THE VOCAL BEHAVIOUR OF THE GREY SEAL (HALICHOERUS GRYPUS) Susanne McCulloch A Thesis Submitted for the Degree of PhD at the University of St Andrews 2000 Full metadata for this item is available in St Andrews Research Repository at: http://research-repository.st-andrews.ac.uk/ Please use this identifier to cite or link to this item: http://hdl.handle.net/10023/10994 This item is protected by original copyright The vocal behaviour of the grey seal (Halichoerus grypus) by Susanne McCulloch submitted in fulfilment of requirements for the degree of Doctor of Philosophy University of St. Andrews August 1999 r f "When angels fell, some fell on the land, some on the sea. The fonner are the faeries and the latter were often said to be the seals." Anonymous Orcadian Abstract This thesis is an observational and experimental study of the vocal behaviour in the grey seal (Halichoerus grypus). It provides the first comprehensive description of in-air and underwater vocalisations for the eastern Atlantic population of grey seals and compares it to the western Atlantic population. Two out of 6 in-air call types were very similar to underwater vocalisations and of the 10 eastern Atlantic underwater vocalisations 5 were comparable to the western Atlantic repertoire described earlier. Most calls were found to occur on their own, while some were preferentially associated in time with other call types. In addition, the number of particular types of underwater vocalisation did not display any diurnal variation, but did vary' across the breeding season. Experimental studies were also carried out on the role of pup vocalisations in mother-pup vocal recognition at two reproductively isolated colonies: the Isle of May, Scotland and Sable Island, Nova Scotia, Canada. Pup vocalisations were found to be both stereotyped and individually distinctive, features normally associated with a system of individual recognition. Allo-suckling was observed to be widespread on the Isle of May but was absent on Sable Island. Playback experiments revealed that mothers on the Isle of May did not respond more to vocalisations of their own pup than to those of non-filial pups. In contrast, on Sable Island, mothers were able to discriminate between their own and other pup calls. This suggests that different selective pressures may be affecting the two colonies, and possible reasons are discussed. Declarations (i) I, Susanne McCulloch, hereby certify that this thesis, which is approximately 41 000 words in length, has been written by me, that it is the record of work carried out by me and that it has not been submitted in any previous application for a higher degree. Date ....................... Signature of candidate ....................... (ii) I was admitted as a research student in October 1996 and as a candidate for the degree of PhD in October 1997; the higher study for which this record was carried out in the University of St. Andrews between 1996 and 1999. Date ....................... Signature of candidate ....................... (iii) I hereby certify that the candidate has fulfilled the conditions of the Resolution and Regulations appropriate for the degree of PhD in the University of St. Andrews and that the candidate is qualified to submit this thesis in application for that degree. Date ....................... Signature of supervisor.. ..................... In submitting this thesis to the University of St. Andrews I understand that I am giving permission for it to be made available for use in accordance with the regulations of the University Library for the time being in force, subject to any copyright vested in the work not being affected thereby. I also understand that the title and abstract will be published, and that a copy of the work may be made and supplied to any bOlla fide library or research worker. Date ....................... Signature of candidate ....................... CONTENTS Abstract Declarations Acknowledgements..................................................... 1 Chapter 1: General Introduction...................................... 4 SENSORY MODALITIES AND SIGNAL DESIGN................................................ 5 Chemical signals................. ............................................... ................... ........ 6 Visual signals............................................................................................... 7 Tactile signals............................................................................................... 7 Acoustic signals............................................................................................ 8 SOUND TRANSMISSION IN W ATER ..... ,........................................................... 9 SIGNAL INFORMATION................................................................................... 10 Group membership recognition......................................................................... 10 Parent-infant interaction.................................................................................... 11 Territory defence............................................................................................. 12 GREY SEAL ECOLOGY: OVERVIEW.................................................................. 13 Classification................................................................................................. 13 Distribution................................................................................................... 13 Dispersal....................................................................................................... 15 Breeding ........................................................ ,............................................... 17 !.1ortality....................................................................................................... 19 GREY SEAL AUDITORY SySTEM ...................................................................... 20 GEOGRAPillCAL VARIATIONS IN REPERTOIRE................................................ 24 INDIVIDUAL VOCAL RECOGNITION IN PINNIPEDS........................................... 29 AIMS OF TillS THESIS...................................................................................... 36 Chapter 2: In-air and underwater vocal repertoire of grey seals.... 40 ABSTRACT....................................................................................................... 40 INTRODUCTION................................................................................................ 41 METHODS ......................................................................................................... 44 Study animals, sites and data collection............................................... ................ 44 Sound analysis................................................................................................ 52 Ill-air repertoire................................................................................................ 52 Underwater repertoire........................................................................................ 52 Statistical analysis........................................................................................... 53 RESULTS .......................................................................................................... 54 In-air repertoire................................................................................................ 54 Classlfication and description........................................... .................................. 54 Underwater repertoire........................................................................................ 57 Classification and description........................................... ............. ..................... 57 Frequency of occurrence of each call type............................................................. 62 A specific case: type call 1................................................................................ 63 DISCUSSION..................................................................................................... 66 A specific case: type call 1................................................................................ 70 Chapter 3: Temporal variation in underwater vocalisations........ 73 ABSTRACT....................................................................................................... 73 INTRODUCTION................................................................................................ 74 METHODS ......................................................................................................... 76 Study sites and data collection...... ....... ....................................... ......... ......... ...... 76 Temporal variation........................................................................................... 79 Associations between call types.......................................................................... 79 RESULTS ........................................................................................................... 81 Temporal variation........................................................................................... 81 Behavioural observations................................................................................... 82 Associations between call types.......................................................................... 87 DISCUSSION..................................................................................................... 91 Chapter 4: Individually distinctive pup vocalisations