Context :

Aims : We establish the mean metallicity from high-resolution spectroscopy for the recently found dwarf spheroidal galaxy Boötes I and test whether it is a common feature for ultra-faint dwarf spheroidal galaxies to show signs of inhomogeneous chemical evolution ( e.g .
as found in the Hercules dwarf spheroidal galaxy ) .

Methods : We analyse high-resolution , moderate signal-to-noise spectra for seven red giant stars in the Boötes I dSph galaxy using standard abundance analysis techniques .
In particular , we assume local thermodynamic equilibrium and employ spherical model atmospheres and codes that take the sphericity of the star into account when calculating the elemental abundances .

Results : We confirm previous determinations of the mean metallicity of the Boötes I dwarf spheroidal galaxy to be –2.3 dex .
Whilst five stars are clustered around this metallicity , one is significantly more metal-poor , at –2.9 dex , and one is more metal-rich at , –1.9 dex .
Additionally , we find that one of the stars , Boo-127 , shows an atypically high [ Mg/Ca ] ratio , indicative of stochastic enrichment processes within the dSph galaxy .
Similar results have previously only been found in the Hercules and Draco dSph galaxies and appear , so far , to be unique to this type of galaxy .

Conclusions :