Non-human animal culture can be defined as the inheritance of behavioural traditions through social learning (Whiten, Reference Whiten2021). Social learning occurs as individuals observe or interact with other individuals or their products, such as tools (Brakes et al., Reference Brakes, Carroll, Dall, Keith, McGregor and Mesnick2021). Most research on non-human animal culture has focused on mammals, particularly cetaceans, primates and elephants (Brakes et al., Reference Brakes, Carroll, Dall, Keith, McGregor and Mesnick2021). Other work, however, has also revealed the prevalence of socially learned behaviours in a range of taxa, and in some cases these behaviours may also extend into cultures (Aplin et al., Reference Aplin, Crates, Flack and McGregor2025; Brown & Webster, Reference Brown and Webster2025; Wilkinson et al., Reference Wilkinson, Reber, Root-Gutteridge, Dassow and Whiting2025). Given that many species with documented cultures are also species of conservation concern in the USA, this concept could have considerable implications for laws and policies affecting wildlife conservation (Brakes et al., Reference Brakes, Carroll, Dall, Keith, McGregor and Mesnick2021). For example, non-human animal culture could conceivably be integrated into decision-making under multiple provisions of the Endangered Species Act (ESA), as well as other USA environmental laws such as the Marine Mammal Protection Act.

Here, we focus on the ESA, the primary law for conserving imperilled species in the USA. Specifically, we explore two particularly appropriate processes in the ESA that could integrate non-human animal culture: (1) listing distinct population segments, and (2) recovery-related documents. Understanding how non-human animal culture has been considered in these processes, if at all, should help to improve its application in laws and policies affecting wildlife conservation. In doing so, we can better identify the adaptive features of species requiring conservation, as well as support conservation goals for those species more generally by ensuring these features are considered when evaluating how species respond to both potential threats and conservation interventions.

The ESA mandates that the agencies with principal responsibility for implementing the law designate as endangered those species at risk of extinction, and as threatened those species at risk of becoming endangered in the foreseeable future. When Congress passed the ESA in 1973 it recognized the importance not just of conserving species globally but also intraspecific diversity. The ESA therefore includes an expansive definition of species, encompassing recognized species, subspecies and ‘any distinct population segment…of vertebrate…’.

Consistent with this expansive view of what should be protected under the ESA, listing distinct population segments is a way for the U.S. Fish and Wildlife Service (USFWS), and the National Marine Fisheries Service (NMFS, and collectively with USFWS, the Services) to designate populations for ESA protection or delist them. Although the ESA does not formally define what constitutes a distinct population segment, the Services’ policy requires that a species must be designated as a distinct population segment if it is discrete, significant and meets the status required to be threatened or endangered (USFWS & NMFS, 1996).

Under the Services’ distinct population segment policy, a vertebrate population can be considered discrete if it is markedly separated from other populations of the same taxon because of (1) physical, (2) physiological, (3) ecological or (4) behavioural factors, or if it is (5) delimited by international governmental boundaries within which differences in control of exploitation, management of habitat, conservation status or regulatory mechanisms exist that are significant in light of ESA section 4(a)(1)(D) (USFWS & NMFS, 1996). A vertebrate population can be considered significant if (1) it persists in a unique ecological setting, (2) losing the population would cause a significant range gap for the taxon, (3) the population is the only surviving natural occurrence of a taxon or (4) the population differs markedly in genetic characteristics (USFWS & NMFS, 1996). Finally, if a population is discrete and significant, the Services consider whether it is threatened or endangered under the factors listed in ESA section 4(a) (USFWS & NMFS, 1996). Given the behavioural basis of non-human animal culture, the Services therefore have the flexibility to consider it under at least one discreteness condition (‘behavioural factors’), and two significance conditions (‘persists in a unique ecological setting’ and ‘losing the population would cause a significant range gap for the taxon’), when determining whether a species meets the requirements of the distinct population segment policy.

To examine the extent to which the Services have considered non-human animal culture in distinct population segment listings, in June 2024 we searched the Environmental Conservation Online System (ECOS; USFWS, 2024) for species with distinct population segments. Our search returned results for 146 distinct population segments and evolutionary significant units (the latter are how certain salmonid distinct population segments are referred to); these data do not necessarily represent every distinct population segment, however, because the ECOS database is incomplete. For consistency, we excluded evolutionary significant units and species with populations not formally evaluated under the 1996 distinct population segment guidance (USFWS & NMFS, 1996) from further review, resulting in a set of 98 populations. For these remaining populations we reviewed distinct population segment listing determinations in the relevant Federal Register documents to identify which of the five discreteness conditions, and four significance conditions, were expressly considered by the Services. We also quantified whether the terms ‘culture’, ‘cultural diversity’ or ‘social learning’ were used in the discussion of these conditions, to identify the extent to which non-human animal culture was specifically considered in any of the determinations.

The 98 distinct population segment listing documents (representing 56 species) dated from 1997 to 2023. Means of 2.4 ± SE 0.1 discreteness conditions and 2.1 ± SE 0.1 significance conditions were provided per listing. Behavioural factors were relied on in 49.0% of discreteness findings. Additionally, almost all significance findings (91.8%) determined that the loss of the distinct population segment would lead to significant range gaps for the taxon, and 53.1% relied on the condition of persistence in a unique ecological setting. However, non-human animal culture was considered in distinct population segment listing determinations only twice, both of which were for discreteness findings; once for the orca Orcinus orca in 2005, and once for the false killer whale Pseudorca crassidens in 2012. This is perhaps unsurprising, however, given the taxonomic distribution of species listed and the state of knowledge regarding non-human animal culture at the time of many of these listings.

The Services are also required to produce specific documents intended to plan and monitor recovery of listed species. Recovery plans are statutorily-required documents that set out the Services’ strategy to address threats and recover listed species, and recovery outlines are draft or initial versions of those plans. Similarly, 5-year reviews are statutorily-required accounts of listed species, their threats, recovery progress (or lack thereof), and recommendations regarding status changes. All these document types should be able to integrate non-human animal culture when appropriate. Cetaceans are an ideal group for which to explore the extent that ESA recovery-related documents have included non-human animal culture; not only has culture been studied relatively broadly in this group, there are also currently 20 ESA-listed cetaceans.

To investigate how often NMFS has considered non-human animal culture for ESA-listed cetaceans, in June 2024 we conducted a review of recovery plans, recovery outlines, and 5-year reviews available in the NMFS’s public database (NMFS, 2024) for cetaceans listed under the ESA, searching for the terms ‘culture’, ‘cultural diversity’ and ‘social learning’ in the context of non-human animal culture. We gathered 36 ESA recovery-related documents for cetaceans dated from 1991 to 2024. Eleven of these documents (30.6%) mentioned at least one of the three terms to some extent; the species involved were the beluga whale Delphinapterus leucas, false killer whale, gray whale Eschrichtius robustus, orca, southern right whale Eubalaena australis and sperm whale Physeter macrocephalus. Five of these 11 documents were published during 2008–2016, and six during 2021–2023.

Our findings indicate that the concept of non-human animal culture has not, thus far, been widely considered by the Services. But the best available science mandate for listing decisions under the ESA already provides a vehicle through which the Services are required to, when appropriate, integrate non-human animal culture into their work. The interpretation of best available science is often context-specific because the term is not defined in the ESA. Nonetheless, it typically involves at a minimum conducting adequate searches of peer-reviewed scientific literature (Jesup, Reference Jesup, Baur and Li2021). Consequently, at this point, for several species, such as the sperm whale and the humpback whale Megaptera novaeangliae, the inclusion of culture could defensibly be used within the parameters of the best available science mandate. As the science develops it will become difficult to omit it for many species, in the future possibly including the grizzly bear Ursus arctos horribilis and gray wolf Canis lupus, and still comply with the best available science mandate (Morehouse et al., Reference Morehouse, Graves, Mikle and Boyce2016; vonHoldt et al., Reference vonHoldt, Blumstein, Berger and Carroll2025). Listing decisions involving distinct population segments must, however, still follow the requirements of the ESA and be used sparingly and not solely to divide a species and delist a specific population. Implementing the ESA for a distinct population segment based on distinctive cultures would potentially be challenging, given, for example, that cultures can be dynamic, and that conserving them may not always be as straightforward as simply protecting habitat.

In addition to listing decisions, non-human animal culture should be more widely integrated into other ESA documents reflecting species status and threats when appropriate. So far, cultures have only been documented for relatively few species. But machine learning and other emerging technologies are enabling scientists to analyse and decode non-human animal communication, and consequently our knowledge of the extent of the cultures of species such as the sperm whale is likely to improve (Andreas et al., Reference Andreas, Beguš, Bronstein, Diamant, Delaney and Gero2022). Recognizing and conserving these cultures is important because socially transmitted behaviours can contribute to fitness, as well as indicate the extent to which groups may be able to adapt to changing environmental conditions (Eguigeren et al., Reference Eguigeren, Avila, Mesnick, Cantor, Hersh and Perez-Puig2025).

Given human impacts on behavioural diversity (Kühl et al., Reference Kühl, Boesch, Kulik, Haas, Arandjelovic and Dieguez2019), we recommend the Services take the following actions to ensure they adhere to the ESA’s best available science mandate to list appropriate entities and manage their recovery. Firstly, given that non-human animal culture is still a relatively nascent subject area, a guidance document specifically tailored for practitioners should be an effective starting point for this process. Secondly, although both Services have claimed to adopt Shaffer & Stein’s (Reference Shaffer, Stein, Stein, Kutner and Adams2000, p. 308) concept of representation, in which successful conservation means saving not just the species themselves but ‘the ecological and evolutionary patterns and processes that not only maintain but also generate [those] species’, they have in some cases adhered to a narrower definition that focuses on genetic diversity (USFWS, 2016; NMFS, 2020; Malcom & Carter, Reference Malcom and Carter2021). The Services should instead use a more expansive, scientifically rigorous definition of representation, including not only intrinsic characteristics such as genetic diversity, but also extrinsic characteristics such as how species interact in communities and ecosystems through social learning and cultures (Malcom & Carter, Reference Malcom and Carter2021; vonHoldt et al., Reference vonHoldt, Blumstein, Berger and Carroll2025). Thirdly, in the meantime, where relevant, actions should be taken to protect non-human animal cultural diversity, such as through consideration in the determination of distinct population segments under the ESA and through recovery plans that recognize the importance of culturally transmitted behaviour. More generally, we also recommend that non-human animal culture be more expressly integrated into the concept of biodiversity conservation in relevant USA laws and policies affecting wildlife, particularly the ESA. Although the concept of biodiversity entered common parlance only after the ESA (and similar laws) were first passed, the ESA’s stated purpose of conserving both endangered and threatened species as well as the ecosystems upon which they depend necessitates the conservation of all components of native species biodiversity.