Unit 4: Population Estimation
Methods of
population estimation:
1.
Sex
ratio computation;
2.
Fecal
analysis of ungulates and carnivores:
3.
Hair
identification,
4.
Pug
marks and census method.
5.
Application
of biostatistics in Biodiversity estimation: Analysis of Shannon and Simpson‘s
Diversity Indices.
: Sex ratio computation
Sex Ratio?
Populations change in size based on their birth rates,
death rates, and rates of immigration. When individuals are born, populations
increase. When individuals die, populations decrease. Immigration results in
individuals moving into a population, while emigration results in individuals
removing themselves from a population.
Sex Ratio Types
Sex ratios may be taken at intervals to capture multiple
developmental stages within a population. The sex ratios calculated at these
different stages are called:
- Primary sex ratios
- Secondary sex ratios
- Tertiary sex ratios
- Quaternary sex ratios
Sex ratios may also be utilized to represent only a
specific subset of the population that is reproductively viable, which is
referred to as an operational sex ratio.
Primary Sex Ratios
Primary sex ratios are the sex ratios of individuals at
conception.
In many populations, the number of males and females at
conception is generally equal. This is due to the fact that many sexual
organisms have a 50% chance of producing either a male or female offspring.
Secondary Sex Ratios
Secondary sex ratios are the sex ratios of individuals at
birth or hatching.
In many organisms, the primary and secondary sex ratios
are equal. However, this is not always the case.
Many organisms
have temperature dependent sex-determination. This means that the sex of a
hatchling depends on the temperature at which it was incubated. This is a
common phenomenon in turtles and crocodilians. In fact, as temperatures rise
due to global warming, researchers are noticing large changes in sex ratios in
these temperature sensitive organisms. Unfortunately, this is resulting in
population declines in many of these species.
Tertiary Sex Ratios
Tertiary sex ratios are those that are calculated for
individuals in their later years of development.
For instance, a tertiary sex ratio may be calculated for
the number of one-year-olds in a population of starlings.
Tertiary sex ratios are often defined as juvenile sex
ratios, though some researchers may use the term "tertiary sex
ratios" to define sex ratios of older adults within a population as well.
Quaternary Sex Ratios
Quaternary sex ratios are like tertiary sex ratios. These
ratios are used to represent the sex ratios that occur at a later point in
life, often within adults. Many times quaternary sex ratios are used to
represent the sex ratios of adults that are no longer reproductively viable.
Operational Sex Ratios
Operational sex ratios are used to define the number of
reproductively available males and females. These ratios can cross age
boundaries and may give a better idea of a population's reproductive potential.
Fecal analysis of ungulates and carnivores:
Fecal analysis of Ungulates and carnivores
Based on the mode of
nutrition, animals can be classified into two categories:
- Carnivores
or Carnivorous animals
- Herbivores
or Herbivorous animals
Carnivorous animals
derive their nutrient requirements from other animals. Conversely, herbivores
are animals that depend on plants for their nutrition. Read on to discover the
characteristics of herbivorous and carnivorous animals, and explore how the two
differ from each other.
Herbivores
Herbivores or
herbivorous animals are those animals that feed on plants, leaves, fruits and
other plant-based food for nutrition. They are known as primary consumers and
occupy level 2 or higher in the food chain. Cow, goat, giraffe, sheep, and
zebra are common examples of herbivores. Interestingly, there are herbivores
that specialize in feeding on certain parts of the plant – for example, animals
that feed on fruits are known as frugivores while folivores are herbivores
that feed on leaves.
Carnivores
Carnivores or
carnivorous animals rely on other animals for their food. These animals have
several adaptations that help to hunt prey. For instance, most big cats such as
lions and tigers have robust bodies, accompanied by powerful jaws capable of
crushing bones and tearing flesh.
They can also
be classified on the basis of their feeding habits and the kind of animals they
consume. Let us have a look at some of these characteristics and
classifications of carnivorous animals.
Hair
Indication
The
morphological identification of animal (non-human) hairs (MIAH) is based on
fundamental aspects of microscopy, biology, and zoology. The purpose of MIAH is
to categorize the animal source of an unknown hair sample to a particular taxon
based on well-defined, genetically-based features that are characteristic to
that group.
The
breadth of knowledge required to identify mammalian hairs from all potential
taxa is extensive but may be relatively simple in certain contexts,
for
example identification of mammal hairs as encountered in biological fieldwork,
in museum curation, or in the textile industry. In contrast, the forensic
examination of hair involves knowing not
only the range of expression of mammalian hairs within taxa, but also being
aware of other structures that may
resemble hairs, such as man-made wig fibers and faux fur fibers, insect seta, and plant tendrils. The forensic context
is thus wider and more complicated than a controlled +
mammalian
orientation.
Evidence
of animal hair, is ofen discovered at crime scenes. Pet or other animal hairs
can be found on the clothes of the victim or on other items of physical
evidence collected at the crime scene. Teidentification and analysis of human
and animal hairs from a crimescene can indicate physical contact between the
victim and a suspect, orprovide other investigative leads. transferring of pet
hairs to the victim,to a suspect, or to the crime scene may happen when the
perpetrator is a pet owner (or when the victim owns a pet), or when the crime
wascommitted in a place where animals are kept, such as barns, stables, basements,
or transport vehicles Forensic hair analysis is a scientific method of analyzing
traceevidence from a crime scene. It involves examining the hair shaf,including
its medulla (inner core), cortex (intermediate layer) and cuticle (outer
covering) through powerful microscopes. Hair evidencemust be collected properly
and analyzed according to protocols. The first step of the examination involves
verifying whether the hairin question is that of a human or an animal. If the
hair is from an animal, the examiner can potentially identify the species from
which it originated Hair can be moved from
location to location by physical contact, the presence of a specific person’s
hair can link a suspect or a victim to a crime scene. transfer of hair is very
common with animal hairs, which are commonly found on pet owners and in the
environment of pet owners and can be used to link suspects to crime scenes. In
hairs from animals, the diameter of the medulla is larger than half the
diameterof the entire shaf. Animals produce different types of
hair. Tey ofen have coarse guard hair external to sofer fur hairs. Tey also
producewhiskers and longer hairs in such places as the tail and mane [3]
Dorsal guard hair was characterized by using light microscopyby studying features including color, hair thickness, cuticularcharacteristics, medulla pattern, medullary index etc. Medullarcharacteristics, we found a high medullary index and a vacuolatedmedulla. Medulla continuous, usually less than half overall shafdiameter, Unbanded: pigment coarse, granular and fairly evendistribution. Scales imbricate
Manipuri deer
Deer
hair is about 300-1000 micron meter wide from the root tonear the tip. It has a
lattice type medulla that nearly fills the hair. thecuticle patterns is
imbricating flattened to broadly acuminate and hasa scale count about 3-7/100
micron depending upon the scale pattern.Te characteristics diamond pattern is
3-4 scales/100 microns and theflattened to vermiform scales are around 7 [10].
Deer has a refractive index along its length of about 1.56 and perpendicular to
its length ofabout 1.55. It has a birefringence of about 0.01 and a positive
sign ofelongation. Diameter: very coarse over all diameters
(approximately300m). Medulla; composed of spherical cells that occupy entire
hair.Diameter constant throughout most of hair. Wine glass shape root.Regular,
wave or crimp. Scale margins are round and isodiametric andresemble fish scales.
Diameter:
fine, little variation. Medulla: Uniserial ladder (fur hairs),continuous,
occasionally vacuolated in coarser hairs. Scales: Tey arenot so prominent, may
be banded. Root; elongated, no distinct shape,fibrils frayed at base of root.
Black or melanistic colored tigers havebeen reported but further research is
required before assessing whetherthese sighting were of true melanistic tigers
or darker version of theorange tiger(with few large broad dark stripes) [13]. tiger
with whitebackground coloration are not considered albinos. An albino wouldbe
pure white in color (no striping) and would have pink or red eyes,White tigers
are leucocystic meaning that they have a recessive genethat causes them to lack
dark colors.
As
in all other mammals, some hair follicles are in anagen, somein catagen, and
some in telogen. Shedding, length of hair and presenceor absence of an
undercoat depends upon the timing of these cyclesand the ratio of hair follicle
in the various stages. Differences betweensummer coat and winter
coat occurs because during the summer agreater numbers of follicles remains
inactive [17]. Some breeds for e.g. poodles, tend to be low shedding because
almost all of their follicles in anagen (growth cycle) almost all the time;
their hairs continues to growand has to be clipped. Some breeds of dog for e.g.
Chinese crested havemost of their follicles in telogen and thus may be almost
completelyhairless. Both breed are ofen listed as recommends for allergysufferers.
A dog’s coat may be a double made up of a sof undercoat.Diameter; fine to coarse
(usually coarser than cat hair): diameter may vary to give short hairs a
barrel-like appearance. Medulla: Continuous, vacuolated to amorphous,
occasionally very broad. Scales: generallynot prominent. Unbanded; pigment
occasionally very coarse andextending into roots .
Whenever an animal moves through the jungle
over a suitable ground, leaves mark or impressions it called as pugmarks (paw
marks). In simple terms, pugmarks refer to the footprints of almost all the
animals.
Every individual animal species have distinct
pugmarks and numerous features contained in it can be used to support the
identification of an animal. Many people have learned to read wildlife
pugmarks with a remarkable skill for hunting purposes.
Pugmarks are produced
under the following circumstance:
The impressions of the
pug may be caused in mud, dust, sand, and snow or similar surfaces. These
impressions will be depressed or three-dimensional type and these are known as
sunken pug mark impressions. These type of pug marks are most commonly found.
If the pug mark is
produced by deposition of material like dust, dirt, blood, colored powdery
substance, etc., on hard and smooth surfaces, giving rise to a two-dimensional
print, which is called surface pug mark.
Pugmarks may also be
produced by lifting dust or liquid material in which case a negative print will
be left on the surface.
The different species
of animals, especially the large carnivores that are traditionally tracked with
the help of pugmarks are divided into two broad categories:
The members of the
‘Dog family’ or the ‘Canidae’ that typically move and hunt in packs often
walking long distances in a file. In the members of this family, the claw marks
are usually noticeable in front of the toe pads. As compared to the heel pad
the toes are larger which helps them to run down the prey and the gap between
the top of the heel pad and the two middle toes is evidently more than what is
found in cats (hyenas is an exception). The front points of the two middle toes
occur side by side (aligned).[1]
The members of the
‘Cat family’ or the ‘Felids’ that lead a solitary existence, depending on
stealth for hunting down prey. They are acceptable climbers and some like the
leopards take their hunt to a tree for abstaining from poaching by different
carnivores. The claws or nails are hardly ever visible, the soft heel pad is
comparatively larger (to encourage stealth) and the middle toes are put nearer
to the pad. The middle toes of the felids are at different levels, especially
for the hind paws.[1]
Mostly the large carnivores leave the soft
padded four-toed pugmarks in the jungle.
Pugmarks are the marks
which are left by different animal’s species while they are walking, running,
or moving from one place to another place. Pugmarks refer to the footprints of
most animals’ species. “PUG” also means foot in Hindi. Pugmarks of some animals
are denoted by some different terms. Pugmarks denote “paw print” of most feline
animals for e.g. like dog, cat, etc. Herbivore footprints are called as
hoofmark. Some of the herbivore animals are like cow, goat, buffalo etc. Mostly
the footprints of tigers are termed as pugmarks. Every animal species has
different type of pugmark and this factor can be used for their identification
purpose. Through pugmark it is not only possible to identify the animals, but
also identify its sex whether it is male or female, age, and its size is also
possible to identify accurately.
The
pugmarks of different animal are different they are not same. Each of the
pugmark has its own unique individual characteristic and class characteristic
which help in differentiating from other groups of animals .Pugmark can also be
examined in forensic science as it can provide reliable data of presence of
different species in the area of study, population of the species, sex ratio,
etc
Pugmark plays a major role in identifying a given
specific animal in terms of sex, age or size as well as total accuracy of the
given individual species. Pugmark denotes "paw print" of most feline
animals. Herbivore foot prints are called as hoofmark (Deer, Antelope) or
simply foot print (Elephant). Every specific individual has its own distinct
pugmark and as such, this is used for identification purposes.
The best example is the tiger census programme
which is completely based on pugmark technology. The method is simple and easy
to count the animal in a very special manner, sometimes bias may happens.
Camera trapping, Scat analysis or GIS application are the new advance formula
for getting total occupancy in a given forest environment. Similarly, pug-mark
is also helpful in tracking those animals that are stray away from the boundary
areas, conflicting with the human environment or create problems of their own
because of injury.
India
has both an All India Wild Animal Census, and a formal tiger census. On top of
this, most National Parks carry out their own count each year. The All India
Wild Animal Census takes place every four years and this is going on this year
(2005) in May. In Tiger Reserves the formal tiger census is carried out every
two years in a massive way.
Study of Wildlife Population (Census) /
Pugmark-based population monitoring:
The population of the remaining rare animals
in the forests needs to be protected. An animal footprint is the unique
identity of the animal world. There are several techniques available to study
animal behaviour. This method is a safe and brilliant way to spot the presence
of an animal in a place. The main objective of the wildlife census is to find
out the density of the population of the species and to procure basic data for
its management.
(6) The pugmark is also helpful in estimating
time when an animal moved and direction in which the animal traveled. The
major problem with pugmark impressions based on the identification of species
includes is an undetectable footprint on hard surfaces and sometimes these
footprint sites are often contaminated by the presence of other animals.
Undetectable pugmarks and erosions by the other animals in pugmarks analysis
are the major limitations in the field of wildlife forensic. If pugmarks
analysed skilfully and lawfully, they can provide reliable data.
Equipment:
The
principal requirement of the census is the detection and record of tiger
pugmarks. The equipment necessary is a tiger tracer, sketch pen, tracing paper,
field note book and ball pen, prescribed census format, topographic counting
unit/beat map, a large scale range map showing counting units, a two metre
tape, plastic mug, plaster of paris and a water bottle. field compass, etc.
Shannon
Diversity Index: Definition & Example
The Shannon Diversity
Index (sometimes called the Shannon-Wiener Index) is a way to measure the
diversity of species in a community.
Denoted as H,
this index is calculated as:
H = -Σpi * ln(pi)
where:
·
Σ: A Greek symbol that means “sum”
·
ln: Natural log
·
pi: The proportion of the
entire community made up of species i
The higher the value of H,
the higher the diversity of species in a particular community. The lower the
value of H, the lower the diversity. A value of H = 0 indicates a
community that only has one species.
The Shannon Equitability
Index is a way to measure the evenness of species in a community. The term
“evenness” simply refers to how similar the abundances of different species are
in the community.
Denoted as EH,
this index is calculated as:
EH = H / ln(S)
where:
·
H: The Shannon Diversity Index
·
S: The total number of unique species
This value ranges from 0
to 1 where 1 indicates complete evenness.
The following
step-by-step example shows how to calculate the Shannon Diversity Index and the
Shannon Equitability Index for a given community.
Step 1: Collect the Data
Suppose a biologist
wants to measure the diversity of species in a local forest. She collects the
following data:
Next, the biologist can
calculate the proportion of the community made up of each species.
For example, there are a
total of 105 individuals and 40 are classified as species A. Thus, species A
makes up 40 /105 = 0.38 of the total community.
She can perform a
similar calculation for each species:
Step 3: Calculate the Natural Log of the Proportions
Next, she can calculate
the natural log of each proportion:
Step 4: Multiply the Proportions by the Natural Log of the
Proportions
Next, she can multiply
the proportions by the natural log of the proportions:
Step 5: Calculate the Shannon Diversity Index
Lastly, she can use the
following formula to calculate the Shannon Diversity Index:
H = -Σpi * ln(pi)
For this example, she
can take the sum of the last column and multiply by negative one:
The Shannon Diversity Index
for this community is 1.49.
She can also use the
following formula to calculate the Shannon Equitability Index:
EH = H / ln(S)
For this example, there
are S = 5 total species, so see can calculate this index to be:
EH = 1.49 / ln(5) = 0.92.
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