That Reptile Blog – Reptile, Amphibian and Exotic Pet Care and Information

Click: The Marine or Cane Toad, Bufo marinus (Rhinella marina) in Nature and Captivity – Marine Toads as Pets – Part 1 to read the first part of this article.

Many pet keepers feed their toads heavily on pink and even adult mice. This is a bad idea and will eventually lead to eye, kidney and liver problems. While these aggressive predators certainly take the occasional rodent or lizard in the wild, research has shown that insects, spiders and other invertebrates form the vast majority of their natural diet. In captivity, a goldfish, minnow or shiner can be offered every month or so, perhaps a pink mouse every 6-8 weeks, but limit their intake of vertebrates. Do not feed mice other than pinkies – toads swallow their food alive, and sooner or later they will be injured by a mouse’s sharp teeth.

Marine Toads take readily to tong or even hand feeding (use plastic tongs). Canned insects, such as Can O’ Grasshoppers and Can O’ Pillars should be hand-fed to increase dietary variety.

Wild caught insects, collected from pesticide-free areas, should be offered whenever possible. Zoo Med’s Bug Napper is an excellent insect trap. Sweeping a net through tall grass and searching around outdoor lights will also yield a wide variety of tasty treats. Avoid using spiders, stinging and brightly -colored insects and fireflies, and do not collect during times when your area is being commercially sprayed for mosquito control.

My Marine Toads relish cicadas, katydids, grasshoppers, beetles of all types, moths, tree crickets, caterpillars, sow bugs and most everything else I come up with. Most of my amphibians feed largely upon wild-caught invertebrates throughout the summer, but even a few beetles plucked from a screen door every night or so will go a long way in keeping your pet in the peak of health.

Social Groups
Marine Toads coexist fairly well together, but bear in mind that they need a lot of room and must be kept scrupulously clean. Fighting is rare, but large animals will out-compete smaller ones for food, so hand-feed if in doubt.

Captive Longevity
The published longevity record is 24 years. Two that I acquired as adults are, at last report, still going strong after 16 years.

Handling and Enrichment
Marine Toads learn very quickly where their meals lie, and will soon greet you as you approach their terrarium. They do not enjoy being held, however, and like all amphibians are subject health problems once the skin’s mucus covering is removed. Handle them – carefully and with clean, wet hands – only when necessary.

Toads in general and this species in particular secrete extremely virulent skin toxins and must be treated with care. Always wash thoroughly after handling them, and never touch your mouth or eyes before doing so. Do not handle Marine Toads if you have a cut in your skin, no matter how tiny it may be. Children and pets must be prevented from coming in contact with these animals, to the point of installing a lock on the terrarium if you are at all unsure. Toads that are licked or swallowed can cause life-threatening reactions.

Marine Toads benefit from hunting opportunities, and remain much more active and alert when provided such on a regular basis. Allow non-threatening insects (crickets may chew on cold or debilitated animals) such as caterpillars, katydids and grasshoppers to roam about their tank when possible. Better still, set your toads up in a secure area outdoors near some over-ripe fruit (to draw beetles and butterflies) or a bush crawling with caterpillars, sit back and enjoy!

Breeding
Egg-laying in the wild is generally in response to the onset of rainy periods, and such may occur if the toads are provided with “artificial rain” in captivity (more on this in the future). Captives sometime breed spontaneously as well. The tadpoles are fairly hardy – please write in if you are fortunate enough to have a breeding pair.

Miscellaneous
In some situations, Marine Toads fare well in semi-freedom. They stay quite close to favored territories – the same 5-6 individuals hunted outside my kitchen in Costa Rica every night for several weeks.

While working at the Bronx Zoo, I kept a few at liberty below a row of exhibits, and another small group in a greenhouse. Here they fed upon crickets, roaches, centipedes, spiders and the like, and grew quite fat. They never failed to emerge from their shelters when I arrived each morning, waiting in a semi-circle for the treats (earthworms and crayfish) they had come to expect. They really are among the most responsive of the amphibians – I highly recommend one if you have the space.

A great deal of information about Marine Toads is posted at:
http://www.globalamphibians.org/servlet/GAA?searchName=Bufo+marinus

General
I have always found Marine Toads to be among the most engaging of amphibian pets.  Toads in general seem to be (externally at least) more responsive than frogs- they “watch” everything, and appear to deliberately consider their next move.  Protected as they are by powerful skin toxins, Marine Toads in particular seem possessed of real “confidence” in captivity, and we can get to know them well if we take the time.

Please see Marine Toads – Natural History for information on Marine Toads in the wild.

Enclosure and Physical Environment
Some Marine Toads grow quite large – to 10 inches, and even small individuals can be quite active and consequently need a large terrarium.  An averaged-sized adult can be kept in a 30 gallon “long” aquarium – while a really large one or a pair will do best in a tank of 55-75 gallon capacity.

During warm weather, Marine Toads can be housed in secure outdoor enclosures as well.  Insects lured by a small light or over-ripe fruit will supply your toads with important dietary variety.

Their enclosure should be topped by a screen cover secured by clamps  and the substrate should be kept damp but not wet.  Compressed Frog Moss, Fir and Sphagnum Moss Bedding and Reptile Cage Carpet all work well.  Marine Toads have a tendency to swallow substrate when feeding – usually they pass this without incident, but tong-feed your animals or use a feeding bowl –prod- if you notice this happening frequently.

Despite being quite bold, Marine Toads require a hide-a way where they can get out of sight (Rock Den or Turtle Hut).  Be sure to provide a cave for each of your toads, as animals that cluster in one shelter seem prone to fungal infections of the skin.

Marine Toads need to soak frequently, so always have a bowl of de-chlorinated water available.  Be sure that small toads can exit the water bowl easily, as they are poor swimmers.

While small toads can be kept in planted exhibits, adults will mangle all but the sturdiest of plants (try Cast Iron Plants and Snake Plants).  They will clamber about on smooth logs – just be sure that these are secured in place as these brutes are quite strong and may roll a log onto themselves or a tank-mate.

Light, Heat and Humidity
Marine Toads do not require UVB radiation, and so will get along with a regular fluorescent bulb.  Use a low UVB output plant light if you keep live plants, as high levels may cause eye damage.

The terrarium should be maintained at 72-80 F.  Marine Toads can tolerate much warmer conditions – I have uncovered them below boards at temperatures of 100 F – but such is stressful and should be avoided.

Despite being largely terrestrial, Marine Toads seem quite prone to desiccation – spray their terrarium each morning and keep a water bowl available at all times. They often defecate in the water bowl – be sure to clean this as soon as possible, lest they absorb ammonia and other toxins through their skin.

Feeding
Your pets should be given as much dietary variety as possible.  I have observed wild Marine Toads consuming over 2 dozen insect species in a very short time, and other researchers have documented a huge range of prey items (please see Marine Toads – Natural History article).

The main portion of their diet should not be crickets, but rather a mix of earthworms (these can be used as the bulk of their diet if necessary), roaches, crickets, and waxworms.  Silkworms and Tomato Hornworms, available via internet dealers, should be offered from time to time.  I use super mealworms sparingly, but others have done so frequently without incident.  I have found crayfish to be an important food item for a wide variety of creatures, including Marine Toads.  I remove their claws, just to be on the safe side.

Adults fed a varied diet require a vitamin/mineral supplement  only once each week at most.  The food of growing animals should be supplemented 2-3 times weekly.

Check back Wednesday for the conclusion of Marine Toads as Pets.

Introduction
An outdoor pond or other such habitat will expose you to facets of your pets’ behaviors that are difficult if not impossible to observe in indoor terrariums. I am a great fan of naturalistic, outdoor enclosures and from time to time will write about some of the many creatures that will thrive in them.

Surprising Colonizers
In most cases, the animals within our terrariums have been put there on purpose. However, if you establish an un-fenced outdoor pond, you may be in for a few pleasant surprises, even in densely populated areas.
Surprisingly, creatures that seem incapable of moving great distances, such as frogs, salamanders, snakes and turtles, are actually quite adept at sensing the presence of new water sources and traveling to them.

Especially skilled in this regard are bullfrogs, leopard frogs, pickerel frogs, grey tree frogs, American toads, water snakes and snapping turtles. There is an incredible amount of pressure on young animals (in the form of territorial and hungry adults) to leave their natal homes, so it makes sense that they would be equipped with keen abilities to find new habitats. So surprising is the arrival of frogs at isolated ponds that, in earlier times, people believed they rained down from the sky or were spontaneously generated from the mud!

An Impressive Pond Resident
The American bullfrog, Rana catesbeianus, is the largest North American frog and a truly spectacular addition to the garden pond. Bullfrogs do not like to be crowded – most backyard ponds will support but 1 male and 1 or 2 females. Bullfrogs have large appetites and have been known to consume small birds, bats and mice, and especially favor smaller frogs (related or otherwise!) If you move about slowly and cautiously when the frogs are out sunning, they will soon accept your presence and will reward your patience by swallowing earthworms or crickets tossed nearby.

Introducing Bullfrogs to Your Pond
If you decide to add bullfrogs to an unenclosed pond, be sure to start with tadpoles – frogs introduced to a strange area will nearly always leave, apparently in search of their original homes. Tadpoles that mature in your pond will be quite content to stay nearby.

Bullfrog Tadpoles
The large tadpoles may take up to 2 years to mature. The tadpoles will eat whatever algae and dead insects they may find. However, they require a good deal of food for proper development, and should be given supplementary green vegetables that have be soaked for a few minutes in hot water (this breaks down the tough cell walls, which are indigestible) and held below water by rocks . Vegetables such as romaine, kale and dandelion are necessary foods when fish are about, as fish will out-compete the tadpoles for food items such as flakes and algae tablets.

Frogs in Winter
Although bullfrogs and other temperate species can be over-wintered in the pond, it is safer to bring them indoors. They should be kept in a large aquarium with a good deal of cover in the form of floating plastic plants and enough water in which to submerged themselves, along with a smooth rock or piece of wood on which to rest. If kept at temperatures of 50 F or so (i.e. in a basement, if available), they will be fairly calm and will require but 1 weekly feeding. The Green Frog, Rana clamitans, and Leopard Frog, Rana pipiens, can be kept in small groups in outdoor ponds, as they are far less territorial than their larger cousin.

The accompanying photo shows 2 female albino American Bullfrogs. Albino bullfrogs are striking additions to the outdoor pond, but will quickly be captured by predators if the pond is unenclosed. The animals pictured here are yearlings, and have a good deal of growing left to do.

Frogs are full of surprises when it comes to reproduction – there are species that incubate eggs below the skin of their backs and in the vocal sacs, while others carry them wrapped about their rear legs or construct foam nests on land.  But in May of this year Boston University biologists working in Panama uncovered what may well be the oddest reproductive strategy of all – a frog that actively chooses to lay its eggs on either land or in water, depending upon the threats presented by each habitat.  To date this is the only example of an egg that can hatch in either environment, and these frogs are the only vertebrates known to show such reproductive flexibility.

When breeding near shaded ponds, hourglass frogs lay their eggs on tree leaves overhanging the water (the tadpoles drop into the water upon hatching), thus avoiding fish and other aquatic predators.  However, when utilizing ponds exposed to the sun, the majority of the frogs lay their eggs directly in the water, lest they dry out before hatching.

The “decision” is not governed genetically, because the same female frog will choose different egg laying sites when placed in a shaded or un-shaded pond.

Amphibians were the first group of vertebrates to evolve some independence from water.  Biologists are now studying the hourglass frog to determine if its unique egg-laying flexibility might shed light on the evolution of terrestrial amphibian eggs.

You can read more about the hourglass treefrog and its relatives at:
http://research.amnh.org/herpetology/amphibia/references.php?id=10041

Overview
Recently I wrote about those tiny jewels of the frog world, Latin America’s poison frogs (Article Part I and II).  Today I’ll introduce you to a behemoth that is largely their direct opposite, the massive Marine Toad – at once one of the world’s most interesting and troublesome of amphibians (actually, the people who have transported it around the globe are troublesome, not the toads!).

Physical Description
This largest of the world’s toads may reach 10 inches in length.  Generally brown to tan in color, some individuals show a yellow or reddish tint.  One that I received from a friend working on Guam was clad in several shades of yellow and quite beautiful. Enormous paratoid (poison) glands extend from behind the eyes to the sides of the body.  The body is squat and rounded in profile.

There seems to be a great deal of variation in size among different Marine Toad populations, with the true giants that came out of Colombia and Suriname in the 1960’s and early 70’s being rarely seen in the trade today.  I examined a great many in working in Venezuela, and most were in the 4-6 inch range (this comports with locally published accounts).  Florida’s introduced animals are relatively small in size (but large as toads go), as are those in south Texas.

The photo accompanying this article shows me holding a large female that was collected, I believe, in Colombia.  She has inflated her lungs with air to prevent my swallowing her (fat chance!) – the stick is to discourage the two 18 foot long anacondas that share her exhibit from attempting to swallow me!

Range and Habitat
People are sometimes surprised to learn that the Marine Toad is a US native, but those living in southern Texas are indeed part of a naturally occurring group.  Florida and Hawaii’s large populations are introduced.

From Texas, this toad range south from southern Sonora, Mexico through Central America to central Brazil, Amazonian Peru and Bolivia.  Marine Toads have been widely introduced and are well established in Florida, Hawaii, Taiwan, Japan, New Guinea, Australia, and throughout the islands of the Caribbean (i.e. Puerto Rico, Antilles, St. Lucia) and the South Pacific (i.e. Fiji, Guam).

Marine toads dwell in a wide variety of habitats, including open forest, overgrown scrub, grasslands, fields and marshes.  They adjust well to disturbed sites and are common in agricultural areas, suburbs and urban parks (i.e. within Miami, Fla.).  Several I observed on Tortuguero, Costa Rica, crossed a 30 foot stretch of mowed lawn each evening to feed near my bedroom’s outdoor light.

Status in the Wild
Generally common within natural range and usually very common, to the point of being a harmful invasive, where introduced.

Diet
Marine Toads consume nearly any creature that fits within their cavernous mouths – centipedes, roaches, beetles, millipedes, earthworms, land crabs, spiders and other invertebrates, frogs, lizards and snakes.  Mice, birds and similar creatures are taken when encountered, but stomach analysis of toads in the Venezuelan llanos (grasslands) showed this to be a rare occurrence in that habitat.

This is one of only a very few frog species to consume non-living food items (African Clawed Frogs, Xenopus spp. will take carrion and, amazingly, Izecksohn’s Treefrog of Brazil eats berries).  While in Costa Rica, I regularly observed a large toad eating dog food (after pushing open a screen door to get at it!), and those kept by co-workers at the Bronx Zoo ate salad set out for tortoises.  Field reports from New Guinea indicate that Marine Toads there rely upon vegetation as food during the dry season.  Stomach analysis of wild individuals indicates that they also will take carrion (chicken and fish) and the eggs of other Marine Toads.

In addition to hunting by sight, these toads apparently utilize olfaction (rare for a terrestrial frog) as well.

Reproduction
An extremely flexible reproductive biology accounts for this animal’s success as an invasive species.  Unlike most amphibians, it can reproduce throughout the year in favorable habitats, in brackish (saline) water and in waters containing high fish populations.

Large females may lay as many as 36,000 eggs, attached in strings to aquatic vegetation.  In contrast to most frogs, both eggs and tadpoles are protected by virulent toxins.  The tadpoles take 10 days to 6 months to transform, depending upon temperature and diet, and can survive 10 hours without water.  They consume algae, dead plants, carrion and each other, and generally out-compete or eat the tadpoles of other species.  Newly transformed toads disperse widely and often establish new limits to existing ranges.

Miscellaneous
Marine toads are likely the world’s most widely introduced amphibian (American Bullfrogs and Greenhouse Frogs are close competitors for this title).  They are generally transported to agricultural areas to control insect pests, a strategy that rarely works.  In Australia, for example, the toads seldom catch cane beetles, their intended prey – the beetles dwell high above the ground and the toads do not climb.

Introduced populations expand rapidly, consume native animals and out-compete others.  On Oahu, Hawaii, 148 introduced toads multiplied to over 100,000 in a 2 year period.

The Marine Toad’s toxins are powerful and complex.  Threatened toads will lower their heads and attempt to bring the poison-containing paratoid glands in contact with the attacker.  In Australia, 3 species of quoll (a medium-sized mammal) and 8 species of monitor lizards prey upon the toads and are declining due to deaths caused by the toad’s skin toxins.  Dingoes, snakes, foxes, dogs and other animals have also expired after eating Marine Toads.

Most predators occurring within the Marine Toad’s natural range leave them strictly alone.  I have, for example, housed them with green anacondas for many years – despite that fact that the snakes will avidly consume other frog species.  However, several snake and possibly bird species have evolved toxin immunities and prey upon them.  In Australia, White-Tailed Water Rats have apparently learned to avoid the skin toxins by flipping the toads and chewing through the belly skin to reach the internal organs.

Marine toads are quite responsive to their surroundings.  Captive animals anticipate food upon seeing their keepers, and those living in developed areas learn to gather under street lights to capture insects.

A field report detailing some of the unusual foods and other items found in the stomachs’ of free-living Marine Toads is posted at:
http://www.jstor.org/pss/1564710