Better for Animals: Background
Animal Charity Evaluators’ Better for Animals: Evidence-Based Insights for Effective Animal Advocacy resource is an ongoing project in which we distill key research on different animal advocacy interventions to help us evaluate their impact in different contexts. We have made this research publicly available to support informed decision making about how to help the most animals. You can read more about the methodology here.
This is a living document and we want to make it as helpful, accessible, and up-to-date as possible, so please feel free to reach out with feedback! To keep up to date with ACE’s research and the work of the amazing organizations that we support, be sure to sign up for our mailing list.
While we hope advocates find this resource helpful for their strategic and tactical decisions, it is subject to various limitations. In particular:
This is not a systematic review. Due to capacity constraints, we were unable to conduct a full and comprehensive literature review and instead used our best judgment to select studies for inclusion.
We are working with a limited evidence base. For some interventions, we had to rely on lower-quality evidence or less relevant evidence from adjacent fields. Evidence on the long-term or indirect impacts of interventions is particularly limited.
It is not fully comprehensive. Our Menu of Interventions captures the interventions the charities we evaluate for recommendation or assess as potential grantees use most commonly, but it doesn’t capture every approach that exists in the movement.
Interventions do not operate in isolation. The available evidence largely evaluates interventions independently, but their real-world effectiveness is shaped by the broader ecosystem of actors, complementary interventions, and contextual factors. This limits how much findings can be generalized to specific advocacy environments.
As such, we encourage advocates to consider the evidence presented alongside their on-the-ground knowledge of how interventions function and complement one another in specific contexts.
To help share our Better for Animals findings more widely, we are spotlighting one intervention each month through a series of social media and blog posts. This month we are focusing on the evidence around investigations.
Intervention Spotlight #6: Investigations
What is this intervention?
This category refers to conducting investigations to document animal welfare violations and expose the mistreatment of animals on farms, in transport facilities, and in slaughterhouses. It can also include the development and implementation of tools and systems to make it easier for individuals to report animal welfare violations, such as online reporting platforms. Among other things, investigation footage is often shared (through social media, television, or other channels) to encourage people to reduce their consumption of animal products, sign petitions calling for improved animal welfare standards, and support other animal advocacy efforts. It is also used as evidence in legal proceedings. As such, it can be used to complement many of the other interventions listed in the Better for Animals resource.
What is our overall assessment of this intervention? How confident are we in this assessment?
The evidence that we found is subject to various limitations. Much is theoretical or subjective, and the empirical studies are often over five years old, have small sample sizes, or show correlation without being able to prove causation. Most evidence pertains to the U.S., with questionable generalizability to other regions. Evidence also typically focuses on the effect of investigations used for vegan outreach, rather than, e.g., legislative change or corporate campaigning. As such, our confidence in our assessment is low.
Overall, our evidence review suggests that investigation footage is likely to elicit positive changes in attitudes toward animals, at least in the short term, but less likely to elicit meaningful behavioral change, such as dietary change or active pro-animal engagement. Public attitudes toward investigations appear to be positive, especially when abuse is uncovered, property damage is limited, and the footage highlights both the plights of individual animals and the systemic cruelty of intensive animal agriculture.
We expect the effectiveness of this intervention to vary significantly depending on the context and the approach taken. We believe it is likely stronger when:
Investigations highlight systemic abuse and clearly show that cruelty is widespread, while telling individual animal stories to keep the suffering personal.
Footage is produced or supported by experienced organizations, with investigators’ bravery emphasized and common industry rebuttals (for example, claims of deception or “bad apples”) anticipated.
Campaigns target regions with less prior exposure to investigation footage and align releases with other pro-animal media coverage.
Evidence is gathered through legal and varied methods such as drones, mobile surveillance, or whistleblowers, allowing use in court cases or legislative efforts and reducing risk of prosecution.
Conversely, the intervention is likely weaker, or may have unintended negative consequences, when:
Footage is framed as a rare incident, is overly repetitive, or relies on outdated tactics that face tighter security and audience fatigue.
Investigators use illegal methods, creating legal risk and public distrust.
Releases fail to counter industry narratives or lack fresh, campaign-relevant material, leading to diminishing media impact.
Investigations are also frequently used in tandem with other interventions listed in the Better for Animals resource, such as corporate welfare campaigns and social media outreach, so for context, we recommend also reading the summaries for those interventions.
We would welcome more empirical research that tests the impact of investigations on public attitudes toward animals and dietary habits, especially well-designed studies that provide reliable evidence of causation (or lack thereof), rather than merely correlation. We would also welcome research testing how investigation footage impacts the effectiveness of other interventions. Further case studies of the impact of specific investigations and research into the impact of direct rescue work are also warranted.
What does the research say about how effective this intervention is?
Empirical evidence suggests that exposure to footage of undercover investigations has a positive impact on participants’ attitudes toward animals. Indications of positive behavioral change are less certain. For example, a 2016 study by Mercy for Animals found some indicators of positive medium-term attitudinal change toward animals following exposure to footage of farmed animal cruelty, but the changes detected were small and the generalizability of these findings is limited by a narrow demographic group.1
A randomized controlled trial (RCT) by Animal Equality and Faunalytics that used a larger, more representative sample found that people who watched footage of pigs being confined and slaughtered in intensive farms expressed stronger anti-pork attitudes immediately after watching and one month later, relative to the control group.2 The group that viewed the footage also reported eating marginally less pork one month after the intervention. However, the follow-up response rate among participants was only 58%, which could have skewed the survey’s findings through selective attrition, and other types of meat consumption were not measured, so it is unknown whether some participants increased consumption of other meats to make up for reduced pork consumption. This could be particularly problematic if participants switched from larger-bodied animals such as pigs to smaller-bodied animals such as fishes or chickens, leading to higher overall animal suffering associated with their diet.3 In general, dietary self-report is also subject to limitations such as recall bias (difficulty accurately remembering consumed foods and amounts) and social desirability bias (the tendency to report eating habits in a way that is perceived as more socially acceptable).4
A 2024 study found that participants showed increased concern about welfare-washing and the credibility of welfare certification schemes after watching an undercover video showing animal abuse at an RSPCA Assured farm. 28% of viewers stated that they were considering eliminating meat from their diet after watching the video, compared to 22% before.5
Two studies from 2012 and 2015 (both by the same researchers) found that media coverage of farmed animal cruelty elicited a strong negative emotional reaction in most viewers, but that only a very small proportion took action such as contacting politicians or writing to newspapers.6 In contrast, one 2024 study of over 3,000 French citizens found that viewing an undercover video of animal abuse led to a 23% increase in charitable donations to animal advocacy organizations.7 However, this study took place in a highly controlled environment using very small amounts of money (with each participant able to donate at most one euro).
Most of the public appear to support undercover investigations. A 2023 online survey of 292 German citizens found the general public accepting of undercover investigations, particularly when animal abuse was uncovered and investigators did not cause any property damage.8 A 2016 survey of 716 U.S. citizens indicates that most people are unaware of so-called “ag-gag legislation” (laws designed to prevent the documentation of conditions and practices on farms, often by penalizing undercover investigators or whistleblowers), but are opposed to such legislation once made aware of it. Respondents also expressed lower trust in farmers and stronger support for animal welfare regulations after learning about ag-gag laws.9
Investigations have been cited as an important factor in the success of historic corporate outreach efforts, as they help prime companies and the public to be receptive to such campaigns.10 Investigators whom we consulted highlighted that investigative footage is useful for validating claims made by activists about poor animal treatment, supporting legal actions and public outreach, and refuting fraudulent claims made by animal agriculture companies.11 We are not aware of any studies directly testing the added benefit of using investigations to support other campaigns.
A 2024 Faunalytics report lists several examples of legal victories that were reportedly supported by undercover investigations.12 These include: an E.U. ban on rabbit cages; the closure of a U.K. pig farm and a Spanish foie gras farm; and a ban on sex-selective chick culling in Italy. Investigative footage has also been used in various civil lawsuits and criminal prosecution cases, as well as the Supreme Court amicus brief submitted by Harvard’s Animal Law and Policy Program (ALPP) in support of California’s Proposition 12.
A 2016 report by ACE, based on conversations with leaders in the animal advocacy movement, highlighted the risk of diminishing returns if the public becomes desensitized to footage of farmed animal cruelty. The report noted that Mercy For Animals capped the number of investigations released in 2015 for this reason, and in 2016 was working on expansion into other countries where saturation is less of a concern.13 We did not find any empirical evidence that directly tested this assumption.
Cost effectiveness
While we did not find any cost-effectiveness estimates for investigations, several studies highlighted the relatively high cost of undercover investigations in the U.S.14 This applied especially to those that involve investigators gaining employment at animal agriculture facilities (which are the investigations that appear to gain the most media coverage in the U.S.).15 However, one U.S.-based organization that we consulted reported that high costs are avoidable, noting that smaller groups (such as their own) are able to carry out investigations for under $10,000. In practice, costs depend on the experience of the investigation team, whether there is a need for training prior to entering the field, the length of the investigation itself, and the number of support staff assigned to the investigation.
Experts based outside the U.S. also reported that assumptions of high costs do not necessarily apply to the same extent elsewhere, given that employment-based investigations are fairly uncommon in e.g. Europe, Asia, and Australia, where investigations are typically much shorter.
Strength of evidence
Evidence on the effectiveness of investigations is subject to various limitations. Much of the evidence is theoretical or based on subjective opinion rather than empirical evidence. The empirical studies are often over five years old and/or subject to limitations such as small sample sizes or failure to provide evidence of causation (rather than just correlation).
Under what conditions is this intervention more or less effective?
The 2016 ACE report noted various factors, based primarily on subjective reasoning and conversations with others in the movement, that may increase the impact of investigations. This includes:
Focusing on systemic abuse in the farming system to avoid footage being dismissed as an extreme, rare incident (and when publishing instances of extreme cruelty, emphasising that such cruelty is highly common throughout the industry)
Telling stories of individual animals, to avoid people becoming desensitized to the animals’ suffering and depersonalizing them
Ensuring that investigations are carried out by, or with the support of, experienced organizations
Emphasizing investigators’ bravery and preempting any accusations of deceit
Carrying out investigations in regions where there has been less of a “saturation” of investigation footage
Aligning with other pro-animal messaging currently in the media.
A 2020 Farm Forward report also highlighted common industry strategies to dismiss the importance of any footage, including framing the footage as deceptive and blaming individual workers as “bad apples”, and in some instances; firing them.16 Making efforts to preempt such strategies, by emphasizing the cruelty inherent to routine animal practices (rather than highlighting illegal welfare violations) could help to increase the effectiveness of such footage.
Investigation footage may be particularly powerful when used as evidence in legal action: Investigation footage has supported criminal prosecutions, civil lawsuits, and legislative wins, including bans on chick culling and rabbit cages, and defense of Proposition 12.17
The U.S.-based organization that we consulted cautioned against a “rinse and repeat” mentality (such as continuing to use employment-based investigations despite tougher security and hiring protocols within the industry), as this could soon face diminishing returns. To avoid media fatigue, they emphasized the need to use varied tactics for gathering evidence to ensure that footage remains provocative, relevant for specific campaigns, and well-suited to collaboration with law enforcement. They also encouraged the use of legal investigation techniques (such as mobile surveillance, drone work, and working with whistleblowers), as illegal methods (such as open rescues) risk leading to prosecutions and creating public distrust in animal advocacy organizations.
A 2018 report also highlighted the convenience of using drones to record investigative footage, although the authors noted they are not suitable for gathering in-depth footage or footage of indoor activities.18
Our priorities for improving this evidence review
We plan to improve future iterations of this evidence summary by including more exploration of:
Evidence outside the U.S. (as this evidence review is currently highly U.S.-centric)
The specific ways in which investigations can support other interventions, such as legal work for animals
The overlap with the effectiveness of documentaries
The state of play with ag-gag laws and to what extent they have hindered an organizations’ ability to conduct investigations
Case studies of specific investigations and direct rescue work, and their effectiveness
Any issues with recruitment and retention of undercover investigators, and the best ways to address these issues.
See, e.g., Rothgerber (2019)
Tiplady et al. (2012); Tiplady et al. (2015)
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