Feeding amphibians

and Cultures of invertebrates

Gerardo Garcia, DurrellMaterials produced by:

Amphibian nutritional requirements unknown

Stomach contents best we have in most cases

Few studied throughout the year, life time

Incredible diversity of species

Background

Feeding Considerations

• What will they eat?

• Can I supply enough of the food item all year long?

• How is the food going to be offered?

Are they eating?

• Hand feeding

• Counting the food in and out

• Presence of feces

• Periodic massings

Supply and Demand

• Variety is the spice of life.

• To culture or not to culture

How is the food going to be offered?

• Hand feeding

• Broadcast feeding

• Feeders

All adult amphibians are carnivores

Larvae (tadpoles/efts) may be herbivorous, carnivorous, omnivorous or pass through one or more diet preferences throughout development

Dietary items are mostly invertebrates of appropriate size but large species can consume vertebrates including other amphibians, reptiles, birds and small mammals

Amphibians capture their prey with a sticky tongue or directly with their jaws and swallow their prey whole, often alive

Diet

Food composition

• Water• Protein• Carbohydrates• Fats• Minerals• Vitamins• Hormones• Toxins• Indigestible

– chitin– fiber

Water

• Important Nutrient• Makes food Palatable• Facilitates intestinal motility• Facilitates absorption of vitamins, sugars • Important to evaluate nutritional components

in diet on dry weight basis

Carbohydrates

Provide EnergyDigestible Sugars

provide energyIndigestible Sugars

CelluloseImportant to peristalsis

Largest nutrient by weight and volumeOften overlooked as a nutrientProvides no energy (calories)If not present in sufficient quantity:

Not palatablePoor intestinal motilityPoor absorption and distribution of sugars, B-vitamins and other

water-soluble nutrientsMust compare food on a dry matter basis to see accurate content of nutrients in food

ProteinsAmino AcidsBuilding BlocksLow protein diets

Muscle weaknessCardiac arrhythmiasHydrocoelomPoor reproductionSkin lesions (collagen tears)Immunosuppression

High protein diets (unbalanced)Gout (excess purines)Excess water demand to flush out nitrogenous wastes (ammonia,

urea, uric acid)

Fats

Provide most energy per gramEssential for building cell membranesToo much causes corneal lipidosis

Minerals

Calcium, phosphorus, potassium, sodium, magnesium, etcMaintain osmotic pressureCalcium essential in skeletal formationAcid-base balanceCan replace each other in metabolic pathways

Calcium Recommendations

• Calcium carbonate– Pharmaceutical grade only– Certified free of metal

contaminants• Calcium citrate• Calcium lactate

• Fine grade– Powdered form has higher

clingability• Probably unnecessary to

supplement with lots of Ca every feeding– Rotate with low calcium-

mineral mix

General ‘rules’ of feeding

Present all diet in a whole, natural, state wherever possible

Present invertebrate prey live – chilled and dusted with multi-vit/mineral powder or gut-loaded

Present vertebrate prey dead – thoroughly defrosted and at room temperature

Provide as varied a diet as possible to minimise the risk of deficiencies – supplement commercially produced invertebrates with wild-caught ‘sweepings’ from pesticide free habitats

And don’t forget to feed the invertebrate prey first. Don’t feed them to the amphibians first if weren’t feed correctly/abundantly during the last 48 hours

Nutritional Disorders Common

• Metabolic bone disease (MBD)• Obesity• Immuno-suppression

Symptomsbone lossrubbery jaw/bonesfracturesseizurestetany

Causeshypocalcemiainadequate D3inadequate UVBother minerals replacing Calcium in metabolic pathway

Metabolic Bone Disease

Preventing MBDAppropriate Calcium to phosphorus ratio 1.5:1.0

Vitamin D3

Some amphibians need UVB

Obesity• Very Common• Keepers frequently overestimate amphibians’ metabolic demands• Food to fatty or rich in carbohydrates• Bloating• Fat deposits• Renal gout• Lipid deposits in the eyes• Don’t feed out rodents

– common mistake (it is really cool to see a frog eat a mouse)

– rodents have extremely high fat contentImmunosuppressionCommon effect of dietary problemsOpportunistic organisms like bacteria or parasites to flourishResult is that the underlying nutritional problem is overlooked in necropsyImportant to have good communication with vets, keepers, and pathologists

Supplements

DustingFine powdered supplementFood bowlcan wash off items must be eaten quickly

Gut loadinggut loading diet fed to cricketssupplement doesn’t wash offless availablecrickets must be eating for 48 hours before fed outcricket must only be offered gut loading dietextremely high calcium content inappropriate for cricket maintenance diet

Storing Supplements

Quality of powdered supplements degrades when exposed to heat, moisture or light.

Do not store vitamins in areas of heat (>80Fº) and moderate to high humidity. Store in cool, dark, dry places

Many vitamins are photosensitive and must be kept in the dark or in brown glass bottles

Least stable vitamins are B1, B9, A, E and K

Consider purchasing smaller amounts

Supplements

High calcium supplement with approximately 1.5:1.0 calcium to phosphorus ratio

Lots of commercially available pet products available. Unfortunately many are not effective.

Human supplements are regulated. Unfortunately the products are not formulated for amphibians.

Food Sources

• Commercially Produced– least labor intensive– can be extremely reliable– expensive– availablity?

• Culturing your own– reliable– more control– more labor intensive

• Catching your own– greatest variety– may be closer to wild diet– most fun– seasonally availability?– Pollution– insect chemical defenses

Collecting Your Own

Field Sweeping

Light Trap

Tuley Funnel

Infested logs/termite traps

Domestic CricketsAcheta domestica• Can be maintained in variety of sizes• Gut loading diets available• Easy to maintain• Palatable• Do not allow excess to remain in cage

Housing Crickets

• Utility tub, wood box, glass aquarium, dresser drawer• Line top with smooth packing tape• Gut-loading diet available• Do not allow uneaten crickets to remain in enclosure

• Shallow plastic container (shoebox)• With metal screen cover• Substrate of damp vermiculite, peat moss or potting soil• Place egg laying trays in adult container overnight• Remove and incubate at 30C• 10-12 days later baby crickets

Breeding Crickets

Fruit FliesDrosophila melanogaster or heidii

• Deformed wing or missing wing • commercially available medium• Basic formula: 1part brewer’s yeast to 10 parts potato flakes mix with water 1:1

by volume• Coffee filters for lids• temp 24-25C• May have to protect from ants

Springtails, Collembola• Carbon/plaster substrate• plastic boxes with small amount of ventilation(covered)• Broken chunks supply hide spots• Keep damp • Feed brewer’s yeast or fish • Flakes standing water at bottom of cup• spring tails can be poured off into cup

1 cup banana (about 2 bananas)1 cup apple sauce1/8 cup vinegar (or 2 tablespoons or 15 ml)2 cups oatmeal

Put the banana and apple sauce in blender or bowl and mix until the bananais liquified. Heat in the microwave for approximately 2 min. or until hotenough to kill off any wild fruit fly eggs that were in the bananas, and toreduce mold. Add the vinegar and mix in oatmeal until it becomes firm, butstill moist. I then put the mixture into a large freezer bag and keep it inthe fridge.

When it's time to make a culture, I scoop what I need and put it in theculture container (usually microwaving it a bit to warm it up). I then mixup a cup of sugar water and throw a few pinches of bakers yeast on top.After a few minutes of letting it 'activate' I scoop some of it off thesurface and drip it over the surface of the media.

Some examples of Drosophila formula (internet)

3 bananas1-2 cups of water1 cup of oatmeal (Avena sativa)1 cup of brewers yeast (Saccharomyces cerevisiae)

sometimes I mix in:1 spoon molasses1 tea-spoon Spirulina1 tea-spoon milk powderbeer (instead of water)

This gives me 6-10 culture bottles.Paper/ excelsior etc for the flies to climb on.Wet kitchen tissue with rubber band as lid3 minutes in micro.Then into freezer (if I dont need all at once)

Comment: Spirulina changes color from green to yellow whenthe right temp is reached in the micro oven.Comment 2: Milk powder enhances production, but unfortunatelyalso smell. If you are sensitive to the smell of baby diapers, youshould probably not try the milk powder.

Some examples of Drosophila formula (internet) II

Some examples of Drosophila formula:

The easy…and expensive option

Larval Amphibian Diets

Even more poorly known than adultsTadpoles

DetritivorousHerbivorousCarnivorous

Cannibalistic morphsOophagousEtc.

LarvaeCarnivorous

Cannibalistic morphs

Laval Caecilians• Very little known about wild diets• Seem to be precocial or mothers’

provide nutritional support• Feed very much like little versions

of the adults• Aquatic species can be fed with the

same diet for caudata larvae • Sometimes with red meat (e.g.

heart beef)

Larval salamanders

• Carnivores

• Cannibalistic

• Aquatic larva require small aquatic food – brine shrimp– black worms – white worms– grindal worms – daphnia– microworms

Live Blood Worms

Live Black Worms

Night Crawlers (Lobe Worms)

White Worms

Daphnia and Scuds

Live Tubifex Worms

www.caudata.org/

Live Crickets

Live Wild "Bugs"

Live Grubs

Tadpoles• Greatest variety• Filter feeders• Flake fish foods• Algae powders• Dark leafy greens (avoid spinach, kale and

cabbage)• SeraMicron

Culturing Brown Algae

PVC Pipe

Seeding the tank Feeding

measure “parts” in weight, not volume

10 parts fish flakes8 parts trout pellets 8 parts grass pellets3 parts cuttlefish bone1-2 parts Tubifex (dependant on availability)1-2 parts river shrimps (dependant on availability)2-3 parts Spirulina algae

Tadpole standard diet

How is the food going to be offered?

Hand feedingcan keep close track of food intakelabor intensivenot always possible

Broadcast feedingeasiest can be timed to coincide with mist or rainharder to monitor animals’ food intake

Feederscan be used to prolong feeding periodencourages more natural feed behaviorscan be used to condition animals to display betterExamples: plastic tube, box + branches, bamboo, plastic balls,…

Obligate CarnivoresMust consume animals, not plant material

Adapted to diets high in protein and fat and low in carbohydratesCricket, 65% protein, 14% fat and 9% Acid Detergent Fiber (ADF)Mouse, 57% protein, 40% fat and 3% carbohydrates.

These animals have evolved consuming whole prey rich in protein and very low or devoid of carbohydrates

Derive most of their circulating blood glucose from gluconeogenesisPrimarily utilizes amino acids as substrate

Similar to felids, birds of prey and other obligate carnivoresMay have unusual essential amino acids

E.g., taurine in felids

All adult amphibians are obligate carnivoresAlthough Hyla truncata consumes fruit

No data as to capacity to use fruit as energy source

Things to RememberAdult amphibians’ wild diet likely varies by season and by year

In the wild, fasting is common for weeks to yearsEstivation, hibernation

Wild diets are very different from captive dietsCaptivity uses limited prey baseCaptivity makes assumptions about nutritional needsCaptivity often results in nutritional diseases unreported from wild: corneal lipidosis, metabolic bone disease, obesity, cachexia, hypovitaminosis

Things to Remember

• If it doesn’t look right and taste okay, the amphibian won’t eat it!

• Nutrient consumption is on a rolling average, not an exact daily intake– Balance on a kilocalorie basis

• Corneal lipidosis common due to excess cholesterol intake

• Obesity common due to misunderstanding of metabolic rate of amphibians

‘Tricks of the trade’ for problem feeders

Increasing temperature by a couple of degrees (rarely decreasing)

Increasing humidity and providing ‘rain showers’ – often in conjunction with above

Increasing photoperiod

Decreasing light intensity (rarely increasing)

Alter feeding times – dusk for crepuscular and nocturnal species

Vary the food items offered and presentation