Deathly Silent: Exploring the Global Lack of Data Relating to Stranded Cetacean Euthanasia

Abstract

The compromised state of stranded cetaceans means that euthanasia is often required. However, current knowledge and implementation of euthanasia methods remain highly variable, with limited data on the practicalities and welfare impacts of procedures. This study evaluated the available published data on cetacean euthanasia, highlighting knowledge gaps and providing direction to improve stranded cetacean welfare. A total of 2147 peer-reviewed articles describing marine mammal euthanasia were examined. Of these 3.1% provided details on the method used, with 91% employing chemical methods. Two countries, the United Kingdom (UK) and New Zealand (NZ), provided euthanasia reports to the International Whaling Commission (IWC) between 2007 and 2020. Methods employed were reported for 78.3% and 100% of individual cetaceans euthanised in the UK and NZ, respectively. In the UK, chemical euthanasia was most common (52%), whilst in NZ only ballistics methods were used. Few data were available about time to death/insensibility (TTD); 0.5% of peer-reviewed articles provided TTD, whilst TTD was reported for 35% of individuals in the UK and for 98% in NZ. However, IWC reports lacked detail on how death/insensibility were assessed, with multiple individuals “presumed instantly” killed. Overall, the findings highlight the lack of available information on cetacean euthanasia, and suggest increased data collection and the application of appropriate methods to improve welfare.

Assessing animal welfare during a stranding of pygmy killer whales (Feresa attenuata)

“…Notably, the initial shot placement observed appears misaligned with the euthanasia guidance in the New Zealand SOP which states that shots should be a “handspan behind the blowhole” (Boren, 2012; Boys et al, 2022d). Skull morphology among cetacean species is highly variable (Galatius et al, 2020; Gol'din, 2014) and thus species‐specific reference points are required for accurate projectile placement (Boys et al, 2021). However, the cranial morphology of pygmy killer whales, including the anatomical location of the blowhole, is similar to that of pilot whales detailed in the generic New Zealand SOP, meaning that species differences are unlikely to explain melon penetration on this occasion.…”

“…While these are recommended in the New Zealand SOP (Boren, 2012; Boys et al, 2022d), soft point projectiles are understood to have reduced penetration ability and lower killing efficiency (Hampton et al, 2014; Knox et al, 2018; Øen & Knudsen, 2007). Indeed, international recommendations suggest the use of only solid projectiles for cetaceans (Boys et al, 2021; Duignan & Anthony, 2000; Hampton et al, 2014; Øen & Knudsen, 2007). The implications of using soft projectiles at this event are unknown since postmortem examination of the cranium was not possible.…”

“…The sea state hindered an immediate refloat attempt, and as the animals were judged by DOC to show signs of deterioration, they made the decision to euthanize in consultation with members of a subtribe (hapū) of local indigenous Māori (Patuharakeke). Euthanasia was undertaken by a warranted DOC officer via ballistics, following the Standard Operating Procedure (SOP) that guides strandings management in New Zealand (Boren, 2012; Boys et al, 2021, 2022d). Following euthanasia, Patuharakeke permitted opportunistic postmortem sampling of some tissues prior to burial.…”

“…However, the information required to inform end-of-life decision-making and guide euthanasia procedures is also lacking (Barco et al, 2016;Boys et al, 2021Boys et al, , 2022d. This may compound welfare concerns at stranding events where animals are deemed nonviable for refloatation.…”

Euthanasia Complications in Non-Domestic Species

“…However, a recent study has shown that immersion with tricaine methanesulfonate (MS-222) is not always efficacious, and a secondary method such as pithing is now recommended [3]. Although additional research is continually being conducted to determine the most appropriate methods for euthanizing non-domestic species, there is still a paucity of information as to what methods work, what does not work, and where improvements can be made to provide the best care for these patients [4,5].…”