Nutrition is perhaps the most important aspect of keeping your favorite amphibians. Although it is true that crickets are the "go to" food item for the majority of amphibians, there are many options out there with which to feed your amphibian. Aquatic or terrestrial amphibians all have specific dietary needs, and understanding what they are is needed to help your animal flourish. Anyone can sustain a frog, but we want to show you how to make your animals thrive. Zoos and aquariums have amphibian nutrition down to a science. This section will discuss how zoos look at amphibian nutrition and what to emulate in your collection.
Enough Science, tell me what to do!
In reality, there are dozens of pages out there about amphibian nutrition. The problem is they are either too simplified, or way too scientific for the hobbyist to really take note. Nutrition is really quite simple once you understand the basics. Although the science of amphibian nutrition is very complex, the general practice can be boiled down to a few simple ideas and principles. Anyone can do it, but there is credence to learning why we feed certain items to animals. A little extra effort will show dividends in the end.
The basic: Metabolism and why they eat.
Like human nutrition, foods can be broken down into protein, fat and carbohydrate (sugars) content. Amphibians in the wild have many unique ways of hunting for their food sources. "Sit and wait" predators generally have slow metabolisms and will wait for large meals (think giant salamanders). This strategy requires less energy to live every day, so one big meal every now and then suffices. Grazers and hunters actively forage for their food source. These animals will hunt for and eat many small food items throughout the day. This strategy requires lots of energy to help the animal actively hunt, but that extra energy helps them find many food items to off set the high energy expense. Understanding your animal’s lifestyle is needed to know what your animal is likely to eat and its frequency of feed times. Do you need to know the anuran eye associates cylindrical items as a food source do to adaptations in the eye? No. Feed anurans stuff that moves. They may associate shapes as possible food sources, but the more a food item moves, the more frogs and toads will eat it. Aquatic amphibians are even easier. Throw something into their tank and they will do the rest. Scavenging is naturally en-grained in an animal’s brain. If a captive animal is lazy, tong feeding is always an option, but that does get old quickly.
Nutrient Break-Down.
So now we know what to look out for. But how much is enough and how do we find a correct balance? Before all other things, a few things need to be considered. Whether your attractive new dart frogs aren't able to forage all day, or your salamander is moving around more than they would in the wild because of temperature fluctuations, your animal is not in a natural environment. A keeper has to recognize that rules in captivity do not follow the rules of the wild. Generally speaking, we try to mimic nature as best we can, but in many cases we can not. Nutrition can play a big part in this problem.
Dart frogs, for example, feed all day on tiny insects. They hunt on the forest floor, in brush, and in some cases in the canopy of the rain forest. That is a LOT of exercise. Evolution has a way of making a dart frog’s mind prefer fatty foods because they are so rich in energy. This energy helps them continue foraging throughout the day. In captivity there is limited space, they may be fed once a day, or every other day. Because of this staccato feed method, foraging and expending energy is decreased significantly. So feeding the fatty foods to a non-foraging ‘couch potato’ dart frog could be a bad idea! (Experienced dart frog keepers will call me on this analogy, obesity is fairly hard to find in captive dart frogs, but the example serves my purpose!)
Biochemistry and metabolism plays another huge role in deciding what our animals should be fed. I know biochemistry is a scary word, but I assure you I won’t quiz you on the Krebs-Cycle. Keeping it simple, proteins can be broken down to produce sugars, lipids (fats) can be broken down to produce sugars and aid protein synthesis. What's the take away message? Sugars and proteins can NOT be used to produce FAT. Fat is important, all living things need it. Having a lazy animal does not mean you strip fat from its diet to keep it healthy. Without fat, cell membranes wouldn't exist, and without cell membranes life would be very messy.
Sugars in captive zoo (and especially human) diets is a major factor normally taken into consideration. Not in amphibians. Carbs are generally minimal in food items and also poorly absorbed by amphibian digestive tracts, so we can put our amphibians on Atkins.
AZA has posted a great resource for the most commonly used food items in the zoo industry. Because of the cost, crickets are more than likely going to be your staple food source. Enriching your amphibian with a varied diet is essential and this table can help reach a nutritional balance.
AZA, Nutrition Advisory Group Handbook, 14. Finke, 2002. Complete Nutrient Composition of Commercially Raised Invertebrates Used as Food for Insectivores. Zoo Biology 21:286-293. Bernard and
Ullrey 1997. Feeding Captive Insectivorous Animals: Nutritional Aspects of Insects as Food. AZA, Nutrition Advisory Group Handbook, 8. Nagy, Girard and Brown 1999. Energetics of Free-Ranging
Mammals, Reptiles and Birds. Annual Review of Nutrition 19:247-278.
Looking at the chart you'll see a wide range of possibilities and what to do in situations of emaciation or obesity. Do you have a really thin animal or fat animal? Highest and lowest metabolizable energy is the column to look at. I think this is a great resource every herptile keeper should have on hand. Print it out and stick it on your wall or bring it to work. It is nice to have.
Ok so what do I feed?!
Every situation is different. If you have animals that are very active you'll be formulating a different diet than a diet proposed for an inactive animal. I will break down each food source's pros and cons to help guide you.
Mazuri Amphibian and Carnivorous Gel- This is the Lamborghini of amphibian food items. Mazuri is specifically designed for the captive amphibian. 55% protein, 15% fat 14% ash and 2% fiber. As someone who tries to stay away from high fat diets, this combination is perfect. Quality protein, enough fat to keep the cells happy and that makes me a happy keeper. Downfalls? It doesn't move. After all, it is a gel. It may be the greatest nutritional source since sliced bread, but if amphibians don't eat it, you're wasting money. I have successfully fed this to many aquatic amphibians (Giant Salamanders, Pipas, mud-puppies, etc) and a few terrestrial salamanders. As for frogs and toads, this may only be an option for force feeding or cricket gut-loading. I believe the diet comes by the kilogram, so you will get a lot and it may be too expensive if you keep only a few animals. If you have a lot of aquatic animals though, I would say it is definitely worth a try!
Night Crawlers
I’d consider this the best invertebrate to feed to captive amphibians. At a glance the protein may seem low compared to other inverts, but from a Protein:Fat ratio standpoint we are mimicking the Mazuri Amphibian diet. Moisture is misleading. It is important to realize that moisture will be excreted once the body has reached the necessary amount to function. After this point Protein:Fat ratio is what matters because the body will begin metabolizing these next. Studies also show night-crawlers are an excellent source of Vitamin-A and calcium. I’ll discuss these later, but it is something to keep in mind. The downfall of night-crawlers is they seem to not make all amphibians' mouths water. Aquatics love worms. Worms will more than likely be an aquatic amphibian keeper's staple food item. The trick is making worms wiggle when they are fed out. Cutting worms in half right before feeding out helps elicit a feeding response in most frogs and toads. If you can't seem to get your phib to eat night-crawlers, don't feel bad, it happens. The biggest problem I have found is night-crawler suppliers. Don’t go to a fishing store to get worms. Bass-Pro is probably angry now, but more often than not, commercial fishing worm suppliers harvest worms early in the morning on golf courses where pesticides and nitrogen based products run wild. The worms found on golf courses also likely carry diseases such as Chytrid fungus or Dermacoides. Be careful! Better to be safe than sorry.
Crickets (and Fruit Flies)
These have a good (not great) protein:fat ratio. Frogs, toads and salamanders think they are delicious. There are many cricket breeders throughout the US making prices very competitive. I highly recommend ordering a regular shipment and keeping them fully stocked at home. The start up cost may be more, but the long term savings are big and it is much less of a hassle when feeding your animals. The real problem with crickets is Vitamin-A and calcium. Vitamin-A is extremely important to prevent short-tongue disorders. Supplementing will generally be required if you are only feeding crickets. Aside from that, crickets are a great food source and are economically the easiest choice on the list. Fruit flies are in the same nutritional category. Just be aware you are purchasing fruit fly cultures, which may be a little pricier.
Silkworms and Hornworms
These interesting little invertebrates are easily right behind night-crawlers as the most nutritious food source on the list. The major problem (which is why they are positioned after crickets) with silkworms is their cost and poor taste. Silkworms are not expensive, but they are not cheap either if you feed only silkworms. A lot of times they grow too large for your amphibian to eat before you can even feed out. They also seem to have a poor taste. Silkworms are kept on a mulberry based gel diet that some amphibians seem to avoid at all costs. So why are silkworms on the list? Vitamin-A!! This invertebrate is the best for animals displaying signs of Short-tongue disorders or bloat due to kidney/liver problems. Vitamin-A in many cases stops bloat and reverses any renal disease in amphibians, toads especially. If you have a vitamin-A problem, you could also try Aqua-sol Vitamin A as a topical, but silk worms are cheaper. Another similar invert with a comparable price is hornworms. The only downfall to hornworms is their powerful jaws. Remove their jaws before you feed out to prevent the food item from fighting back.
Meal and Wax worms
Do NOT use any of these as a staple diet source for your amphibian. These are a treat you can feed every now and then. The fat content is way too high to keep your amphibian at a manageable body score. I caution anyone who uses wax and meal worms as a dietary source because amphibians love the fatty taste. Many times amphibians (and I have heard reptiles) will get so spoiled that wax worms are the only food items they will eat. Again, don't feed these a lot! It can cause serious problems down the road when you have obese animals. What if you just acquired a very emaciated animal? If you are still not ready to force feed a very thin animal, wax worms will get the job done. If your amphibian is thin, won’t eat wax-worms but will eat crickets, gut-load your crickets with high caloric cat food or even crushed up wax worms!
Calcium and Vitamin-A
These are the only two nutrients I honestly worry about when keeping amphibians. If you are properly gut-loading crickets and dusting with high quality multi-vitamins, you will likely never see deficiencies in any other Nutrient or Micro-nutrient.
Calcium is life for vertebrates. Yes it helps build our strong bones but it also is needed for proper muscle function. Amphibians in captivity are prone to thin bones due to poor calcium intake. I always recommend, regardless of frequency of feedings, dusting food items at-least once a week with a high quality calcium supplement. These can be found at any major pet store in the terrarium supply section. Generally these supplements will contain Vitamin-D3 as well. This is used to help absorb more calcium giving you greater "bang for your buck". Proper lighting can also be extremely important for diurnal amphibians. A high quality UVB light will increase Vitamin-D3 levels in your amphibian and further increase calcium absorption to thicken the skeletal structure. This is not true for all amphibians, so do research on your animal before you go spend $150 on expensive UVB lighting. Aquatics rarely need any form of UVB as it does not penetrate the surface of water more than a few inches.
After calcium requirements are fulfilled, you will more than likely have a healthy amphibian. The only other major nutrient watch out for is vitamin-A. Toads are notorious for vitamin-A deficiencies. Many believe vitamin-A deficient animals have insufficient lighting to help Vitamin-A production, others believe food items are of poor quality or lack vitamin-A levels found in the wild. Whatever the argument, deficiency is a real problem. Vitamin-A is used in the kidneys, liver and is a major nutrient in healthy anuran tongues. A frog that frequently misses, or can not catch food, more than likely has "short-tongue". Over a long period, short tongue hastens the Vitamin-A deficiency and causes eventual death from kidney/liver failure. How to treat it? Refer to the most vitamin-A rich food source on the chart. Aqua-sol A is also another viable option. Aqua-sol A is a topical dilution of vitamin that is readily absorbed through the porous amphibian skin.
Dusting
Don't forget to dust and gut-load your feeder inverts. A high quality multi-vitamin will have enough nutrients and vitamins for most captive amphibians, but you have to remember to use it. Dust your food items with multivitamin and calcium at least once a week. Depending on the animal and predisposition to deficiency, dusting more frequently may be required. Developing amphibians require lots of calcium. It is crucial to add enough calcium to cover growth requirements. When raising tadpoles, it is even a good idea to mix in calcium and multivitamin to their diet. As long as you don't overfeed, tadpole water quality will not be affected.
Amphibian nutrition is generally overlooked due to its small niche in captive animal husbandry, but now you should at least have a basic understanding. There could be an entire book written about captive amphibian nutrition, but the majority of your knowledge will come from experience. I've written some extra nutrition tips to look out for in more specialized situations below. Any questions or comment, feel free to comment!
Tricks of the Trade
- Tadpoles can be tricky due to their variety of mouth physiology. Remember, tadpoles are able to digest plant matter. This is generally the only time you will consider salads for your phib. To feed your tadpoles, look on the internet for care sheets and tips from breeders on how to feed specialized tadpoles. 1:1:1:1:1 fish flake, Sera-Micron, worm flake, calcium and multivitamin is a good combination for many tadpoles. It caters to many types of tadpole mouths and is fairly balanced in nutrition. Surface feeders can use the same mixture of food left on the surface of the water. By dropping a pinch or so into tadpole tanks and spraying the surface of the water, you can have this same diet sink and cater to bottom feeders. Placing frozen and thawed lettuce is also a good way to feed tadpoles. As tadpoles age, start switching over to a more protein rich diet.
- Brine-Shrimp (or atremia) are actually fairly nutritious. Freshly hatched shrimp still contain a yolk sack that is very rich in nutrients. This is a great option for freshly hatched aquatics or sometimes tadpoles. If you do feed out brine shrimp, remove all egg casings! If you fail to remove egg casings of freshly hatched brine shrimp, you will kill your phib by impacting their digestive tract.
- Tong feeding is a good way to ensure all animals are eating the proper amount in a particular tank. Do not tong feed too regularly though. This can lead to a lazy amphibian that refuses to hunt. Although it is fun to tong feed your phib every now and then, there will be days you do not have time to tong feed. Making sure amphibians retain hunting instinct is going to save a lot of hassle in the long run.
- Spirulina is sometimes used as a cricket dust to help with vitamin-A deficiencies. Although it may be true it is a good source of vitamin-A, spirulina is a plant cell based algae. Spirulina has only anecdotally raised vitamin-A levels in captive animals. The fact is many amphibians begin having bloat issues after accidental plant matter ingested. Even crickets gut-loaded with very high fiber based plants can cause the toads they are subsequently fed to bloat. Adult amphibians are not equipped to handle plant based foods and generally have osmoregulation issues when fed green items. This is not to say you should not try it, but understanding why it could be a problem is important. Be cautious!
- Supplementing with vitamins is always best done with a smaller size cricket. A gram of large crickets and a gram of small crickets has different surface areas. If you are interested in quality supplementation, smaller crickets always have a higher surface area. Each smaller cricket will have a greater percentage of dust. You may never worry about something as insignificant as this, but I keep it in mind every now and then.
- Fish are great when it comes to aquatic amphibians. They contain good quality fat, mimic natural diets and taste very good to your pet. They are, however, too fatty and thiamine deficient to feed regularly. Some keepers have very picky eaters that will only eat fish. A few ways to balance their diet is; inject the fish with Mazuri Amphibian diet, insert thiamin pills into the feeder fish's stomach to offset any deficiencies or stuff fish with nutritious night-crawlers.
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