Head of Division
Prof. Dr. Michael Taborsky

Institut für Ökologie und Evolution
Telefon: +41 31 631 91 11
Telefax: +41 31 631 91 41
E-Mail:   claudia.leiser@iee.unibe.ch

Ethologische Station Hasli
Wohlenstrasse 50a
CH-3032 Hinterkappelen

How to find us ...

Universität Bern


PNAS - Predation risk drives social complexity in cooperative breeders. Groenewoud, Frommen, Josi, Tanaka, Jungwirth & Taborsky
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The evolution of cooperation based on direct fitness benefits. Phil Trans theme issue compiled and edited by Taborsky M., Frommen JG & Riehl C. (2016)
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NATURE COMMUNICATIONS Kinship reduces alloparental care in cooperative cichlids where helpers pay-to-stay
Zoettl M., Heg D., Chervet N. & Taborsky M. (2013)
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Social competence: an evolutionary approach
Taborsky, B. & Oliveira, R.F.
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Larval helpers and age polyethism in ambrosia beetles
Biedermann P.H.W. & Taborsky M.
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Animal personality due to social niche specialisation
Bergmueller R. & Taborsky M.
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Environmental Change Enhances Cognitive Abilities in Fish
Kotrschal, A. & Taborsky, B.
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Extended phenotypes as signals
Franziska C. Schaedelin and Michael Taborsky
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On the Origin of Species by Natural and Sexual Selection
G. Sander van Doorn, Pim Edelaar, Franz J. Weissing
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Cambridge University Press
Alternative Reproductive Tactics: An Integrative

Oliveira R., Taborsky M. & Brockmann H.J.
more information

Dr. Dolores Schütz - Living in two Worlds


Email: Dolores.schuetz@gmx.net

Research Interests

In science, I am mainly interested in the evolution of different body sizes in males and females within one species, particularly when the two sexes show exceptional or extreme body size differences (sexual size dimorphism, SSD). I tried to identify different selection pressures on the body sizes of males and females (1) in a shell brooding cichlid, Lamprologus callipterus, which shows the most extreme SSD with males larger than females among animals, and (2) in the water spider Argyroneta aquatica, where males are much larger than females, which is very exceptional among spiders. Current projects in co-operation with many colleagues concern alternative reproductive tactics of bourgeois and parasitic males in L. callipterus. We investigate reproductive investment, spawning and sperm characteristics of both male types, and test in a theoretical approach whether they have equal fitnesses.

L. callipterus: Male carrying an empty snail shell

Males are on average 12 times heavier than females. The biggest males defend nests of empty snail shells, which females use for spawning. The extreme sexual size dimorphism corresponds with extreme levels of polygyny, with harem sizes reaching up to 30 females per male. Nest male spawning may be parasitized by two other male types. Males growing towards nest male size first behave as sneakers, by entering a territory during spawning, to fertilise eggs while the territory owner is inattentive. Dwarf males play another tactic and remain even smaller than females and parasitic throughout life. They attempt to enter shells in which females are spawning to fertilize the eggs from inside the shell (“wriggling”).

During my PhD thesis, I performed experiments in the lab and in the field and used a life history model of sexual size dimorphism to test which selection pressures can explain the extreme sexual size dimorphism in L. callipterus. Female choice seems to be only of minor importance for the evolution of large male size, because females did not prefer larger males as mating partners. Intrasexual competition clearly favours larger males, who win fights against smaller ones and take over their territories. However, additionally natural selection mechanisms are responsible for the origin and stability of the extreme sexual size dimorphism in this species, because of the peculiar breeding substrate they use. Males must have a minimum body size to be able to transport empty snail shells, and females must stay below a maximum body size to still fit into the snail shells for breeding.

Concerning alternative reproductive tactics, we could show that nest males differ from dwarf males in several behavioural, morphological, and physiological traits, with nest males usually bearing much higher costs than dwarf males. Both male types differ in their ejaculate and sperm characteristics, and seem to have equal fitnesses, which is stabilised by frequency dependent natural selection (manuscripts in preparation).

Agryroneta aquatica: Female with cocoon in her air bell

A. aquatica is the only spider that spends its whole life under water and one of the very few spiders in which males are larger than females. Water spiders need air to digest their prey, moult, deposit eggs and sperm, copulate, and raise offspring under water. For these purposes they construct air bells under water, which are usually built between water plants and fixed with spider thread to plants or stones. The opisthosoma and legs bear hairs that keep an air bubble around the body and help to transport air from the surface down to the air bell. Water spiders use the air bell as an Oxygen reservoir, therefore it functions as an external lung and can be viewed as an extended phenotype. A. aquaticais not a good diver, as it struggles to compensate buoyancy when moving under water. Males are less sessile than females; they rove around more often and catch their prey mainly by active hunting. Females spend most of their time inside their air bell. They catch prey mainly from there when detecting vibrations caused by prey touching the underwater net.

In a PostDoc project, I tested in the lab, which constraints determine male and female body sizes. I found that in males the necessity of moving under water efficiently and in females the costs of building a retreat and breeding shelter are important determinants of body size and morphology. Larger males are able to move under water more efficiently than smaller males, and female size is probably limited by the costs of building air bells, which they use as a retreat and for brood care. It also turned out that females prefer to court, mate or build cocoons with the larger of two males, and that competition between males was very high. From these results I conclude that the reversed sexual size dimorphism in A. aquatica is greatly influenced by natural selection mechanisms, but that also intra- as well as intersexual selection mechanisms are involved in determining the body sizes of the two sexes.

Curriculum Vitae

Since 2003 Part time: Assistant in various projects about “Alternative reproductive tactics in the shell brooding cichlid, Lamprologus callipterus” at the Ethological Station Hasli, Berne, Switzerland (Prof. Michael Taborsky)

Part time: Life in Southern Thailand to relax and find inner peace.
1999 – 2002 PostDoc project Zoology "Reversed sexual size dimorphism in the water spider, Argyroneta aquatica" at the Konrad Lorenz Institute for Comparative Ethology in Vienna, Austria (Prof. Michael Taborsky).
1998 – 1999 Assistant in the project "Vögel als Bioindikatoren der Oesterreichischen Kulturlandschaft" with Birdlife Austria, Vienna (Dr. Michael Dvorak).
1993 – 1998 PhD project Zoology about "Sexual size dimorphism in a shell brooding cichlid, Lamprologus callipterus" at the Konrad Lorenz Institute for Comparative Ethology in Vienna, Austria (Prof. Michael Taborsky).
1992 – 1993 MSc Project Zoology on "Verhaltensstrategien der Gesichtsfliege Musca autumnalis am Kuhauge" at the Max-Planck-Institute Seewiesen, Germany (Prof. Peter Hammerstein).
1986 – 1993 Biology at the Ludwig - Maximilian - University, Munich, Germany.


Schütz, D., Tschirren, L., Pachler, G., Grubbauer, P., Taborsky, M. (2017): Sperm-limited males save ejaculates for future matings when competing with superior rivals. Anim. Behav. 125: 3-12 [pdf]

Schuetz, D., Wirtz Ocana, S., Maan, M.E., Taborsky, M. (2016) Sexual selection promotes colonial breeding in shell-brooding cichlid fish. Animal Behaviour, 112: 153e161. [pdf].

Schütz, D., Heg-Bachar, Z. Taborsky, M. and Heg, D. (2012) Spawning coordination of mates in a shell brooding cichlid. International Journal of Evolutionary Biology, 2012: 1-10 doi: 10.1155/2012/517849

Schütz, D. and Taborsky, M. (2011) Sexual selection in the water spider: Female choice and male-male competition. Ethology, 117: 1101-1110.

Schütz, D., Taborsky, M., Pachler, G., Ripmeester, E. & Goffinet, O. (2010) Reproductive investment of giants and dwarfs: Specialized tactics in a cichlid fish with alternative male morphs. Funct. Ecol. 24: 131-140 doi: 10.1111/j.1365-2435.2009.01605.x.

Schütz, D., Taborsky, M., Drapela, T. (2007) Air bells of water spiders are an extended phenotype modified in response to gas composition. J. Exp. Zool. 307: 549-555.

Schütz, D., Parker, G. A. P., Taborsky, M., Sato, T. (2006) An Optimality approach to male and female body sizes in an extremely size dimorphic cichlid fish. Evol. Ecol. Res. 8: 1393-1408.

Schütz, D. & Taborsky, M. (2005) Mate choice and sexual conflict in the size dimorphic water spider, Argyroneta aquatica (Araneae: Argyronetidae). J. Arachnol. 33: 767-775.

Schütz, D. & Taborsky, M. (2005) The influence of sexual selection and ecological constraints on an extreme sexual size dimorphism in a cichlid. Anim. Behav. 70: 539-549.

Schütz, D. & Taborsky, M. (2003) Adaptations to an aquatic life may be responsible for the reversed sexual size dimorphism in the water spider, Argyroneta aquatica. Evol. Ecol. Res. 5: 105-117.

Schütz, D. & Taborsky, M. (2000) Giant males or dwarf females: what determines the extreme sexual size dimorphism in Lamprologus callipterus? J. Fish Biol. 57: 1254-1265.

Personal Information - the other world

Working in science only part of the year, I spend the rest of my life in Southern Thailand, in the jungle of Khao Sok National park and in a Buddhist monastery on Koh Samui Island

Visitors welcome!

In Khao Sok, I have a little house together with a Thai family, a dog, five cats, and a wonderful garden, for which I take care about nine months per year. Apart from enjoying the tropical climate, the beautiful nature, the lovely people, and the good food there, I love to life for the moment and sometimes just do nothing or sit together with friends.

Poh, Khun Siriwan, Dara

Every month, I take part and help in organising a 6-day silent meditation retreat in a Buddhist meditation centre called Dipabhavan on Ko samui Island (www.dipabhavan.org). There I want to find out more about myself, how to get rid of unwanted thoughts and feelings, and how to live a happy live without any worries.