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Line transect survey: A study of changing primate densities within a
co-managed reserve and their implications in inter-specific
interactions, Pacaya Samiria, Peru
Adam Brown
Pratical Research Project 2010 (DI512)
Durrel Institute of Conservation and Ecology
University of Kent
Ackowledgements
Firstly I would like to thank Peter Bennett for his much needed insights into the direction of my
project after its unforeseen change in the field. If not for his insistence to rest, in spite of my own
disregard for my welfare, my ankle injury would definitely have ended in much greater
complications. Thanks also to Natalie Swan who following my removal from my project kept me
entertained of a morning. Apologies and thanks have to be said to all the students who’s projects
were performed on the “brown boat” for allowing me to come along on your daily boat rides, sorry
if I was a bother or source of distraction.
Thanks must go to Miguel and Genes my guides or rather instructors for the completion of my
data collection as well as putting up with my inability to walk quietly through the Amazonian mud.
I must thank David Birch for being an extremely tolerable and continual source of amusement in
our cramped lodgings as well as the rest of the students on the trip for making it a fantastic and
memorable trip.
Thanks to my proof reader Christopher Lamming for not laughing at my terrible grammar and
mistakes.
Finally my thanks go to Rebecca Lindsay, my girlfriend, for bringing me endless cups of tea and
coffee and generally being there for me while I waded through my dissertation.
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Abstract
Following a tragic incident the management of Pacaya Samiria nature reserve under went
drastic change transforming from a policy of exclusion of locals to one of Comanagement. By using a line transect survey the current density of primate populations is
calculated. With 12 species of primate occurring within the reserve the chance of interspecific interactions occurring is extremely high. The densities calculated from the line
transect surveys can be used in order to assess the strength of association between
species. By comparing this years findings with those recorded in previous years we are
able to assess the success of the co-management of the reserve. The population densities
display a recovery following a poor year in 2008. It is apparent that a culmination of
reasons account for fluctuations within population density, but, a more general reduction
such is this is more likely to be from a random climatic event such as La Nina. Our
findings support earlier work showing that Woolly and Howler monkeys display a strong
negative correlation while Squirrel and Capuchin monkeys show a strong positive
correlation. The use of these relationships as a conservation tool is assessed, however,
without further work into the impacts of a reduction in one of these species the
effectiveness is still unknown.
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Contents
1. INTRODUCTION……………………………………………………………………………………….6
1.1 Primates under threat………………………………………………………………………6
1.2 Pacaya Samiria……………………………………………………………………………..6
1.2.1 A history of co-management in Pacaya Samiria Nature Reserve…………6
1.2.2 Source Sink models as a control for subsistence…………………………..7
1.2.3 The study site……………………………………………………………………8
1.3 Interspecific Interactions……………………………………………………………………9
1.3.1 Competition……………………………………………………………………..10
1.3.2 Polyspecific association……………………………………………………….11
1.4 Examples of interspecific interactions found in Amazonia…………………………...11
1.4.1 Howler vs. Woolly………………………………………………………………11
1.4.2 Association of Brown Capuchin and Squirrel monkeys……………………12
1.4.3 Further possible interactions………………………………………………….13
1.5 Line transect Surveys……………………………………………………………………..13
1.6 My research objectives……………………………………………………………………13
2. Methods ……………………………………………………………………………………………….14
2.1 Collection of data…………………………………………………………………………..14
2.2 Analysis of data…………………………………………………………………………….14
3. Results………………………………………………………………………………………………….15
3.1 Results section one- My original analysis……………………………………………….15
3.1.1 Ind/km for primate species…………………………………………………….15
3.1.2 Association……………………………………………………………………...17
3.2 Results section two- DISTANCE…………………………………………………………17
3.2.1 Overall and individual species densities……………………………………18
3.2.2 Correlation of associations…………………………………………………...22
4
4. Discussion…………………………………………………………………………………………….24
4.1 Immediate impression……………………………………………………………………24
4.2 Population density………………………………………………………………………..24
4.2.1 Possible reasons for termporary density reduction………………………25
4.3 Interspecific interactions………………………………………………………………...26
4.3.1 Howler vs Woolly…………………………….………………………………26
4.3.2 Capuchin and Squirrel Monkeys…………………………………………...27
4.3.3 Arguments against the manipulation of habitat……………………….....27
4.4 Problems encountered within my methodology…………………………………..…28
4.4.1 Data collection………………………………………………………………28
4.4.2 Data analysis………………………………………………………………..29
4.5. Suggestions for the future……………………………………………………………30
5. Final Conclusion…………………………………………………………………………………..30
6. References………………………………………………………………………………………...31
7. Appendix ……………………………………………………………………………………….….33
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1. Introduction
1.1. Primates under threat
Habitats within rainforests are being destroyed and increasingly fragmented as a result of human
activity (Gonzalez-Solis et al 2001). For larger bodied mammals with large range requirements,
such as primates, this can lead to localized disappearances of species (Redford and Robinson
1991). This is one of the three primary threats identified to non-human primate populations
alongside hunting for subsistence and live capture for sale within the pet trade or for medical
research (Mittermeier 1986). The recent increases in legislation has caused a down turn in some
markets such as that of Peru who exported over 300,000 primates between 1961-1971 prior to its
complete ban. The numbers effected by this extraction are much higher as for every one primate
exported out of Peru during this time up to 4 or 5 primates are said to have died either in traps or
within captivity. Legislation in one country is only as strong as it’s neighbours with markets
moving from Peru to Guyana and Bolivia (Smith 1977). This use though is minor in comparison to
subsistence use previously seen in Loreto, Peru where a population of less than 250,000 had
reportedly killed over 370,000 individuals in a single year. A majority of the meat found at markets
within Iquitos was supposedly made primarily from Woolly monkeys (Lagothrix poeppigii)(Smith
1977). 90% of all primate species are confined within tropical habitats and perform vital actions
such as seed dispersal (Mittermeier 1988). The creation of protected areas combined with
conservation action can be pivotal in preserving viable populations as well as maintaining stable
ecosystems. This study explores the history of management within Pacaya Samiria as a case
study for changing primate densities and their importance within conservation.
1.2 Pacaya Samiria
1.2.1 History of Pacaya Samiria and the importance of co-management
The approach to wildlife protected areas has changed significantly since their creation. Previously
people were completely removed from these areas and most or all use of products from the area
was prohibited. This was the case in the Pacaya Samiria nature reserve who expelled many of its
residents in the early days of it’s creation in the 1940’s. Restrictions and guards were fully
introduced within the management plan of 1986-1992. However this approach to management
fostered negative attitudes towards the park, locals lived in fear of even tighter restrictions being
imposed at any time influencing them to poach as much as possible to guard against an uncertain
future. This attitude, combined with limited funding for sufficient patrols, led to an increase in
poaching and hunting pressure within the reserve causing many species rapidly deplete in
number. During the 1990’s an increase in funding and pressure from western organizations saw
an increase in patrols, however this only led to an increase in conflict between park rangers and
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the locals. The tensions between locals and guards escalated when fishing nets were confiscated
due to over exploitation which resulted in the murder of two biologists and a guard. It took this act
to encourage a drive for change, beginning with a replacement at the head of management.
An over haul of the out dated management strategy saw locals, who were once poachers, given
the responsibility of management of areas in exchange for a limited use for subsistence. This
subsistence is performed in accordance with a management plan drawn up with the assistance of
biologists and approved by INRENA and the park administration. This has led to a change in the
local’s perception of the park allowing them to see the long term benefits it could provide.
Monitoring over the transition form one management type to another, has seen an increase in
many important species within the reserve such as the Howler (Alouatta Secniculus) and Woolly
monkey. It is becoming increasingly apparent that this interdisciplinary approach, bringing social
economics into conservation is needed in order to move forwards in the conservation and
sustainability of Amazonian habitats (Bodmer et al In press). Country wide legislation states that
“Subsistence hunting is permitted in Peru only in rural and native communities according to
Article 230 of the Reglamento de la Ley Forestal y de Fauna Silvestre (Forestry and Wildlife Law
2001) and the consumption or the sale of bush meat is restricted to settlements of fewer than
3,000 inhabitants” (Bodmer et al 2007). The consistent regulation of the use is still needed
despite the change in locals with punishments being enforced to those that abuse their
agreement within the management of the reserve.
1.2.2 Source Sink models as a control for Subsistence
In an effort to maintain subsistence hunting, a source sink model is utilised within Pacaya
Samiria. The Source Sink theory is based on having an area of high quality habitat in which the
population continually growing and surplus individuals then disperse into an area of low quality,
known as the Sink (Pulliam 1988). The reasons as to why animals choose to disperse comes
under much contention (Dias 1996).Within our habitat the quality is determined by hunting
pressure, i.e. we have a lightly, moderately and heavily hunted zone (Map 1.). So for the
purposes of this, individuals should disperse from the highly populated lightly hunted zone to
supplement the reducing populations within the other zones.
This also provides a second benefit by consistently having an area in which to disperse, the area
as a whole is prevented from becoming saturated or reaching its carrying capacity. Keeping
populations at this level increases reproduction rates as they never have to compensate for
density with regards to resource use. Over all this increases the number of individuals that can be
harvested each year while simultaneously maintaining a buffer that will avoid complete extirpation
of any species from the area.
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Map 1. A display of the three hunted zones within Pacaya Samiria (Bodmer 2007)
1.2.3 The Study Site
Pacaya Samiria is one of Peru’s largest protected areas spanning across 2000km2 covering 2%
of the entire countries land (Bodmer 2009). It is defined by two rivers the Maranon to the north
and the Ucayali to the south. Much of the reserve is flooded forest known as Varzea and has two
main river basins, the Pacaya and the Samiria. It exists within a cycle of high and low water
caused by differing rain fall in the Andes throughout the year. This mass of water carries a high
amount of sediment causing the structure of the rivers to be ever changing, this is also the reason
as to why so many oxbow lakes occur within the river basins. The Samiria river itself is actually
sourced and runs into the same river, the Maranon however unlike the cloudy sediment water
found there the waters of the Samiria have a richer tea like quality, this is caused by the flooding
of the forests where the water picks up tanin from the leaves (Bodmer 2007 and Bodmer 2009).
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Much of the mammal life is dependant on these shifts in water levels due to the increase and
decrease in land mass available. During high water seasons, Terrestrial mammals can be found
at a much higher density and are therefore much easier targets for hunting. This hunting pressure
is also increased by the fact that fish are highly dispersed among the flooded forest making them
a harder target. When the water recedes and the land mass increases, hunters turn their efforts
to fish caught in pockets of water and away from the mammals that are now free to disperse in a
much wider area. With subsistence hunting for bush meat being an important resource for locals,
especially those located at a greater distance from civilization, it is important that balance is
established so as not to overexploit populations (Bodmer et al 2009).
1.3 Inter-specific interactions
Within the Pacaya Samiria national park there are twelve species of primate as well as a
multitude of other mammalian species (Bodmer 2009), therefore it could safely be assumed that
these species will have at least some contact with each other. These all fall under the umbrella
term of interspecific interactions. These interactions have been segregated into several
categories dependant on whether the process has a negative, positive or neutral effect on the
population.
Table 1. Display of possible interactions between species
By studying these interactions it could be possible to determine the effect they have on the
behaviour or success of individual species. In turn this could provide valuable information for
short term management strategies e.g. if species A is having a negative effect on species B to the
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point of increasing threat level. A controlled reduction of species A, through an increased hunting
quota or action of a similar ilk, could alleviate this threat.
There is a large amount of work on the study of interspecific interactions, enough to cover a
whole thesis, primarily debating the intricacies of these relationships and suggesting that these
definitions are either wrong or too black and white (Soukhovolsky 2004). However due to the fact
that there are very few theories which have not brokered a certain degree of criticism it would be
impractical not to adopt a certain stance. If this were to happen no work would be achieved.
Therefore for the purposes of this study I will be using the definitions identified above as they are
perfectly adequate for use in a project to this degree.
1.3.1 Competition
Competition is a primary relationship that must be addressed as no party benefits. Any increase
in competition can result in the complete extirpation of a weaker species. With habitat destruction
causing fragmentation of resources, limitations imposed by competing species are becoming a
greater threat where previously larger areas could easily sustain similar populations. This was
coined as the competitive exclusion principle or Gause’s Hypothesis, it was defined in several
ways following the British Ecological Society’s 1944 Symposium by a multitude of ecologists,
however, the final result was “two species with similar ecology cannot live together in the same
place” (Anon 1944 see Gilbert 1952) (Hardin 1960). This is an extremely bold statement and has
given rise to a lot of contention with parties citing an inability to know how much two species’
ecology must overlap in order to meet this criteria. Also this statement does not directly allow for
the ecological plasticity displayed by many primates who in a time of high competition can resort
to other food sources and other ecological preferences (Hardin 1960).
90% of all aggressive interactions have been shown to occur at fruiting trees. Despite an
abundance of fruit species, it was found that four species of primate, including the two mentioned
above, still chose to feed on similar fruits displaying a large amount of niche overlap. It is
suggested that although competition for these fruits may be predominant, the impact is mitigated
due to a retention of preferences dissimilar to their competitors (Stevenson 2000)
1.3.2 Poly-Specific Association
At the other end of the scale a better understanding of mutualism could provide conservationists
10
with an invaluable tool. By understanding the benefits one species can provide to another,
conservation efforts can be aimed at particular species safe in the knowledge that this will have a
beneficial effect on further species.
Poly-specific association is determined as the interaction of two or more species that
exceeds, that, which would normally occur by chance. A majority of work shows that it occurs
more often in old world primates, however, there are several accounts of it persisting in new world
primates (Gautier-Hion 1983).
The benefits of poly-specific association are said to be similar to those that arise within
intra-specific association, that is those found within larger group size. The formation of polyspecific groups can provide all the benefits of a larger group size but without increasing the costs
that would occur with a larger con specific group (Strier 2007). Within these mixed species troops
the competition for mates will not be as high, in addition two species will usually demonstrate a
minimum amount of niche variation meaning that competition for food sources will not be as high
as it would be in a group of a similar size solely of one species. The two primary benefits to
mixed species groups have been highlighted as foraging efficiency and anti predatory benefits
(Strier 2007) such as the herd effect in which an increase in numbers decreases the chance for
any single animal to be predated upon (Turborgh 1983).
1.4 Examples of interspecific interactions in Amazonia
When researching poly-specific association in new world mammals a majority of papers are
focused on the relationship between Saddle backed, Moustached and other species of Tamarin
which are often found in mixed species groups, along with Goelldi monkeys (Pook and Pook
1982). However our study area within the Pacaya Samiria only contains a single species of
Tamarin, so much of this current work is not directly applicable. However by understanding the
relationships displayed it could greatly increase the ability to look for similar actions within other
species. One such association is that of the Saddle back and Moustached Tamarin
1.4.1 Howler vs. Woolly
There are several examples of competition that have been identified in work performed in
previous years within Pacaya Samiria. One of these relationships is that of the Woolly (Lagothrix
Poeppigii) and Red Howler monkey (Alouatta Seiculus) which display a negative correlation in
association i.e. when one species occurs in a high density the other occurs at a low density or is
not found in that area at all. This density can be in favor of either species (Bodmer 2009). A
reason as to why this may occur has not yet been ventured, however, I will be using this years
data to ascertain whether this relationship continues. By looking at the two species’ ecology it
may be possible to find an immediate reason for the relationship. In terms of feeding habits,
Howlers tend to be more generalist feeders whereas Woolly monkeys are primarily frugivorous.
11
The largest difference I noticed within their ecology was group size, although being roughly the
same size individually, Woolly groups can range from 20 to 70 (Di Fore 2004) whereas the
Howler is more often found in groups of less than 10. This major difference in biomass would
suggest that should the species ever come to head over resources then the overall larger
biomass of the Woolly monkeys would force the retreat of the other species. However, data on
actual visual interaction between the two species is lacking at this current time.
1.4.2 Association of Brown capuchin and Squirrel Monkeys
A relationship that has not been touched on in prior reports from Pacaya Samiria is the
polyspecific association of Squirrel Monkeys (Saimiri Sciureus) and Brown Capuchins (Cebus
Apella). It has been found that the two species can form mixed species troops associating for
over 50% of their time. These troops have been seen to coexist from a few hours to up to twelve
days (Podolski 1990). As to why this association occurs, it has been found that Saimiri specifically
seek out Cebus groups and from there predominantly initiate, maintain and dissolve the mixed
species troops (Terborgh 1983). It was first suggested that this association occurred due to a
benefit in foraging success because of an increased association during times of food scarcity, in
addition when travelling the troops were led by Capuchin groups (Terborgh 1983). However, it
was also noted that this association persisted in a time when food was abundant, therefore,
increased foraging could not be the only benefit from the association. Anti predatory tactics were
then found to be a contributing factor as to why Squirrel monkeys actively seek out these
associations, having no true predator alarm call of their own they have been observed responding
to those performed by the Capuchin group (Terborgh 1983). Of all the poly-specific associations
recorded amongst primates these two demonstrate the largest difference in body size with
Capuchins averaging 3kg while Squirrel monkeys only average 0.74kg (Leonardi et al 2010). This
allows the two species to employ vastly different niches with Capuchins primarily making use of
medium sized branches while their smaller associates climb the more delicate thinner branches
(Fleagle et al 1981 see Leonardie et al 2010). Although it is not immediately clear what benefits
Capuchins receive from this association it can be presumed that there is a certain degree of
dilution in their chance of being predated upon (Podolski 1990). It is still under contention as to
whether this benefit out ways the negatives cause by the association
The use of Saimiri Sciureus, as a general term for South American squirrel monkeys
varies from one paper to the next, however, in recent years it has been accepted that it no longer
covers species found within Peru which is now designated Saimiri Bolivensis (Jack 2007). I will
be using data collected within this study to identify whether this relationship occurs within Pacaya
Samiria and to what extent.
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1.4.2 Further examples of interaction
Another suggestion made was that of the increase in Larger bodied primates forcing out the
smaller bodied primates (Bodmer 2009). This was one explanation put forward for the reduction
in Tamarins and the increase in Woolly monkeys. However it is suggested that it is indeed the
overall biomass of a group that would cause a species group to have the upper hand in conflict
due to their increased agility and numbers, making it harder for the larger slower primates to flush
them out (Strier 2007).
1.5 Line Transects
In order to achieve these objectives I will be employing the use of a line transect survey such that
has been carried out and used by the monitoring staff in Pacaya Samiria over previous years.
Line transects estimate the density of not just the animals you see but also the animals you don’t
see, this is achieved by using a detectibility function. There are several assumptions that must
occur in order for this technique to work. These are:

Objects on the line are detected with certainty

Objects are detected at their initial location

Measurements are exact
(Buckland et al 1993)

Animals of target species move slowly relative to the speed of the observer

detections are independent events.
(Peres 1999)
1.6 Research Objectives
After considering all the above information I have produced the following objectives to achieve
within my research:

A continuation of the monitoring of terrestrial mammal species recovery and stability
using a line transect survey method.

Investigate interspecific interaction to identify strong correlations, explain why they might
occur and explore uses that may come from exploitation of these relationships.
13
2. Method
2.1 Collection of Data
Transects were established by cutting a path using machetes. Once the desired or maximum
length was reached, the transect was measured using a 30m tape measure between two people.
A label was placed at every 100 metres along the transect in a clearly visible position displaying
the cumulative distance reached. We used a permanent marker on ribbon so the numbers
persisted through out the consistent rain.
We aimed to start our transects between 7 and 8:30 to ensure that we caught a majority of our
transect before the heat of midday. On beginning the line transect survey several observations
were recorded, the weather, the time and date and which transect was being walked. After all
this information was noted the transect began, an average walking speed of 1-2mph was
attempted and noise was kept to a minimum in order to avoid causing disturbance to the animals
before they were noted, in addition it increases the chance for species to be seen. When an
animal or group of animals was observed the perpendicular distance from the transect to the
point of sighting, or first member of the group, was recorded using a tape measure along with the
number of individuals. The habitat it was found in as well as the action it was performing on first
being sighted and undisturbed were also recorded.
On reaching the end of the transect we rested and remained there for a period of at least one
hour. After this time we proceeded to repeat the transect in reverse. This is done with assumption
that any disruption caused would have little or no effect after this time.
2.2 Analysis of data
When it came to analysing my data I had always intended to use the program DISTANCE as
suggested by most texts relating to the analysis of this kind of survey. However due to an inability
to produce effective results using the program I resorted to a simpler unit of measurement,
sightings per kilometer. Although not providing a species density it still allows for a comparison to
be drawn from the previous years data right back until 2006. Unfortunately any comparisons
predating this will be unavailable as the raw data for these times is not available. In order to
calculate this I divided the total number of a singles species sighted and divided it by the total
distance travelled along all transects for the year.
For the purposes of the species interaction between Howler and Woolly monkeys I took the
individuals per kilometre from each different area that was surveyed during 2009 using the same
method as stated above.
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3. Results
3.1 Results section one- Original analysis
3.1.1 Ind/km for primate species
The following graphs represent the ind/km of the primate species within the reserve. Four of the
Six primates displayed a consistent increase in the number of ind/km over all three years. The
final two, Brown Capuchin (Cebus Apella) and the Saki Monkey (Pithecia Monachus) displayed a
decrease between 2007 and 2008 then proceeding to show an increase from 2008-2009.
Fig 1. Ind/km of Pithecia Monachus from 2007-2008
Pithecia Monachus
0.18
0.16
0.14
Ind/km
0.12
0.1
0.08
Series1
0.06
0.04
0.02
0
2006
2007
2008
2009
2010
Year
Fig 2. Ind/km of Saimiria Bolivensis from 2007-2009
Saimiri Boliviensis
3
2.5
Ind/km
2
1.5
Series1
1
0.5
0
2006
2007
2008
2009
2010
Year
Fig 3. Ind/km of Lagothrix Lagotrica for 2007-2009
15
Lagothrix Lagothrica
0.4
0.35
Ind/km
0.3
0.25
0.2
Series1
0.15
0.1
0.05
0
2006
2007
2008
2009
2010
Year
Fig 4. Ind/km of Alouatta Seniculus for 2007-2009
Ind/km
Alouatta Seniculus
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
2006
Series1
2007
2008
2009
2010
Year
Fig 5. Ind/km of Cebus Apella for 2007-2009
Ind/km
Cebus Apella
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
2006
Series1
2007
2008
2009
2010
Year
Fig 6. Ind/km for Saguinus Fuscicollis for 2007-2009
16
Saguinas Fuscicollis
0.7
0.6
Ind/km
0.5
0.4
Series1
0.3
0.2
0.1
0
2006.5
2007
2007.5
2008
2008.5
2009
2009.5
Year
3.1.2 Association of Woolly and Howler Monkeys
The association between the Woolly and Howler monkey demonstrates a mildly negative
correlation. Further analysis was not performed on this correlation due to its replacement by a
more reliable source.
Fig 7. Correlation of ind/km for 2009 based on separate locations within the Pacaya Samiria
reserve.
1.2
Woolly Monkey/km
1
0.8
Series1
0.6
Linear (Series1)
0.4
0.2
0
0
0.2
0.4
0.6
0.8
1
1.2
1.4
Howler Monkey/km
3.2 Results Section two- Analysis using DISTANCE
After performing my analysis and achieving the results displayed above I was sent the published
analysed data performed using the DISTANCE program. Although not performed by myself this
data is more reliable due to the experience and knowledge of those that have been producing
similar reports for several years in addition to my inability to use distance. The following analysis
17
and graphs were created by Rick Bodmer and his team who kindly permitted their use within my
project.
3.2.1 Overall and Individual Primate densities
The total density of primates for the four years recorded fluctuates mildly other than a large
reduction within the year of 2008. With the values 134.7±11.95 , 128.7±21.16, 88.2±18.19 y
133.2±21.73 ind./km 2. However according to calculations the difference is not significant.
Fig 8. The total density of primate populations from 2006-2009.
180
Densidad (ind./km2)
160
140
120
100
80
60
40
20
0
2005
2006
2007
2008
2009
2010
The individual density graphs are displayed below, these show that although the total density may
seem consistent the make up of that density in terms of different species fluctuates a lot more.
The differences in these fluctuating population vary in their significance suggesting that
environmental pressures may have different effects dependant on the species.
The populations for Lagothrix Poeppigii from 2001 to 2009 appeared to be fluctuating however
the differences were not sigificant.
Fig 9. The density of Lagothrix Poeppigii from 2001-2009
18
0.6
10
0.5
8
0.4
6
0.3
4
0.2
2
0.1
0
Abundancia (ind./km)
Densidad (ind./km2)
12
0.0
2001
2004
2006
Densidad
2007
2008
2009
Abundancia
Unlike the prior species the fluctuations within the density of Alouatta Seiculus were found to be
significant from 2001-2009 (X2=16.905, df=5, P=0.0047)
30
1.4
25
1.2
1.0
20
0.8
15
0.6
10
0.4
5
0.2
0
Abundancia (ind./km)
Densidad (ind./km2)
Fig 10. The density of Alouatta Seniculus from 2001-2009
0.0
2001
2004
2006
Densidad
2007
2008
2009
Abundancia
The population density of Cebus Apella appeared to be fluctuating (Figure 11), however, the
values shown do not differ significantly (X2 = 7.65, df = 5, P = 0.1767)
Fig 11. The density of Cebus Apella from 2001-2009
19
1.2
20
1.0
0.8
15
0.6
10
0.4
5
0.2
0
Abundancia (ind./km)
Densidad (ind./km2)
25
0.0
2001
2004
2006
Densidad
2007
2008
2009
Abundancia
The population density of Pithecia Monachus demonstrated a fluctuation but this different was
found to be insignificant (X2 = 9123, df = 5, P = 0.1042)
Densidad (ind./km2)
14.0
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
12.0
10.0
8.0
6.0
4.0
2.0
0.0
2001
2004
2006
Densidad
2007
2008
Abundancia (ind./km)
Fig 12. The density of Pithecia Monachus from 2001-2009
2009
Abundancia
The population density of Saimiri Boliviensis from 2001 to 2009 was fluctuation with high peaks in
2001, 2006 and 2009 and lower peaks in 2004 and 2007, this fluctuation was found to be
significant (X2 = 35.008 df = 5, P <0.0001)
Fig 13. The density of Saimiri Boliviensis from 2001-2009
20
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
Abundancia (ind./km)
Densidad (ind./km2)
100
90
80
70
60
50
40
30
20
10
0
0.5
0.0
2001
2004
2006
Densidad
2007
2008
2009
Abundancia
The population density for Saguinus Fuscicollis over time seems to be fluctuating (X2 = 10,533,
df = 5, P = 0.0615), with high peaks in 2001 and 2009, while the lowest density was recorded in
2008.
25
0.6
20
0.5
0.4
15
0.3
10
0.2
5
0.1
0
Abundancia (ind./km)
Densidad (ind./km2)
Fig 14. The Density of Saguinus Fuscicollis from 2001-2009
0.0
2001
2004
2006
Densidad
2007
2008
2009
Abundancia
The trend of population density seems to fluctuate over time but these differences between years
is not significant (G = 1.7371, df = 5, P = 0.8842)
Fig 15. The density of Cebus Albifrons from 2001 to 2009
21
0.20
0.18
0.16
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0.00
5.0
4.0
3.0
2.0
1.0
0.0
2001
2004
2006
2007
Densidad
2008
Abundancia (ind./km)
Densidad (ind./km2)
6.0
2009
Abundancia
3.2.2 Correlation of associations
An analysis of correlation identified two significant relationships there was a negative interspecific
relationship demonstrated by the large bodied Alouatta Seniculus and Lagothrix Poeppigii. This
shows that an increase in one species population density has a direct negative effect on the
density of the other (Fig 16.). With the calculation of a correlation coefficient we can see that it is
an extremely strong negative coalition (r=-0.9542). The second relationship shown (Fig 17.) is a
highly positive corelation between Cebus Apella and Saimiri Boliviensis inferring that the two
species’ density increase and decrease at the same time with variables accounting for 93% of the
change in one another.
Fig 16. The negative relationship demonstrated between the densities of Alouatta Seniculus and
Lagothrix poeppigii
Lagothrix Poeppigii
20
18
16
14
12
Pearson r= -0.9542, R2 = 0.9104, P= 0.0117
10
8
6
4
2
0
0
5
10
15
20
25
30
35
40
45
Alouatta seniculus
Fig 17. The Positive relationship demonstrated by the densities of Cebus Apella And Saimiri
Boliviensis
22
25
Pearson r= 0.9679, R2 = 0.9369, P=0.0069
Cebus apella
20
15
10
5
0
0
10
20
30
40
50
60
70
80
Saimiri boliviensis
A further correlation was found in both the medium and heavily hunted sites among Alouatta
Seniculus and Pithechia monachus. This correlation vecomes slightly stronger within the hunted
site, this can be seen in the comparisson of Fig 18 and 19.
Fig 18. Correlation of association between Alouatta Seniculus and Pithechia monachus in the
Pithecia monachus
medium hunted zone.
10
9
8
7
6
Pearson r= 0.8363, R2 = 0.6991, P=0.0775
5
4
3
2
1
0
0
5
10
15
20
25
30
35
Alouatta seniculus
Fig 19. Correlation of association between Alouatta Seniculus and Pithechia monachus in the
heavily hunted zone.
23
Pithecia monachus
10
9
8
7
6
Pearson r= 0.8363, R2 = 0.6991, P=0.0775
5
4
3
2
1
0
0
5
10
15
20
25
30
35
Alouatta seniculus
4. Discussion
4.1 Immediate Impression
It is instantly clear from comparing the graphs in results section one and two that there is very
little or no similarity between them. Results section two displays heavy declines in the same years
that my results have shown an increase, one such example is the density displayed from Alouatta
Seniculus in Fig 4 and Fig 10 within the year 2007-2008. There could be several explanations for
this however I’m not sure which, if any, may explain the difference. My first thought is of the data
sets that I received and essentially interpreted to the best of my ability, these may have passed
hands and computers a couple of times, data may have been altered accidentally or different
copies may have been sent. Another suggestion is that the very process of analysis themselves
do produce these wildly different results. Finally it is most likely that the my interpretation of the
data and my analysis were just wrong.
For this reason the discussion of results will be based on the results shown in section two,
however, the discussion on the methodologies used will be based on the analysis and work I
performed and produced in section one.
A positive to be drawn from the comparison of the two results is that even with the vast
differences the correlation displayed in Fig 7 is consistent with that produced in both previous
years (See Appendix 1) and this year’s data however its strength is very clearly not as strong.
This is most likely because of the fault occurring within the data analysis that was performed.
4.2 Population Density
The overall population density displayed in Fig 8. shows a continuation of the success of comanagement within Pacaya Samiria. The only negative, is the dip observed within 2008 however
24
this is not a major problem due to the recorded return to previous levels in 2009. There could be
several explanations as to why there was a dip in 2008 with regards to several stochastic events.
By looking at related primate declines we can gain a better understanding of why a decline like
this may suddenly occur.
4.2.1 Possible reasons for temporary density reduction
It is commonly known that populations fluctuate even across taxa (Krebs 1996) however
investigations into why, especially into tropical primates, are some what restricted (Rudran 2004).
Rudran and Fernandez-Duque attributed this to two primary reasons, firstly the common
misconception that tropical habitats are far more stable compared to those in more temperate
regions (Stenseth 1999). Secondly, many studies do not persist for a sufficient length of time to
gather proper understanding of population dynamics (Dobson and Lyles 1989).
Rudran and Fernandez-Duque performed a 30 year study on the red howler
monkey in Venezuela during which the population over went three tiered increase only to result in
a population crash. This crash was primarily attributed to disease within populations due to a
discovery of several skeletal remains within close proximity of known habitats. However due to a
larger proportion of newly formed groups dying out it was found that this was not the only causal
factor. These new groups persisted in newly regenerated areas and were comprised of dispersing
individuals therefore foraging success was not as high as those recorded in larger, more
experienced groups. This is thought to have led to stress from food shortage, poor diet and
intimidation, which has been linked to an increased risk of disease contraction in other Howler
species (Otis et al 1981, see Rudran 2004).
This may however be a specialised case involving newly regenerated forests. Howler
monkeys, in other populations, have been shown to display little or no fluctuations and no
significant relationship to fruit production (Milton 2006). Within the same study, Capuchin
monkeys displayed a much great annual fluctuation but again they did not seem to be
significantly related to the fruiting of plants. Milton concludes with the notion that factors that may
affect one species within any given year may not have any effect on another. Much greater
weight is given to the effects of top down factors such as predation or disease (Milton 2006)
It is understood that primate populations can fluctuate largely in seemingly stable habitats
(Hanya 2004). Work performed on Japanese Macaques shows a similar scenario to that found
within Rudran’s Howlers. During a particularly harsh year, number of troops became extinct while
simultaneously others saw moderate to large declines as well as a few who were completely
unaffected. This was put down to a particularly harsh summer followed by low fruiting productivity
in the autumn causing individuals to be malnourished resulting in the contraction of pneumonia
25
(Hanya 2004).
Unfortunately I cannot comment, with any assuredness, on the reasons specific to the
populations found within my study site. Had I had the foresight to know where my studies would
have taken me, I would have made greater attempts to gain at least anecdotal data on food
scarcity or disease increases, from those that have been performing this study for a number of
years. However speculations of a food shortage leading to disease seems to be a consistent
reasoning for temporary dips in population density.
What has not been addressed is why there would be a species wide decline in a single year.
Milton (2006) briefly makes note of the possibility of “rare environmental events”. El NinoSouthern Oscilation (ENSO) is a climatic event, involving the warming of seas, that occurs
roughly once every 5 years but can vary from 2 to 7 years. Its opposite is the event know as La
Nina which incurs cold waters and limited rainfall along the coast of Peru. Severe drought and
cold temperatures can have an impact on some plant production
(http://www.ccb.ucar.edu/lanina/report/ordinola.html). La Nina occurred during 2007 which may
have had an impact on the reproductive success, having a knock on effect on population
densities in 2008.
Although the total population density seems to remain at a fairly consistent level we can see by
comparing it to the graphs at a species level that it’s make up does not display the same
consistency. All primate species were recorded to fluctuate to some extent to a statistically
significant degree. This could be due to the cycles of particular plant species not all displaying
poor fruiting in similar years (Milton 2006). With each primate displaying at least some example of
preference over food type this could be a single contributing factor. Further to this is the
relationship that individuals may have with predation or competition for resources, this is
demonstrated by the Lotka Volterra fashion of these fluctuations.
4.3 Interspecific Interactions
The range of interspecifc relations I could analyse is restricted to those that have been provided
within the report . By chance both of the predominant interactions I wished to study were both
included within this report so
4.3.1 Howler vs. Woolly
While performing my study a simultaneous project was being performed solely on the behaviour
of Red Howler monkeys. From discussions with the student it became clear that the relationship
between the species and Woolly monkeys was very much one sided. A whole section of
26
behaviour was given to “hiding” in which the Howlers would move up into a higher canopy or even
away from the area when a group of Woolly monkeys either travelled through or occupied the
surrounding area. From this behaviour it would not be ridiculous to assume that Howlers are
hindered to an extent because if there were to be a continual rise in Woolly monkey density at the
cost of a lower density in Howler Monkeys until eventually they were wiped out, there would be a
demonstration of the competitive exclusion principle (Hardin 1960). However this is not the case
as by looking at the densities of the two species it can be seen that they have intermittent peaks
and troughs that directly oppose each other. This could be answered by the phenomenon of
density compensation in which the decline of a species is often offset by the increase in its
competitors (Peres and Dolman 2000). A study on over 56 populations showed that in larger
bodied primates this phenomenon occurred when one species was reduced either by hunting or
other means such as those explained above. With Woolly Monkeys being a primary target for
subsistence hunters this would provide an explanation as to why they have yet to exclude Howler
monkeys from the area. Further work into the relationship between these two species primarily on
their direct competition is needed.
Should either of the species become locally or even globally threatened action based on the
knowledge of this relationship could serve in reducing pressure on the threatened party by
increasing subsistence hunting on the plentiful species.
4.3.2 Capuchin and Squirrel
The association highlighted in previous work in other study sites between Squirrel and Brown
Capuchin monkeys is very apparent within our results in Pacaya Samiria (Fig 17 ). By gaining
further understanding of this association it would allow management to make much wider and far
reaching decisions in terms of population control or hunting quotas. However it would first need to
be finitely defined as to whether Squirrel monkeys association with Brown Capuchins is in the
form of commensalism (almost to the point of parasitism)(Terborgh 1983) as some people
suggest or if it is indeed mutually beneficial to both (Podolsky 1998). What could be gained for
certain from this deduction is that any rapid decline in Brown Capuchins, caused by disease or
any stochastic event, could have an extremely negative impact on Squirrel monkey populations
within the surrounding area. By consistently monitoring numbers we could gain invaluable time in
mitigating this reduction.
4.3.3 Arguments against the manipulation of habitat
If research shows that one species is being out competed by another that is not invasive or alien
27
to that area, for example if the Woolly were to begin consistently outcompeting the Howler, it
could bring into question our reasoning for management and additionally our purpose in
conservation. Even amongst my peers, at our early stages within our careers, this is an issue of
contention with ideologies ranging from the overly pragmatic to the hopelessly idealistic. The
question I’m referring to is that just because we could potentially manipulate an environment and
save a species, should we if that species is not locally under threat from human based activities?
By doing so are we going against nature and primarily, is that wrong? By looking at the mission
statements of several leading conservation organizations it is difficult to gain a clear idea on what
their stance may be. The Wildlife Conservation Society have “the clear mission to save wildlife
and wild places across the globe” (http://www.wcs.org/about-us.aspx) while the Wildlife
Conservation Network is “dedicated to protecting endangered species and preserving their
natural habitats” (http://wildlifeconservationnetwork.org/about/). Conservation internationals's
mission states “Building upon a strong foundation of science, partnership and field demonstration,
CI empowers societies to responsibly and sustainably care for nature for the well-being of
humanity.” (http://www.conservation.org/discover/mission_strategy/Pages/mission.aspx).IUCN,
the International Union for Conservation of Nature, helps the world find pragmatic solutions to our
most pressing environment and development challenges. (http://www.iucn.org/about/). Chris
Packman in an interview with the Guardian made note of the issue surrounding the Great Panda
suggesting that the idea of species specific conservation is out dated and instead a habitat
approach should be adopted. By this argument, the natural decline of a species should be
allowed and human intervention becomes a waste of resources that could be used in other
needed areas. This is an issue that may be greatly discussed but as of yet does not bare a
distinctive answer.
4.4 Problems and bias encountered within my methodology
4.4.1 Data collection
There were several constraints with the methodology used that may have produced bias and
should be considered and taken into account. High water meant that transects of a desired length
were nigh on impossible to find without hitting an impassable flooded area. For this reason the
period in which our transects were set out took much longer than anticipated. It also meant that
rather than having an ability to sample a multitude of areas and habitat types transects were
merely placed wherever we could find dry land.
Any action performed by that of the observer that disturbs an animal before it has been
sighted will cause a bias, either because it will move away before being seen or the perpendicular
distance from the transect would have been effected. Although attempts were made to keep as
silent as possible when an animal was observed this was often forgotten during the period of
28
measuring the perpendicular distance. This could have caused animals within close proximity
further along the transect to move away from their original position meaning that even if they were
sighted perpendicular distances would have been altered due to this foreign noise.
Towards the end of a transect my mind began to wonder and observations of other
members of the team also displaying similar characteristics such as fiddling with equipment
suggest that our chance of detection may have been slightly decreased . This was especially the
case when sightings were already few and far between. Although personally having very little
experience with regards to line transects and all aspects of rainforest walking much of this was
potentially mitigated by the presence of experienced guides.
On reflection of the second transect it is apparent that the timing causes it to occur during the
middle of the day during the period when some species are in a period of reduced activity. It is
suggested that a resting period of 3 hours pass so that the transect does not begin until 1400h
4.4.2 Data analysis
When analysing the data that was provided for the previous years there were numerous mistakes
or mistyped errors. One such example was the change of subspecies from one year to the next in
Lagothrix Lagotrica to Lagothrix Poeppigii. This was the case so much so with the data of 2006
that I decided not to use it at all in my original analysis. Although potentially losing an important
resource the result I would have attained from its analysis would not have been, in my eyes,
accurate.
The ability to reliably compare abundance between years could be called into question with most
of the data being collected by different groups the methodology may differ slightly and those in
the following years would not know. A series of notes accompanying data sets would highlight
any discrepancies between data collection methodology that may have occurred. For example
the first few transects performed during my survey were carried out without a tape measure
meaning perpendicular distances were estimated. The names or experience of surveyors would
also allow anybody analysing the data in the future to assess how reliable data sets are or at
least allow them to be aware that certain data points may have a more face value cause for
discrepancies rather than an intrinsic cause. That is not to say that discrepancies labelled in such
a fashion should be ignored, just highlighted.Although several members of the surveying team
are consistently present throughout the years this additional information could be essential.
The need for a standardised approach to transect surveys was highlighted by Pares in
1999 in the hope that one could be created. By not having a standardised technique it makes
comparing densities between sites and surveyors extremely un reliable.
29
4.5 Suggestions for the future
First and foremost a continuation of the total density monitoring must continue. This will ensure
that the current status of the co-management persists and will highlight any alterations in its
effectiveness. Further work into environmental, and other stochastic, impacts on total primate
densities are necessary to fully determine their importance.
I have only begun to scratch the surface of the possibilities that could arise from the
understanding of interspecific interactions. There are many more relationships that have not even
been touched upon within this assignment that could play vital roles within the ecosystem. As well
as a continuation of monitoring of the current relationships, work could be performed on the
association between arboreal and terrestrial mammals such as the possibility of Agouti’s following
frugivorous primates due to a chance of food being dropped or shaken from branches.
By monitoring the fluctuations in density it could be possible to identify an indicator species. This
would allow work to focus solely on a particular species easing up resources for other projects.
There is a suggestion that density of Opossums could be a potential source as an indicator
species for the health of the rainforest as a whole.
5. Final Conclusion
It can safely be said that to date the introduction of a co-management strategy has been a
success in terms of restoring population numbers. By achieving this it gives the populations a
much greater chance of surviving possible stochastic events like those that may have been
responsible for the reduction of numbers within 2008. Based on the conclusions of association we
can see that some relationships displayed are extremely strong however in terms of their use this
is something that as of yet could not be effectively defined. A much greater deal of behavioural
and qualitative study into these relationships, in order to understand them in greater detail, is
needed if they are to move from a note of interest to a tool in conservation.
In general the original analysis of data was extremely poor primarily due to inexperience and an
inability to analyse it in a way that would make it completely of use to my project. However one
problem that occurred was the complete upheaval of my project, much of what I’d like to have
explored with my data is not possible as my hypothesis or any notion as to what to do with the
data I collected had to be decided after it had already been collected. This also attributes to a lot
of the bias’ and problems with my methodology, had I known that I was going to be collecting this
sort of data, research into line transect surveys beforehand would have provided me with a much
greater platform of knowledge from which to conduct my surveys. As it was, being in the
presence of others who have been running these sorts of surveys for several years my
30
inexperience and lack of knowledge dwarfed most of my ability to take hold or really put a stamp
on my own project and how it was run. The most valuable lesson the project has taught me is
that within field work one should always have a contingency plan because the likelihood of being
able to conduct a survey as planned will very rarely occur.
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Appendix
Appendix 1. Shows the relationship between Howler monkey and woolly monkey as shown by
Bodmer et al in the report of 2008 for Pacaya Samiria.
33
Appendix 2. Ungulate Density from 2001-2009 within the Pacaya Samiria Reserve.
34
Densidad (Ind./km2)
14
12
10
8
6
4
2
0
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
35