Between a Rock and a Hard Place: Habitat Selection in Female-Calf Humpback Whale (Megaptera novaeangliae) Pairs on the Hawaiian Breeding Grounds

The Au'au Channel between the islands of Maui and Lanai, Hawaii comprises critical breeding habitat for humpback whales (Megaptera novaeangliae) of the Central North Pacific stock. However, like many regions where marine mega-fauna gather, these waters are also the focus of a flourishing local eco-tourism and whale watching industry. Our aim was to establish current trends in habitat preference in female-calf humpback whale pairs within this region, focusing specifically on the busy, eastern portions of the channel. We used an equally-spaced zigzag transect survey design, compiled our results in a GIS model to identify spatial trends and calculated Neu's Indices to quantify levels of habitat use. Our study revealed that while mysticete female-calf pairs on breeding grounds typically favor shallow, inshore waters, female-calf pairs in the Au'au Channel avoided shallow waters (<20 m) and regions within 2 km of the shoreline. Preferred regions for female-calf pairs comprised water depths between 40–60 m, regions of rugged bottom topography and regions that lay between 4 and 6 km from a small boat harbor (Lahaina Harbor) that fell within the study area. In contrast to other humpback whale breeding grounds, there was only minimal evidence of typical patterns of stratification or segregation according to group composition. A review of habitat use by maternal females across Hawaiian waters indicates that maternal habitat choice varies between localities within the Hawaiian Islands, suggesting that maternal females alter their use of habitat according to locally varying pressures. This ability to respond to varying environments may be the key that allows wildlife species to persist in regions where human activity and critical habitat overlap

Satellite Tagging and Biopsy Sampling of Killer Whales at Subantarctic Marion Island: Effectiveness, Immediate Reactions and Long-Term Responses

Remote tissue biopsy sampling and satellite tagging are becoming widely used in large marine vertebrate studies because they allow the collection of a diverse suite of otherwise difficult-to-obtain data which are critical in understanding the ecology of these species and to their conservation and management. Researchers must carefully consider their methods not only from an animal welfare perspective, but also to ensure the scientific rigour and validity of their results. We report methods for shore-based, remote biopsy sampling and satellite tagging of killer whales Orcinus orca at Subantarctic Marion Island. The performance of these methods is critically assessed using 1) the attachment duration of low-impact minimally percutaneous satellite tags; 2) the immediate behavioural reactions of animals to biopsy sampling and satellite tagging; 3) the effect of researcher experience on biopsy sampling and satellite tagging; and 4) the mid- (1 month) and long- (24 month) term behavioural consequences. To study mid- and long-term behavioural changes we used multievent capture-recapture models that accommodate imperfect detection and individual heterogeneity. We made 72 biopsy sampling attempts (resulting in 32 tissue samples) and 37 satellite tagging attempts (deploying 19 tags). Biopsy sampling success rates were low (43%), but tagging rates were high with improved tag designs (86%). The improved tags remained attached for 26±14 days (mean ± SD). Individuals most often showed no reaction when attempts missed (66%) and a slight reaction-defined as a slight flinch, slight shake, short acceleration, or immediate dive-when hit (54%). Severe immediate reactions were never observed. Hit or miss and age-sex class were important predictors of the reaction, but the method (tag or biopsy) was unimportant. Multievent trap-dependence modelling revealed considerable variation in individual sighting patterns; however, there were no significant mid- or long-term changes following biopsy sampling or tagging

Mark–recapture of individually distinctive calls—a case study with signature whistles of bottlenose dolphins (Tursiops truncatus)

Robust abundance estimates of wild animal populations are needed to inform management policies and are often obtained through mark–recapture (MR) studies. Visual methods are commonly used, which limits data collection to daylight hours and good weather conditions. Passive acoustic monitoring offers an alternative, particularly if acoustic cues are naturally produced and individually distinctive. Here we investigate the potential of using individually distinctive signature whistles in a MR framework and evaluate different components of study design. We analyzed signature whistles of common bottlenose dolphins, Tursiops truncatus, using data collected from static acoustic monitoring devices deployed in Walvis Bay, Namibia. Signature whistle types (SWTs) were identified using a bout analysis approach (SIGnature IDentification [SIGID]—Janik et al. 2013). We investigated spatial variation in capture by comparing 21 synchronized recording days across four sites, and temporal variation from 125 recording days at one high-use site (Aphrodite Beach). Despite dolphin vocalizations (i.e., echolocation clicks) being detected at each site, SWTs were not detected at all sites and there was high variability in capture rates among sites where SWTs were detected (range 0–21 SWTs detected). At Aphrodite Beach, 53 SWTs were captured over 6 months and discovery curves showed an initial increase in newly detected SWTs, approaching asymptote during the fourth month. A Huggins closed capture model constructed from SWT capture histories at Aphrodite Beach estimated a population of 54–68 individuals from acoustic detection, which overlaps with the known population size (54–76 individuals—Elwen et al. 2019). This study demonstrates the potential power of using signature whistles as proxies for individual occurrence and in MR abundance estimation, but also highlights challenges in using this approach

The host-specific whale louse (Cyamus boopis) as a potential tool for interpreting humpback whale (Megaptera novaeangliae) migratory routes

The whale louse Cyamus boopis is a host-specific amphipod that parasitizes humpback whales (Megaptera novaeangliae) across the world. Humpback whales from the Southern Hemisphere are currently separated into seven breeding stocks, each with its own migration route to/from Antarctic waters. The aim of this study was to determine the population structure of C. boopis from the Southern Hemisphere using cytochrome oxydase I sequences, and compare it to that of its host species found in previous studies. High haplotype and nucleotide diversities in C. boopis were observed, and the populations from western south Atlantic (WSA: Brazil + Argentina − Breeding stock A) and western south Pacific (WSP: Australia - Breeding stock E) did not show any significant difference but were differentiated from populations of eastern south Atlantic (ESA: Namibia - Breeding stock B) and the north Pacific. The genetic homogeneity between WSA and WSP populations, might reveal a higher genetic transfer within the Southern Hemisphere, since the feeding grounds of whales which are distributed throughout the circumpolar Southern Ocean could allow inter-mixing of individuals from different breeding populations during the feeding season. The present data reinforces that population dynamics of humpback whales seem more complex than stable migration routes, which could have implications for both management of the species and cultural transmissions of behaviours.Fil: Iwasa Arai, Tammy. Universidade Federal do Rio de Janeiro; BrasilFil: Serejo, Cristiana S.. Universidade Federal do Rio de Janeiro; BrasilFil: Siciliano, Salvatore. Fundación Oswaldo Cruz; BrasilFil: Ott, Paulo H.. Universidade Federal do Rio Grande do Sul; BrasilFil: Freire, Andrea S.. Universidade Federal de Santa Catarina; BrasilFil: Elwen, Simon. Universiteit Van Pretoria; SudáfricaFil: Crespo, Enrique Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Colosio, Adriana C.. Instituto Baleia Jubarte; BrasilFil: Carvalho, Vitor L.. Associação de Pesquisa E Preservação de Ecossistemas Aquáticos; BrasilFil: Rodríguez Rey, Ghennie T.. Universidad de Caldas; Colombia. Universidade Federal do Rio de Janeiro; Brasi

Transit station or destination? Attendance patterns, movements and abundance estimate of humpback whales off west South Africa from photographic and genotypic matching

Humpback whales found off west South Africa (WSA) are known to display an atypical migration that may include temporary residency and feeding during spring and summer. At a regional scale there is uncertainty about how these whales relate to the greater West African Breeding Stock B as a whole, with evidence both for and against its division into two sub-stocks. A database containing sighting information of humpback whales intercepted by boat in the WSA region from 1983 to 2008 was compiled. It included a total of 1,820 identification images of ventral tail flukes and lateral views of dorsal fins. After systematic within- and between-year matching of images of usable quality, it yielded 154 different individuals identified by tail flukes (TF), 230 by left dorsal fins (LDF), and 237 by right dorsal fins (RDF). Microsatellite (MS) matching of 216 skin biopsies yielded 156 individuals. By linking all possible sightings of the same individuals using all available identification features, the periodicity and seasonality of 281 individual whales were examined. Sixty whales were resighted on different days of which 44 were between different calendar years. The most resightings for one individual was 11 times, seen in six different years, while the longest interval between first and last sightings was about 18 years. A resighting rate of 15.6% of whales at intervals of a year or more indicates long-term fidelity to the region. Shorter intervals of 1 – 6 months between sequential sightings in the same year may suggest temporary residency. The TF image collection from WSA was compared to TF collections from four other regions, namely Gabon, Cabinda (Angola), Namibia and the Antarctic Humpback Whale Catalogue (AHWC). Three matches were detected were between WSA (in late spring or summer) and Gabon (in winter), confirming direct movement between these regions. The capture-recapture data of four different identification features (TF, RDF, LDF and MS) from six successive subsets of data from periods with the highest collection effort (2001 – 2007), were used to calculate the number of whales that utilise the region, using both closed and open-population models. Since dorsal fins have never been used to estimate abundance for humpback whales, the different identification features were evaluated for potential biases. This revealed 9 – 14% incidence of missed matches (false negatives) when using dorsal fins that will result in an overestimate, while variation in individual fluke-up behaviour may lower estimates due to heterogeneity of individual capture probability, by as much as 57-69%. Taking into consideration the small dataset and low number of recaptures, the most consistent and precise results were obtained from a fully time-dependent version of the Jolly-Seber open-population model, with annual survival fixed at 0.96, using the MS dataset. This suggests that the WSA feeding assemblage during the months of spring and summer of the study period numbered about 500. The relationship of these whales to those (perhaps strictly migratory) that may occur here in other seasons of the year, and their links to possible migratory routes and other feeding or breeding areas remain uncertain.National Research Foundation (NRF), South Africa, under Grant Number 2047517. Earthwatch Institute (funding), The Mazda Wildlife Fund (through the provision of a field vehicle), SASOL (through the donation of two four-stroke engines), PADI Project AWARE (UK) (funding), the South African Navy (access to the shore-based look-out), the Military Academy, University of Stellenbosch (accommodation) and Iziko South African Museum (office space and support). JB gratefully received financial support in the form of bursaries from the NRF, the Society for Marine Mammalogy, University of Pretoria, and the Wildlife Society of South Africa (Charles Astley Maberley Memorial bursary). The Namibian Dolphin Project is supported by NACOMA (Namibian Coastal Conservation and Management Project), the Nedbank Go Green Fund, Mohammed bin Zayed Species Conservation Fund, the British Ecological Society, the Rufford Small Grants Foundation and the Namibia Nature Foundation. JB and TJQC received funding from the International Whaling Commission (IWC) to conduct between-region matching.http://www.tandfonline.com/loi/tams20nf201