questions about common toads

[lucy]

I've got some questions for the growing band of herpetologists on the forum.

How long can a common toad stay under water without drowning?  For example, when they form mating balls, with several males clinging to the female under water, how long can she survive without rising to the surface?

Why do these mating balls form?  Do males outnumber the females, resulting in this kind of competition? Is there a gender imbalance in the population?

[Mel]

What interesting questions.

I am not sure of the 'drowning threshold' of the females but I am aware that the males arrive in advance of the females at the spawning grounds and the first females to arrive are, therefore, greeted by a disproportionate amount of excited suitors. As the season progresses and more females arrive, the numbers become more equitable, and less hazardous for the females!

Males also become sexually mature earlier than females in this species and are therefore likely to be more numerous at any given time at the spawning grounds.

Presumably this earlier development is to offset their losses when they have to make themselves more conspicuous in courtship than the females and are therefore more exposed to predators.

I once came upon hundreds of empty common toad skins, all male judging by their size, at a small freshwater loch on Islay in the Inner Hebrides. Each poisonous skin was perfectly turned inside-out like a woolly jumper, and discarded.

I am fairly certain that this was the work of (hooded) crows, which are known to be adept at toad skinning!

[lucy]

Thanks Mel, that's helped me understand what I witnessed the other day. 

I found a reference to crows eating toads: http://en.wikipedia.org/wiki/Exploding_animal

In this case it seems they were only interested in the liver, a delicacy for the local crows, but with an unusal side-effect.