Crash Course: Field Methods for Sampling Natural Habitats

When you’re a researcher working out in the field, the act of collecting data can be split into two places: on a sample site, and somewhere independent of a sample site.

Some examples of working on a sample site include dung beetle traps, bird point counts, pitfall trapping, collecting plant specimens and habitat structure data, and conducting opportunistic searches for reptiles and amphibians.

Some examples of working somewhere independent of a sample site include bird mist netting and bat mist netting in an area adjacent to the transect, sample routes for small mammal and herptile trapping, and large animal monitering.


Habitat Survey

If your team wants to survey the habitat, divide into 4 groups and measure off a 20x20m plot, taking a 10x10m plot each.

Record the position, slope, level of disturbance, and any fallen trees and stumps.

Tag the trees with a circumference over 30cm, measure the circumference of the trees over 15cm, and estimate the height of the four tallest trees.

Draw a “plan profile” and mark the trees >30cm in circumference.

Have the vegetation over group estimate the canopy openness, estimate the ground covered by bare rock, soil, leaf litter, and vegetation, and count the woody saplings in 4 quadrants of 2x2m randomly positioned in the plot.

Invertebrate Survey

Invertebrates are the division of organisms without a backbone, and the term most commonly refers to insects when out in the field.

Use dung baited traps at each main and subsidiary site, and empty every 4 days (or at a constant rate).

Herpetology Survey

Concerned with reptiles and amphibians, herpetologists walk prescribed sample routes through a variety of habitats at a pace of 500 m/h and recording individual specimens sighted.

There are two further methods for going about a herpetology survey: opportunistic surveys and pitfall trapping.

Opportunistic surveys consist of river walks and night walks: looking under rocks, breaking up dead logs, and raking through leaf litter. These surveys are usually the main source of data for nocturnal species, and following streams and rivers makes amphibian data more complete as well.

Pitfall traps are rather simple to set up, the key is just consistency when checking them for specimens.

Bird Survey

Conduct 10 minute point counts, informal opportunistic sightings, and/or set up mist-nets.

During the point count, note the species, the number in the group, the method of observation (spotted vs. auditory), distance, habitat data, cloud cover, rain, and wind. Over 90% of data is heard, not seen.

For mist-netting, ID the species, age, sex, molt condition, and morphometric measurements.

Small Mammal Survey

Set up wire-cage traps at dusk, and check in the morning. Mark the animals uniquely with ear clippings. They should be weighed, sexed, aged, and morphometric data, trap number, the date of capture/recapture, fate, and any comments noted.

Bat Survey

Use mist nets to observe bats (see bird survey for technique).

Monkey Survey

I never actually conducted this type of survey myself, but (in my notes it says to) note their appearance and behavior in 10 minute intervals.

I hope this gives an insight into what real researchers do out in the field! These figures are normally inputted into a database so that sophisticated queries can be made for papers and graphs. It is necessary to keep in mind that acquiring more data does not mean that the population of the species surveyed are increasing, but that the effectiveness of the method used is being proved.

This post was based from my notes that I prepared before my trip to Honduras with the conservation group Operation Wallacea, or OpWall for short. I definitely recommend the program for anyone!


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