IAP-24-060

Humpback whales sentinels of ocean health: population dynamics and drivers for occurrence in breeding locations off East Africa

This proposed project address’ SDG 14: Life Under Water to conserve and sustainably use marine environments and resources. Baleen whales, including the humpback whale (Megaptera novaeangliae), are sentinel species for ocean health and important for carbon capture and oxygen production to combat climate change. Humpback whales have global distribution and migrate between high latitude foraging areas and low latitude breeding areas (Dawbin 1966). Male humpback whales sing competitively in the breeding areas which allow for passive acoustic monitoring of whale spatial and temporal occurrence, and relative abundance (Payne & McVay 1971). Individual whales can be identified by photographing (photo-id) the whales’ flukes and dorsal fins which can be catalogued and analysed using capture-recapture methods to estimate abundance, residency patterns, social structure and reproductive success (Hammond 1986). In recent years, humpback whale photo-id catalogues have been significantly expanded through researcher and citizen science platforms facilitating automated image identification matching (Cheeseman et al. 2022; www.happywhale.com). Southern hemisphere humpback whales primarily forage on krill (Euphausia superba) in the Antarctic during December-May and return to breeding areas in June-November to birth to a single calf every 3-5 years (Clapham 2000). As capital breeders, they fast during the breeding period and their reproductive success rely on the preceding foraging, migration and conditions (including disturbance) in the breeding area (Owen et al 2024). However, recent research has shown that they also exploit schooling prey during their migration possibly in response to environmental change (Bury et al 2024). Coastal waters off East Africa (Mozambique, Tanzania and Zanzibar) provide important breeding, calving and nursery areas for humpback whales and opportunities for locally operated whale watching tourism (Minton et al 2011; Rosenbaum et al 2009). Unfortunately, whales off East Africa experience anthropogenic threats from unregulated boat-based whale watching and incidental (bycatch) in fisheries (Berggren 2009). The bycatch both cause whale mortalities and threaten fisher livelihoods when animals swim away with the fishing gear attached to their body (Johnson et al 2005). Humpback whales are important in low nutrient tropical ecosystems by creating nutrient circulation and mixing through cavitation and turbulence created through their large-bodied movement in shallow areas. Humpback whales also provide nutrients by urination and defecation and recent research has indicated a behavioural shift in East Africa where feeding have been documented (Kalashnikova et al In press). Understanding spatial and temporal (current and past) trends in humpback whale distribution, abundance and behaviour is crucial to mitigate threats from fisheries and vessel disturbance, and to predict climate change. Such changes can negatively affect the whales’ breeding success with potential negative impact on both individual and population levels, and on human activities relying on the presence of healthy whale populations and habitats. To date only initial research efforts have been conducted on humpback whales off East Africa and it is now crucial to address this by conducting a comprehensive and dedicated research project in the area.
Relevant research questions to be addressed:
– What are the temporal and spatial drivers of humpback whale occurrence off East Africa?
– How many whales use the area?
– Are there specific whales using the area within and between years?
– To what extent are the humpback whales threatened by human activities?
The overall aim for the project is to investigate population dynamics and drivers for humpback whale occurrence in breeding locations off East Africa. This will be addressed in four objectives:
1. Assess spatial and temporal trends in humpback whale occurrence and residency using photo-id and acoustics
2. Assess reproduction (breeding interval) and calf survival.
3. Assess interactions with anthropogenic activities (fisheries bycatch and disturbance from whale watching vessels).
4. Use the information from Objectives 1-3 to conduct evidence-based status assessment of humpback whales as sentinels for marine ecosystem health, for whale watching opportunities and to inform conservation and management strategies.

Two field seasons (July-October) will be conducted in 2026 and 2027 at four locations: Jangamo and Bazaruto in Mozambique and Mtwara and Zanzibar in Tanzania. Data will be collected using acoustic recorders (e.g. SoundTrap, https://www.oceaninstruments.co.nz), remote sensing of environmental parameters (https://marine.copernicus.eu/), shore- and boat-based surveys (data on whale-vessel interactions and photo-id). Acoustic and environmental data will be collected at all locations. Shore-based surveys will use a theodolite (Sokkia DT5 and www.mysticetus.com/ software) to track whales and vessels and record animal group size, composition and behaviour, and distance to and interaction with vessels. Dedicated boat-based surveys will be conducted by the student at one location (Bazaruto) to collect photo-id data. Project collaborators will provide additional data from Jangamo, Mozambique and Mtwara, Tanzania. In addition, citizen science marine mammal and fisheries WhatsApp reporting networks in Mozambique and Tanzania will be engaged to collect further data. All photo-id images will be uploaded to www.happywhale,com which will also be used for matching within and outside East Africa. Historical data are also available for use in this project including 14 environmental parameters from 2019-2024 and acoustic data from 2012 and 2022-2024 for Tanzania and Mozambique and photo-id data from Tanzania from 2008-2012 and 2018-2024.
Drivers for whale occurrence will be investigated using generalised additive models implemented in Programme R. Humpback whale song data (past and new) will be catalogued and analysed in ravensoundsoftware.com/software/raven-pro/ to investigate whale temporal and spatial occurrence. The photo-id data will be analysed using Capture-Recapture models in RMark (Laake 2013) to investigate whale abundance, residency and calf presence. Whale-tourism vessel interactions will be assessed using Markov-chain analyses implemented in R and data collected on whale entanglements will be used to assess occurrence and nature of the entanglements. Finally, collected data will be used for assessment and to facilitate capacity building e.g. for best practice guidelines for whale tourism and bycatch mitigation and disentanglement training (https://iwc.int/management-and-conservation/entanglement).

Year 1

– Comprehensive literature review and take relevant University modules.
– Software training including R-packages, Raven and Mysticetus.
– Design all data collection protocols.
– Submit first manuscript for publication (literature review).
– Conduct first field season July-October.

Year 2

– Analyse first field season and historical data.
– Prepare second manuscript: Environmental drivers for whale occurrence.
– Conduct second field season July-October.

Year 3

– Analyse field data and prepare third and fourth manuscripts addressing whale-human interactions.

Year 3.5

– Submit manuscripts to high-ranking peer-reviewed journals.
– Attend conference to present findings.
– Use results to conduct assessment and to facilitate capacity building.
– Thesis completion.

The prospective student should have experience in conducting cetacean focused fieldwork in a developing country. Experience in collecting photo-id and acoustic data necessary. Further experience in working with government agencies is desirable. Swahili language highly desirable. University modules and the supervisory team will provide the necessary methodology and software training. Additional training will be identified to meet the needs throughout the studentship.