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Type A

Used aggressively while individual bats are in dispute with each other within the roost (Middleton et al., 2020).
Recorded in the vicinity of a roost. Examples: 911706, 928994, 913247, 913241 

Type B

Variant 1: an agonistic call. Often a longer sequence of FM components. Examples: 917428, 910880
Variant 2: roosting sounds. Components often clustered in small groups, but can be in long sequences too. Examples: 917062, 917123, 918331, 915538, 913297, 911024

Type C

Type C social calls can be classified in subgroups according to their function (Middleton et al., 2020; adapted from Pfalzer and Kusch, 2003).

Type C.d: used as advertisement, agonistic or in chase.
High frequency FM calls. Examples: 910880, 911803, 911804, 916805 

Type C.t or type C.c: used for tandem flight (C.t) or for co-ordination and group cohesion in connection to foraging or roosting activities (C.c). Often recorded in the vicinity of swarming bats.
These calls can vary in shape and frequency. The calls can be FM sweeps with or without a qCF ending and with or without harmonics. The end frequency can be around 40 kHz, 30 kHz or 20 kHz. Examples: 911738, 911804, 910936, 913612, 915766, 915120, 915131, 916039, 917078, 920840

Type C.i: used in mother/infant communication and interaction within the roost.
Variant 1: These calls can vary in shape and frequency. Examples: 913224, 914877
Variant 2: a low frequency qCF call. Examples: 913233, 913235, 911368, 913236, 913218, 913072, 917416 

Modified echolocation: an FM sweep with a hook at the start of the call, giving it a resemblance to the shape of a walking stick. Examples: 915128, 917142 

Type D

The most general type D social call of the common pipistrelle will be categorized as type D1. More rarely, I came across other complex calls that show similarity to slow trills. I will categorize these calls as type D2. All of the type D2 social calls have been recorded in the vicinity of maternity roosts.

Type D1: variable in the number of components. Examples*: 935325 (one-c.), 935114 + 917140 (two-c.), 911806 + 934344 (three-c.), 932495 (four-c.), 934344 + 911329 (five-c.), 933072 (six-c.), 925302 (seven-c.), 926374 + 913612 (eight-c.). Sometimes the first components are joined. Examples: 932935, 933072

* c. = component version

Type D2: an upward opening parabola followed by a downward opening parabola. Recorded in the vicinity of a maternity roost. Examples: 913231, 914876, 914875, 914874

Sequences

Foraging bats can emit a type D1 social call followed by a type C.d social call.

Initially, the Type D call is used to claim a resource and to warn conspecifics about this claim. When ignored, the high frequency call is used as a warning that further ignoring might lead to an escalation (Götze et al., 2020; Middleton et al., 2020). Example: 913914 

All images on this page are licensed under the following Creative Commons Attribution-NonCommercial-NoDerivs 4.0 license and in courtesy of Sarah Mahie. 

Literature list:

- G. Pfalzer & J. Kusch (2003). Structure and variability of bat social calls: implications for specificity and individual recognition. Journal of Zoology, London. 261: 21–33. https://doi.org/10.1017/S0952836903003935

- Neil Middleton, Andrew Froud and Keith French (2022). Social Calls of the Bats of Britain and Ireland (second edition). Pelagic Publishing.

- Simone Götze, Annette Denzinger and Hans-Ulrich Schnitzler (2020). High frequency social calls indicate food source defense in foraging Common pipistrelle bats. Scientific Reports. 10(5764).