We have been the first to conduct an experimental study on an issue which has been around in the literature on cooperatively breeding animals for many years: Might predation risk explain why subordinate individuals ("helpers") delay dispersal and instead remain at home and assist the dominant group members raising offspring (so called "ecological constraints hypothesis")?

We have shown that experimentally altered predation risk increases the likelihood of helpers staying in their natal territory, and show that helpers benefit from staying because of increased survival, particularly in larger groups.

The number of experimental studies addressing the effects of ecological constraints on the propensity of helpers to disperse is very limited and ours is the first to experimentally test the effects of predation risk. I hope that due to our publications, scientists will realize how excellently the cooperatively breeding cichlids of Lake Tanganyika are for experimental studies, addressing for instance basic questions in behavioral, ecological , and evolutionary science, both in the field and in the laboratory.

The Great East African Lakes (Lake Tanganyika, Victoria, and Malawi) all contain unique endemic cichlid fish species schools and have been hotspots of biological research during the past decades. Lake Tanganyika stands out as having about 20 species of Lamprologine cichlids showing cooperative breeding.

In these species, subordinate, smaller group members assist a dominant breeding pair in raising offspring by engaging in, for instance, territory defense and brood care. This is an exceedingly rare phenomenon in fish, but occurs often in insects, mammals, and birds.

We have been conducting many experimental studies on the social systems of these cichlids. In this particular study, we erected large 2x2x2 meter underwater cages, encompassing the territories of two to three breeding groups of the cichlid Neolamprologus pulcher (dominants with subordinates).

In some cages, all predators were removed, and, in others, one medium or one large predator was added. These predators pose a severe threat to these cichlids and can catch and kill the subordinates. We show that subordinates rather stay in the natal group when predators were around and hide in the shelters provided by the group.

However, subordinates readily disperse and breed by themselves when predators were removed—supporting the so called "ecological constraints hypothesis." This shows that subordinates take account of the risk of leaving the natal territory, and this may explain why subordinates usually stay at home rather than disperse under natural circumstances when many predatory fish are around.

I have been conducting studies on the social behavior of birds and beetles before I joined the group of Professor Michael Taborsky in 2001. This meant a change from being a terrestrial biologist to an aquatic biologist, although my major research interest remained the same—ecological and evolutionary questions concerning behavior.

Doing ecological research while SCUBA diving is like training for a space shuttle flight for three years, three months-per-year, two dives-per-day of two to three hours each! It is interesting to see how things which are simple on land start to get pretty complicated, when you are 10 meters down, under water, and breathing through a regulator.

Using underwater cages of this size was not easy, but due to the excellent design by Rolf Eggler and the help of people from the Lake Tanganyika Diving Expeditions 2002 & 2003, the Tanganyika Lodge, and the Fisheries Department in Mpulungu, we were able to do this study.

I hope our research helps to protect the Lake Tanganyika cichlids for future generations, by increasing people’s awareness of this splendid Lake (see also "The Cichlid Fishes: Nature’s Grand. Experiment in Evolution" by George W. Barlow, Perseus Publishing, Cambridge, MA, 2000).

Luckily, no major ecological catastrophes have been detected (yet) in Lake Tanganyika, in contrast to Lake Victoria where the introduction of the Nile perch has exterminated many endemic cichlid species—see the excellent popular book Darwin’s Dreampond by Tijs Goldschmidt, MIT Press, Cambridge, Massachusetts, 1998.

I hope our research will support the continued funding of the Fisheries Department in Mpulungu (Dr. Harris Phiri and his co-workers, Ministry of Agriculture and Co-operatives of Zambia) to continue their monitoring of the hydrological, limnological, and ecological state of the Lake, to detect changes and take action when needed, and also as soon as necessary.