(Bufo Americanus)
The American Toad is one of the most interesting species found in the early
spring months on Trent campus. These toads are not shy at all and one can walk
right up to them and observe them call, mate, wrestle and swim. This is the
fourth ephemeral species that frequents the Trent Nature Areas in the spring,
following the Wood Frogs, Spring Peepers and Chorus Frogs. Generally you will
hear the males calling during the evening of a warm day, with temperatures ranging
during the day from 20-27oC. If the evening temperatures drop to
as low as 10oC one may still find this species calling. However, if the temperature
drops dramatically during the evening, the toads may not be out. Occasionally
these guys can be heard calling during the daylight, especially if one can imitate
their call well enough. Generally though, a tape recorder will have the same
effect.
Identification:
The identification features of this species is the light to dark
brown colour of the animal and the large poison glands, or warts covering its
body. Males are considerably smaller than the females of this species, and are
the only sex that possesses a vocal sac (which is used to make their call).
In addition to the vocal sac, males also have thumb pads located behind their
thumbs on both front legs. Two large raised kidney-shaped glands are located
on the back of both sexes of the toads eyes. These glands are the paratoid glands,
which produce the toxins that deter many animals from eating this species.
The American Toads can be found calling in semi-shallow sections of the Archaeology
marsh and the Archaeology pond. Most of the toads call and mate in the marsh,
so if you really want to find one, search there first! Unlike most of the other
species found in the Trent Nature Areas, toads generally locate themselves in
open areas without many cattails to hide in.
Calling:
The vocal sac is inflated by opening their mouths and sucking air
in. When observing these animals, one can see the individual gulps of air by
watching the vocal sac blow up, much like a balloon. Once the vocal sac is inflated
to its maximum size, the toad will close most of its mouth and let out a long
trill of sound. If one toad starts to call, generally other toads in the vicinity
will join in with the initiator. You can hear this call by clicking on the frog
here.
Sometimes you can catch a toad in a stance that appears to able the toads
call to be heard at a greater distance. When observing this toad, he seemed
to be listening intently for something. He would often quickly move from one
area to another, take this stance and blast out his call. If you look closely
you can see that his front legs are close to his body, this forces his back
to be straighter, and his vocal sac to be in a raised position.
Competition:
The competitive behavior of the American Toads is the most easily observed of
any of the anuran species located on campus. Since this species calls and breeds
in open areas, there is often some behavioral action to observe. The males are
often found close together, all calling in one general area, sometimes staring
at each other as they call.
This species is often found wrestling with each other for the different spots in the calling area.
It seemed that if the toads loose too many battles, they chose to evade this
physical contact by calling from behind the protective covering of some grass
nearby. However, this is just my own personal observation. This guy was observed
wrestling in three different battles before he began to call in the grass here.
Amplexus:
This is the mating position that anurans pose when they are laying and fertilizing
their eggs. Although these animals are not performing any form of sexual intercourse
with internal fertilization, they position themselves in the same manner as
animals that do perform intercourse. The males of the American toads wrap their
front legs under the armpits of the female and hold on. His back legs are scrunched
up in a way that does not seem to hinder the females movement. The female releases
her eggs while the male ejects his sperm to fertilize them.
As the male is fertilizing the eggs the female toad walks or swims around to
disperse her eggs around the area.
Eggs:
These eggs are released from the body in long strands of three or four lines.
The individual eggs are oval in shape and have an equal amount of black as the
do white. The white portion of the egg is the yolk sac, which will nurture the
developing tadpole as it grows. The black portion of the egg is the animal portion,
the portion that develope into the living tadpole.
When one observes these eggs a few hours after they are fertilized, the eggs
look totally different. A clear gelatinous membrane is now encasing the individual
eggs. The white that was previously half the colour of the egg has almost completely
disappeared, leaving the eggs almost totally black.
