PA Naturalist Gardening Buddies : The Eastern American Toad

Have a lot of insect problems in your garden? Perhaps you should dream for a resident Eastern American Toad.

eastern_american_toad_anaxyrus_americanus_americanus_-_london_ontario_01

Scientific Name: Anaxyrus americanus

Habitat: Eastern United States and Canada, adaptable to almost any condition: meadows, forests, agricultural lands, suburban yards, rocky hills, etc. Eggs and tadpoles require fresh water pools or ponds.

Size: 2-3.5 inches in length

Status: Very common and abundant!

Physical Characteristics:

  • Brownish-gray skin that could even range to dark-red or dark-green
  • White or yellow belly
  • Warty
  • Black spots on back that differ from other toads
  • Broad head with squat and stout body
  • Males have dark brown to black throat, females have lighter throat coloration

When can I see these?

Eastern American Toads have an almost telephone like ring to their chirp. Inactive in hot, dry temperatures, you are most likely to see an one of these fellows in your backyard after a rain during between the months of April and November. They are most active at night when they emerge to feed on insects. During the winter months, they burrow deep into the soil for hibernation. Dig carefully in the spring! As a younger child, my neighborhood friends and I used to uncover these friends hiding in the basement window crevices and in moist soil after rain. They are diurnal and are active during the night and day.

Breeding Season

The first time I actually identified the Eastern American Toad was in a shallow lake during their breeding season, which only lasts a few days in the spring! The female and male pair sit pretty motionless in the shallow waters, male on top of the female. Their lack of movement sometimes makes them harder to spot, but that is on purpose! Other jealous non-paired males may try to disrupt their intimacy. No too macho here, although males need some size to ward off other potential dads from latching on to their mom, Eastern American Toads must be small enough to ensure that their sperm is effectively released to fertilize the female’s eggs. The female will release their eggs in a string, which is then fertilized by the sperm that is then woven into the substrate of the pond.

These eggs will quickly become cute little tadpoles! Depending on the temperature of the water, the eggs will hatch in 3 to 12 days. Just like fish, these tadpoles will form schools also known as aggregations. The yummy algae in many backyard ponds make the tadpole’s belly happy. 12 to 20 days after hatching, these babies grow their back legs. 2 weeks later their front legs emerge! Their front legs also come with their right of passage to land, and the closing of the gills. 35 to 70 days later, the tadpoles abandon their water nurseries and become terrestrial toadlets. All of these days are relative, as the wide time range of individual growth allows form avoidance of mass extinction through predation and rejuvenation of pool resources.

frog-egg-mass

Egg mass

american_toad_tad

Tadpole with hind legs (12-20 days after hatch)

american_toad_metamorph

Tadpole with front legs (around 2 weeks after front legs emerge)

Good for my garden you say?

Beetles, caterpillars, slugs, and snails are a few common headaches in the garden. They are also a few of the Eastern American Toad’s favorite meals! It is estimated that 88% of their prey are invertebrates classified as agricultural pests, say what! Just one toad can consume just under 10,000 insects during their active season. Sounds like you should be installing a shallow pond for our friends right next to your tomatoes.

Eastern American Toads near human habitation and agricultural fields eat cucumber beetles, potato beetles, and other butterflies and caterpillars that prey on crops.

Other favorite foods include flies, crickets, locusts, bees, earthworms, spiders, and wasps. The first thing you might associate with the toad, its long sticky tongue, is rapidly extendable and is used as the utensil for gathering its food. Quite fascinating to watch, the toad will sit motionless and wait until the prey is 2 inches away before its tongue shoots out and captures the poor buggy. The toad will approach its prey slowly with a “leap-sit-leap-sit” pattern as to not scare them away. Think of the toads as always wearing a pair of 3D glasses, as their binocular visual fields and motion detection account for their efficiency in eating.

Chameleon cousin?

Few predators actually eat the Eastern American Toad, thanks to its highly sophisticated adaptions. Thought chameleons were the only animals that changed color? The toad can also alter coloration to match its substrate! They too share a trait with the opossum, playing dead in the presence of a potential predator. Their most advanced defense mechanism is the poisonous secretions they produce in two glands located on their heads. It is interesting that toads raised in captivity do not always produce these toxins. Some predators that still take a stab at the toad are garter snakes, hognose snakes, hawks, herons and raccoons. Babies need to be a little more careful, as fish may also like eggs for breakfast.

The real non-breathing predator

Despite all of their crazy defense mechanisms, an aquatic fungal pathogen is a possible threat to the abundant Eastern American Toad population, and other native amphibians of the area. Chytridiomycosis is an infections disease caused by this fungal pathogen Batrachochytrium dendrobatidis (Bd). Bd infects the keratin-containing layers of the skin. You can tell a tadpole has been affected by Bd when there is depigmentation around their mouthparts, the only area of the body with keratinized skin. As they grow older, the infection can spread over the rest of their body. Skin will become thicker and will eventually cast off. Actual death from Bd occurs because the loss of skin compromises osmotic regulation of the blood, leading to cardiac arrest.

Protect our friends from heart attacks

Bd has been found on all continents that are homes to amphibians. Nearly all of the United States has been tested positive for Bd. Humans are the biggest culprit for Bd spread! Through the international amphibian trade, we have carried the disease all over the world. It is also hypothesized to be occurring through bait trade. Additionally, climate change and warming temperatures can indirectly affect the spread of Bd as many amphibian species are expanding their elevation range.

  • NEVER purchase frogs as pets, they are happier in the outdoors.
  • NEVER release frogs or tadpoles into a location other than where they came from (this also includes taking an Eastern American Toad from one pond in PA to another).
  • NEVER dump tank water from amphibian enclosures into bodies of water.
  • AVOID contact with amphibians without proper sanitation (hand sanitizer does not count, and may actually be harmful). Their permeable skin is quick to absorb  bad things  off of you!
  • WASH your boots after hiking or traveling, this is a common way to spread invasive pathogens of all sorts!

Resources:

http://www.psu.edu/dept/nkbiology/naturetrail/speciespages/americantoad.htm

http://www.lpzoo.org/animal/american-toad

http://amphibiaweb.org/chytrid/chytridiomycosis.html#spreading

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