  Pulsar glitches, i.e. the sudden spin-ups of pulsars, have been detected for
most pulsars that we known. The mechanism giving rise to this kind of
phenomenon is uncertain, although a large data set has been built. In the
framework of star-quake model, based on~\cite{Baym1971}, the glitch-sizes (the
relative increases of spin-frequencies during glitches) $\Delta \Omega/\Omega$
depend on the released energies during glitches, with less released energies
corresponding to smaller glitch sizes. On the other hand, as one of dark matter
candidates, our Galaxy might be filled with the so called strange nuggets (SNs)
which are the relics from the early Universe. In this case the collisions
between pulsars and SNs is inevitable, and these collisions would lead to
glitches when enough elastic energy has been accumulated during the spin-down
process. The SNs-triggered glitches could release less energy, because the
accumulated elastic energy would be less than that in the scenario of glitches
without SNs. Therefore, if a pulsar is hit frequently by SNs, it would tend to
have more small size glitches, whose values of $\Delta \Omega/\Omega$ are
smaller than that in standard star-quake model (with larger amounts of released
energy). Based on the assumption that in our Galaxy the distribution of SNs is
similar to that of dark matter, as well as on the glitch data in ATNF Pulsar
Catalogue and Jodrell Bank glitch table, we find that in our Galaxy the
incidences of small size glitches exhibit tendencies consistent with the
collision rates of pulsars and strange nuggets. Further test of this scenario
is expected by detecting more small glitches (e.g., by the Square Kilometre
Array).
