Act [8]. The National Institute for Environmental Studies' invasive species database lists their food as insects, earthworms, spiders, land snails, rodents, frogs, lizards, snakes, other small ground animals, bird eggs, and fruits.
European hedgehogs live in forests and grasslands in lowlands and mountains, eating frogs, snakes, insects, and others. Their weight is 400 to 1000 g (14 to 35 oz), and their total length is 23 to 27 cm (9 to 11 in). Those in cold regions hibernate [10]. Although the species are different, the point that small ground-level animals are included in the diet is similar. However, because the details of the lists differ by source, direct comparison is not made.
In Odawara City, Kanagawa Prefecture, a report from the Kanagawa Prefectural Museum of Natural History states that a family of 3 appeared in a garden in 1987, and multiple individuals were captured in 1988 and 1989. The origin is said to be escaped captive individuals [9]. Two captive individuals were observed to be active after 7 PM, searching for food, and preferring raw meat, boiled eggs, and raw eggs. They slept under cloth during the day.
Since this is an observation of 2 captive individuals, it is not representative of wild food. Still, the behavior of moving and searching for food at night overlaps with descriptions of nocturnal European hedgehogs [1].
For specific invasive alien species, it is good to check guidance from the Ministry of the Environment or local governments if you find them, without touching or feeding them.
7. How to try counting small creatures on the ground after rain
The percentage of earthworms eaten increased with more rain [4]. So, does the number of visible small creatures on the ground differ between sunny days and the day after rain?
Choose an area of about 1 square meter (10 square feet) in a park or garden the day after rain and count the visible insects and earthworms. Count in the same place on a sunny day and compare. The counting method can be simple, but it is important to keep conditions the same. Repeat this over several days, as one day includes other differences besides weather.
Stinging insects and centipedes may be under stones or fallen leaves. Do not touch unknown insects; just look. Wash your hands after touching.
The results are from a different place and under different conditions than the hedgehog studies. By counting over several days and comparing, you can observe if the number found changes the day after rain. However, this is not a survey to confirm hedgehog meals or the cause of number changes, and the relationship with rain is not determined by numbers alone.
For further research, the National Institute for Environmental Studies' invasive species database [8] and the Ministry of the Environment pamphlet [10] are available in Japanese.