WALLACE RESOURCE LIBRARY
Lecture 04 – Terrestrial Survey Techniques
in Guyana
This is an ‘example’ of a lecture that is given to A level students as part of their
academic lecture series whilst on their expedition.
It has been produced for the exclusive use of the lecturer conducting the series
and is solely intended for educational purposes.
Most of the material comes from Operation Wallacea sources and any other
material that has been used has been credited (as far as is possible) to the
appropriate author wherever possible.
This lecture is only to be used for EDUCATIONAL purposes.
WALLACE RESOURCE LIBRARY
Lecture 04 – Terrestrial Survey Techniques
in Guyana
Lecture overview
• Sampling methods
– Replication
– Mark Recapture methods
– Distance Sampling (point counts and line
transects)
– Patch occupancy
• Biodiversity monitoring methods
– Trapping, netting etc
• Research design
General census techniques
• True census involves counting all individuals in the
population
• Rarely possible in a natural setting but part of the
population can be studied using sampling
• Must ensure that samples are representative of the
population
• Possible to extrapolate from representative samples
to give a reliable estimate of the population as a
whole
Sampling strategies
• Random sampling
– Used when sampling the abundance or diversity of a given
species – all squares have equal chance of being sampled
– Usually used for homogenous habitats
Random number tables
used to decide which
squares within the grid are
sampled
Sampling strategies
• Cluster sampling
– Used when the study area is very large and thus
travel times to each randomly chosen sample
point are large
Idea is to take multiple
samples within each
randomly chosen
sample point
Sampling strategies
• Stratified sampling
– Individual habitats are rarely uniform, therefore random
sampling may not cover all areas of a habitat equally
– Stratified sampling avoids missing out important areas of
habitat by locating a proportional number of samples
within each habitat type
Sampling strategies
Line transects
– Transect routes may be used to create ‘pseudorandom’ sampling locations, by following a
straight line through a given strata.
Sampling strategies
• Replication
– Repeated counts at each sample site is a way of improving
the precision of the estimate of the total population
– Estimated mean values less affected by outliers when
sample size is large
– Repeated counts can also control for extraneous variables
such as weather, time of day etc.
Mark-recapture sampling
• Method
– Catch sample individuals from the population, mark them
and release them
– Allow marked individuals to mix with general population
– Catch a second sample
% of marked individuals
caught in second sample
representative of % of those
species present in the
population
Mark-recapture sampling
Marking
– numbered rings most popular
marking method for
recognising individuals from a
large population
– Combinations of coloured
dots can be used for smaller
populations
– Simple mark used if not
necessary to recognize
individuals
Mark-recapture sampling
• Assumptions
– Marks on individuals are permanent or last for the
duration of the study
– The population is closed so no new individuals join
the population once the first individuals have
been marked
Distance Sampling – Line Transects
• Assumes that all animals on the transect line are detected and
detectability of animals decreases when they are further away from the
line
• As animals are encountered their perpendicular distance from the
transect line is measured
• This model allows estimates of population density
Diagram by Sutherland, 2006
Line transect distance sampling
• Commonly used for
monitoring large mammals
• Also for other species that
range over large areas –
game birds
• Also species that can be
surveyed using transects amphibians
• Suitable for species
detected by vocalisation
• A simple and robust
technique
Distance sampling
• Assumptions
– All animals 0 metres from the line are detected
– Animal locations are not affected by observers at
the time distance is measured
– Density of animals is roughly constant in the area
around the transect lines (on average)
Distance sampling
• Point counts
– Observers stays at a set point
for a fixed period of time and
records all individuals seen or
heard during this time
– Often used to monitor birds
– Most commonly done by
people who know the bird
calls, usually done by
experienced ornithologists
Patch occupancy sampling
• Identifies the total proportion of the
survey area occupied by the target
species
• Does not directly measure
population density but produces
values that positively correlate with
density
• Used when studying rare or elusive
animals and/or when visibility in the
study area is poor (e.g. studying
anoa in tropical forest)
Biodiversity monitoring methods
• Trapping by conventional methods using traps:
– Small mammals, large mammals, reptiles, amphibians,
invertebrates etc…
• Mist netting – bats and birds
• Visual census – point counts, line transects
• Camera ‘trapping’
Population monitoring – small mammals
• Usually surveyed using
capture-mark-recapture
(CMR)
• Range of methods for
marking
• Baited traps placed along a
transect line
– Tomahawk trap
– Longworth trap
– Sherman trap
Discussion 1 - Designing research
?
Sutherland,W.J. 2006. Ecological census techniques.
Research question/research objectives
• Is there a clear question?
• Can it be answered within the time frame,
sample size, logistics etc?
• Is the question even possible to answer?
– How does logging effect Jaguars?
– What is the difference in relative abundance of
Jaguars in selectively logged and unlogged forests in
central Guyana?
– Changes in Jaguar abundance before and after
selective logging.
Research question/research objectives
• How do birds react to savannah fires?
• The effect of savannah fires on bird diversity
and abundance.
• How do savannah fires affect ground-nesting
birds?
• The effect of savannah fires on ant diversity
and abundance.
Methods
• Is the researcher ‘re-inventing the wheel’, or
using more widely recognised methods.
• In some cases, data may be comparable across
surveys and locations.
Sample size
• Whether you are looking at presence/absense,
or relative abundance, sample size MUST be
suitable.
• Sample sizes for Jaguars will be much harder
to obtain than sample sizes for ants.
Sample size & sample locations
• What is a data point?
– an item of factual information derived from
measurement or research
• So how do we know what the sample size
actually is?
• Are the sample locations random?
Spatial artefacts in comparison studies
• Comparisons of different treatments must be
conducted across the same habitat.
• Sample sites should be placed in a suitable
place (i.e. not too close to one-another), and a
good distance from different treatments.
– The distance depends on the home range of the
study species. Larger animals often have larger
home ranges.
– Animals that fly have large home ranges to.
Control sites
• Control sites are used to validate that changes
can be attributed to the treatment.
• Control vs. pseudo-control.
– Burned vs unburned = Unburned is Pseudocontrol, burned is treatment.
– Before burning = Treatment 1.
– After burning = Treatment 2.
– Need control – to ‘control’ for other factors.
Data analysis
• Has the researcher indicated what kind of
data-analysis they will use?
• Statistics?
• The best studies will have thought about the
analysis before the study design – reverse
planning.
Discussion/Activity 2 -Quiz time!
• Using the bird identification pictures classify
the birds into the most appropriate survey
method for them:
– Line transect
– Point count
– Mist netting
Which sampling method?
Blue and yellow macaw
Ara ararauna
IUCN category – LC
This species has an extremely large range, and hence does not
approach the thresholds for Vulnerable. Despite the fact that
the population trend appears to be decreasing, the decline is
not believed to be sufficiently rapid to approach the thresholds
for Vulnerable. The population size has not been quantified, but
it is not believed to approach the thresholds for Vulnerable.For
these reasons the species is evaluated as Least Concern.
Voice – Flight call a loud rasping screech, loudest and often
with a stuttering effect at the end “g’RAA’A’AH!”
Habitat/behaviour – Typically found in low lying forest,
including varzea, swamp forest and palm swamps.
Occasionally seen flying high over cleared areas and major
rivers. Usually found in small flocks, but occasionally in large
groups
Which sampling method?
Hoatzin Opisthocomus hoazin
IUCN category – LC
This species has an extremely large range, and hence
does not approach the thresholds for Vulnerable under
the range size criterion. The population trend appears to
be stable, and hence the species does not approach the
thresholds for Vulnerable. The population size has not
been quantified, but it is not believed to approach the
thresholds for Vulnerable. For these reasons the
species is evaluated as Least Concern.
Voice – Common calls include hoarse coughing and
grunting sounds, also loud hisses.
Habitat/behaviour – Always found over water, usually
encountered perched low over still or slow moving water
such as oxbow lakes or sluggish rivers.
Which sampling method?
•
Egret •
Great
Casmerodius
albus
•
•
IUCN category – LC
This species has an extremely large range, and hence does not
approach the thresholds for Vulnerable under the range size criterion
(Extent of Occurrence <20,000 km2 combined with a declining or
fluctuating range size, habitat extent/quality, or population size and a
small number of locations or severe fragmentation). The population
trend is not known, but the population is not believed to be
decreasing sufficiently rapidly to approach the thresholds under the
population trend criterion (>30% decline over ten years or three
generations). The population size is very large, and hence does not
approach the thresholds for Vulnerable under the population size
criterion (<10,000 mature individuals with a continuing decline
estimated to be >10% in ten years or three generations, or with a
specified population structure). For these reasons the species is
evaluated as Least Concern.
Voice – The great egret gives a variety of calls, including a low-pitched
‘kraak’ call that is given in flight, when disturbed, and as a threat call
Habitat/behaviour – inland and coastal waterways
Which sampling method?
•
•
Razor-billed curassow
Mitu tuberosum
•
•
IUCN category - LC
This species has an extremely large range, and
hence does not approach the thresholds for
Vulnerable under the range size criterion.
Despite the fact that the population trend
appears to be decreasing, the decline is not
believed to be sufficiently rapid to approach
the thresholds for Vulnerable under the
population trend criterion.The population size
has not been quantified, but it is not believed
to approach the thresholds for Vulnerable
under the population size criterion. For these
reasons the species is evaluated as Least
Concern.
Voice – At dawn deep booming notes, first 3
rising last 2 an even pitch – often followed by
sharp ‘BMM’
Habitat/behaviour – forest floor.
Which sampling method?
•
•
Golden-headed manakin
Pipra erythrocephala
•
•
IUCN category – LC
This species has an extremely large range, and
hence does not approach the thresholds for
Vulnerable under the range size criterion .The
population trend appears to be stable, and hence
the species does not approach the thresholds for
Vulnerable under the population trend criterion.
The population size has not been quantified, but it
is not believed to approach the thresholds for
Vulnerable under the population size criterion. For
these reasons the species is evaluated as Least
Concern.
Voice – Song bouts include variable high metallic
sounds and deep buzzes, but a characteristic sound
is a series of quiet, descending notes followed by a
loud, descending thin whistle that ends with a
loud buzz “tsew tsew-tchew SEEEEEEEE’ BZZANG”
Habitat/behaviour –
Which sampling method?
Black-collared hawk
Busarellus nigricollis
IUCN category – LC
This species has an extremely large range,
and hence does not approach the
thresholds for Vulnerable under the range
size criterion. Despite the fact that the
population trend appears to be decreasing,
the decline is not believed to be sufficiently
rapid to approach the thresholds for
Vulnerable under the population trend
criterion. The population size may be
moderately small to large, but it is not
believed to approach the thresholds for
Vulnerable under the population size
criterion. For these reasons the species is
evaluated as Least Concern.
Voice –
Habitat/behaviour –
Which sampling method?
Harpy Eagle
Harpia harpyja
•
•
•
•
•
•
IUCN category – NT
This species is classified as Near Threatened
because it is suspected to be declining
moderately rapidly owing to hunting and
habitat loss.
Voice – Call a long, descending, mewing
whistle, lower pitched than other large raptors
“HEEleww”
Habitat/behaviour – Rare in humid forest of
eastern lowlands. Rarely soars. Hunts within
vegetation, waits from perch in canopy or
subcanopy, then weaves through foliage to
capture large mammal prey or to move to new
perch. Large and bulky eagle.
Which sampling method?
Grey Cheeked Parakeet
Brotogeris pyrrhoptera
IUCN category – EN A2cd + 4cd
This species qualifies as Endangered
because it has been affected by very rapid
rates of population decline caused by
trapping for the cagebird trade, plus habitat
loss. Future population declines are
projected to be slower, but still a serious
cause for concern.
Voice – Flight calls include a low rolling
“jurt” as well as a series of scratchy calls;
also conversational vocalizations including
calls given between members of a pair.
Habitat/behaviour – Usually seen in pairs
and small flocks. Feeds on flowers and
seeds of large trees. Orange under wing
coverts are prominent in flight.
2. Ecological census techniques
Part 2: Bird sampling challenge
Before conducting a bird survey you need to
clarify why you are doing the study,
e.g.
• To investigate the total number of bird species in a
given area and the relative abundance of each
• To monitor changes in bird abundance and diversity
over time
• To use birds as indicators of ecosystem changes
FOR THIS EXERCISE – you are going to choose
the best method to find out the abundancy and
distribution of a specific species.
Which SURVEY method would you
use?
Part 2: Bird sampling challenge
• Biodiversity management needs an accurate, precise and unbiased
assessment of the numbers of birds of a particular species.
• To get these figures the correct and most suitable sampling
method/technique needs to be chosen.
• In this challenge you are going to choose the most suitable sampling
method for 6 different birds that you find locally.
• You are given the choice of using ONE of three possible methods for
each bird (you should see some of these techniques in action during
your week here).
Part 2: Bird sampling challenge
Instructions:
1.In a few moments get into groups of 3 people.
2.Read the THREE sheets on the different techniques you might use to find out
how many birds of each species there are – take ONE card each.
3.Then explain your technique to the other members of your group.
4.Now take TWO bird info. cards each – read them very carefully and decide on
which technique would suit that bird the best – there may not be a correct
answer and it could be open to discussion!
5.Fill in the answer sheet with the rest of your group.
6.There is also a summary table comparing the techniques which you will find
useful.
At the end – discuss your choices
Click big
picture to
run the clip