Many territorial animals interact less aggressively with neighbours than with strangers, a phenomenon known as the ‘dear enemy’ effect, although some species show the opposite behaviour. Rock hyraxes, Procavia capensis, are social mammals that communicate via a rich acoustic repertoire. Male hyraxes produce elaborate advertisement calls (i.e. songs) both spontaneously and in response to occasional attention-grabbing events (e.g. pup screams, agonistic interaction), as well as to conspecific male songs. When replying to conspecific songs, male hyraxes tend to respond more to familiar males than to strangers, reflecting the ‘nasty neighbour’ effect. Our study relates to the general question of why some species respond aggressively towards neighbours, while others are more aggressive towards strangers. We hypothesized that male hyraxes eventually familiarize themselves with a stranger, subsequently perceiving its intentions as highly threatening and deserving of a vocal response. To simulate the presence of a stranger in the area we exposed wild hyrax groups to playbacks of natural songs of unfamiliar hyraxes. Male rock hyraxes became more likely to reply to a stranger's song over time, but this was independent of the number of times they heard the song. This suggests that either (1) the threat presented by a stranger increases when it is no longer perceived as transient or (2) because listeners do not physically encounter the stranger, they perceive replying aggressively as a low-risk response. Our work implies that species may demonstrate a range of condition-dependent behaviours instead of a dichotomy between the ‘nasty neighbour’ and ‘dear enemy’ strategies.
Bibliographical noteFunding Information:
We are grateful to the Ein Gedi Nature Reserve staff for their logistic support, to the Nature and Park Authority for permission to work in the Ein Gedi Nature Reserve and to the Ein Gedi Field School for their hospitality. We thank all project students, field assistants and guests for their valuable help in the field. We are obliged to N. Paz for her editorial services. This study was supported by four grants from the Israel Science Foundation ( 577/99 , 488/05 , 461/09 , 550/14 ). Appendix Table A1 Group ID, number of playback sets, the number of playbacks played using each set and the characteristics (i.e. age and residency status) of the strangers used for the playback Table A1 Group ID Series ID No. of playbacks Stranger age Stranger status A15 S1 7 6 Bachelor A15 S2 5 5 Resident A11 S5 3 Not known Not known A11 S6 3 4 Bachelor A11 S7 3 4 Bachelor A11 S8 4 Not known Not known D11 S15 7 4 Bachelor D11 S19 6 Not known Not known D13 S11 3 5 Bachelor D15 S9 4 6 Resident HC15 S21 3 5 Bachelor K15 S22 7 4 Bachelor S15 S24 7 7 Resident S15 S25 4 2 Bachelor T15 S26 6 4 Bachelor T15 S27 7 4 Bachelor
© 2017 The Association for the Study of Animal Behaviour
- animal communication
- floating territory
- neighbour–stranger relationships
- social mammals