Bonobo radio: In the field

18 June 2013 by Kerstin Hoppenhaus, posted in Primatology

Rodolphe and Matthis are now very well into their task of tracking apes and other wildlife in the Congolesian rainforest, but they have yet to see their first bonobo. Most of the time, they are dealing with indirect signs of their presence: sleep nests, dung, or chew marks like this:

Leftovers from a bonobo meal: Haumania stalks in the Congolesian rainforest (Photo: Barbara Fruth, MPI/Arcus)

It is still early days, but everybody is quite excited to find out how many bonobos really live in the area. The whole ecocamp idea that is intended to provide a livelihood for the communities nearby and help to protect all the wildlife around it depends very much on the presence of the bonobos. The ongoing viablility assessment, of which Matthis and Rodolphe are now a part, is funded by the Arcus Foundation, but ultimately, the goal is to build something that is sustainable on its own. For this, the bonobos not only have to be there, but one also has to have a solid understanding of their habits and whereabouts.

The Pactor-antennae in the LuiKotale field station is working again, so Matthis and Rodolphe can coordinate with Barbara Fruth in Leipzig to make sure they are collecting the right data in the right way. Their exchanges give a good impression of what their everyday work in the forest looks like.


Dear Barbara*,

*Thank you very much for the protocol, we just tried it on Me4 with Mams.
..We have some points to highlight a bit :
1.We tried to take the perpendicular distance for direct observations of 
animals but it not really doable, we need to estimate the distance from 
transect and to take the bearing. Is it fine like this or do you have 
another idea?
2.If the traces of the same animal/group of animal (footprint, 
scratch...) are along a long distance on the transect, should we record 
it as different observations or just as one?
3.Vocalisations of the same group of animals can be heard several time, 
should we just record the first one?
4.How the distance from the start of the transect needs to be accurate? 
We could have an estimation (e.g 10m range) or do we always need to use 
the measurement tape*?
*5.Do we record very old traces of animals (e.g. pig scratching)?
6.Sometime, several animals use the same path, do we have to record 
these paths?

Thanks a lot for your help, we should learn tomorrow how to use the 
camera traps. We will try to fix the GPS issue with Gottfried in the 
next days.
Have a nice week,


Rodolphe and Matthis


+++ Dear Rodolphe & Matthis,

great you got all and were able to try out some of it already!

1. perfectly ok. Please see manual - I wrote: , vocalizations and direct observations (note time of day, direction, estimated distance(close, average, far); direction = compass bearing. If we have this and your estimated distance, we can calculate perpendicular distance: (perpendicular distance = estimated distance * sin of angle (I transect bearing - compass bearing I ))
2. Record just as one! In this case you are walking along an animal path. Take approximate midpoint of e.g. footprint-path and note species and whether or not there is just one or several individuals of given species, and age-estimate (when traces have been produced, check for clear-cut edges, last rain, ...). I think you have a particular problem here with the Meike transects as they are meanwhile trails and thus used by animals as paths. So the sampling is not anymore random - and we have to deal with that for the comparison - but I thought it was good anyway to redo the same transect as it will give us some additional hints concerning nestsite-fidelity of bonobos.
3. You have to record the 1st one with all the bearings. What counts in the end are the groups. If you have different species vocalizing - even if these are likely to forage in a mixed group - they need to be counted separately. Before being uncertain whether or not that's the same group you are recording, better use a distance to impose yourself a new record upon vocalization - I'd suggest 100m. With our line being apart only 500m the probability of encountering the same monkey-group walking the one and the neighbouring one is high anyway - but that can be figured out with your GPS & distance/angle data!
4. Yes, accuracy is appreciated. Please use the tape-measure (25m) and take it along with you walking - one stays back - the other advances, so you can give precise distance from 0 or waypoint xy respectively.
5. Yes, please do so and - if possible - estimate age (has bark regrown, have algae grown?) If you have doubts or is an unusual thing, just make a photo and add its number to the check-sheet.
6. The important thing are the animals, not the paths. If you have evidence for species x - that's what you need to note 1st as we wish to investigate available mammal-population.

I'll send you the paper of Buckland et al. 2010 that perfectly summarizes the needs/problems for primate surveys (Title: Design and Analysis of Line Transect Surveys for Primates). One important part already now, I forgot to explicitly write in the protocol: Although cutting of vegetation should be minimal, you ideally should do it ≥1 wk before the line is surveyed. It is not essential that you walk exactly on the transect line; you can leave it, to move around a fallen tree for example, so long as detection of animals/signs on the line is still certain. However, the measured distances must be of detected animals from the line, and not from the route taken.

Did we talk about some preliminary investigations on dung-decay? I think it would not be bad if you could mark duiker-dung and have a look on how it decomposes to better judge dung density - same for other dung. Of course you need fresh ones for this, just as with nests ...

I'll try out the transfer to the GPS tomorrow and give you feedback latest early next week.

All the best



Leave a Reply

two + 1 =