A review of:

“Frogs flee from the sound of fire”

(T. Ulmar Grafe*, Stefanie Do¨bler and K. Eduard Linsenmair,

Department of Animal Ecology and Tropical Biology, University of Wu¨rzburg, 97074 Wu¨rzburg, Germany

Published online 25 April 2002)

 

 

By: Johanna Bengtsson

Budapest, 2007-04-25

 

 

Summary.

Some years earlier than this study, one of the researchers found a Hyperolius nitidilus frog flee from a fire. The interesting thing was that the fire was more 20m away. And then the assumption came up that the frog used auditory ways to detect a fire.

This lead to a study on the same place, that precise frog was detected, Comoé National Park, Ivory coast, in January 2001. Where the H. nitidulus frogs using their hearing to detect and flee from fire?

 

The study was performed in three steps.

1. To see if the frogs reacted as predicted.

2. To check if the dehydration state affected the reaction.

3. Full documentation of ten frogs escape.

 

In the first experiment three different sound stimulus was presented to twenty aestivating frogs. The different sound stimuli were: the sound of a fire, the backwards sound of a fire and a control noise containing no fire. The speaker was placed 1m from the frog.

The result showed an obvious reaction rate to the normal fire stimulus and a smaller reaction rate to the backwards fire stimulus. None of the frogs reacted to the control noise.

In the second experiment, dehydrated frogs’ reactions were compared to frogs with unknown dehydration stadium. There were no differences in reactions.

In the third experiment ten frogs were presented the normal fire stimulus and followed until they went into water- conserving state. The speaker was first posted 90° from what seemed like nearest fire resistant area and when the fogs jumped the speaker followed the frog and that way simply ruled out that the frog was just moving away from the speaker.

All frogs except one jumped towards the assumed fire resistant area. That deviating frog that didn’t move away from the speaker moved towards the speaker instead. All frogs went into water conserving posture on (or near) a tree or a small bush.

 

Own discussion.

I’m arguing about the distance between the speaker and the frog. A fire doesn’t just start 1m from the frog. I agree with that it can ensure the researchers about a result, but since it’s not produced like a real fire you can’t be sure of a correct reaction.

 

Types of fire resistant area are mostly a tall tree or a dense bush in the report. Is that a typical fire resistant place? I want the frogs to be near water or at least jump into a moist area when they’re reacting to a fire. In my mind a tall tree or a lower bush are excellent nutrition for the fire and least suitable for a frog to hide in.

They haven’t mentioned much about the alternative surroundings at all. Maybe their nearest fire resistant place wasn’t the best at all and there were other factors to decide where to flee. I’m not questioning that the frogs reacted to the sound but how and why they reacted. We will never know if that frog that went opposite the other frogs and towards the speaker, was a clever one since the researchers dismissed it without thought or explanation.

 

I want to know more about the surrounding at that very moment the experiment was done. Was it a calm and sunny day and only the frogs visible or where there any other animals nearby? Maybe some predators or other threats that could have affected the results were present? When was the last fire in that area and how often does a fire occurs on the same place? The report only says that: “most fire occur in the first half of the dry season” and that “the core dry season lasts from December to February” (T. Ulmar Grafe et al, 2002) 

If it was windy at the time for experimenting, maybe the frogs were smelling some danger that we don’t know of. Like it says in the beginning of the report; frogs were unlikely to react to the fire that was more than 20m away by other ways than hearing. But we don’t know about the circumstances, so what do they rely their assumption on?

 

In the discussion you’re told that experiments were done in February and March too, but at that time the frogs didn’t respond. Why? Was it because of the sound or other effects, like circumstances in the surroundings? Or did the frogs just stopped listen? If a fire is approaching, every frog should flee for their life, (including mankind), you don’t stay and hope that the wind will change its direction, especially since nothing is mentioned about if the frogs recognise which direction the fire is travelling. If I knew a little more about the habitat and the frogs’ natural behaviour maybe I would reason differently.

 

What I learnt about this specific frog is that it’s probably very tiny. Then I assume it would be difficult to follow only one frog, without loosing the sight of it. Especially since they’re often gathered in big crowds. The researchers haven’t mentioned anything about that risk or how to prevent mixing escaping frogs. Besides that, the frog should feel that it’s hunted and probably respond to a threat, instead of reacting normally to the sound of fire.

 

And the last thing I miss in the report is the frogs other signal systems. Does it have good sight, is it affected by weather, can it smell danger or maybe other system we don’t know about yet? These points are also relevant to the result and the explanation of the result.

 

 

 

References

T. Ulmar Grafe*, Stefanie Do¨bler and K. Eduard Linsenmair, (2002)

        Frogs flee from the sound of fire

        Proc. R. Soc. Lond. B (2002) 269, 999–1003

Kathrin P. Lampert ˇ K. Eduard Linsenmair (2001)

      Alternative life cycle strategies in the West African reed frog

      Hyperolius nitidulus: the answer to an unpredictable environment?

        Oecologia (2002) 130:364–372