4.2-Sampling animals Flashcards
Why is it difficult to obtain quantitative data?
Many animals are not easy to spot and are more difficult to count. Larger animals can detect the presence of humans and before we see them, and will hide away. Small animals will also hide and often move too quickly to count accurately. Therefore obtaining quantitative data on animals is difficult.
How can you sample animals by observation?
You can note the presence of many lager animals by careful observation- looking for signs that they have left behind. For example, many animals leave footprints or easily identified droppings. Ecologists often rely on these signs to estimate population sizes
Give examples of animals who can be identified through observation:
Owls deposit pellets of undigested food
Rabbits have obvious burrows
-Deer damage the bark of trees in a particular way.
What has recent advancement allowed scientists to do?
Recent advances allow scientists to use DNA sequencing to distinguish droppings from different individuals. This provides a more accurate way to calculate the population.
How do you catch invertebrates?
The technique of sweep netting involves walking through the habitat with a stout net. You sweep the net through the vegetation in wide arcs. Any small animals, such as insects will be caught in the net, then you can empty the contents on to a white sheet to identify them. This type of sampling is suitable for low vegetation that is not too woody. You can use as similar techniques to take samples in water.
Why do you need to be careful when catching invertebrates?
As many of the animals may crawl or fly away as soon as you release them form the net. You can use a pooter to collect animals before they fly away.
What other technique is used to can invertebrates for, trees?
- Collecting invertebrates form trees using a sweep net is unlikely to work well- here it is better to spread a white sheet out under a branch , and knock the branch with a stout stick. The vibrations dislodge any small animals, which then drop on to the sheet. You need to be quick to identify and count the animals before they crawl or fly away.
What is a pitfall trap?
A pitfall trap is a trap set in the soil to catch small animals. It consists of a small container buried in the soil so that its rim is just below the surface. Any animals moving through the plants or lead litter on the soil surface will fall into the container. The trap should contain a little water or scrunched paper to stop the animal form crawling out.
Why does the trap need to be covered during rainy weather?
In rainy weather the trap should be sheltered from the rains that it does not fill up.
What is a tullgren funnel?
It’s a device for collecting small animals from leaf litter. You place the leaf litter in a funnel. A light above the litter drives the animals downwards as the litter dries put and warms up. They fall through the mesh screen to be collected in a jar underneath the funnel
What can a light trap be used for?
A light trap can be used to collect flying insects at night. It consists of an ultraviolet light that attracts the insects. Under the light is a collecting vessel containing alcohol. Moths and other insects attracted to the light eventually fall into the alcohol.
How can small animals be trapped?
Small animals can be trapped and population estimated calculated. The technique that you will use depends on the habitat and the type of animals you are hoping to catch.
What do you need when trapping animals?
You may need a license to trap some animals and care should also be taken not to harm the animals in any way
What type of trap can be used to catch small animals?
Small animal s can be trapped using a Longworth trap. This is a humane trap that does not harm the animal. These traps must be monitored regularly to release any trapped animals. Trapping with a Longworth trap enables the population size to be calculated using the mark and recapture technique
What is the method of trapping small animals using Longworth trap?
- First you need it capture a sample of animals.
- Mark each individual in some way that causes it no harm. The number captured will be C1.
- Release the marked animals and leave the traps for another period of time.
- The number captured on this second occasion will be C2 . The number of already marked animals captured on the second occasion is C3.
- You can calculate the total population using the formula:
Total population= (C1*C2)/C3
