NR Behaviour Calls

Northern Resident Killer Whale, Orcinus orca, Behaviour Calls

ABSTRACT

The Northern Resident community of killer whales (Orcinus orca) in British Columbia is known to swim close to shore and rub on pebbles at certain beaches.  The purpose of this study was to investigate discrete calls used by the Northern Residents during this unique behaviour.  Thirty Orcalab digital recordings from 2004 were analyzed through the Orchive.  Calls used while rubbing at Main Beach, Robson Bight Micheal-Bigg Ecological Reserve were compared to calls used at Cracroft Point, West Cracroft Island during foraging activity.  The N1 and N23 calls were used significantly more during beach-rubbing behaviour.  The N4 and N16 calls were used more while foraging.  Further research is required to increase samples from different years to conclude specific calls are used at higher rates during certain behaviours.

INTRODUCTION

Killer whales are known to live in long-term family groups.  There are three types of killer whales in British Columbia (Residents, Bigg’s / Transients, and Offshores).  Residents forage on salmon, Bigg’s are larger and hunt marine mammals, Offshores are a smaller ecotype specializing on sharks.  Morin et. al. (2010) recommended three known ecotypes of Orcinus orca be named separate species (Bigg’s, Antarctic Types B, and C) the remaining types be recognized as subspecies. Another new possible species has been discovered off New Zealand, Type D (Foote et. al. 2013).

There are two different communities of fish eating killer whales in British Columbia, Northern and Southern Residents.  They are genetically, morphologically, and acoustically distinct. Structure and use of calls suggests they serve as contact signals to maintain family cohesion (Ford 1991).  Dialects reflect family relatedness with call variation building over time (Deeke et. al. 2010).  Discrete calls contain abrupt shifts in pitch and wide-band energy content.  Variations in signal structure can reflect emotional state and reaffirm relationships (Ford 1989).  During close proximity and social behaviour there is an increase in production of irregular calls relative to foraging and traveling activities.  All calls are used during most killer whale activities (Ford 1989).  The N3 and N12 calls are emitted more frequently during socializing and beach-rubbing activities (Ford 1989).

This study compared average rate of Northern Resident calls used during beach-rubbing and foraging activities to determine if vocalizations may indicate behaviour.  Characterization of unique behaviours could assist sub-species definition of killer whale ecotypes.  This information is notable for killer whale classification and conservation plans.  This research increases awareness of the marine environment.

METHODS & MATERIALS

Northern Resident killer whale calls were analyzed through digital recordings on the Orchive database (Ness et. al. 2013, Orcalab 2013).  In 2004, I was in Johnstone Strait as a killer whale researcher on West Cracroft Island.  Orcalab log books and personal field notes were referenced for direction, location, and whale group identification.  Vocalizations were first annotated then aurally and visually identified.  Call classification was determined by comparing call types with acoustic catalogues (Ford 1987, Ness et. al. 2013) and through spectrogram analysis. Average call use per recording was compared between the Main Beach rubbing and Cracroft Point foraging sites.

RESULTS

A total of 983 discrete calls were identified (30 recordings, 2700 min).  Calls used at Main Beach and Cracroft Point included N1, N2, N3, N4, N5, N7, N9, N16, N23, N24, and N25 (Fig. 1). BR_calls
Figure1. Frequency of Northern Resident killer whale discrete calls used during rubbing-beach and foraging activities.

The null hypothesis (Ho) was there is no significance difference in calls used while beach-rubbing.  Average call rate of each type was compared between beach-rubbing and forging behaviour to determine any difference in vocalizations (Table I).

Table I. Results of statistical t-tests comparing call type frequency of use at the Main rubbing-beach (RB) and Cracroft Point (CP).

Call

RB (%)

CP (%)

t

p

Ho

N1

16.9

4.85

2.054

 

p < 0.025

 

Reject

N2

1.54

3.56

0.9035

p < 0.25

Accept

N3

0.305

5.94

1.005

P < 0.25

Accept

N4

14.3

27.4

1.421

 

p < 0.10

 

Accept

N5

5.80

5.93

0.02918

p > 0.25

Accept

N7

0.152

0.8007

0.6471

p < 0.25

Accept

N9

4.89

10.4

1.294

p < 0.25

Accept

N16

0.152

3.50

1.675

 

p < 0.10

 

Accept

N23

34.4

11.9

1.765

 

p < 0.05

 

Reject

N24

1.95

1.52

0.1573

p < 0.25

Accept

N25

3.93

7.71

0.6281

p > 0.25

Accept

The N1 call type was used significantly more on average at the rubbing beach versus while foraging (p < 0.05).  The I15s emitted the N23 call significantly more while beach rubbing activity than during forging behaviour (p < 0.05).  The N4 and N16 call types were used more while foraging with marginal insignificance (p < 0.10).  There was no significant difference found for the N2, N3, N5, N7, N9, N24, and N25 call types.

DISCUSSION

This study analyzed Northern Resident killer whale call use between beach-rubbing and foraging areas.  A significant difference was found for the N1 and N23 discrete calls being used more on average at Main Beach than at the Cracroft Point foraging site.  The N4 and N16 call types were used with a higher rate while foraging with marginal insignificance difference.  The information from this study increases knowledge of call types used during certain Northern Resident behaviours.  Further information from different years is needed to conclude a higher rate of specific calls may indicate beach-rubbing or foraging behaviour.

REFERENCES

Deecke, V. B., Barrett-Lennard, L. G., Spong, P., Ford, J. K. B.  (2010) The structure of stereotyped calls reflects kinship and social affiliation in resident killer whales (Orcinus orca) Naturwissenschaften. Vol. 97 (5), 513-518.

Foote, A. D., Morin, P. A., Pitman, R. L., Ávila-Arcos, M. C., Durban, J. W., van Helden, A., Sinding, M.S., Gilbert, M. T. P. (2013)  Mitogenomic insights into a recently described and rarely observed killer whale morphotype.  Polar Biology, in press.

Ford, J. K. B. (1987)  A Catalogue of Underwater Calls Produced by Killer Whales (Orcinus orca) in British Columbia.  Canadian Data Report of Fisheries and Aquatic Sciences. No. 633.

Ford, J. K. B. (1989)  Acoustic behaviour of resident killer whales (Orcinus orca) off Vancouver Island, British Columbia.  Canadian Journal of Zoology. 67:  727 – 745.

Ford, J. K. B. (1991) Vocal traditions among resident killer whales (Orcinus orca) in coastal waters of British Columbia. Canadian Journal of Zoology. 69:1454–1483.

Morin, P., Archer, F., Foote, A., Vilstrup, J., Allen, E., Wade, P., Durban, J., Parsons, K.,

Pitman, R., Li, L. (2010) Complete mitochondrial genome phylogeographic analysis of killer whales (Orcinus orca) indicates multiple species. Genome Research. 20: 908.

Ness, S., Symonds, H., Spong, P., and Tzanetakis, G. (2013) The Orchive: Data mining a massive bioacoustic archive. International Conference on Machine Learning 2013 Workshop on Machine Learning for Bioacoustics (WBIOAC).

Orcalab (2013) Spong, P., Symonds, H. http://www.orcalab.org