Fostering and allo-suckling are widespread among pinnipeds, and several hypotheses have been formulated to explain their occurrence. Here, we describe the occurrence of allo-suckling in harbour seals from photo-identification data of females and pups in Orkney (Scotland) during the pupping seasons between 2016 and 2019. We used a generalised linear model framework to investigate the effect of allo-suckling on the duration of lactation (females) and of nursing period (pups). A generalised additive model framework was used to explore how the probability of allo-suckling varied throughout the pupping season, and with changes in mother-pup separation time. Allo-suckling was observed in 31 females, at higher rates (18–37% of lactating females and 18–47% of the pups every year) than those observed in other phocid populations, with 13 females allo-suckling in multiple years. The duration of the pups’ nursing period was not affected by allo-suckling occurrence. However, females in mother-pup pairs where both mother and pup allo-suckled had longer lactation duration than when only the pup allo-suckled, or than in pairs where no allo-suckling was observed. The probability of allo-suckling increased during the pupping season and with increased mother-pup separation time. However, the proximate causes and the consequences on future reproductive output and pup survival remain unknown.Significance statementAllo-suckling, where females nurse others’ young, is widespread in pinnipeds, particularly among true seals. Given the high costs of lactation in pinnipeds, allo-suckling is a puzzling behaviour. Using photo-identification and field observations, we examined the occurrence of allo-suckling in harbour seals at a colony in Orkney, Scotland. We found that allo-suckling is common among seals at the study site, and at rates higher than reported elsewhere. Our results show that allo-suckling does not appear to affect the duration of the pups’ nursing period but does increase the lactation duration of females who suckle other pups and whose own pups also allo-suckle. This study highlights an area which requires further investigation as the energetic costs and benefits of allo-suckling remain poorly understood.

Marine mammals are vulnerable to a variety of acute and chronic anthropogenic stressors, potentially experiencing these in isolation, successively and/or simultaneously. Formal assessment of the likely impact(s) of the cumulative effects of multiple stressors on a defined population is carried out through a Cumulative Effects Assessment (CEA), which is a mandatory component of the Environmental Impact Assessment (EIA) process in many countries. However, for marine mammals, the information required to feed into CEA, such as thresholds for disturbance, frequency of multiple (and simultaneous) exposures, interactions between stressors, and individual variation in response, is extremely limited, though our understanding is slowly improving. The gaps in knowledge make it challenging to effectively quantify and subsequently assess the risk of individual and population consequences of multiple disturbances in the form of a CEA. To assess the current state of practice for assessing cumulative effects on marine mammals within UK waters, 93 CEAs were reviewed across eleven maritime industries. An objective framework of thirteen evaluative criteria was used to score each assessment on a scale of 13-52 (weak - strong). Scores varied significantly by industry. On average, the aquaculture industry produced the lowest scoring CEAs, whilst the large offshore windfarm industry (≥ 20 turbines) scored highest, according to the scoring criteria used. There was a significant increase in scores over the sample period (2009-2019), though this was mostly attributed to five industries (cable, large and small offshore wind farms, tidal and wave energy). There was inconsistency in the language used to define and describe cumulative effects and a lack of routinely applied methodology. We use the findings presented here, along with a wider review of the literature, to provide recommendations and discussion points aimed at supporting the standardisation and improvement of CEA practice. Although this research focused on how marine mammals were considered within UK CEAs, recommendations made are broadly applicable to assessments conducted for other receptors, countries and/or environments. Adoption of these proposals would help to ensure a more consistent approach, and would aid decision-makers and practitioners in mitigating any potential impacts, to ensure conservation objectives of marine mammal populations are not compromised.

Photographic identification (photo ID) is a well-established, non-invasive, and relatively costeffective technique to collect longitudinal data from species that can be individually recognised based on natural markings. This method has been improved by computerassisted pattern recognition software which speed up the processing of large numbers of images. Freely available algorithms exist for a wide range of species, but the choice of software can have significant effects on the accuracy of individual capture histories and derived demographic parameter estimates. We tested the performance of three open source, semi-automated pattern recognition software algorithms for harbour seal (Phoca vitulina vitulina) photo ID: ExtractCompare, I 3 S Pattern and Wild-ID. Performance was measured as the ability of the software to successfully score matching images higher than non-matching images using the cumulative density function (CDF). The CDF for the top ranked potential match was highest for Wild-ID (CDF1 = 0.34-0.58), followed by ExtractCompare (CDF1 = 0.24-0.36) and I 3 S Pattern (CDF1 = 0.02-0.3). This trend emerged regardless of how many potential matches were inspected. The highest performing aspects in ExtractCompare were left heads, whereas in I 3 S Pattern and Wild-ID these were front heads. Within each aspect, images collected using a camera and lens performed higher than images taken by a camera and scope. Data processing within ExtractCompare took >4x longer than Wild-ID, and >3x longer than I 3 S Pattern. We found that overall, Wild-ID outperformed both ExtractCompare and I 3 S Pattern under tested scenarios, and we therefore recommend its assistance in harbour seal photo ID.

The rapid emergence of new marine developments (e.g., marine renewables, port infrastructure) alongside the substantial growth of existing industries has ultimately resulted in an unprecedented increase in anthropogenic structures within the marine environment over the previous century. Knowledge of whether marine species interact with, avoid, or accommodate and adapt to such structures is essential to ensure that further development of marine environments do not compromise conservation objectives of marine species. This article documents one such interaction. Herein, we describe the observation of a harbour seal (Phoca vitulina) seeking refuge from a group of foraging killer whales (Orcinus orca) within a blue (aka common) mussel (Mytilus edulis) farm. Aerial video footage (38 min 27 s) was collected using an unmanned aerial system during an encounter at an aquaculture site in Gulberwick Bay, Shetland, UK. Analysis of the footage showed the killer whale group spent 73.7% of the total encounter time exhibiting predatory associated behaviours and that they were observed interacting with the mussel farm infrastructure only during “predation activity” for a total of 26 min 52 s (72.8%). The harbour seal interacted with the mussel farm infrastructure during re- and proactive anti-predator behaviour and when exhibiting fatigue for 27 min 59 s, 94.4% of the total time the seal was observed. It is clear that both marine and terrestrial predator–prey interactions are increasingly occurring in settings that are in some way defined by the Anthropocene. The implications of this are discussed, including potential entanglement risk and human-altered “landscapes of fear.” As comprehension of the potential effects of human-altered risk grows, such knowledge should be taken into consideration prior to further modification of marine habitats.

As an outcome of the creation of the American Petroleum Institute’s (API) Oil Spill Prevention and Response Joint Industry Task Force (OSPR JITF) following the Macondo oil release, and with support from the IPIECA-IOGP Oil Spill Response JIP, a team was formed to evaluate emerging dispersant-related research. It was clear that there was a need to interact with research and development consortia and other oil spill response-related research groups to provide input and potential guidance in order to encourage real world relevance, especially since the Gulf of Mexico Research Initiative (GoMRI) had been created with a funding level of $500 million over a 10 year period. A specific outcome of the effort has been a review of research papers on dispersant fate and effects published post-Macondo. The main objective was to review results of recent dispersant research with a goal of providing a link to existing dispersant knowledge and to spill response management questions facing spill response planners in the post-Macondo environment. This effort was viewed as an opportunity to solidify a working relationship between federal government and industry personnel and academic researchers in an area of oil spill-related research that would be important for the foreseeable future. Dispersants are one of the tools that may be used to respond to oil spills, especially to those that are large and offshore. When used appropriately, dispersants may prevent slicks from reaching shorelines and adversely impacting sensitive coastal ecosystems. The use of dispersants during the Macondo incident resulted in an increased awareness of their use, especially among the academic community and the general public. The review panel had a primary goal to identify recurring misunderstandings and inconsistencies that might arise due to researchers’ inexperience with the real-world aspects of oil spills, spill response, and the way in which dispersants are designed to be used (spraying on slicks, usually in offshore waters) or with applicable oil toxicity research standards (e.g., use of appropriate dispersed oil concentrations during studies). The objectives were to identify:Potential problems for researchers so that they can be avoided in ongoing studiesEvaluate and share potentially misleading results, especially as they might influence global dispersant regulations inappropriately The paper will review results to date and highlight those areas that are viewed to be the most consistent and problematic (e.g., the inappropriate use of nominal versus measured exposure conditions, a focus on dispersant rather than dispersed oil toxicity).