Good morning, everyone. In today's lecture I want to talk to you about a very unpopular animal here in Britain. In fact, you could say that it's one of our least loved animals! It's called the American bullfrog and yes, it does in fact come from America - the east of America, to be exact - and it was brought to Britain in the early 19th century, so you could say that it's been here for quite a long time. It wasn't brought here on purpose - it actually arrived in a big container of aquatic plants. In other words, it was accidentally introduced into Britain.
Now, I'll tell you a little about its appearance. The American bullfrog is a very large - and ugly - species of frog. And when I say it's large, I mean large. Interestingly, female American bullfrogs are usually much larger than the males. In fact, they can weigh up to 750 grams, whereas the males only go up to about 600 grams. Take a look at its head - it's really broad and flat, isn't it? And you can see its mouth -just here - that's quite large too.
Now, both the male and the female American bullfrogs have green or brown bodies and have dark spots on the top. But there's one important difference between them - the male's throat is yellow but the female has a white one instead. And the other difference is their eardrums, here just behind their eyes. Those of the male are much larger than the female's.
So, let's move on to why we so dislike the American bullfrog. Well, this is because it has threatened our own native species of frogs. Firstly, it breeds very quickly indeed. For example, female bullfrogs can lay up to 25,000 eggs every single season. And secondly, the American bullfrog is very greedy. In fact, they eat just about anything they can put into their mouths! As well as other frogs, they eat insects, fish and have even been known to eat birds and snakes! So, in other words, they eat the food sources of our own native species. Thirdly, they carry a disease that is dangerous to other frogs. And finally, they don't just damage our natural world, they cause financial damage too. Around £100,000 has been spent monitoring the American bullfrog in the wild.
So, as scientists, we can learn a lesson from this about the dangers of introducing any living species into a new environment. |
