Vetrarhvalir á hjara veraldar: Ný sýn á aðferðum hnúfubaka (Megaptera noveangliae) til að auka hæfni sína í hratt hlýnandi vistkerfum heimskautasvæðanna - verkefni lokið

Fréttatilkynning verkefnisstjóra

10.8.2022

Tilgangur rannsóknarinnar var að rannsaka hvernig vetrardvöl á heimskautasvæði gæti eflt hæfni hnúfubaka við þær öru loftslagsbreytingar sem standa nú yfir á pólsvæðunum. Niðurstöður þessarar rannsóknar sýna að hnúfubaka af báðum kynjum og ólíkum aldurshópum er að finna við strendur landsins allan ársins hring þar sem þeir nýta sér fjölbreytta fæðu, líklega eftir aðgengi hverju sinni. Jafnframt benda niðurstöðurnar til þess að hnúfubakar frá norðlægari fæðustöðvum ái hér við land á suðurleið sinni. Gefur það til kynna að hvalirnir njóti góðs af íslenskum hafsvæðum á veturna og geti valið milli þess að fara í far þegar æxlunartíminn hefst eða dvelja lengur á fæðustöð til að eiga meiri líkur á að nærast en þá minni líkur á að æxlast. Þannig sveigjanleiki gæti gert tegundinni kleift að bregðast við breyttum aðstæðum í hafinu og þannig aukið viðkomu sína.

Niðurstöðurnar benda til þess að munur sé á viðveru karldýra og kvendýra við landið
sem og einhver munur á því á hvaða svæðum kynin nærast. Líkamsástand hvalanna og hvar á
lífsferlinum þeir eru stýra eflaust miklu um það. Einnig benda niðurstöðurnar til þess að atferli þeirra er verulega háð árstíð en félagslyndi hvalanna virðist aukast mikið á veturna þegar æxlunartíminn ætti að vera að ganga í garð en líkleg ástæða þess er aukin framleiðsla kynhormóna sem ýtir mögulega undir ýmiskonar þarfir til samskipta. Á veturna virðast þeir jafnframt þurfa að leggja meira á sig við fæðuleit heldur en á sumrin þegar fæðu er að jafnaði að finna í meiri þéttleika. Með áframhaldandi greiningu á gögnum verður skýrara ljósi varpað á líkamsástand, frjósemi, fæðuöflun og hegðun hnúfubaka á ólíkum árstíðum við Ísland til að auka skilning okkar á hæfni þessa stóra hvals í hratt hlýnandi vistkerfum sjávar.

English:

Humpback whales are large migrating baleen whales which have been assumed to primarily feed in high latitude regions from spring to autumn in the northern hemisphere while spending the breeding season in the tropics in the winter and/or spring where they hardly feed. Humpback whales were near depletion during the mid-20th century, but for the last two decades they have been recovering rapidly, particularly in Polar Regions the last few years. Now, they are frequently sighted in the winter as well. The fundamental aim of this study was to provide new information about the humpback whales wintering behaviour in Iceland to understand their trade-off strategy between feeding and breeding in a rapidly changing climate. The information collected in this study shows that humpback whales of both sexes and different age classes actively feed in Icelandic coastal waters throughout the year where they utilize different prey types. Thus, updating our prior knowledge on the annual feeding and migrating behaviour of this species. The results also indicate that Iceland may also serve as a feeding stopover for humpback whales migrating southwards from more northerly regions. Instead of routinely migrating every year the whales may choose to either stay on a suitable feeding ground throughout the winter or delay their migration until they have reached a suitable physical condition. The results indicate variation between the sexes in terms of the timing of their occurrence in Iceland and in their choice of feeding spots. Such variation may be driven by their life history at each time which usually varies between the sexes. This study has also shown that their social and feeding behaviour changes between the seasons with more sociality observed in the winter, but also greater foraging effort compared to the more nutritious months of summer where prey may be more abundant and readily available to them. Increased sociality in the winter may be explained by the onset of their breeding season where the levels of sex hormones heighten in adults and as a result divert their behaviour towards increased social interactions. The ongoing analysis of the data will further reveal the life history strategy of humpback whales in terms of optimization of trade-offs between growth, survival, and reproduction on a polar feeding ground. Consequently, providing an insight into how these animals might respond to their rapidly changing ecosystems and what ecological factors drive that response.

∙ Information on how the results will be applied
The results will contribute to an assessment of the humpback whale populations in the North
Atlantic. The photo-identification data provides further information for population assessment with information about the movement and habitat use of individuals and can be used in Mark-resight models. The body condition analysis will be important for a better assessment of the population health, including the levels of stress hormones. The level of the sex hormones in females will provide important information about their reproductive success. Reproductive success could indicate the female’s ability to accumulate the energy reserves necessary to maintain pregnancy and/or meet the energetic demands of lactation.
The isotope analysis provides information about the diversity in the interannual feeding strategies of humpback whales which demonstrates the feeding plasticity of the species. Such information is
important for the development of ecosystem modelling for Ecosystem-Based Fisheries Management (EBFM). The isotope values may also provide an opportunity to trace the large-scale movements of humpback whales using isoscapes.

The results will be used to improve the conservation measures to mitigate negative effects of
anthropogenic activities on the whales. Such as by identifying important habitats of humpback
whales in Iceland and when the whales might be more vulnerable for disturbance such as from boat traffic. Whale watching operators will be provided with the results and their interpretation to
provide them with even better knowledge about humpback whales in Iceland.

∙ A list of the project’s outputs
• Catalogue of all humpback whales identified via photographs (~400 individuals) including a resighting history from 2016-2020. The catalogue has been shared with the Icelandic humpback
whale photo-ID database (https://www.hafogvatn.is/en/research/whale-research/whale-photo-id)
• Skin samples from 87 humpback whales stored at the biobank curated by the Marine and
Freshwater Research Institute
• Skin and blubber samples from ~87 humpback whales stored at the PI’s biobank at the University
of Iceland
• Behavioural dataset of 3700 behavioural logs from humpback whales in all seasons
• Table including isotope values from 87 humpback whales from Iceland, spanning all seasons
• Table including hormonal profile of 114 humpback whales from Iceland and Norway
• Database with multiple information about each sampled whale, including location of sighting, sex, isotope values, hormonal values and behaviour during single or multiple sightings
• Swimming and diving profile from 3 different individuals tagged with digital archival tags for 16 –
26 hours each
• UAV footages of 25 different humpback whales used to assess size, body condition and behaviour
• Underwater footage and sound from one whale recorded by a CatCam tag which was attached to
the whale for 26 hours.
• Genetic information on the 87 whales sampled during this study will soon be shared into a genetic database
• Social media pages on Facebook, Instagram and Twitter
• Fieldwork training of 7 M.Sc. students from four different countries
• Educational material used in two TV science series i.e., Europe from above by National Geographic and Nýjasta tækni og vísindi by RÚV

Heiti verkefnis: Vetrarhvalir á hjara veraldar: Ný sýn á aðferðum hnúfubaka (Megaptera noveangliae) til að auka hæfni sína í hratt hlýnandi vistkerfum heimskautasvæðanna / The Polar Winter Whales: The life history strategy of humpback whales (Megaptera novaeangliae) in the rapidly changing climate of the Polar Regions
Verkefnisstjóri: Edda Elísabet Magnúsdóttir, Háskóla Íslands
Tegund styrks: Nýdoktorsstyrkur
Styrktímabil: 2019-2021
Fjárhæð styrks: 28,744 millj. kr. alls
Tilvísunarnúmer Rannís: 195971