Session Six: Pain and Distress, Euthanasia, Humane Killing, and Lethal Take

Moderator: Robert S. Sikes, University of Arkansas at Little Rock

Robert S. Sikes, professor of biology at the University of Arkansas at Little Rock, introduced himself and added that it was a privilege for him to moderate Session Six on euthanasia, humane killing, and lethal take. He stated that the euthanasia of animals injured during capture or handling is always a contingency for which one must be prepared. Additionally, for many species and activities, animals may be captured and then euthanized, depending on the nature of data required. But if the research target is an armadillo forging just inside a wood line, a bird waiting on a hummock in the everglades, or a diverse sample of fish that are collected as part of a commercial harvesting operation, meeting the conditions expected of euthanasia might be difficult, if not impossible. Consequently, suitable methods of humane killing and lethal take represent one of the constant challenges for investigators and oversight bodies alike. As subject-matter experts for this session, Sikes introduced David S. Miller, who played a key role in crafting the wildlife sections of the American Veterinary Medical Association (AVMA) Guidelines for the Euthanasia of Animals (AVMA Euthanasia Guidelines); Andrew Engilis, Jr., from the University of California (UC), Davis, who is a bird expert and brought additional insights regarding the nature of archival samples needed for systematics collections; Rebecca J. Rowe from the University of New Hampshire, a small mammal specialist in environments where lethal capture is often a necessity; and Jeffrey A. Buckel from North Carolina State University, whose insights included collecting fish samples involving large numbers of individuals and species all in the confines of an offshore fishing vessel.

AVMA PERSPECTIVE ON ENDING THE LIVES OF WILDLIFE SPECIES

David S. Miller provided an overview of the AVMA Euthanasia Guidelines in the context of his role as the lead of the AVMA Reptiles, Zoo, and Wildlife Working Group. The first edition of the AVMA Euthanasia Guidelines was developed in 1963, he said, with a general emphasis on dogs, cats, and small mammals. That edition and all the subsequent editions were developed for U.S. veterinarians, which Miller said creates some challenges when these guidelines are extrapolated to non-veterinarians and to situations outside of the United States. Over time, Miller added, the AVMA has recognized the increasing challenges and the increasing range of information that is available regarding euthanasia, and in 2020 it started developing working groups for different areas, placing an emphasis on the evidence for evaluating different euthanasia methods. For example, he pointed to the Reptiles, Zoo, and Wildlife Working Group, which recruited biologists affiliated with The Wildlife Society and the Association of Fish & Wildlife Agencies, as well as various researchers and veterinarians. He added a note of caution that the term “wildlife” also extends to birds, fish, and invertebrates, which are covered in other working groups. He also stated that context matters. In 2013, the AVMA split off the humane slaughter and depopulation guidelines because there are different considerations for those situations. It is also important to recognize what is not covered by the euthanasia guidelines, and this includes categories such as hunting, fishing, and pest control.

Among the challenges for the AVMA Euthanasia Guidelines¹ is how they are interpreted and applied in the real world, Miller said, particularly considering that researchers work with people who have different views on animals, what they should experience, and how they should be relating to humans. Guidelines must take into account that researchers work with a wide range of species with different characteristics in settings that range from highly controlled to free-ranging, he said. Miller also noted

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¹ See https://www.avma.org/sites/default/files/2020-02/Guidelines-on-Euthanasia-2020.pdf.

another consideration to provide definitions that distinguish euthanasia from depopulation or humane killing. Miller emphasized that people approach this with different views and other biases associated with how they look at animals and humans; those perceptions shape the lens on how they view and apply the AVMA Euthanasia Guidelines.

Miller outlined the new organization for the AVMA Euthanasia Guidelines as of 2013, which is a searchable PDF, making it more user-friendly. In the introduction to the guidelines, there is a section discussing the ethics and justifications of taking an animal’s life, and a list of things for people to consider when they want to determine the best method for a given situation, Miller said. In the general section, the AVMA emphasizes that people consider what the animal experiences in terms of pain, distress, and the duration of that pain and distress, what the humans will encounter in terms of a need for training, and what the impact on the individual performing euthanasia could be as well as those that may be watching it. In addition to the social environment, there is also concern about the natural environment in terms of residues and potential impacts on other animals and the environment. There are also considerations of what is legal for a given set of situations (AVMA 2020).

In the methods section, the guidelines expand on what animals experience before they become unconscious, Miller said. It explains the difference between sedation, where the animal’s sensations are dulled, compared to anesthesia, where pain relief is provided. The document emphasizes the importance of handling for different species and different environments as a way of mitigating negative experiences for the animals during the euthanasia process, he added. The AVMA is interested in how effective a method is in terms of consistency and whether additional training is needed, Miller said. For non-veterinarians in particular, controlled drugs are an issue, he said, because unless they happen to have a Drug Enforcement Administration (DEA) license, they have to have a veterinarian involved. There is also consideration about the quality of the drugs as well as compounding. Because there are no “cookbook methods,” Miller said, the AVMA subjectively developed recommendations using practical experience from both veterinarians and biologists.

In the last section, the guidelines largely provide recommendations for birds and mammals, both domestic and wild. Miller highlighted that there were challenges encountered when coming up with recommendations for poikilotherms, because the data are limited.

While the guidelines were written with an effort to be adaptable for different species and different situations, Miller said, that adaptability comes with ambiguity that requires thoughtful interpretation and application of the guidelines. For a specific situation, Miller continued, there is a need for knowledge about the species, the methods and all of the other circumstances involved in that particular situation, and communication between the researcher and those that have oversight over them. Additionally, there is a need for communication with those that are external to the process, Miller said. There is also tension between what has always been done in the past and new methods that may arise. Often there is limited literature available for different species, making this feat more challenging. Miller stressed the importance that often scientists want more data to make a decision, when in reality they are often dealing with social situations where the challenge is people with different values. People with different values may need to accept that there are trade-offs when making a decision to use a given method for ending an animal’s life.

In closing, Miller pointed out that there have been some positive and creative responses to the new AVMA Euthanasia Guidelines format that demonstrate flexibility in their use. He said, for instance, DeNicola and colleagues (2019) demonstrated that it can be practical to meet euthanasia criteria using firearms on free-ranging cervids that are at a distance. Also, he noted that Gilbertson and Wyatt (2016) had a creative approach to assessing different methods of euthanasia in snails. Miller emphasized his take-home message to thoughtfully consider the information that is available in the different sections of the AVMA Euthanasia Guidelines, and that context matters when trying to pick the best euthanasia method for a given situation.

CHALLENGES IN HUMANE KILLING OF WILD BIRDS AS MUSEUM VOUCHERS SUPPORTING BIODIVERSITY RESEARCH

Andrew Engilis, Jr., curator of the Museum of Wildlife and Fish Biology at UC Davis, discussed the challenges involved in collecting wild bird specimens. Although field collecting is considered controversial by some, Engilis said, it remains an essential tool to characterize and define the world’s biodiversity.

Historic specimens are currently being used in many ways that were unimagined by those who collected them 100 years ago, Engilis said. While the traditional use of specimens’ remains, including vouchers to document diversity, conduct taxonomic studies, and/or document new species, he continued, the tissues and feathers of specimens today are being used to address environmental questions and to reconstruct ancient food webs and address questions through space and time. More recently, they are being used in disease studies. Likewise, the specimens collected in this era will have even more relevance for researchers 50 to 100 years from now to assess distributional, environmental, evolutionary, and ecological patterns. There is strong evidence that passing specimens forward to future researchers is one of the most effective ways to contribute to the accomplishments of future science and conservation biology, he said.

Ornithologists working in the field are faced with many challenges in ensuring that their research is conducted both safely and ethically, Engilis said; for example, working in remote areas and in situations that limit euthanasia choices. Some of these challenges are difficult to articulate in the animal care and use process and Institutional Animal Care and Use Committee (IACUC) protocols, he continued, and the principal investigator (PI) must clearly define the conditions of their field research and address challenges in the available methods of euthanasia. Many researchers find the IACUC process both challenging and at times confusing, said Engilis, but fortunately, many institutions have staff to help guide the IACUC process. Engilis said that the PI should develop contingencies for when things do not go as planned and clearly define the need for alternate euthanasia methods for when conditions warrant. Engilis noted that several methods of euthanasia remain poorly understood and the AVMA Euthanasia Guidelines at times have not yet incorporated recent research findings, which is frustrating to the PI and perhaps also to IACUC members.

Engilis shared other challenges associated with the humane killing of wild birds as museum vouchers for biodiversity research. He emphasized that when properly planned, safety, bird welfare, and specimen quality will ensure the safe and humane collecting of birds. Engilis described proper planning, by first successfully obtaining IACUC approval for the research, which allows researchers to obtain permits and in some cases visas to work internationally. It is also important to develop a field plan and disaster plan. These steps are challenging and at times onerous, but necessary for safety, humane killing, and ultimately for the care of the specimens obtained, said Engilis. Required training of all field personnel can ensure safety for the researchers and proper handling and humane killing of birds, Engilis said, and can yield the highest-quality specimens for research purposes. Most institutions have a required animal care and use training module, he added, but this is just a start. Engilis thinks that each project should also have an Illness and Injury Prevention Plan and documented training for all involved personnel. For example, if firearms are used, he said, the researchers must successfully complete firearms or hunter safety training. Also, there is training for all primary and secondary euthanasia methods whether it is chemical or manual based.

Engilis noted that methods that minimize or alleviate potential pain and distress and that enhance animal well-being are goals of the researcher when studying wildlife, even when death is the endpoint. The optimal situation is when all euthanasia methods are available, which ensures that the animal can be humanely killed within specified guidelines, he said. However, because fieldwork can create challenges where methods and conditions are changing rapidly, he added, a field plan and proper training are needed to meet those unpredictable conditions. Engilis pointed out that rules to safely operate a firearm are important and situations may arise that may conflict with chemical-based methods of euthanasia, presenting challenges to the safety of the user and humane killing of the bird. Engilis emphasized that it is

the job of the PI to clearly articulate these challenges to gain a mutual understanding of the process under complicated situations.

Carrying lethal chemicals or agents into remote areas is not always realistic and can be unsafe or even forbidden by law, Engilis said. In addition, operating a firearm is not safe in the presence of chemical agents. Mist nets generally are used to capture birds in remote research areas, he continued, and they are often used remotely from base camps where it might not be feasible to bring birds back to base camp to euthanize them. Researchers need quick methods for humane killing that yield quality specimens and reduce time of handling. They must rely on manual euthanasia in these circumstances, which is limited when considering a museum specimen. It is difficult to clearly articulate the conditions, long hours, and limitations of working remotely to the IACUC members, and it takes experience to understand the grueling conditions of field collecting remotely, Engilis noted.

Engilis addressed the use of rapid cardiac compression (RCC) also called thoracic compression for euthanasia for small birds. He stated that museum ornithologists view the AVMA decision not to recognize RCC as an approved euthanasia method in the field as one of the biggest challenges facing the field for collecting birds and obtaining IACUC approval. According to Engilis, it is at times the only practical method available to euthanize a small bird safely and humanely. He said, those who use and clearly understand RCC know it to be fast and humane. In addition, he said, there are now clinical and methodological studies completed to support this perception (Engilis et al. 2018). Engilis stated one of the misconceptions about RRC is that it suffocates the animals, which is inhumane, but clinical studies show that birds do not die because of suffocation but rather they succumb to instantaneous blood loss to vital organs (e.g., the brain). Studies show that the method rivals interosseous pentobarbital euthanasia for time to cessation of pulse and isoelectric electroencephalogram (EEG) (Paul-Murphy et al. 2017).

In summary, Engilis thinks that many of the challenges he presented can be addressed when collecting birds in the field, which starts with a mutual understanding of the conditions, methods, and processes among researchers and IACUC members. Clearly defining the variable options of euthanasia and proper planning are critical, he emphasized, and success and safety rely on training.

CONTEXT-DEPENDENT CHALLENGES AND DECISIONS FOR THE HUMANE KILLING OF WILD SMALL MAMMALS

Rebecca J. Rowe, associate professor in the Department of Natural Resources and the Environment and IACUC chair at the University of New Hampshire, discussed context-dependent challenges and decisions for the humane killing of wild small mammals.

Free-ranging or wild small mammals are diverse, distributed worldwide, and occupy all ecosystems or habitat types. Rodents are the most species-rich Order of mammals with more than 2,300 species, many of which are small in size—about 250 grams or smaller, she said. Shrews (“true” shrews, members of the family Soricidae) are also a diverse group with more than 370 species, she added. The many field studies on wild small mammals across a wide range of disciplines, including biology, ecology, and evolution, raise the great potential for circumstances where AVMA-preferred capture techniques or methods of euthanasia are not practical or may be a less than ideal choice, Rowe said (Sikes 2016; AVMA 2020).

Rowe pointed to the variety of techniques researchers use to study wild small mammals in their native environments, which can be non-invasive, including camera traps or hair snares, or it can involve the physical capture of animals. Focusing on physical methods, Rowe said that trap types vary in design, but can be broadly categorized: live traps that hold the animal unharmed and kill traps that kill the animal outright upon capture. An example of a live trap is a Sherman trap, which is an aluminum box trap, and a common example of a kill trap is a Museum Special snap trap. Pitfall traps, which are buried containers where the rim is at surface level, can be designed as either a live trap or a kill trap. Live trapping is an appropriate method for many scientific studies, Rowe said, and both box traps and pitfall traps can be effective in capturing a wide range of small mammals. Under the AVMA Euthanasia Guidelines, the use of live traps is a preferred survey method, and when appropriate or necessary, live trapping can be

followed by methods of euthanasia. Efforts are taken to ensure the well-being of the animal in live traps by providing food and nesting material, Rowe continued, and depending on the environmental conditions, using covers to protect against heat, wind, or rain.

Circumstances where AVMA-preferred capture techniques or methods of euthanasia are not practical or may be a less than ideal choice may include circumstances when live traps pose a risk for pain and distress when approved measures of euthanasia cannot be applied. For example, when researchers need to travel to remote locations, travel time can make it impossible to check live traps frequently, Rowe said. She referenced a case in which researchers needed to travel by helicopter from a base camp to the site of a recent wildfire—a trip that took approximately 1.5 hours.

Species-specific differences in biology or physiology present another scenario where AVMA-preferred methods may be a less than ideal choice, Rowe said. For example, many species of shrews are small, such as the Sorex hoyi, more commonly known as the pygmy shrew, which weighs about 2–4 grams (about the weight of a dime or a nickel). As a result of being so small, these animals have a high metabolism and thus a higher risk of mortality relative to a larger bodied small mammal, even when food and nesting materials are provided to help meet thermoregulatory demands. When these types of environmental, logistic, or species-specific scenarios arise, Rowe said, it is important to recognize that the AVMA Euthanasia Guidelines allow for flexibility where justified.

Although kill traps may not consistently meet the AVMA standards for euthanasia, the technique might provide the best choice under certain circumstances and may be characterized as humane killing, said Rowe. She emphasized that when kill traps are used, the quality of the death is paramount; the traps must provide an efficient and quick death. Both mechanized snap traps and pitfall traps can achieve this, she said, and these methods also eliminate the stress associated with handling and human contact.

Although the AVMA does not consider drowning an acceptable form of euthanasia, Rowe continued, the guidelines do provide IACUCs the latitude necessary to consider alternatives for wildlife that may not always meet all criteria established for euthanasia. When collection or killing are appropriate or necessary, the animal can be prepared as a voucher specimen and deposited in a natural history collection. These specimens contribute to scientific infrastructure, where the tissues, skin, and skeletal material are used to advance science across a wide range of disciplines, including public health, ecology, and evolution. In addition, the impact on wild populations of small mammals has been shown to be negligible; and the number that researchers are permitted to take is regulated (Beacham and Krebs 1980; Stephens and Anderson 2014).

In closing, Rowe suggested that when researchers find that they need to request deviations from the guidelines, it is critical that they are familiar and up to date with those guidelines and provide justification for their request, including referencing studies or taxon-specific guidelines. Researchers could also consider meeting with the attending veterinarian before submitting the protocol, she said, providing the IACUC with educational resources, and offering to communicate directly with the IACUC to explain the circumstances and methods. Rowe explained that while serving on her university’s IACUC, she has seen a wide range of protocols ranging from transgenic mice to net-gunning ungulates, and in each case, it has always been helpful to have both the researcher and the IACUC members present at the meeting. For the IACUC, Rowe ended noting that it is important to make sure they have relevant expertise on the committee or the ability to pull in consultants as needed.

CHALLENGES IN FOLLOWING EUTHANASIA GUIDELINES IN MARINE FISHERIES SAMPLING

Jeffrey A. Buckel is a professor with the Department of Applied Ecology at North Carolina State University where he conducts research on marine and estuarine finfishes. He discussed the challenges in following euthanasia guidelines in marine fisheries sampling, including why researchers sample wild fish, the justification for using gear types that catch large numbers of fish, and the types of gear used in marine fishery sampling. Additionally, he discussed the challenges in meeting euthanasia guidelines for fish and reviewed the language in the AVMA Euthanasia Guidelines related to commercial fishing gear.

Because the wild fish stocks that researchers are studying are targeted by recreational and commercial fishers, Buckel said that it is important to estimate their trends in abundance. It is also necessary to obtain individual specimens across a range of sizes to track their life history attributes, he said, such as reproduction, size and age distributions, and condition. Life history attributes and abundance indices are used as input for stock assessment models to determine stock status and future sustainable fishing levels. Buckel said that is why killing some fish during sampling is necessary to improve or maintain fish stocks for sustainable fisheries. Buckel explained that the aim of the AVMA Euthanasia Guidelines is to “accomplish death for these animals rapidly with the minimum amount of pain and distress practicable” (AVMA 2020, p. 82). Acceptable methods for euthanasia in finfish include non-inhaled methods (e.g., immersion and injection) or physical methods (e.g., decapitation and pithing). Unacceptable methods for euthanasia in finfish include “death by anoxia and desiccation after removal from the water, or by anoxia in the water,” he said.

Turning to the gear types used in marine fishery sampling, Buckel described bottom trawls, which are towed along the bottom of the seafloor and fish are funneled into the mouth of the net and then directed to the back. After the tow is done the net is brought on board, he said, the catch is dumped onto the deck of the boat, and samples are sorted. The large number of fish that can be caught during a tow prevents the use of acceptable methods of euthanasia such as the non-inhaled or physical methods that require handling individual fish or small numbers of fish, Buckel stated (Jennings et al. 2001).

Beach seine nets are set off the beach and encircle a section of water, Buckel explained, and then the net is pulled up onto the beach and the fish are retained in the net. Catches in beach zones can be quite large at times, he said, and these large catches make it impossible or not practical to apply the acceptable euthanasia methods such as the non-inhaled and physical methods. Buckel also described a gill net, which is a wall of mesh suspended in the water column with float lines on the water surface and a lead line weighing down the bottom. Fish do not see the net and they swim into it and are caught in the mesh of the nets by the bones that cover their gills, hence the name gill net. Buckel said that this gear also can catch many fish, making it impractical or not possible to apply acceptable euthanasia methods. Additionally, fish often die before they are retrieved from the gill net.

Buckel then discussed what an IACUC can do when faced with reviewing a protocol that utilizes some of the gear types he described or some other fishing gear type that results in large catches of finfish. If a large catch is encountered, fish will die by anoxia after removal from the water, or in the case of the gill net, by anoxia in the water. Fortunately, the AVMA acknowledges that context matters, Buckel said. On page 88 of the AVMA Euthanasia Guidelines, there is a section (S6.2.6.4) titled “Fish Kept Outdoors and in Fisheries,” and in this section the AVMA acknowledges that field research takes place in a complex environment and often on a scale comparable to commercial fishing (AVMA 2020) and that the large number of fish caught may justify the use of harvest techniques “that may not meet the criteria for euthanasia, but in all situations pain and distress should be minimized to the greatest extent possible.” Buckel noted that this language is useful to IACUCs that are evaluating protocols that are using the gear types that he described or other fishing gear types that might catch large numbers of fish.

Buckel closed the session by stating that marine fishery sampling often results in large catches, and it is not possible to use acceptable euthanasia protocols that are applicable to small samples or to laboratory settings. The AVMA recognizes this and provides language that IACUCs should be aware of when evaluating protocols. While this language acknowledges the “pragmatic realities” that researchers might encounter, Buckel said that fisheries scientists should clearly justify the use of these “high catch” gear types and continue to explore the utility of less invasive gear that collects fisheries data that are used to ensure sustainable fisheries.