It is very easy to know if you are looking at a tree frog or a bullfrog.
Tree frogs are very small – 2-4cm long. They come in two colour phases – either brown with dark blotches or bright green. They always have a black stripe running from their nose past the eye and down to the shoulder. They make a “ricket-ricket” sound way out of proportion to their size http://www.naturesongs.com/frog3.wav
Bullfrogs make a quite different sound, rather like a rapidly repeating foghorn http://www.learnnc.org/lp/media/collections/fieldguide/frogcalls/bullfrog.mp3 They are far bigger than tree frogs – up to 25cm and can weigh up to 2kg.. They expand like balloons when attacked and have teeth on their lower jaw to hold their prey. They eat almost anything. They were introduced from Africa and are a thoroughly nasty species in this area.
Showing posts with label bullfrog. Show all posts
Showing posts with label bullfrog. Show all posts
Thursday, June 17, 2010
A Frog in the Bog
When I moved into my home near Camosun Bog over 30 years ago, the sound of frogs in the spring was deafening. Over the years the sound decreased and in the last few years the bog has been silent.
One major reason for the loss of tree frogs has been bullfrogs. These were introduced to this area in the 1930s to produce frog legs for French restaurants. They didn’t catch on and were released in the Langley area. They have almost no predators – possibly herons – and each female produces 20,000 eggs every year. They can travel 1½ km in an evening and jump 2m high. There are reports of them eating cats! (see http://www.barbelith.com/topic/2486)
They arrived in Camosun Bog 7-8 years ago and very quickly eliminated the remaining tree frogs. Having eaten them all, the bullfrogs then moved on to happier hunting grounds.
Over the last couple of years, the tree frogs have started to move back into the bog. This may be due to us expanding and deepening the pond and particularly this year it may have been helped by the very wet spring we have had. At one work party in April we were deafened by their sound and had to shout to be heard. The inevitable male-female thing happened and now we have lots of tadpoles swimming around in the pond!
Let’s hope the tree frog population continues to increase. It is essential that we do not disturb the tadpoles and we must not allow anybody to collect them. There is a real danger that the sound of the peepers will attract the bullfrogs and they will return to wipe out the population again. Unfortunately there is not much we can do to stop this. We tried to catch them some years ago but we were never successful as they disappear as soon as someone approaches them. Probably we will get into a long-term cycle of gradually increasing population followed by a crash. Rather similar to the lemming – snowy owl cycle in the arctic. We will see…..
One major reason for the loss of tree frogs has been bullfrogs. These were introduced to this area in the 1930s to produce frog legs for French restaurants. They didn’t catch on and were released in the Langley area. They have almost no predators – possibly herons – and each female produces 20,000 eggs every year. They can travel 1½ km in an evening and jump 2m high. There are reports of them eating cats! (see http://www.barbelith.com/topic/2486)
They arrived in Camosun Bog 7-8 years ago and very quickly eliminated the remaining tree frogs. Having eaten them all, the bullfrogs then moved on to happier hunting grounds.
Over the last couple of years, the tree frogs have started to move back into the bog. This may be due to us expanding and deepening the pond and particularly this year it may have been helped by the very wet spring we have had. At one work party in April we were deafened by their sound and had to shout to be heard. The inevitable male-female thing happened and now we have lots of tadpoles swimming around in the pond!
Let’s hope the tree frog population continues to increase. It is essential that we do not disturb the tadpoles and we must not allow anybody to collect them. There is a real danger that the sound of the peepers will attract the bullfrogs and they will return to wipe out the population again. Unfortunately there is not much we can do to stop this. We tried to catch them some years ago but we were never successful as they disappear as soon as someone approaches them. Probably we will get into a long-term cycle of gradually increasing population followed by a crash. Rather similar to the lemming – snowy owl cycle in the arctic. We will see…..
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