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News from the forest 2
Introduction
Dear funders and supporters,
With this second newsletter I hope to inform you on
the progress of the study on the population density
of Callicebus oenanthe in Ojos de Agua, a
conservation concession in North-eastern Peru.
The largest part of this study is now finished: we
have collected all our data! I have been back in the
UK for almost two weeks, have drawn all the
triangulation maps and had the first meeting with my supervisor Prof. Catherine Hill. Analysis
of the data and the writing of the dissertation will start as soon as I have finished this
newsletter.
In this newsletter I will inform you about the last weeks of data collection, expose some
interesting questions I will try to answer in my dissertation, show you some more pictures
from the field and inform you about the very first attendance to a conference where I will
present our work.
Finishing data collection…
… proved to be slightly harder than expected. For a dry forest in the dry season we have
had an enormous amount of rain. Even the villagers of Pucacaca were surprised by the
amount of rain this time of year. And as you might know: titi monkeys do not sing when it
rains. But as soon as the rain stopped, the heat kicked in. Temperatures over 35° C were
not an abnormality. Then there were some logistic problems: motorcars breaking down,
In this newsletter:
 Introduction
 Finishing data collection
 What happens next?
 Upcoming events
 Pictures from the field
 Acknowledgements

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looking for replacement transportation and motorcars not being able to drop us off at the
most convenient points because roads had turned into miles of sticky mud.
Due to these minor setbacks we got slightly behind on schedule and by the time I had to
catch my plane back to the UK we still had three listening areas to go. Luckily we found the
perfect solution…
Over time the people of ABOFOA had grown more and more involved in the research project
and were very motivated to help me collect data at the last three listening areas. After
spending 6 months with Proyecto Mono Tocón, Jaime’s time to go back to Spain had come.
It was up to Eduardo to finish the study together with two people from ABOFOA. Felipe,
president of ABOFOA, and guide Joaquin offered to help out. So the fifth trip was the trip in
which we trained Felipe and Joaquin. Both turned out to be very eager and extremely
precise in estimating distance and angle of a vocalisation. At the end of their training I felt
very confident that they are able to collect these data themselves and train their fellow
ABOFOA associates. Also, non-profit organisation Amazónios por la Amazonía (AMPA) had
donated two GPS devices to ABOFOA. So while Jaime and I spent some afternoons
entering our data into the netbook and pairing up the vocalisations that could possibly
triangulate, Eduardo went on a few trips with president Felipe in order to teach him the
basics of using a GPS.
At the end of the fifth trip, the last days in the forest for both Jaime and me, we held a
presentation on our study for the people of ABOFOA and the villagers of Pucacaca. We
were unable to show them any results, but we explained in detail what we had done, taught
them more about the Critically Endangered titi monkeys living in their forest, showed pictures
of all the animals we had seen and a film of the titi monkeys calling. At the end I thanked
them in my best Spanish for allowing us to be in their forest and their homes.
During one of our first days in the forest, field guide Tiberio had cut me a walking stick,
because I had some trouble getting up the steeper parts of the mountain. I have had that
stick with me every single day and carved into it during some spare hours. Felipe asked me
if they could keep the stick. They wanted to hang it on the wall in their office, together with a
sign with my name on it. I feel like a celebrity! But joking aside, I am glad that our efforts and
presence have been so very appreciated by the people of ABOFOA.
I felt sad having to leave the villagers of Pucacaca, who had taught me about their way of
life, cooked us their traditional meals and who came to see us as part of their family. I will
also miss working with the people of ABOFOA, Proyecto Mono Tocón and Jaime and
Eduardo. Their motivation has been an inspiration to me. Most of all I already miss the
peace and quietness of the forest in the afternoon, and the beautiful sounds of monkeys,
birds and insects during the early and late hours of the day.
What happens next?
The first part of the analysis consists of drawing maps with triangulations. By matching up
vocalisations from all three listening points that occurred around the same time, I hope to
see that some of these vocalisations turn out to be from the same group, and thus show
triangulating lines on the map. Following this, these data will be entered into the program

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Quantum GIS to get the exact coordinates and a map that looks more presentable than a
map drawn by hand (Fig. 1). However, we can’t do without our hand drawn maps, because
the software cannot take into account the time at which the vocalisations started; an
important factor for matching up the vocalisations from the three points. Then, by the use of
a formula (which I will elaborate on in the final report), the total number of Callicebus
oenanthe groups within Ojos de Agua is calculated. Last, with the statistical software SPSS
it is possible to use a t-test to look for any significant differences between population density
in primary and secondary forest and edge versus non-edge areas.
Figure 1. An example of a triangulation map in Quantum GIS.
While drawing the triangulation maps back in Oxford I noticed that some points that I
expected to triangulate, did not. Also, some of the points triangulated much further away
from us than any of us had estimated. I will have to dig into the literature to find an
explanation, but things I will consider are:
 The direction the monkey is facing while singing.
 The direction the observer is facing when they hear monkeys singing.
 Factors in the landscape affecting the directionality of sounds.
 The kind of vocalisations used: there are differences in acoustic properties of each
type of call.
Many of our observations of Callicebus oenanthe co-occurred with sightings of Saguinus
fuscicollis. They were not necessarily in the same tree or around at exactly the same time,
but I think I can safely say that whenever we saw titi monkeys, it was highly likely that we

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saw saddle back tamarins within the same 50 meter radius within a timeframe of
approximately 10 minutes. I will examine the literature to see if:
 These interactions have been seen before (a definite yes!);
 What explanations researchers have given to this co-occurrence;
 What possible explanations there could be for this behaviour in Ojos de Agua.
While analysing the data, we have to keep in mind that the many rainy days and presence of
large fires, alongside men with chainsaws and bulldozers deforesting the area in the valley
may have affected our data.
Achievement of goals
I can proudly say that I am well on my way to achieving the goals I had set for myself and
the study. We have trained the people of ABOFOA in using the methods for triangulation and
gathering data on tree density and in the use of their newly acquired GPS units.
Data collection has been completed successfully. Methodology did not change much while in
the field, but our research questions had to change due to inaccessibility of parts of the
terrain and weather conditions. After analysis I hope to be able to provide both Proyecto
Mono Tocón and ABOFOA with numbers on the population density of Callicebus oenanthe
in conservation concession Ojos de Agua. And perhaps this study can tell us something
about the habitat preferences of the species.
This study has been an important part of my development as a young researcher. I now
know how to keep myself standing (both physically and mentally) in mountainous terrain, as
team leader and as researcher who’s plans never quite work out the way you had in mind
before you entered the field. I have enjoyed every second we spent in the forest. It was a
pleasure sitting in the forest, listening to the titi monkeys singing and at the same time being
visited by saddle back tamarins, hummingbirds (not so shy as they seem!) and other wildlife
(even dogs from hunters!).
Upcoming events
On the conference of the European Federation of Primatology (10-13 September, Antwerp,
Belgium) I will present a poster of this study. The poster presentations will take place on
Thursday 12 September, from 16:10 until 20:00.
I have really enjoyed the collaboration with ABOFOA, but unfortunately they will not be able
to read my dissertation as they don’t speak or read English. Therefore, I will translate my
poster into Spanish and ask Proyecto Mono Tocón to print it in Moyobamba with the leftover
money from the 6th
expedition. They can hand the poster to ABOFOA when they go to
Pucacaca for their conservation classes with the local kids.

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Pictures from the field
Figure 2. Trouble in paradise…
Figure 3. Joaquin learning the ropes of the trade.

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Figure 4. ABOFOA president Felipe writing down his compass bearing. Figure 5. Joaquin and Felipe taking tree measurements.

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Figure 6. Little joys of the jungle: coconut water after work! Figure 7. Anteater spotted by Jaime at one of his listening areas.

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Acknowledgements
This study would not have been possible without the generous support of:

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News from the forest 2

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