A. ABSTRACT 2 Passive acoustic monitoring is an efficient way to study acoustically active animals but species 3 identification remains a major challenge. C-PODs are popular logging devices that automatically 4 detect odontocete echolocation clicks. However, the accompanying analysis software does not 5 distinguish between delphinid species. Click train features logged by C-PODs were compared to 6 frequency spectra from adjacently deployed continuous recorders. A generalized additive model 7

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... then used to categorize C-POD click trains into three groups: broadband click trains, 8 produced by bottlenose dolphin (Tursiops truncatus) or common dolphin (Delphinus delphis), 9 frequency-banded click trains, produced by Risso's (Grampus griseus) or white beaked dolphins 10 (Lagenorhynchus albirostris), and unknown click trains. Incorrect categorization rates for 11 broadband and frequency banded clicks were 0.02 (SD 0.01), but only 30% of the click trains 12 met the categorization threshold. To increase the proportion of categorized click trains, model 13 predictions were pooled within acoustic encounters and a likelihood ratio threshold was used to 14 categorize encounters. This increased the proportion of the click trains meeting either the 15 broadband or frequency banded categorization threshold to 98%. Predicted species distribution at 16