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Ruth Thomsen

Ruth Thomsen

Tel: ++49 30 640 935 29



Senior Research Associate
Dept of Anthropology
Gower Street, London WC1E 6BT


Current projects focus on the evolution of sexual and social behaviours in primates.

Semen quality in wild macaques

In human males, semen quality decreases with age. However, is this also the case in monkeys? To address this question, one has to analyse semen - which isn't an easy biological sample to come by. Fortunately, males of many monkey species masturbate regularly. On the island of Yakushima I habituated several groups of Japanese macaques to my presence. This allows me to collect their semen on a regular basis to then check for various parameters that indicate quality.

Functions of auto-sexual behaviour in non-human primates

Auto-sexual behaviour (masturbation) is the most common sexual activity of humans, but surprisingly little is known about how it evolved and why it occurs. For centuries, masturbation has been tabooed or regarded as an unnatural and thus pathologic behaviour. Instead, my research revealed that masturbation is a common component in the sexual repertoire of primates. It is more prevalent in species with polygynandrous breeding systems but also occurs in harem-groups and in solitarily living taxa. This suggests that masturbation is an ancestral and widespread trait in the primate order and further implies that it is a facet of the sexual repertoire of our own hominid ancestors.

Chemical signalling in hominids

Humans are considered to be apes for which the sense of smell has lost its importance. However, is this traditional view of humans as "microsmatic" animals actually true? My research compares our own species with the other great apes (chimpanzees, bonobos, gorillas, orang-utans). GC-MS (gas-chromatography mass-spectrometry) is used to identify semiochemicals that constitute body odours, and to test whether the ability for chemical signalling was actually reduced during human evolution.

Kin recognition via olfactory cues

Can olfactory cues allow monkeys and apes to discriminate between related and non-related individuals? A prerequisite for this mechanism would be that body odour is heritable. If so, one would suspect that semiochemicals of related individuals are more similar. I test this possibility by comparing the body odour of paternal half-sisters and non-related females in free-ranging rhesus macaques on Cayo Santiago.

Professional career

10/2013–Senior Research Associate, Dept of Anthropology, University College London

10/2009–09/2013 Senior Scientist and Lecturer, Dept of Biology, University of Leipzig & Max Planck Institute for Evolutionary Anthropology

01/2007–04/2009 Research Associate, Dept of Anthropology, University College London

01/2002 – 12/2006 Postdoctoral fellow, Institute for Zoo- and Wildlife Research, Berlin


1997–2001 PhD Zoology, Ludwig-Maximilians University Munich & Kyoto University; PhD thesis: Sperm competition and the function of masturbation in Japanese macaques (Macaca fuscata)

1992–1996 Undergraduate studies in Geography, Ecology, Anthropology and Zoology, Ludwig- Maximilians University Munich; Diploma thesis: An ecological comparison of the home ranges of two troops of Japanese macaques ranging on Yakushima Island, Japan

1989–1991 Undergraduate studies of Japanese language and culture, Ludwig-Maximilians University Munich

Peer reviewed publications

In preparation or under review

Thomsen R, Birkemeyer C, Henkel S, Ruiz-Lambides A, Mundry R, Widdig A. Can odour be a potential cue used for paternal kin recognition in a catarrhine primate?

Henkel S, Thomsen R, Ruiz-Lambides A, Widdig A. Do rhesus macaques (Macaca mulatta) recognize group members via olfactory cues alone?

Birkemeyer C, Thomsen R, Ruiz-Lambides A, Widdig A. Analysing the semiochemical repertoire of rhesus macaques via GC-MS.

Thomsen R. Aging reduces semen quality in a wild primate.

Published papers

Thomsen R, Sommer V (in press) Masturbation in non-human primates In: Encyclopedia of Human Sexuality Vol. 1, P Whelehan & A Bolin (eds), Wiley-Blackwell press, Boston

Thomsen R (2013) Non-invasive semen collection and analysis in wild macaques. Primates. DOI 10.1007/s10329-013-0393-z

Voigt CC, Klöckner P, Touma C, Neuschl C, Brockmann G, Göritz F, Palme R, Thomsen R (2013) Hormonal stress response of laboratory mice to conventional and minimal-invasive bleeding technique. Animal Welfare 22: 449-455

Thomsen R, Voigt CC (2006) Non-invasive blood sampling from primates using laboratory-bred blood sucking bugs (Dipetalogaster maximus, Reduviidae, Heteroptera). Primates 47: 397-400

Thomsen R, Soltis J, Matsubara M, Matsubayashi K, Onuma M, Takenaka O (2006) How costly are ejaculates for Japanese macaques? Primates 47: 272-274

Thomsen R, Soltis J (2004) Male masturbation in free-ranging Japanese macaques. International Journal of Primatology 25: 1033-1041

Thomsen R, Soltis J, Teltscher C (2003) Sperm competition and the function of male masturbation in non-human primates. In: Sexual Selection and Reproductive Competition in Primates: New Perspectives and Directions, Jones CB (ed.), ASP-Book Series, Special Topics in Primatology, Vol. 3, 436-453

Soltis J, Thomsen R, Takenaka O (2001) The interaction of male and female reproductive strategies and paternity in wild Japanese macaques, Macaca fuscata. Animal Behaviour 62: 485-494

Soltis J, Thomsen R, Matsubayashi K, Takenaka O (2000) Infanticide by resident males and female counter-strategies in wild Japanese macaques (Macaca fuscata). Behavioural Ecology and Sociobiology 48: 195-202

Thomsen R, Soltis J (2000) Socioecological context of parturition in wild Japanese macaques (Macaca fuscata) on Yakushima island. International Journal of Primatology 21: 685-696

Thomsen R (1997) Observation of the periparturitional behaviour in wild Yakushima macaques (Macaca fuscata). Folia Primatologica 68: 338-342

Ad-hoc journal reviews

Behavioural Ecology and Sociobiology; Behavioural Processes; Chemical Senses; Ethology; Folia Primatologica; International Journal of Primatology; Journal of Reproduction and Fertility; PLoS Biology; Primates; Proceedings of the Royal Society of London B; Regulatory Toxicology and Pharmacology

Grant reviews

German Academic Exchange Service (DAAD); Japan Society for the Promotion of Science (JSPS); Austrian Science Fund (FWF); The Leakey Foundation


National Geographic; GEO; Galileo

Grants and awards

1993-2013 Shimazu corp., Suzuki corp., Kyocera corp., Canon corp., Japan Society for the Promotion of Science (JSPS)

2005 German top-ten winner of the McKinsey business plan tournament (easyblood corp.)

2004-2005 Stipend from the city of Berlin for women in science

2003-2005 EEF-fond, German Ministry for Education and Science (BMBF), Postdoctoral fellowship

2002-2004 German Science Foundation (DFG)

1996-1999 German Academic Exchange Service (DAAD), PhD fellowship

1988 National winner of the students’ competition, category “Foreign language Japanese” (Bundeswettbewerb Fremdsprachen Japanisch), supported by the Japanese and German governments


Ian Barber & Stephan Grambauer, University of Leicester

Claudia Birkemeyer, University of Leipzig

Tobias Deschner, Max Planck Institute for Evolutionary Anthropology

Barbara Fruth, Max Planck Institute for Evolutionary Anthropology

Roger Mundry, Max Planck Institute for Evolutionary Anthropology

Angelina Ruiz-Lambides, University of Puerto Rico

Joseph Soltis, Disney’s Animal Kingdom Science Team

Volker Sommer, University College London

Hideki Sugiura, Kyoto University

Christian Voigt, Institute for Zoo- and Wildlife Research

Anja Widdig, University of Leipzig


2009-2013 University of Leipzig; Practical classes in Zoology (BSc); Introduction to Behavioural Ecology (BSc); Introduction to statistics and the use of R (BSc); Primate Behavioural Ecology and Evolution (MSc)

2006-2008 Humboldt University Berlin; Primate Behavioural Ecology and Evolution (MSc)

1996-1998 Ludwig-Maximilians University Munich; Practical classes in Zoology (BSc); Practical classes in Primate Behavioural Ecology (BSc)

Thesis supervision


Anja Zschoke (2013 ~ ongoing) Olfactory communication in bonobos

Susann Schunack (2013 ~ ongoing) Chemical signalling in chimpanzees

Stefanie Henkel (2010-2012) Kin recognition by olfactory cues in rhesus macaques


Mirjam Minkner (2013) In the eyes of the opponent – measuring kinship information in rhesus macaque faces

Anja Zschoke (2013) Are there shared semiochemicals among offspring and parents in chimpanzees (Pan troglodytes verus)?

Anja Slama (2013) A comparison of chemical signalling in chimpanzees (Pan troglodytes verus) and bonobos (Pan paniscus)

Susann Schunack (2012) Method development to assess olfactory profiles via GC-MS analysis in great apes

Franziska Stock (2012) The influence of dietary energy and macronutrients on the feeding of great apes

Anke Eckhardt (2011) Olfactory predator recognition in five species of cercopithecines

Stephan Grambauer (2011) The role of parasites in the evolution and maintenance of animal personalities

Kati Drechsel (2011) Evaluation and comparison of different STR markers using fragment analysis (ABI 3130xl) and QIAxcel (Qiagen)

Charlotte Frearson (2005) Masturbation in male primates: taxonomic distribution; proximate causes and potential evolutionary function

Elena Jones (2005) Masturbation in female primates: taxonomic distribution; proximate causes and potential evolutionary function

Pola von Schweinitz (2001) Female choice in the pygmy hedgehog tenrec (Echinops telfairi)

Tobias Merkle (1998) Ranging behaviour in wild Yakushima macaques (Macaca fuscata yakui)


Peggy Weist (2013) A comparative study on olfactory behaviour in great apes

Katja Rudolph (2013) Age-dependent differences in olfactory behaviour in chimpanzees (Pan troglodytes verus)

Josepha Messenbrink (2013) Comparing pairwise relatedness of known pedigrees with estimated relatedness using genetic markers

Sophie Brodführer (2012) Optimizing of PCR conditions for microsatellite typing of low quality samples

Yvonne Hollek (2012) Visual phenotype matching: Do faces contain more information about paternity than about maternity? A resemblance study on rhesus macaques (Macaca mulatta)

Julia Unger (2011) Can men perceive the cycle phases of women via olfactory cues?

Anja Zschoke (2011) Vocal and olfactory communication in three species of guenons

Anne-Christine Auge (2011) Kinship analysis in rhesus macaques using PCR and STR markers

Sarah Nagel (2011) Paternity analysis in rhesus macaques in combination with demographic data




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