Lifecycle: To be a big bad toad...

These toads grow to be huge.  We'll talk of how they get so big in the information below.  Image from being deposited on a substrate, the 8,000-35,000 eggs swell to about 3mm and hatch in about 3-4 days.  Their first food source is jelly of the eggs, but the tadpoles then transition to eating algae, and finally will eat both vegetation and other tadpoles (both their own species and other species).  The duration of the tadpole stage is dependent upon available nutrients, and can range from just over 2 weeks to 6 months.  The tadpole attains a length of 1-3 cm, with itsThe back legs appear first on tadpoles.  Image from Microsoft clipart. tail in equal length to its body.  It is advantageous for tadpoles to develop quickly, as watering holes can dry up –resulting in the death of any tadpoles.  Warm water temperatures result in more rapid tadpole growth and maturation.  The typical tadpole begins maturation (sprouting first back legs, then front legs, and attaining a slightly greenish color) around 1-2 months of age and is then known as a metamorph. 

Of a clutch of 8,000 eggs, between 20-800 of them will survive to the metamorph stage; the average expectation is for 40 tadpoles to survive to the metamorph stage, and at all stages there is greater mortality in native zones than in regions in which the toad has been introduced (mortality is a result of greater predation).  As a metamorph, the tadpole experiences many physical changes (coordination, tail adsorption, lung development, transition to a different feeding method) that make it rather clumsy.  From tip of nose to butt (a measurement kA metamorph; note the size of the head relative to the body size.  The head is large because this little toad must be able to eat prey.  Toadlets will grow to fit their mouths.  Image from as snout to vent, or SV), metamorphs are only 11 mm and weigh only 0.01% of what they’ll likely weigh as adults.  This exceptionally small size also contributes to mortality, yet the risks of small metamorph size must be balanced against the risk of dying if the tadpole stage is prolonged so as to emerge a bigger toadlet.  The metamorph is also losing the toxicity that it has had its entire life (as egg then tadpole) and hasn’t yet accumulated a store of adult toxin.  The “learning curve” of coordination, the need to adapt to life outside the water, and a lack of toxicity contribute to the metamorph stage being most vulnerable time for a cane toad.  The metamorphs stay huddled along the waterhole.

Within several days, the little toads will begin migrating away from the pond, likely in part due to the high competition for prey that results from the high concentration of toadlets, but also to escape the adult toads who camp near the watering holes and will eat the smaller toads.  The toadlets will not return to the breeding site until they are sexually mature, which generally occurs within 1-2 years, depending upon conditions and the climate.  A toad generally reaches sexual maturity between 75-100 mm, and with sexual maturity are more brown to black in color.  The toad may live around 10 years.  The most growth occurs during the annual wet season, with toads growing about 2.5 cm/year after the second year until attaining full size.  Adults often attain lengths of 10-15 cm, with females being larger than males.                                                                                                                                                                       


A cane toad, C2003 Ignacio De la Riva, image from be a big bad cane toad!  Every tadpole's dream.


Cane toads amass more toxin as they get bigger.  Next, read about their poisons! This is a toady dream come true!