We report the detection of oscillations in slender Ca ii H fibrils ( SCFs ) from high-resolution observations acquired with the Sunrise balloon-borne solar observatory .
The SCFs show obvious oscillations in their intensity , but also their width .
The oscillatory behaviors are investigated at several positions along the axes of the SCFs .
A large majority of fibrils show signs of oscillations in intensity .
Their periods and phase speeds are analyzed using a wavelet analysis .
The width and intensity perturbations have overlapping distributions of the wave period .

The obtained distributions have median values of the period of 32 \pm 17 s and 36 \pm 25 s , respectively .
We find that the fluctuations of both parameters propagate in the SCFs with speeds of { 11 } ^ { +49 } _ { -11 } km/s and { 15 } ^ { +34 } _ { -15 } km/s , respectively .
Furthermore , the width and intensity oscillations have a strong tendency to be either in anti-phase , or , to a smaller extent , in phase .
This suggests that the oscillations of both parameters are caused by the same wave mode and that the waves are likely propagating .
Taking all the evidence together , the most likely wave mode to explain all measurements and criteria is the fast sausage mode .