Gas chromatography allows detection of as little as 10–13 g ABA,

TLS Online TPP Program

#Id: 5371

#Unit 10. Ecological Principles

Pitfall traps set into the ground catch wandering species such as beetles and spiders. These have rain covers to prevent the animals from drowning

 

TLS Online TPP Program

#Id: 5372

#Unit 10. Ecological Principles

Baited snap traps, Population density can thus be estimated as the number of animals caught per trap or per unit area where a given number of traps are set.

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#Id: 5373

#Unit 10. Ecological Principles

The mark-recapture technique is that after the tagged animals are released, they mix freely with unmarked individuals. The population is resampled and the numbers of marked and unmarked individuals are recorded. 

TLS Online TPP Program

#Id: 5374

#Unit 10. Ecological Principles

TLS Online TPP Program

#Id: 5375

#Unit 10. Ecological Principles

Mark-recapture technique can have drawbacks;

1. Some animals that have been marked may learn to avoid the traps. 
2. Recapture rates will then be low, resulting in an overestimate of population size.

TLS Online TPP Program

#Id: 5376

#Unit 10. Ecological Principles

Some animals can become trap-happy, particularly if the traps are baited with food. This would result in an underestimate of the population size.