Quantitative description and comparison of the advertisement calls of two species of probreviceps (Anura: Brevicipitidae) from the Uluguru South Mountains, Tanzania

The brevicipitid frog genus Probreviceps is confined to the montane and submontane forests of the Eastern Arc Mountains. In this article, quantitative description and the comparison of advertisement calls of Loveridge's forest frog Probreviceps loveridgei and the Uluguru forest frog P. uluguruensis from the Uluguru South Mountains in Tanzania are provided. The two species share the same habitat but occur at different altitudes. Description of the advertisement calls and analyses were carried out using CANARY 1.2 software. A thorough descriptive analysis of the advertisement calls of the two species is provided, including numerical information about the spectral and temporal features of the calls and species' calling behaviour. A characteristic audiospectogram and oscillogram are presented for each species. Spearman rank correlation analysis was used to identify the temperature-dependent acoustic variables, and the temperature effect on these variables was quantified using linear regression models. The two species exhibited variations in both spectral and temporal structure of the call. Interspecific variations were observed in the dominant frequency, call duration, call rate, pulse rate, note rate and number of notes per call. The advertisement calls emitted by P. loveridgei are higher pitched than those emitted by P. uluguruensis. In both species, dominant frequency and call rate increased significantly with ambient temperature, whereas the call duration decreased (non-significantly) with ambient temperature. Audiospectogram correlation and discriminant analysis showed distinctiveness in the quantitative characteristics of each species' call. Dominant frequency, call duration and call rate were strong discriminating parameters which mostly accounted for interspecific variation in the advertisement calls.