The study was carried out at the biological field station Estación Biológica Quebrada Blanco (EBQB) (Fig. 3-1, Fig. 3-2). The station is situated the north-eastern Peru, in the primeval Amazonian lowland rainforest, on the right bank of the river Quebrada Blanco, which is an affluent of the river Rio Tahuayo. It is positioned about 120m above sea level, with coordinates 4ᵒ21’S and 73ᵒ09’W (Heymann, 1995). I studied five groups of habituated black-fronted tamarins (Leontocebus nigrifrons). Three groups (Gr1, Gr2, Gr3) had already been habituated: Gr1 since May 1999, Gr2 since January 2000 and Gr3 since 2001, and were routinely monitored every month by the field assistants. Another two groups (Gr5, Gr6)3 were known to exist in the area, however, Gr5 has only been habituated since August 2012 and Gr6 since December 2012, and only for the purpose of this thesis. The position of the study groups is presented in Fig. 3-3. The habituation process of both groups started in May 2012 and was completed by the end of July 2012 for Gr5 and at the end of November 2012 for Gr6.
3 Numbering of groups at EBQB is based on the sympatric moustached tamarins (S. mystax) with which the black-fronted tamarins generally form mixed-species groups (Heymann and Buchanan-Smith 2000). Group
Fig. 3-1: The location of the Estación Biológica Quebrada Blanco. Illustrated by Ulrike Walbaum.
Fig. 3-2: Estación Biológica Quebrada Blanco: the housing and the working area.
Illustrated by Darja Slana.
Fig. 3-3: Study area at the EBQB: A) approximate path grid of the EBQB; B) more exact path grid of the EBQB with the territory locations of the five study groups. Each dot represents a GPS location and most of them represent locations of the groups, taken several times per day when with the group. Yellow dots bellow represent Gr1; green dots on the right represent Gr2; violet, pink and light blue dots in the middle up represent Gr3;
dark blue dots on the left represent Gr5; bright green dots on the left represent Gr6. (Figure A was illustrated by Eckhard W. Heymann; figure B was illustrated by Tiziana Gelmi.)
Fig. 3-4: Climate data of the Tamshiyacu weather station, located approximately 30km from the research station. The diagram shows data from the relevant years 2012-2013 (WorldWeatherOnline.com 2018) and long-term climate diagram data (Climate-data.org 2018) as a comparison. The gray-shaded area marks the study period. Bars represent monthly rainfall (left scale), where dark blue bars show the years 2012 and 2013, while light blue bars show long-term climate data as a comparison. Solid lines represent monthly average temperatures (right scale), where the dark red line shows the years 2012 and 2013, while the lighter orange line shows long-term climate data as a comparison. Shaded bands around the respective lines indicate monthly minimum and maximum temperature values.
In the two-month preparatory period, March to April 2012, we started following three study groups (Gr1, Gr2 and Gr3). The purpose was to become familiar with the surroundings, the study animals and the methods of data collection. Finally, the study period started in May 2012 (Gr1, Gr2, Gr3), in August 2012 (Gr5) and in December 2012 (Gr6) until the end of July 2013 (Fig. 4-1). We identified the individual animals through natural markings, like genital size and shape, body size, fur pattern and tail shape (Fig.
3-5). The individuals were assigned to age categories (infant: 0-3 months; juvenile: 4-11 months; subadult: 12-23 months; adult: ≥24 months) based on known age or on the size and the stage of genital development (Goldizen 1989; Goldizen et al. 1996). The latter was assessed by experienced field assistants. The study groups consisted of 1 – 4 adult males, 1 – 2 adult females, 0 – 3 subadults, 1 – 2 juveniles and 0 – 3 infants. Further details of group composition are given in Table 4-1. Observations and data collection were conducted by eight people – five field assistants (Ney Shanuano Tello, Camilo Flores Amasifuen, Migdonio Huanuiri Arirama, Gabriel Cartitimari Arirama, Carlos Cartitimari Arirama), two biology students (Judith Jacira Achong Sánchez, Allison Licett Núñez Levy) and myself – working in groups of two, simultaneously collecting data on three study groups.
Fig. 3-5: Drawings of natural markings of animals, to help with the individual identification.
Illustrated by Ney Shahuano Tello and Darja Slana.
We followed the five study groups daily, from the time they left the sleeping site, between 5:30 – 8:30 hour and until they entered the sleeping site, between 15:00 – 17:00 hour.
We observed each group on average for 7.5 days per month and 8.5 hours per day. We observed Gr1 for 966.8 hours, Gr2 for 938.9 hours, Gr3 for 870.7 hours, Gr5 for 673.1 hours and Gr6 for 419.3 hours, yielding a total of 3868.7 hours of observation. We
collected behavioral data by a) continuous behavior sampling for interactions, markings and rare behavior, like tongue flicking, b) scan sampling, which was conducted on every half an hour for two minutes, to access the differences in individual visibility and their activity budget, and c) 10-minute focal protocol for adults and subadults. In addition to the behavioral data we collected fecal samples from all individuals, for the purpose of genetic and hormonal analyses. The sampling methods are explained in greater detail in the respective chapters.
The genetic analyses of the fecal samples were performed by me, under the instructions and supervision of technical assistants Christina Glaschke and Christiane Schwarz. I extracted the nuclear DNA from fecal samples, amplified it with PCR and used it for microsatellite analyses. The method is explained in greater detail in chapter 4. Considering hormonal analyses, the first part of the laboratory analyses – the extraction of hormones for evaluation – was conducted in the field station EBQB, by myself and the two biology students, Judith Jacira Achong Sánchez and Allison Licett Núñez Levy. The second part – the enzymeimmunoassay (EIA) technique – was performed in the laboratory by the technical assistant Andrea Heistermann. The method is explained in greater detail in chapter 6. The statistical analyses were executed by myself (chapter 4), and together with statistician Holger Sennhenn-Reulen (chapter 5, chapter 6). The methods are explained in greater detail in the respective chapters. Overall supervision of genetic part was done by Christian Roos, overall supervision of hormonal part was done by Michael Heistermann and overall supervision of the thesis was done by Eckhard W. Heymann.