  We present the search methods and initial results for transient radio signals
in the High Time Resolution Universe (HTRU) Survey. The HTRU survey's
single-pulse search, the software designed to perform the search, and a
determination of the HTRU survey's sensitivity to single pulses are described.
Initial processing of a small fraction of the survey has produced 11
discoveries, all of which are sparsely-emitting neutron stars, as well as
provided confirmation of two previously unconfirmed neutron stars. Most of the
newly discovered objects lie in regions surveyed previously, indicating both
the improved sensitivity of the HTRU survey observing system and the dynamic
nature of the radio sky. The cycles of active and null states in nulling
pulsars, rotating radio transients (RRATs), and long-term intermittent pulsars
are explored in the context of determining the relationship between these
populations, and of the sensitivity of a search to the various
radio-intermittent neutron star populations. This analysis supports the case
that many RRATs are in fact high-null-fraction pulsars (i. e. with null
fraction >~0.95), and indicates that intermittent pulsars appear distinct from
nulling pulsars in their activity cycle timescales. We find that in the
measured population, there is a deficit of pulsars with typical emission
timescales greater than ~300 s that is not readily explained by selection
effects. The HTRU low-latitude survey will be capable of addressing whether
this deficit is physical. We predict that the HTRU survey will explore pulsars
with a broad range of nulling fractions (up to and beyond 0.999), and at its
completion is likely to increase the currently known RRATs by a factor of more
than two.
