What do Isopods eat?

Ever looked down as you walked through a forest? Under your feet are layers of decomposed and decomposing leaves, branches, and so much more. Fun fact, the reason we see leaves, tree trunks, and complete plants in coal seams, is that the things that help to decompose plants evolved to eat them after the plants evolved. One of these decomposers are isopods.

Do Isopods Eat Leaf Litter?

  The main part of an isopods diet is leaf litter, studies have shown that they prefer partly decayed leaf litter. This is because it is already partly broken down and easier for them to digest (Zimmer 2002). Whilst isopods do have digestive enzymes, they need the microbes on the food to help it break down and for them to get the maximum nutrition.

 Studies in the late 80s found that isopod growth was best when they were fed on partly decomposed leaves of dicotyledonous plants (Rushton et. al 1987). This is a huge chunk of the flowering plants and trees in the world. In this study, they found that freshly fallen leaves of flowering plants lead to population booms, but populations only fed on 3-month-old grass saw a population crash.

 Interestingly isopods will choose the food that they see as being the most nutritious and will stop eating when they've had enough of the nutrients they need. Most species will select leaves with higher protein levels.

 However, when breeding, isopod females on a high protein diet had smaller offspring, although they did have a higher number. High carbohydrate diets lead to the females releasing a lot fewer babies, and incubating them for a lot longer. But they were larger than the high protein group (Lardies et. al 2004)

Where to Find Leaf Litter for isopods?

 Leaves on trees have a much higher protein content than fallen leaves, and as they go through the season the protein content reduces (Forwood et. al 1985), so fallen autumn leaves dried and kept year-round might not be the best choice, although they are a great starting point.

 For food, as opposed to bedding, consider adding some leaves of flowing weeds. Dandelion, sow thistle, nettle, blanch them in a bit of boiling water first or let them dry out to avoid getting stung, field and hedge bindweed, and so many other sources are great to add to their diet, just make sure that you collect from a place that hasn't had any chemical sprayed on them. Fresh maple, oak, chestnut and more can be added. Again make sure that nothing has been sprayed, and specifically for trees, that they are a safe distance away from roads, as trees are excellent at removing heavy metals from the air and storing it in their leaves.

Fish Food

 So it looks like a high-protein diet is the way to go, and fish flakes are going to be higher in protein, aren't they? Take a second before grabbing that pot of flakes.

 Cheap fish food is often based on a mix of fish meal and wheat, and if you have noticed above, isopods fed on grass do not do well. There is often about 50% or less protein in fish flake. Nettles and dandelions are about 30% and 20% protein once dried. They're also a more natural source of nutrition than fish meal. This isn't to say you should stop feeding fish food, just select a good quality pellet, rather than cheap flakes, with many of the better foods having a percentage of insect meal rather than just fish meal. But feed as a part of a larger diet.

Should I Feed My Isopods Fruit and Veg

 Isopods don't need a lot of carbohydrates in their diets, so sugary fruits shouldn't make up a huge part of their diet. But some shredded carrot, courgette, or similar will often go down well. A varied diet allows them to self-select what they can eat.

Do Isopods Eat Insects

 You will see a lot of suggestions about feeding isopods shrimp or dried fish, and again in small amounts that's fine. But we know that for fish, feeding the wrong sort of protein can lead to diseases, probably due to the wrong mix of fatty acids in their diet, so it's worth looking for food that mimics their natural diet, and in the wild, they do hunt and eat insects as well as helping break down dead insects. So look for dried crickets and similar, or look for an insect-based fish food. Or if you're feeding insects to other creatures in your collection then you could always drop half of something in for the isopods. The exoskeleton of insects can be a great source of calcium for isopods.

Do Isopods Eat Excrement or Poop?

 Remember that bit about isopods needing microbes to help them digest their food? That's why they practice coprophagy, or faeces eating, specifically their own, as well as other animals. Yeah, it's gross, but they're far from the only group of species to do this. This isn't something you need to worry about unless you're polishing everything in their enclosure daily.

 There is some benefit to adding nitrogen-rich faeces to the isopods diet, but studies have shown that it's not something you need to dive out and get. Added to that there is the risk of contamination by adding fecal matter. The stuff you buy for the garden or your potted plants may have come from seabirds, which may have a high heavy metal content.

One caveat to this is cave-dwelling isopods. Caves are a fascinating ecosystem, but the base of the food web normally isn't plants, but bird or more often bat guano. It's worth adding a small amount for cave-dwelling species, but make sure that you source it sustainably, and many cave ecosystems are suffering as guano is collected as a fertiliser.

Calcium

 In general, if you are giving isopods a varied diet then they will be getting plenty of calcium, but it's worth giving them a safe source that they can use when needed. Egg shells are a great source of bioavailable calcium, and in mammals are absorbed as easily as pure calcium. Cuttlefish bone is another good source, or maybe add a little bit of limestone rock.

Isopods Make A Great Clean-Up Crew

 If you have a bioactive viv then isopods are probably on your list of things to buy, I’d suggest any of the Porcellionides Pruinosus isopods or the classic favourite dairy cow isopods

 Isopods will help break down leftover food, waste, bedding, and everything else. Often the bedding you are using for your reptile or whatever is the star attraction of the viv will contain foodstuff for your isopods. Consider adding springtails as well, and you will have a great clean-up crew.

Diet For Pet Isopods

 If you are keeping isopods for their own charms then you can spend some time and do some great research. What plants are native to the area these isopods are from, and what might they live alongside? Have they evolved to live in caves alongside bats or birds? Do they thrive in the intertidal zone where there might be a washed-up fish?

Above all else feeding a variety of foods, based around fallen leaves and small amounts of other naturally occurring foods will help you have a thriving colony of isopods.

Forwood, J. R., & Owensby, C. E. (1985). Nutritive value of tree leaves in the Kansas Flint Hills. Journal of Range Management, 38(1), 61-64.

Lardies, Marco & Carter, Mauricio & Bozinovic, Francisco. (2004). Dietary effects on life history traits in a terrestrial isopod: The importance of evaluating maternal effects and trade-offs. Oecologia. 138. 387-95. 10.1007/s00442-003-1447-5.

1. P. Rushton, M. Hassall Effects of Food Quality on Isopod Population Dynamics

Functional Ecology, Vol. 1, No. 4 (1987), pp. 359-367 (9 pages) https://doi.org/10.2307/2389792

ZIMMER M. Nutrition in terrestrial isopods (Isopoda: Oniscidea): an evolutionary-ecological approach. Biological Reviews. 2002;77(4):455-493. doi:10.1017/S1464793102005912