Assistant Professor at Leiden University

Tom Roth, MSc.

PhD student
2019 – present
I received my bachelor’s degree in Biology (2015, with honours) and my master’s degree in Environmental Biology (specialization: Behavioural Ecology; 2018, with honours) from Utrecht University.

I am a behavioural biologist/primatologist with a wide range of interests. Therefore, I conducted research on a variety of subjects related to primates during my BSc and MSc. For my bachelor research project, I investigated the locomotion behaviour of zoo-housed orang-utans at Apenheul Primate Park (Apeldoorn, The Netherlands). In my bachelor thesis I discussed the socio-ecology of leaf-eating primates (subfamily: Colobinae). During my master, I researched social vigilance in gorillas at Apenheul Primate Park (supervised by prof. Liesbeth Sterk, UU). Additionally, I studied the aggregation behaviour of Sumatran orang-utans in low-productive forest (supervised by prof. Serge Wich, LJMU). For my master thesis, under supervision of dr. Mariska Kret, I identified long-distance methods that can potentially be used to test partner preferences of orang-utans. During my PhD, I will further look into this subject.


Conservation breeding is an important task of modern zoos, with the goal to maintain large and genetically healthy zoo populations. This is mainly done by pairing certain animals that are genetically “compatible”: they are not related (no inbreeding) and when these individuals reproduce, this will either maintain or increase the genetic representation of the original founder population. However, this process virtually precludes mate choice. While mate choice is a complex process, it is clearly useful: when animals are allowed to choose their own partner, they will almost always produce more and/or healthier offspring. Therefore, letting individuals choose their own partners can be very useful for zoo populations as well. Because individuals of the same species are scattered among zoos around the world, it is not so simple to let them choose their own partner. Therefore, it is very important to develop long-distance methods of partner selection, for which physical presence of the potential partners is not necessary. This may help to identify preferred partners before translocating animals to a new zoo.


For my PhD, I will test the partner preference of the Bornean orang-utans at Apenheul Primate Park. The orang-utans will participate in a number of touchscreen tasks, during which they will see photos of other orang-utans. The results of the tasks can help to determine which orang-utans capture their attention, or which individuals they prefer to see. If they show attention towards certain individuals, this may indicate that they find these individuals attractive. The final goal of the project is to combine some of these tasks into one tool, that can be used across zoos to test partner preferences of orangutans.

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