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hedgehogsofasgard · 7 years

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Hedgehog nutrition

Hedgehog nutrition is probably one of the most widely debated topics when it comes to hedgehog care. Why? It’s because we don’t really know what hedgehogs need. We know what they eat, but breakdowns of ratios and percentages of their nutritional requirements are still unknown or very vague, or too difficult to replicate in captivity. Very little research has been done towards pet hedgehog nutrition so a lot of what’s recommended right now has been discovered through trial and error over the years and by looking at their natural diet and attempting to recreate it as best as we can.

In the wild

Hedgehogs are not just insectivores (and definitely not rodents!) but more like opportunistic omnivores: scavengers who will eat nearly everything they find, but the staple of their diet consists of invertebrates. The term that would describe them best would probably be ‘insectivorous omnivores’.

The studies that have been done on hedgehog diets in the wild mainly look at the frequency of occurrence of certain food types. While this works well for large sample sizes and makes it easier to compare various studies, it doesn’t give us full insight when it comes to the importance of different foods; it is more difficult to say which foods are actively selected or avoided by the animals in question. A single small arthropod occurring in twenty stomachs might show as a 20% occurrence, while twenty large arthropods in one stomach might be a 1% occurrence, even though they form a much larger proportion of the diet (Yalden, 1976). This is illustrated in the following figure:

(Source: The food of the hedgehog in England by D. W. Yalden, 1976)

This is one of the problems we’re facing: we do know what hedgehogs eat, but we’re unsure about the specific ratios and the nutritional importance of those various food types in relation to the hedgehog. Still, these studies can give us important insight and can help us recreate the most natural diet for our pets.

Invertebrates

Researchers in the Waitaki Basin, New-Zealand kill-trapped European hedgehogs (which are an invasive species in NZ) to examine the contents of their guts and found the following percentage occurrence:

Image source: Diet of hedgehogs (Erinaceus europaeus) in the upper Waitaki Basin, New Zealand: Implications for conservation by C. Jones et al. (2005)

From left to right: beetles (Coleoptera); butterfly and moths (mainly larvae) (Lepidoptera); bees, wasps and ants (Hymenoptera); grasshoppers, locusts and crickets (Orthoptera); flies (Diptera); birds; spiders (Arachnida); lizards; larvae (excl. Lepidoptera); eggshell; true bugs (Hemiptera); dragonflies (Odonata); worms (Annelida); stoneflies (Plecoptera) and alderflies, dobsonflies and fishflies (Megaloptera).

With the exception of birds, lizards and eggshells, these are all invertebrates. This includes the first five food types found in the highest occurrence. The ratios per hedgehog differed and some invertebrates were found in large quantities: three hedgehogs had consumed over 30 butterfly/moth larvae (and one over 52)! One animal contained 40 bumblebee legs and 52 spider wasp wings were found in another. Another study found the remains of 85 beetles in a single stomach. This abundance of one or two particular food types suggests the ability to focus on and exploit a locally abundant food source, a good example of the hedgehog’s opportunistic nature.

This corresponds with data from other studies (from Europe, Africa, Asia and NZ), such as that of Yalden (see first figure), or Jones and Norbury (2010) who examined faecal matter of NZ hedgehogs in an arid habitat and found “the most commonly eaten foods were beetles, including rare native species (in 94% of droppings), earwigs (92%), spiders (25%) and native skinks (14%)”.

Image source: Feeding selectivity of introduced hedgehogs Erinaceus europaeus in a dryland habitat, South Island, New Zealand by C. Jones and G. Norbury, 2010

While we might not know all the details about hedgehog nutrition yet, every study agrees on the following basis: the hedgehog displays an opportunistic, omnivorous nature but with a strong reliance on invertebrate prey with it being the staple of their diet.

Vertebrates and eggs

The amount of vertebrates found in several studies is quite low and they do not seem to make up a very large part of the hedgehog’s diet. Yalden (1976) notes an occurrence of 12% when it comes to mammals, 16% for birds and 11% for eggs. Those numbers are most likely higher than usual since the trapped hedgehogs were mainly baited with (dead) rabbits, hares and eggs. Most mammalian remains found in other studies came from small animals such as mice and shrews and ranged from small bone and fur fragments to (although rare) entire mice skeletons. Fly eggs and maggots found in hedgehog stomachs suggest the feeding on carrion as does the occurrence of larger mammal remains.

Most occurrences of birds are based on just a few feathers. It is difficult to say whether or not these all belonged to avian prey; the feathers could have been ingested while raiding nests e.g. those of bumblebees which sometimes use them for nest lining, as the remains of those nests were found in some stomachs as well (Yalden, 1976). However, in several instances skin was still attached to the feathers.

When it comes to eggs it is difficult to say whether or not the eggshells found in faeces or guts are a good estimate because hedgehogs are more likely to leave the shells and only eat the contents of the egg (which is difficult to retrieve from stomachs or faeces).

One study found that adult female guts contained three times as many lizard remains than those of adult males (with a combined percentage occurrence of 6%). This might relate to higher energetic demands (protein) of the female during breeding season (Jones et al., 2005). Some studies didn’t find a noticeable difference between males and females. Identifiable lizard remains ranged from a few scales to whole feet and bone fragments (Jones and Norbury, 2010).

Plant matter

Since the hedgehog is considered to be somewhat omnivorous some plant matter in its diet was expected. Yalden (1976) found a percentage occurrence of 44%; however, the vast majority came from finely chewed plant matter from the guts of ingested invertebrates (mainly caterpillars). Most other plant matter, such as grass or pine needles, seemed to have been accidentally ingested. In most stomachs the quantity of plant matter was not or barely noticeable. In the stomachs where more and larger plant matter was found it had not been chewed nor digested; even though animal remains in those same stomachs were reduced to nothing more than bits of fur, feather and exoskeleton. Other studies reached a similar conclusion, with undigested plant matter found in both faeces and guts (Jones and Norbury found it in 49% of samples): it seems that most plant matter is not deliberately eaten and hedgehogs might not be able to digest it very well. Hedgehogs have a very simple gut system with no external distinction between large and small intestine and no caecum, the part where cellulose is digested in herbivores. There’s an exception to be made for fruit (and possibly young shoots); several studies have found fruit and seed remains in larger quantities, although never in many animals.

No plant matter was found in long-eared hedgehogs (Maheshwari, 1983).

The African pygmy hedgehog (Atelerix albiventris)

All studies cited here - except for one - have been done on European hedgehogs (Erinaceus europaeus). Other studies with different species show corresponding results: a primarily insectivorous diet and an opportunistic nature. This goes for the most common pet species as well, the African pygmy hedgehog (Atelerix albiventris). Not many studies have been done on this species but their results suggest a similar diet selection: a staple of invertebrates, primarily termites, beetles, worms, millipedes, ants, grasshoppers and slugs as well as small vertebrates such as reptiles (both snakes and lizards), frogs, and young and eggs of ground-nesting birds (Cansdale 1960; Haltenorth and Diller 1988). They might eat some fruits, roots, groundnuts and fungi as well.

In captivity

Based on the information above one might expect a diet of primarily invertebrates with some meat and a little plant matter (fruit). However, this is not the standard. In most places the recommended diet for hedgehogs is high quality cat food with insects and other things as treats. This recommendation is based on the easy and relatively cheap availability of cat food and the simple fact that there currently isn’t a better, nutritionally balanced option when it comes to commercially available processed foods.

Commercially available foods

Cat food has been fed to hedgehogs for a long time even though it is not made for them and therefore in several ways ill-suited. When pygmy hedgehogs were first domesticated in the US a lot of the info about hedgehog care came from British hedgehog rescues working with European hedgehogs. In Europe it is common to feed rescue hedgehogs cat food (wet food) because it is a cheap and easy option and a good way to fatten them up when they are malnourished and sickly. With nothing better on the market, the cat food diet stuck with the pet hedgehog community through the years and kibble is still the most commonly used staple food around the world.

Cat or dog food?

Both cat and dog food can be given to hedgehogs but most people give cat food because of the smaller kibble pieces. Dog kibble can be crushed to an appropriate size before feeding. When considering the more omnivorous nature of the hedgehog and not counting the insectivorous part they might more closely resemble canids than felids in terms of dietary needs; specific problems linked to obligate carnivores (such as taurine deficiency) have not been seen in hedgehogs. There is the possibility dog kibble might actually be a more suitable food for the hedgehog (out of what’s available at the moment).

Because cat and dog foods are not made with the intention to be eaten by hedgehogs, not all kibble is suitable. The current recommended percentages for protein, fat and fibre are as follows:

Protein: 28%-35%

Fat: 10%-15%

Fibre: as high as possible

These percentages have been estimated through trial and error in the past. Common food-related problems in hedgehogs are obesity, FLD (fatty liver disease), diabetes and renal problems, amongst other things (it has to be noted that it can be difficult to pinpoint whether or not a condition is completely diet-related).

Why most hedgehog food isn’t good for hedgehogs

In some countries special hedgehog or insectivore food is available (such as Exotic Nutrition or Mazuri), so why not feed those? Because the majority of these foods are of very bad quality. Unfortunately hedgehog food is often recommended by vets - though this is usually through no fault of them, since many (including exotic vets) often know very little to nothing about hedgehog nutrition as hedgehogs are not a common pet and most medical (US) papers on hedgehog nutrition are outdated. Hedgehog foods tend to contain lots of useless fillers and there are plenty of cat (and dog) foods of higher quality with better ingredients. The only plus side of some of the hedgehog/insectivore foods is the higher fibre content, but with such low quality ingredients and the fibre mainly or only coming from powdered cellulose it’s usually not worth it (or only as part of a mix) as fibre can be supplemented in other, healthier ways, such as feeding your hedgehog insects.

The importance of good ingredients

Not all kibble is created equal! There are huge differences in quality of ingredients when it comes to both cat and dog food. Many of the cheaper foods (although price doesn’t always guarantee quality) contain mostly fillers. Fillers such as grain, corn, potatoes and rice, which will fill your hedgehog’s belly but have very little nutritious value. What you’re looking for in a good food is meat in the first or preferably first few spots of the ingredient list. Don’t look at pretty labels and advertising, because companies - even those of so called ‘high quality’ foods - often have great marketing while the food in question might not be that great.

In general, things you want to avoid as a main ingredient are: corn, wheat, brewer’s rice, unnamed meats, unnamed meat meals, unnamed fats and by-products. Those are fillers or can be ‘waste’ like feet or intestines or other animal parts with very little nutritious value. Unnamed meats and such don’t necessarily have to come from animals slaughtered for the pet food industry so it’s a good idea to stay clear of vague unnamed ingredients. Ingredients to watch out for because they might be linked to health issues in cats or dogs are BHA, BHT, ethoxyquin, menadione sodium bisulfate and food dyes.

Good ingredients are: named meats (e.g. chicken, lamb, turkey etc.), named meat meals, named fat, minimal amounts of grain and foods with multiple sources of protein. Another way to provide multiple protein sources is by mixing different foods together. Since we know so little about hedgehog nutrition, offering a wide variety increases the chances of including the right things. Ideally, you want the first few ingredients on the list to be meat or meat meal, since the first ingredients (up till the first fat/oil) make up the bulk of the food. Be wary however of grains listed after the meat(s) - if it lists a lot of different fillers, such as corn, rice, barley, etc. all those grains together probably still make up more of the food than the meats. Manufacturers of ‘grain free’ foods sometimes trick their customers by splitting their ingredients on the label (e.g. dried potatoes and potato protein) while it’s essentially the same thing.

Both dry kibble and wet food can be fed, although the latter tends to make the poop smellier. When feeding wet food it can be a good idea to calculate the dry matter basis (DMB) for protein and fat since the percentages listed don’t account for the extra moisture in the food, and the protein/fat recommendations for hedgehogs are based on the DMB percentages of kibble. Canned foods are often very high in protein and fat so this is especially important if you’re using wet food as a staple - the only way to compare a dry food to a canned food is to compare their DMB values. You can calculate the DMB with the following formula:

100% - moisture content = dry mass % fat or protein % / dry mass % = fat or protein DMB %

Protein

It is recommended to keep protein levels below 35% because dry food with high protein can be hard on the kidneys. With wet (canned) foods or other high protein foods such as meat and insects this is less of a concern because the moisture in the food helps flush everything out - in the wild, animals rarely eat food as dry as kibble, so their bodies are made for a diet with more moisture. This means that when they’re eating a dry kibble diet they do not always drink the needed extra water. Because of this it is best to err on the side of caution and don’t go (far) over the 35% protein limit when choosing a dry food (for wet food it’s wise not to go too high either, just to be safe). Pregnant and nursing females might benefit from higher protein (preferably from meat and/or insects).

Fat

Hedgehogs in captivity have the tendency to become overweight which is why a low fat percentage is recommended: under 15%, but preferably under 12%. This depends on the hedgehog in question though, as some are more active than others and might benefit from a higher fat percentage, as do nursing mothers and hoglets under 4-6 months old who can be fed food with 15%-20% fat. It is important to keep an eye on the weight and body shape of your hedgehog and adjust diet/feeding accordingly.

The fibre issue

In the wild hedgehogs seem to have a relatively high fibre diet. Feeder insects have a fibre content between 14% and 52%, and it’s likely the insects consumed by wild hedgehogs contain similar amounts of fibre. Most cat (and dog) food however has a much lower fibre content, usually around 2-4% and rarely above 6%. This lack of fibre in the diet of pet hedgehogs might be linked to common dietary problems, such as obesity. A small-scale study has tested the ability of hedgehogs to digest two types of fibre: chitin (from crab shells) and cellulose (powdered cellulose). Hedgehogs possess chitinases which implies they can use chitin, which is found in the exoskeletons of invertebrates, as a source of dietary fibre. The animals in the study were either given the control diet (no added fibre), added chitin or added cellulose. 64% to 68% of the dietary fibre added as chitin was digested, compared to 38% of the added cellulose (Graffam et al., 1998). Another thing that stood out was how the digestibility of fat increased with the diet where the highest amount of chitin was added (25% in dietary dry matter). This suggest there might be some interaction between the chitin and the fat because this diet also showed the highest fibre digestibility (as well as the lowest faecal ash content, suggesting some fibre/mineral interaction as well). Visually, the quality of the faeces also appeared to improve with added fibre. While this preliminary study was too small to draw any hard conclusions from, its results in combination with the natural diet of the hedgehog suggest a preference for chitin and adding insects to your hedgehog’s diet (and/or like this study, ground crab shells) might create a more nutritionally appropriate diet and could possibly help against common diet-related issues.

Ca:P

Ca:P (also written as Ca/P sometimes) stands for the calcium:phosphorus ratio. Calcium and phosphorus are important minerals and deficiencies can affect the body in a negative way. A 1:1 ratio would mean calcium and phosphorus are found in equal quantities, 0.5:1 means there’s half the amount of calcium versus phosphorus. Calcium is absorbed by phosphorus - but excess phosphorus binds calcium and impairs its absorption by the intestines. On top of that, the excess phosphorus can actually start to take calcium that’s already present in the body: for example from the bones or teeth. An imbalanced Ca:P ratio in an animal’s diet where the phosphorus is too high can lead to diseases such as MBD (metabolic bone disease) or tooth decay, amongst other things. Deformed bones due to a lack of calcium are quite commonly seen in animals that are fed primarily insects, such as lesser hedgehog tenrecs and some reptile species. In Husbandry and Nutrition of Hedgehogs (Smith, 1999) a ratio of 1.2-1.5:1 is recommended. With regards to the little info we have on hedgehog nutrition and the recommended ratio for most other vertebrates (1.5-2:1) it might be best to stick around 1.5:1. When feeding a lot of insects or a raw diet it is extra important to check the Ca:P ratio, since many feeder insects and deboned meat have an imbalanced Ca:P ratio. Calcium can be supplemented by adding bonemeal, ground eggshells or commercially available calcium powder to the food. While calcium deficiency is more common than calcium overdose it is a possibility so keep an eye on the recommended ratio when using a calcium supplement.

(Live) insects should not be optional: they are a staple

This is something that cannot be stressed enough: considering the importance of invertebrates in the hedgehog’s natural diet, insects are a must for hedgehogs in captivity. Unfortunately many hedgehogs only get insects as a minor treat and some never get them at all. Insects are often (falsely) accused of making hedgehogs fat or people are simply told they are not necessary because “hedgehogs do just fine on cat food”. However, doing just fine doesn’t mean an animal’s natural needs are met (all the dietary problems found in hedgehogs are a good example). Depriving insectivores of insects may cause malnutrition and allow opportunistic pathogens to become active (Campbell, 1997). Opportunistic viruses and bacterial infections are given a change to infect an animal when it has a weakened immune system or disrupted gut flora, while those same pathogens usually don’t cause sickness in a healthy animal.

Mealworms are the most commonly fed insects but there are many more (and better) feeders available. Some are more nutritious than others; while insects such as wax worms are quite high in fat and might not be ideal for hedgehogs which gain weight easily or are already overweight, there are plenty of other options available. While live insects are best there’s also canned insects or freeze dried ones, although the latter should be fed in moderation since they can cause impaction. See ‘Feeder insects for hedgehogs’ for more information about adding insects to your hedgehog’s diet.

Live insects do not only have nutritional value - such as the importance of chitin-based fibre - but also provide and stimulate mental and physical activity (like foraging). No animal should be deprived of the staple food of its diet!

Variety is key: the “ideal”diet

The hedgehog is an opportunistic, insectivorous omnivore - so let’s feed them accordingly, as best we can! Based on their natural needs and everything we’ve learned over the years through trial and error, the ‘ideal’ diet (with what’s available to us right now) would look something like this:

(Live) insects daily or at least several times a week (and as much variety as possible)

Another staple ‘backup’ food (kibble)

Eggs and some meat (f/t pinkies, mice, day-old-chicks, (raw) meat)

Very minor amounts of plant matter (preferably fruit or veggies that are easy to digest)

Insects are, as mentioned before, an important staple of the diet. Kibble has many downsides - so why still feed it? The simple answer is because it doesn’t seem to be awfully bad (if meeting the right requirements) and given how little we know about hedgehog nutrition, it functions as a ‘backup’ food nutrition-wise: since hedgehogs are able to survive on it it must have some good things too. This doesn’t mean a diet where kibble is the only food (except for occasional treats) is a great diet for hedgehogs. Taking their natural needs into account it should be clear it isn’t: a primarily kibble-based or kibble-only diet might be able to sustain a hedgehog, but is not ideal.

A much more natural diet can be created by adding (live) insects as a staple food, together with kibble and meat. Feeding just insects creates an unbalanced diet as there are only a few species available as feeders as opposed to the wide variety hedgehogs encounter in the wild (not to mention the other things they eat). Portions of (raw) meat can be fed; the most natural would be f/t pinkies or mice and day-old chicks as well as meat from chicken and other poultry and rabbit/hare. Eggs can be fed too, as well as very minor portions of vegetable matter. Considering the seemingly limited ability of the hedgehog to digest cellulose, and their inclination towards consuming fruit, feeding vegetables and fruits that are easy to digest might be the best option (watch the high sugar content of fruit). The easiest way to add some plant matter to your hedgehog’s diet is by gut loading insects with vegetables and fruits before feeding them.

Raw/home-made diets

Another option is feeding an entirely raw/home-made diet where the kibble is left out and replaced by other foods such as raw meat. Special raw diets for cats, dogs and ferrets can be used for hedgehogs too. Because there is no kibble in the diet to work as a ‘safety net’ against deficiencies, a 100% raw diet should only be considered after thorough research. Because there’s so little known about hedgehog nutrition it is more difficult and time-consuming to set up a completely raw diet that’s properly balanced. A separate post about raw feeding will go into more detail about this way of feeding pet hedgehogs.

We still have a long way to go before we will know everything about hedgehog nutrition. While this means hedgehogs aren’t an easy pet to feed with no commercially available diet (yet) that covers all their needs, the little research we have as well as the trial and error from the past forms a stable basis which will hopefully lead to more research and maybe even a proper hedgehog food in the future. For now, the key to a happy, healthy hedgehog seems to lie in high fibre, low fat, a varied diet and lots of insects!

Sources: - Diet of hedgehogs (Erinaceus europaeus) in the upper Waitaki Basin, New Zealand: Implications for conservation by C. Jones et al. (2005) - The Impact of Molluscicide Application on Hedgehog Populations: A Review by J. Bunner (2002) - The Food of the Hedgehog in England by D. W. Yalden (1976) - Feeding selectivity of introduced hedgehogs Erinaceus europaeus in a dryland habitat, South Island, New Zealand by C. Jones and G. Norbury (2010) - Atelerix albiventris (Erinaceomorpha: Erinaceidae) by E. M. Santana et al. (2010) - Intestinal candidiasis in an African hedgehog (Atelerix albiventris) by T. Campbell (1997) - Beginner’s Guide to Hedgehog Nutrition - Feeding behaviour and nutrition of the African pygmy hedgehog (Atelerix albiventris) by E. S. Dierenfeld (2009) - Necropsy and histopathologic findings in 14 African pygmy hedgehogs (Atelerix albiventris): a retrospective study by J. T. Raymond et al. (1999) - Husbandry and Medical Management of African Hedgehogs by M. Mori and S. E. O’Brien (1997) - Fiber Digestion in the African White-Bellied Hedgehog (Atelerix albiventris): A Preliminary Evaluation by W. S. Graffam et al. (1998) - Husbandry and Nutrition of Hedgehogs by A. J. Smith (1999)

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