On Thu, 19 Jun 1997, Alex Appleman wrote:
> Following on from Shane Raidal's commemts; raptors are hardy critters and
> also
> intelligent. There is evidence in North Queensland of black kites preying on
> the dreaded cane toad, flipping them over and feeding the legs and soft
> underbelly to their chicks, avoiding the poison glands. We can only assume
> that the kites ate poison in small doses, identified which part of the toad
> was toxic
> and are teaching their offspring how to avoid them.
There is a summary of what is known about Cane Toads's effects on
the Australian biota is a chapter in Mike Tyler's Australian frogs.
He notes deaths of Kookaburra, a Crow species and two Bittern
species as recorded as being killed by eating Cane Toads.
This list probably reflects most the poverty of the data that
Tyler could find.
He also notes a number of bird species recorded as successfully
preying on toads including Tawny Frogmouth, Whistling Kite,
Ibis, Cranes, Swamp Hens and Herons.
Mike Tyler also notes some native frog species posssess poison
glands and native predators avoid these.
So some possibilities are:
a) Black Kites pre-Toad feeding techniques don't expose them to
much toad toxin. Certainly if they don't tackle live toads their
risks are reduced.
b) Black Kites could (pre-Toads) detect and avoid the toxins. Cane Toad
secrete cocktail of chemicals. Some of these chemical are only found in
toads but perhaps Black Kites already could detect and would avoid
one of the cocktail components.
c) Black Kites have (pre-Toad) techniques for eating poisonous native
frog species which have also allowed them to eat Cane Toads.
d) New techniques were "discovered" by Black Kites (or other raptors)
which allow them to eat toads and these have been communicated by
observation among Black Kite populations.
e) Immigrant Black Kites from Asia where Bufo species are native
have brought suitable toad eating techniques to australia
and these have been communicated by observation
f) Black Kites (currently) eat Cane Toads and die and no one notices.
I don't want to seem rudely skeptical but there are lot of claims
about Toads but very little data.
Andrew Taylor
|
