Question: wont taking all the animales out decrease their population?

Zara Gladman answered on 20 Jun 2011:

Hi candle95, nice chatting earlier! 🙂

You’ve raised an important question! For many scientific studies, it is important to make sure that capturing animals won’t have a bad effect on the population. Especially if the animal is endangered and the population isn’t very big to begin with! I think I would get into a lot of trouble if I decided to capture and study lots of Giant Pandas, for example – since there are only about 1000 left!

However, for other studies – e.g. of pest species – decreasing the population is not a concern, because there are loads of animals (and the animals are causing trouble…. like the signal crayfish: http://www.tinyurl.com/imascientist for info on what they do!) – we actually WANT to decrease the population! Because it is having a bad impact on other animals and plants.

I’ve been studying a population of signal crayfish at a Loch in Scotland. A couple of summers ago, fisherman removed over a MILLION signal crayfish from the loch! I visited the loch afterwards and did a study to see how many crayfish were left… I discovered that even though the fishermen had removed LOTS of animals, there were still LOTS left! The population was only slightly smaller… it must be absolutely enormous!

I think it’s very important that scientists do population studies and keep a record of how many animals are in populations over a long time – that way we can look for trends and try and figure out what is causing increases or decreases, e.g. global warming, overfishing, habitat loss, non-native species.

Hope that answers your question!