In order to compare between diet and guano **dataset**s, Principle Component Analysis (PCA) was undertaken using R function prcomp using default settings [32]. PCA plots comparing principle component 1 (PC1) and principle component 2 (PC2) for the diet **dataset** and the guano **dataset** were created using R and **data** was coloured by 1) species, 2) dietary guild and 3) size of bat. To assign dietary guilds, diets as determined from the literature (S2 Table, Fig 1) were sorted using complete-linkage clustering using the hclust package in R, to group diets by the average composition for each species. This allowed us to delimit the **data** into 7 dietary guilds (M. alcathoe was excluded from later analysis, so was not assigned to a guild. To assign size categories, the minimum and maximum weight for each bat species were gathered from the Bat Conservation Trust (http://www.bats.org.uk/pages/uk_bats.html#Resident) and plotted to visualise size groupings (please see S1 Fig).