  (abridged) The dynamical V-band mass-to-light ratios of ultra compact dwarf
galaxies (UCDs) are higher than predicted by simple stellar population models
with the canonical stellar initial mass function (IMF). One way to explain this
finding is a top-heavy IMF, so that the unseen mass is provided by additional
remnants of high-mass stars. A possible explanation for why the IMF in UCDs
could be top-heavy while this is not the case in less massive stellar systems
is that encounters between proto-stars and stars become probable in forming
massive systems. However, the required number of additional stellar remnants
proves to be rather high, which raises the question of how their progenitors
would affect the early evolution of a UCD. We have therefore calculated the
first 200 Myr of the evolution of the UCDs, using the particle-mesh code
Superbox. It is assumed that the stellar populations of UCDs were created in an
initial starburst, which implies heavy mass loss during the following
approximately 40 Myr due to primordial gas expulsion and supernova explosions.
We find at the end of the simulations for various initial conditions and
(tabulated) mass-loss histories objects that roughly resemble UCDs. Thus, the
existence of UCDs does not contradict the notion that their stellar populations
formed rapidly and with a top-heavy IMF. We find tentative evidence that the
UCDs may have had densities as high as 10^8 M_sun/pc^3 at birth.
