Besides the common noctule, the Nathusius' pipistrelle is the most diverse in its social calls of the bats from the Netherlands. The species can create complex songs with a variety in different type D social call motifs, regardless of whether it is outside their mating season.

Click on the following buttons to see all relevant recordings of that specific year:

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. Example: 934342, 998883

Type B

Variant 1: an antagonistic call. Often a longer sequence of FM components. No example.
Variant 2: roosting sounds. Components often clustered in small groups, but can be in long sequences too. Examples: 934342, 911980, 911977

Type B2:

Type C

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

Type C.d: used as advertisement, agonistic or in chase.
Variant 1: a high frequency FM call. Example: 913335
Variant 2: a lower frequency FM call, on rare occasions supplemented by a warbled qCF component. Thought to be agonistic in nature, since they have been observed in areas where other species of bats were foraging: 911624, 911550, 916811, 912750, 917046, 917979, 934063 

Modified echolocation: a FM sweep with an ascending hook at the start of the call. Examples: 912056, 931846, 931847, 931845, 1006719, 1006732, 1008337

Type D

Different motifs have been described in the type D social calls of the Nathusius' pipistrelle and these motifs were named part A1, A2, B, C, D and E (Jahelková, 2011; Hargreaves et al., 2017; Russ and Racey, 2017; Middleton et al., 2020). However, I renamed part E as described by Jahelková to part D0, since this motif acts more like a pre-motif of part D than a stand-alone motif. Another motif consisting of FM sweeps, but actually used as a stand-alone motif, gained the name part E.

Part A can differ in the number of components. Part B and part C are variable in appearance and can differ between individuals. The most general sequence for the type D social call of the Nathusius' pipistrelle is the sequence part A(1), part B and part C, but the species is able to shuffle the different motifs to create new songs. The sequence and different combinations of parts can convey a more complex message to other bats (Middleton et al., 2020).

Part A0: additional components  starting higher in frequency before the main part A1 motif. Example: 1006731, 927475, 914575, 924994, 927477, 919195
Part A1: a multi-component motif and the 'main' motif of the general type D social call. Example: 917084, 911808, 911811 
Part A2: additional components going higher in frequency after the main part A1 motif. Example: 913412, 911808 
Part B: a single FM sweep. A type C social call on itself. Variable in use. Example: 913613, 914575, 911931 
Part C: a fast trill made of several 'v-shaped' syllables. Often used after a part B. Example: 914575, 911550 
Part D0: FM sweeps, often emitted after the part A-B-C sequence and before the main part D1 motif. Example: 936327, 930026, 935107, 936324, 936319 
Part D: multiple FM sweeps bending into a qCF ending. Example: 911808, 911810, 911692, 914884, 930316
Part E: a series of FM components. Possibly agonistic in nature. Example: 918721, 913335, 911811 

W-type calls (Jahelkova, 2011): a continuous social vocalization of calls in a long “wavy line” pattern with the peak frequency of 14–36 kHz, accompanied by standard or modified echolocation calls.". Example: 999877, 999879, 999881, 1006719
Wavy-line calls: calls in a "wavy line" pattern with the peak freqfrequency of 10-20 kHz, often accompanied by other motifs. Example: 911931, 1034179, 1036918, 918721
Trills: Some appear to joined-up part A motifs (example: 914575, 929731), some consis of small components arranged in a line that I call mordents (example: 929731, 917429, 920400), and some seem to be true trills often with harmonics clearly present (example: 911811, 913306).

Read more about how I categorized the unusual social calls of the Nathusius's pipistrelle in this blog post.

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

Bibliography:

- Daniel Hargreaves, Helena Jahelková, Oliver Lindecke and Guido Reiter (2017). Bat Species of the Year 2015: Nathusius’ pipistrelle (Pipistrellus nathusii). Facts compiled for BatLife Europe.

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

- Helena Jahelková (2011). Unusual social calls of Nathusius' pipistrelle (Vespertilionidae, Chiroptera) recorded outside the mating season. Institute of Vertebrate Biology, Czech Academy of Sciences. Folia Zoologica, 60(1): 25-30. https://doi.org/10.25225/fozo.v60.i1.a4.2011

- Jon Russ and Paul Racey (2007). Species-specificity and individual variation in the song of male Nathusius’ pipistrelles (Pipistrellus nathusii). Behavioral Ecology and Sociobiology, 61(5): 669-677. DOI:10.1007/s00265-006-0295-9

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