Vistfræðilegir og félagslegir drifkraftar í hljóðrænum samskiptum háhyrninga (Orcinus orca) - verkefni lokið

Fréttatilkynning verkefnisstjóra

3.7.2024

Rannsóknir á háhyrningastofnum Norður-Kyrrahafs sýna að sérhæfing þeirra í fæðuvali hefur mótað félagsmynstur og hljóðmynd þeirra þegar horft er til þeirra sem éta fisk samanborið við þá sem éta sjávarspendýr. Stofninn sem fyrirfinnst í Norður-Atlantshafi er ólíkur þar sem háhyrningar hafa fjölbreytt fæðuval og frekara samneyti og samskipti milli hópa. Þessi áhugaverði munur milli stofna sömu tegundar er einstakur og kallar á sérstaka rannsókn og samanburð á þessum tveimur kerfum og hvernig vistgerðir og félagsmunstur mótar mismunandi hljóðheim rándýrs sem er efst í fæðukeðjunni. Til þess að geta rannsakað hljóðheim háhyrninga þarf að vera til flokkunarkerfi yfir öll mismunandi hljóð sem þeir gefa frá sér og útskýringar á því hvenær og af hverju þessi hljóð eru gefin frá sér í líffræðilegum skilningi.
Í þessari rannsókn var fyrirliggjandi flokkunarkerfi bætt með því að auka nákvæmni í flokkun með því að innlima alla þætti hljóðsins. Þetta nýja og bætta flokkunarforrit eykur styrk, samanburðarhæfni og skilvirkni samanborið við að flokka hljóð á mannlegan hátt sem er frekar viðeigandi í rannsókn með minni sérhæfni, svo sem samanburður mismunandi tegunda. Dreifing og þéttleiki fæðuhópa spilar stóran þátt í mótun átthagatryggðar og færslumunstri sjávarrándýra. Í þessari rannsókn var útbreiðsla háhyrninga um Ísland skoðuð til þess að sýna fram á átthagatryggð og samtengingu milli svæða með mismunandi fæðuöflunaraðferð. Niðurstöðurnar
sýna hversu flókið þetta kerfi er með tilliti til viðveru háhyrninga og samtengingar þeirra við
mismunandi svæði við Ísland. Það bendir til svæðisbundins munar sem vert er að rannsaka frekar
ef horft er til verndunar ákveðinna svæða og stofna. Að auki er fæðuöflun þekkt fyrir að hafa áhrif á hljóðaval og samskipti háhyrninga og markmið þessarar rannsóknar er að skilja hvernig fæðuval hefur áhrif á hljóðferli íslenskra háhyrningastofna. Fyrir þessa rannsókn var lítið vitað um
mismunandi „mállýskur“ eða hljóðmyndun íslenskra háhyrningahópa, fjölþátta samfélagsgerð án
skýrra skila í fæðuvali. Fyrstu niðurstöður benda til þess að íslenskir háhyrningahópar eigi sérstök
samskipti (köll) innbyrðis, líkt og aðrir stofnar annarsstaðar í heiminum. Í þessari rannsókn erum
við að skoða breytingar í myndun hljóðs neðansjávar með samanburði á fæðu og fæðuframboði til
hliðsjónar. Niðurstöður munu auka þekkingu og skilning okkar á því hvaða þættir stýra atferli
háhyrninga með tilliti til hljóða og fæðuöflunar og mikilvægi hljóðs og heyrnar í því að lifa hjá tegund sem þessari sem trónir á toppi hinnar flóknu fæðukeðju hafsins. Þá mun þetta sömuleiðis auka þekkingu á hljóðfræðilegu atferli háhyrningsins í öllu Norður-Atlantshafi og hvernig atferli og
samskiptum við aðra hópa og stofna er háttað.

English:
The aim of this PhD project is to investigate the interplay between ecological specialization, sociality and communication in a marine top predator, the killer whale (Orcinus orca). In the best-studied populations from the North Pacific, strict diet specializations have heavily shaped the respective social organization and vocal behavior of fish vs. mammal eating ecotypes. In contrast, North Atlantic killer whales have diverse foraging strategies and fluid social structure. Therefore, they pose an interesting case study to investigate how sociality and ecology shape different patterns of acoustic communication in this apex predator. In order to study acoustic signals properly, accurate categorization of animal sounds into biologically meaningful categories is of great importance. In this study, the categorization performance of a neural network was greatly improved by including all the components of a sound. The improved categorization program provides a more powerful, replicable and time efficient alternative to human categorization that is relevant to broad studies of animal communication. Prey distribution and abundance play a major role in driving site fidelity and movement patterns of marine predators. In this study, the distribution of killer whales around Iceland was investigated to determine site fidelity and connectivity between areas displaying different foraging strategies. Results elucidate the complexities of killer whale occurrence and connectivity in Iceland and suggest regional differences indicating population structure that should be further investigated for appropriate regional conservation assessments. In addition, foraging strategies are also known to impact their acoustic communication and this study aims to understand how diversity in diet affect the vocal behavior of the Icelandic killer whale population. Before this study little was known about the existence of group-specificity of the acoustic repertoires of Icelandic killer whales, a multilevel society without clear hierarchical tiers. Preliminary results suggest group specific call production by Icelandic killer whales, as described for other regions around the world. In addition, this study is investigating changes in sound production with underwater behavioral context and prey availability. Results will advance and broaden scientific understanding of the dynamics driving vocal behavior in an apex predator that heavily relies on acoustic communication for survival. It will deepen our knowledge of the acoustic behavior of the North Atlantic killer whale, and consequently improve our understanding of behavioral and social connectivity to other
populations.

Information on how the results will be applied:
The neural network categorization program developed in this study is relevant to broad studies of
animal communication and will be shared online in an open-source repository. It also markedly
improves classifications of killer whale calls to type, which can be particularly difficult in cases where calls vary gradually, as seen in some call types recorded in Iceland. Moreover, it will facilitate
comparative research of killer whale vocalizations around the oceans, by providing a replicable
method to compare different populations, also applicable to other species. The results of the geographical movements, site fidelity and connectivity of killer whales in Iceland show that depending on the region, individuals display different site fidelity, as well as a mosaic of movement patterns, suggesting population structure. This study highlighted the need of dedicated research in regions outside herring grounds. This is the case, for example, for East and Northeast Iceland, areas to which the Norwegian spring spawning (NSS) herring has made a return in recent years, which may indicate that connectivity with the Norwegian killer whale community is already or
will be established soon. Therefore, increased survey effort in areas outside herring grounds is
undeniably needed in the near future to fully understand the connectivity and potential structure of the Icelandic and the wider North Atlantic killer whale community. Moreover, this study also
highlighted the importance of the herring grounds for Icelandic killer whales. However, long-term
patterns of occurrence show these are not stable and may vary on a multi-year basis. This is likely
related to other changes in the ecosystem, such as prey availability, which should be monitored in
the future. Collecting information on prey availability and combining it with observations of feeding events will, in the future, allow for an assessment of the ecological determinants of killer whale site fidelity patterns. Finally, all of these would be of great importance for appropriate regional conservation assessments. Finally, studying the influence of sociality on group-specificity of acoustic repertoires and the influence of behavior and ecology on killer whale sounds production will allow us to understand how divergences in society and ecology have shaped the acoustic behavior of Icelandic killer whales. This will increase our knowledge of the acoustic behavior of the North Atlantic killer whale, but also of the factors influencing vocal behavior dynamics. This is of great importance for a species that heavily relies on acoustic communication for its survival.

A list of the project’s outputs:
As outlined below, the main outputs of the project to date were related to the work conducted in
WP1. Outputs related to WP 2-4 will be coming out during the year 2024 and are listed below.
Outputs to date:
- Publication
o Marchon TMJ, Rasmussen MH, Basran CJ, Whittaker M, Bertulli CG, Harlow C, Lott R,
Boisseau O, Gendron F, Guo L, Hudson T, Jónsson H, Kershaw A, Kinni J, Lionnt LAMG,
Louis M, Messina M, Michel H, Neubarth BK, Ovide BG, Podt AE, Rempel JN, Ryan C,
Savage E, Scott J, Smit R, Verdaat H, Vignisson SR, Samarra FIP (2023) Geographical
movements, site fidelity and connectivity of killer whales within and outside herring
grounds in Icelandic coastal waters. Marine Biology 171, 30.
https://doi.org/10.1007/s00227-023-04345-7

- Conference presentations
o Friday Seminar, University of Iceland
[ Reykjavík, 19/01/2023 ] Oral presentation: Ecological and social drivers of acoustic communication in killer whales (Orcinus orca)

o Animal Behaviour Live Conference – ABL2023 [ Online, 16/11/2023 – 17/11/2023 ]
Oral presentation: Geographical movements, site fidelity and connectivity of killer whales (Orcinus orca) within and outside herring (Clupea harengus) grounds in Icelandic coastal waters.

o 24th Biennial Conference on the Biology of Marine Mammals [ Palm Beach, Florida, 01/08/2022 – 05/08/2022 ] Poster presentation: Geographical movements, site fidelity and connectivity of killer
whales (Orcinus orca) within and outside herring (Clupea harengus) grounds in Icelandic coastal waters.

o 33rd Conference of the European Cetacean Society [ Ashod, Israel, 05/04/2022 – 07/04/2022 ]
Oral presentation: Geographical movements, site fidelity and connectivity of killer whales (Orcinus orca) within and outside herring (Clupea harengus) grounds in Icelandic coastal waters.

- The scientific Publication was shared with whale-watching companies around Iceland
so that they can teach citizens about the latest news of killer whales in their area and any
connectivity with other areas of Iceland.

- Blog post on the Icelandic Orca Project:
o https://www.icelandic-orcas.com/post/unravelling-the-site-fidelity-and-movementsof-killer-whales-around-icelandIRF Final report Page 9 of 9
- Facebook/Instagram posts on the Icelandic Orca Project:
o https://www.facebook.com/photo?fbid=861209252672228&set=a.46323949246920
8 / https://www.instagram.com/p/C04ZxHOorR-/
o https://www.facebook.com/photo?fbid=864153025711184&set=a.46323949246920
8 / https://www.instagram.com/p/C1Cs9YNsEyl/
o https://www.facebook.com/photo/?fbid=498279545631869&set=a.4632394858025
42 / https://www.instagram.com/p/ChhAg5ZKu7N/
o https://www.facebook.com/icelandic.orcas/posts/pfbid02iu1NUN8zEwvnbmCDN3y
DFpHBYr9KVVnrztZhx8vt9gQmGC4cAhJ3kPaHpPvfmp5Jl /
https://www.instagram.com/p/CGR0xr8BXaC/
o https://www.facebook.com/icelandic.orcas/photos/a.528036140658116/438017800
2110558/ / https://www.instagram.com/p/CW2i6fdKEOr/
o https://www.facebook.com/icelandic.orcas/photos/a.528036140658116/355092896
8368803/ / https://www.instagram.com/p/CLe0V6RBN76/
o https://www.facebook.com/icelandic.orcas/photos/a.528036140658116/363454522
6673843/ /
https://www.facebook.com/icelandic.orcas/photos/a.528036140658116/363454522
6673843/

Future outputs:
- The photo-identification catalogue of Icelandic killer whales is in process to be updated, and
a report will be published.
- An online photo-identification catalogue is currently under construction by Icelandic Orca
Project.
- The categorization neural network, smARTwarp, will be available in open access on GitHub.
- 3 more scientific publications will result from WP2, WP3 and WP4 respectively.
- Conferences presentations of results from WP2, WP3 and WP4 are planned.
- PhD thesis will result from this project.

Heiti verkefnis: Vistfræðilegir og félagslegir drifkraftar í hljóðrænum samskiptum háhyrninga (Orcinus orca)/Ecological and social drivers of acoustic communication in killer whales (Orcinus orca)
Verkefnisstjóri: Tatiana Marie Joséphine Marchon, Háskóla Íslands
Tegund styrks: Doktorsnemastyrkur
Styrktímabil: 2021-2022
Fjárhæð styrks kr. 12.945.500
Tilvísunarnúmer Rannís: 217642