Maternal care is a central determinant of offspring survival in long-lived mammals (Foster et al. 2012; Mann and Würsig 2019; Morrison et al. 2021; Parker et al. 2021; Rilling and Young 2014; Stanton et al. 2020). Prolonged dependency on the mother provides protection, nutritional provisioning, and opportunities for social and ecological learning that are essential for navigating complex environments (Foster et al. 2012; Gibson and Mann 2008; Morrison et al. 2021; Parker et al. 2021; Rilling and Young 2014; Stanton et al. 2020). Development trajectories for orphaned animals have been documented in long-lived and highly social mammals, such as primate species. Chimpanzees (Pan troglodytes) exhibit patterns of extended maternal care (Lonsdorf et al. 2020), with offspring typically weaned between 3 and 5 years of age, and juveniles continuing to maintain close associations with their mothers and younger siblings for an additional 4–5 years post-weaning (Lonsdorf et al. 2020). In chimpanzees, the youngest orphaned individuals to survive beyond 2 years were at least 30 months old at the time of maternal loss (Boesch et al. 2010; Stanton et al. 2020). In another primate species, the Phayre's leaf monkey (Trachypithecus phayrei), offspring reach independency around 2 years of age, and have been recorded to survive without the mother if they were at least 15–17 months of age (Borries et al. 2014). These studies suggest critical developmental thresholds below which independent survival is unlikely, reinforcing that early-orphaned individuals in long-lived mammals have low chances of surviving in the wild. Similar vulnerabilities are expected in cetaceans, which share slow life histories, prolonged maternal dependence, and strong social bonds (Jefferson et al. 2008; Würsig et al. 2018). Indo-Pacific bottlenose dolphins (Tursiops aduncus) inhabit shallow coastal and estuarine environments across the Indian and western Pacific Oceans (Jefferson 2024; Würsig et al. 2018). They exhibit slow life histories and prolonged maternal investment (Kemper et al. 2019, 2014; Mann et al. 2000; Miketa et al. 2018; Perrin et al. 2009). Calves rely on their mothers for nutrition, protection, and access to social and ecological information for several years, gradually acquiring the skills required for independent foraging and social integration (Foster et al. 2012; Gibson and Mann 2008; Morrison et al. 2021; Parker et al. 2021; Rilling and Young 2014; Stanton et al. 2020). Female dolphins occupy central positions within social networks, forming stable, long-term bonds with their offspring and with other females. These relationships support social learning, cultural transmission, and cooperative behaviors that contribute to calf development and survival (Rendell et al. 2019). Behavioral development studies show that neonates and young calves rely heavily on maternal positioning, locomotor support, and behavioral scaffolding, with independent foraging and social skills emerging only gradually. Alloparent care, defined as caregiving behaviors provided by individuals other than the biological mother, has been observed in bottlenose dolphins and other cetaceans, including sperm whales (Physeter macrocephalus), pilot whales (Globicephala melas), common bottlenose dolphin (Tursiops truncatus), and Atlantic spotted dolphins (Stenella frontalis) (Augusto et al. 2017; Conry et al. 2022; Dudzinski et al. 2022; Gero et al. 2009; Mann and Smuts 1998; Weinpress and Herzing 2015). These behaviors include escorting, babysitting, protection from conspecifics, and occasional nursing of non-filial calves, as well as rare cases of spontaneous lactation and adoption of unrelated calves (Gaspar et al. 2000; Howells et al. 2009; Sakai et al. 2016). There is also growing evidence that bottlenose dolphins, along with other cetaceans and terrestrial mammals, may exhibit behavioral responses that resemble grief or mourning in response to the death of a calf or close social companion (Pedersen 2019; Reggente et al. 2016). Together, these behaviors underscore the strong bonds between mothers and their dependent calves and support the idea that premature loss of maternal care can significantly reduce offspring survival (Parker et al. 2021; Stanton et al. 2020), with effects that may persist beyond the weaning period (Foster et al. 2012; Morrison et al. 2021; Parker et al. 2021; Stanton et al. 2020). Nevertheless, the survival of orphaned young-of-the-year dolphins has rarely been documented despite the many longitudinal studies encompassing hundreds of birth-to-weaning events (Henderson et al. 2014; Mann et al. 2000, 2021; Robinson et al. 2017). Few cases of successful intervention or rehabilitation of orphaned cetaceans have been documented, including rehabilitation efforts (Mazzoil et al. 2008) and hand-rearing attempts (Kasamatsu et al. 2025). Hand-rearing requires intensive resources and specialized expertise, and even when calves survive the initial rehabilitation period, their ability to be socially integrated into wild populations later or develop species-typical behaviors is uncertain (Barbara 1999; Rilling and Young 2014). Within this background, this paper presents two rare case studies of orphaned female Indo-Pacific bottlenose dolphin calves that survived the loss of their mother and maternal care at 7–10 months of age without human intervention in a marine protected area in South Australia. In Australian waters, T. aduncus occurs along the entire coastline and in South Australia, at least five genetically distinct populations have been identified (Bilgmann et al. 2007; Möller and Beheregaray 2001; Pratt et al. 2018, 2023), including one inhabiting the Adelaide Dolphin Sanctuary (ADS) (Government of South Australia 2005a, 2008). Established in 2005 by the South Australian Government, the ADS is an area of 11,880 ha that was designated to protect a resident population (Bossley et al. 2017; Government of South Australia 2005a; Haigh et al. 2025) (Figure 1). Like many coastal zones adjacent to major urban centers, the ADS has undergone extensive anthropogenic modification over time due to a long-standing history of industrial and commercial activity. Key stressors include channel dredging, the removal of aquatic vegetation, wastewater discharge, thermal pollution from industrial operations, and increased stormwater inflows (Government of South Australia 2003, 2007). The sanctuary also contains the city's principal industrial precinct, which has historically contributed to environmental degradation through the release of contaminants such as heavy metals, organic pollutants, sewage effluent, and heated wastewater (Kirkwood et al. 2022). While many questions remain about the current status, overall health, and viability of the ADS's dolphin population, it is well documented that these pressures contribute to sublethal health effects or, in severe cases, mortality of dolphins, particularly calves and juveniles (Culloch et al. 2016; Government of South Australia 2022; Graham et al. 2017; Haigh et al. 2025; Kirkwood et al. 2022; Tomo and Kemper 2022a, 2022b). The ADS dolphin population has been subject to continuous monitoring for almost three decades using photo identifications techniques (Bossley et al. 2017; Haigh et al. 2025). In addition to this long-term monitoring program, a dedicated dolphin health study led by Flinders University has been underway since 2022, with boat-based surveys conducted under favorable weather conditions (Beaufort Sea State ≤ 3, swell < 1 m, and no rain or fog) monthly from March 2022 to March 2023 and fortnightly from July 2024 to July 2025. Individual animals were photographed and information was recorded about time of sighting, dolphin group location, number of animals within the group and their behaviors, following CEBEL's established survey protocols (Shane et al. 1986; Zanardo 2018). Good-quality photos (Hupman et al. 2018; Markowitz et al. 2003) were used for photo-ID as part of the health study. The Department for Environment and Water (DEW) is the South Australian government agency responsible for managing the sanctuary since its establishment 20 years ago. DEW has documented key demographic events in the population, including calf births, health-compromising events, and mortalities. Additionally, when carcasses were recovered, postmortems were typically conducted by researchers of the South Australian Museum, or more recently the veterinary lab at University of Adelaide, to determine cause of death and assess overall health status. Complementing these official efforts, citizen scientists conducted regular land-based monitoring, particularly within the inner port and adjacent coastal waters, which are surveyable by land. These observers provided valuable reports on newborns, unusual behavior, and signs of ill health in individual dolphins. Information was disseminated via social media platforms (Facebook) and communicated directly to government representatives and researchers, if pertinent, enabling integration into formal datasets and official records. The information derived from the official government records, the Flinders University health study, and the long-term citizen science observations were used to document the case of two orphaned female T. aduncus that lost their mothers and maternal care at under 10 months of age but survived without any intervention or observed alloparent care. Longitudinal observational data demonstrate that both dolphins survived for several years after orphaning. One survived to adulthood, giving birth in 2025 (14 years after maternal loss) and remains alive and physically healthy at the time of writing. The other, although she remarkably survived the early years without maternal care, died at approximately 3 years of age in October 2025 due to an anthropogenic cause (boat strike). The first case involves a female, informally named Ali, born in February 2011. Ali (Figure 2a,b) was orphaned in October 2011 following the sudden death of her mother, Millie, who exhibited acute thoracic hemorrhaging of unknown etiology upon post-mortem investigations (Government of South Australia 2005b). At the time, Ali was approximately 9 months old, well below the typical weaning age of 3 to 5 years (Krzyszczyk et al. 2017; Würsig et al. 2018) for the species and her survival prospects were considered extremely poor. However, Ali was sighted in the months after becoming orphaned and was observed regularly over the following years. In March 2025, Ali gave birth to a calf (Figure 2b), but unfortunately it did not survive the neonatal period. The calf was first observed on March 8, 2025 and last sighted alive on March 11, 2025. Post-mortem examination identified the cause of death as blunt force trauma to the head (The Adelaide University 2025), suggested as a potential case of infanticide or vessel strike. It remains unknown whether Ali's early orphaning influenced the timing at which she reached sexual maturity given the natural variation in the age of female maturation for this population (Kemper et al. 2019, 2014). It is also not possible to know whether being an orphan at an early age had any impact on the loss of her calf. It is well-documented from other studies that bottlenose dolphin calves exhibit high mortality rates (Cheney et al. 2019; Henderson et al. 2014; Mann et al. 2000, 2021; Robinson et al. 2017). Ali was often observed alone and showed a marked tendency to approach vessels, engaging in behaviors such as bow-riding or exploratory interactions around boats (personal communication by citizen scientists and personal observation by the first author). This tendency may represent a maladaptive behavior linked to her early orphaning. Nonetheless, Ali remained in good physical health at the time of writing. The second case pertains to another female calf, named Rocket, born between January and February 2022 (Figure 3a,b). Rocket was orphaned in early September 2022 following the disappearance and presumed death of her mother, Ripple. Both Rocket and Ripple had shown several lacerations, lesions (Figure 4), and signs of declining body condition in the weeks prior to Ripple's disappearance. Rocket and her mother were monitored during this period, and an investigation (Government of South Australia 2022) was also undertaken into other dolphins that exhibited similarly poor body condition and subsequently died; however, the specific causes and drivers of Ripple's and Rocket's health issues remained unclear. Despite her young age at the time of orphaning, which was estimated to be around 7 to 9 months, and her poor health condition at the time of her mother's disappearance, Rocket managed to recover from the health-compromising events that her mother succumbed to and survived until September 2025 (Figure 4). She exhibited atypical behavioral patterns after the loss of her mother. A comparison of sightings of Rocket and a second resident calf of similar age, Piki, that remained under maternal care illustrates a broader spatial range of sightings for the maternally dependent calf compared to the orphaned individual (Figure 5). In addition, Rocket also exhibited a heightened tendency to approach vessels. During all recorded sightings of Rocket during the Flinders health study surveys, the “boat interaction” behavior, defined as deliberate engagement with vessels such as bow-riding, inquisitive approaches, or other close interactions, was consistently observed. Similarly, citizen scientist reports of Rocket approaching recreational and commercial vessels were common (personal communication by citizen scientists; corroborated by government records and publicly available social media posts). Although Rocket was mostly observed alone during systematic surveys, she was recorded associating on two occasions with two conspecifics (Piki and its mother) when they were present within her usual use area. Citizen science observations also provided anecdotal accounts of Rocket's interactions with several other individuals in the population; however, these reports were not systematically documented or verified. Rocket ultimately died from a boat strike at approximately 3 years of age (personal communication by government authorities; corroborated by photographic evidence). Although both calves appeared to develop an increased tendency to approach vessels, neither exhibited other visual signs of illness, maladaptation, or long-term impairment. Rocket's survival to nearly 3 years of age, together with Ali's long-term survival, provides rare empirical evidence that young-of-year calves can persist without maternal care. Ali's survival extended to sexual maturity and she remains physiologically healthy at the time of writing. These observations add case-specific evidence that may inform management decisions regarding orphaned calves. These two case studies on the survival of orphaned dolphin calves provide evidence that, beyond a certain age, calves may be capable of surviving without their mothers. Therefore, decisions to euthanize orphan calves should not automatically assume that survival is impossible. However, given the limited number of cases, clear criteria for making such decisions cannot yet be established. Catherine M. Kemper: writing – review and editing. Luciana M. Möller: writing – review and editing, supervision. Guido J. Parra: writing – review and editing. Cristina Vicente-Sánchez: conceptualization, investigation, writing – original draft, methodology, writing – review and editing, formal analysis, visualization. The authors declare no conflicts of interest. The data that support the findings of this study are available from South Australia Department of Environment and Water. Restrictions apply to the availability of these data, which were used under license for this study. Data are available from the author(s) with the permission of South Australia Department of Environment and Water.
Vicente‐Sánchez et al. (Wed,) studied this question.