Body slap: An innovative aggressive display by breeding male gray seals (Halichoerus grypus)

Abstract

Aggression in male gray seals has been extensively studied; however it is often simplistically assumed that threat signals are mainly cephalic in nature for this species. We report on an undescribed and apparently new kind of threat signal used by male gray seals we term a Body Slap. The behavior has been observed at breeding sites in eastern England since 1993 but has not been studied ethologically or reported elsewhere. The aims of this study were to describe the behavior, test the influence of topographic variation on its frequency of occurrence, examine if it is used to signal dominance or submission, and to place it in intra‐ and interspecific contexts. Our results show Body Slaps were performed in 66.3% of interactions and by 57.2% of males; it was not performed by females. The Body Slap was positively associated with the Approach and Open‐Mouth Threat behaviors but was not related to dominance; nevertheless, display rates were greater for subsequent winners. These findings suggest that the Body Slap carries information about male resource holding potential and does not signal submission. This study furthers our understanding of geographic variants of male threat behaviors and of pinniped nonvocal communication.

Good vibrations by the beach boys: magnitude of substrate vibrations is a reliable indicator of male grey seal size

“…We recorded events for 39 individual 277 males (within-male sample sizes ranging from 1-255 events, median for males with >4 events = 22.5) for 278 a total of 470 observed events comprised of 990 individual slaps matched in the seismic trace. Similar to 279 findings of Bishop et al (2014), 9.45% of events consisted of a single slap, 61.5% consisted of 2 slaps, 280 and 28.9% consisted of >3 repetitions. Inter-repetition intervals were typically 1s apart and separately 281 distinguishable (Figure 2a).…”

“…Furthermore, while the frequency of the percussive display was broadband, 310 the maximum generated magnitudes of this display were reliable indicators of male size. Previously, the 311 rates of percussive displays of the BS were linked to success in agonistic interactions (Bishop et al, 2014) 312 and this study suggests that the magnitude of the BS contains information regarding RHP that could be 313 used by opponents in assessment. The results of this study also indicate that, while the breeding colonies 314 at which the BS has been observed are all open-access beach sites with variable surface water pooling due 315 to tidal and rain fluctuations, individuals' maximum and mean magnitudes were not significantly different 316 across wet or dry surface sand conditions.…”

“…Recently a geographically isolated addition to the repertoire was noted: the Body Slap (BS), which 82 is used during the breeding season in male-male conflict and male-female interactions at some beach 83 breeding colonies in the UK (Bishop et al, 2014). In the performance of the BS, males lie prone, push 84 serves to display lateral area; and vibrations can be felt through the substrate by observers (AB, SDT pers.…”

“…89 obs.) suggesting that the display likely serves as a multi-modal form of non-vocal communication (Miller, 90 1991 repetitions (Bishop et al, 2014). Events were labeled as being performed on 'wet' or 'dry' sand; wet sand 146 being any sand exposed to tidal inundation within the past 12 h or with visibly pooled water.…”

Variability in individual rates of aggression in wild gray seals: fine-scale analysis reveals importance of social and spatial stability

“…Male-male aggressive interactions (AIs) were defined as any agonistic interaction between two or 153 more males (Twiss 1991; Bishop et al 2014). Inter-male aggression is typically characterized by low-154 cost, noncontact displays, but some interactions escalate to fights (Boness 1984;Twiss 1991 Bishop et al 2014).…”