https://doi.org/10.1038/s42003-025-08161-1

Infectious diseases cause mass mortalities in wildlife populations globally, but the impact of host sociality on the spread of pathogens is often unknown. While host behaviors drive pathogen transmission, these behaviors vary individually which impacts both individual- and population-level disease outcomes. For example, delphinid species are regularly affected by serious respiratory diseases, but a lack of social behavior data means the structure of vulnerability in these ecosystem sentinels is poorly understood. To assess the role of variable social behavior on disease risk empirically, we collected behavioral data from two wild bottlenose dolphin populations (Tursiops spp.), developed network models that synthesize transmission contacts, and used an epidemiological model to predict disease consequences. We find that contacts are highly structured by age and sex, and that individuals preferentially contact others in their own demographic group. These patterns, in turn, drive heterogeneity in infection risk, which we support using empirical data from a past disease outbreak. Our work characterizes the impact of social dynamics on infectious disease risk, which can inform the structure of vulnerability for future epizootics across diverse delphinid species.

http://doi.org/10.1098/rspb.2025.0698

Infectious diseases have detrimental impacts across wildlife taxa. Despite this, we often lack information on the complex spatial and contact structures of host populations, reducing our ability to understand disease spread and our preparedness for epidemic response. This is also prevalent in the marine environment, where rapid habitat changes due to anthropogenic disturbances and human-induced climate change are heightening the vulnerability of marine species to disease. Recognizing these risks, we leveraged a collated dataset to establish a data-driven epidemiological metapopulation model for Tamanend’s bottlenose dolphins (Tursiops erebennus), whose populations are periodically impacted by deadly respiratory disease. We found their spatial distribution and contact is heterogeneous throughout their habitat and by ecotype, which explains differences in past infection burdens. With our metapopulation approach, we demonstrate spatial hotspots for epidemic risk during migratory seasons and that populations in some central estuaries would be the most effective sentinels for disease surveillance. These mathematical models provide a generalizable, non-invasive tool that takes advantage of routinely collected wildlife data to mechanistically understand disease transmission and inform disease surveillance tactics. Our findings highlight the heterogeneities that play a crucial role in shaping the impacts of infectious diseases, and how a data-driven understanding of these mechanisms enhances epidemic preparedness.

The Chesapeake Bay is the largest estuary in the U.S. and one of its best studied estuarine ecosystems. However, beyond the Bay’s mouth, little is known about one of its most visible and charismatic predators, the Tamanend’s bottlenose dolphin (Tursiops erebennus), posing challenges to conservation efforts. Here, I use a multidisciplinary approach to gain insights into the population dynamics, behavior, and ecology of Tamanend’s bottlenose dolphins that occupy the Potomac River and middle Chesapeake. My research aims to inform current management and conservation efforts, as well as generate questions and hypotheses for future study.

First, I evaluate the existing narrative that dolphins were extirpated from the Potomac River and have only recently returned. In the absence of long-term ecological monitoring, I reconstructed the historical occurrence of dolphins in the tidal Potomac through synthesis of local ecological knowledge and historical texts. To do this, I conducted semi-structured interviews with highly knowledgeable, long-time watermen and charter fishermen and systematically searched through newspapers published between 1787 and 2023. I found that dolphins were present in the Potomac every decade from the 1830s to the 2020s. However, a lack of both newspaper records and watermen’s and charter fishermen’s sightings suggest that dolphins were extirpated from the upper portion of the Potomac (114 to 191 km upriver) since the 1930s. Both sources of information indicated that dolphin occurrence throughout the river peaks during the summer and is related to temperature and the presence of prey, specifically spot (Leiostomus xanthurus), Atlantic croaker (Micropogonias undulatus), white perch (Morone americana), and menhaden (Brevoortia tyrannus). Interviews revealed that sightings were sporadic in nature and group sizes were highly variable. Dolphins were observed in more months and seasons, as well as in larger groups further downriver. Further upriver, observations were less frequent within a year and years would pass between sightings. Salinity was mentioned by watermen and charter fishermen as an important driver of the presence of dolphins further upriver. That is, upriver sightings increased during periods with higher salinity.

Next, I established a baseline of the current occurrence, behavior, and ecology of Tamanend’s bottlenose dolphins at the mouth of the Potomac River by assessing individual and population-level metrics. I used behavioral survey and focal follow data collected by the Potomac-Chesapeake Dolphin Project between 2015 and 2022. From a subset of those years 2015 to 2019, I used photo-identification methods to identify 2,013 unique individuals, of which 1,141 met restrictive criteria of dorsal fin distinctiveness and quality. Dolphins were observed traveling most often (69% of behavioral surveys) in groups ranging from 1 to 260 and in depths ranging from 0.6 m to 43.5 m. Dolphins were observed foraging (18% of behavioral surveys) on at least four different prey species, including spot, weakfish (Cynoscion regalis), striped bass (Morone saxatilis), and a flounder species within the suborder Pleuronectoidei. They also exhibited a novel foraging behavior named silt circle foraging, similar to mud ring foraging. Dolphin presence, corrected for field effort, peaked from June to August and varied across months and was positively correlated with water temperature. The percentage of dolphins seen on more than one day, month, and year was 45.1%, 36.6%, and 27.5%, respectively. Repeat sightings of the same individuals from spring through fall across years suggested that the area is important dolphin habitat for foraging and reproduction, given that 87 neonates and 242 mother-calf pairs were observed. The number of unique neonates, corrected for field effort, peaked in August and varied significantly across months; most estimated birth dates were in May and June. In addition, three incidents of calf-directed aggression are consistent with previous findings of infanticide adjacent to the study area. The rate of first-year mortality was estimated to be 22% and calves are dependent on maternal care for 1.47 to 3.41 years. The presence of the ectoparasite Xenobalanus globicipitis in 13.7% of surveys and 4.8% of individuals, suggests that coastal dolphin stocks use the area.

Lastly, I identified seasonal clusters among dolphins in the Potomac River, assessed whether these clusters differed in ecological and behavioral traits, and compared sighting histories of individuals from these clusters along the mid-Atlantic to current definitions of stock structure. I then generated hypotheses about the identity of possible stocks of the dolphins that inhabit the area. Specifically, I used monthly sighting records of individuals observed by the PCDP (2015 to 2019) to determine three clusters. All three clusters differed significantly in habitat use (depth and distance to shore), sociality (group size and social module membership), the presence of ectoparasites, and site fidelity to the study area (number of years). I determined the sighting history patterns of individuals matched to other sites along the mid-Atlantic using the Mid-Atlantic Bottlenose Dolphin Catalog (MABDC) and compared them to current stock definitions used in management. Based on these findings, I hypothesized that a previously undescribed stock exists in the Chesapeake Bay. I predicted that this proposed stock occupies the Chesapeake Bay and/or coastal Virginia waters year-round. Based on seasonal cluster assignment of individuals with this sighting history pattern, I predicted that defining characteristics of this stock are use of shallow waters close to shore, moderately large group sizes, very low presence of Xenobalanus globicipitis, high cohesion, and high resight rates within and across years. Analysis of sighting histories also supported use of the area by the Northern North Carolina Estuarine Stock (NNCES) and Northern Migratory Coastal Stock (NMCS). I hypothesized that the NNCES uses the Chesapeake for a greater extent of the year (late spring through summer) than currently recognized and that the NMCS moves between the Chesapeake and New Jersey during the spring and summer.

Together, these findings highlight the value of taking a multidisciplinary approach to understand the ecology and behavior of an important, but understudied, predator and generating data critical for conservation. Tamandend’s bottlenose dolphins have used the Potomac River and middle Chesapeake Bay since at least the early 1800s. Today, well over a thousand dolphins, including mothers and calves, use the area each year from spring through fall and are important upper-trophic level predators in this iconic ecosystem.

https://doi.org/10.1016/j.ecoinf.2024.102942

Anthropogenic global change is occurring at alarming rates, leading to increased urgency in the ability to monitor wildlife health in real time. Monitoring sentinel marine species, such as bottlenose dolphins, is particularly important due to extensive anthropogenic modifications to their habitats. The most common non-invasive method of monitoring cetacean health is documentation of skin lesions, often associated with poor health or disease, but the current methodology is inefficient and imprecise. Recent advancements in technology, such as machine learning, can provide researchers with more efficient ecological monitoring methods to address health questions at both the population and the individual levels. Our work develops a machine learning model to classify skin lesions on the understudied Tamanend's bottlenose dolphins (Tursiops erebennus) of the Chesapeake Bay, using manual estimates of lesion presence in photographs. We assess the model's performance and find that our best model performs with a high mean average precision (65.6 %–86.8 %), and generally increased accuracy with improved photo quality. We also demonstrate the model's ability to address ecological questions across scales by generating model-based estimates of lesion prevalence and testing the effect of gregariousness on health status. At the population level, our model accurately estimates a prevalence of 72.1 % spot and 27.3 % fringe ring lesions, with a slight underprediction compared to manual estimates (82.2 % and 32.1 %). On the other hand, we find that individual-level analyses from the model predictions may be more sensitive to data quality, and thus, some individual scale questions may not be feasible to address if data quality is inconsistent. Manually, we do find that lesion presence in individuals suggests a positive relationship between lesion presence and gregariousness. This work demonstrates that object detection models on photographic data are reasonably successful, highly efficient, and provide initial estimates on the health status of understudied populations of bottlenose dolphins.

https://doi.org/10.1101/2025.08.20.671308

Cetaceans (whales and dolphins) are important ecosystem sentinels but face growing threats from major disease-related mortality events expected to intensify under climate change. Because both environmental factors (temperature, salinity) and demographics (age, sex) influence health and disease risk, understanding these relationships is essential for effective management. Direct health assessments are challenging in cetaceans, but skin lesions can indicate active infection and tooth-rake marks reflect social stressors that increase transmission risk. Yet, traditional photographic analysis of these indicators is inefficient, creating processing bottlenecks that limit timely evaluation of population health. To address this gap, we applied machine learning to rapidly assess lesions and rake marks in Tamanend’s bottlenose dolphins (Tursiops erebennus) photographed in the Chesapeake Bay, a known hotspot for disease-related die-offs. This represents the first analysis of environmental and demographic contributions to dolphin health in this region. We found significant negative relationships between lesion prevalence and both temperature and salinity for some lesion types. Adult males also showed higher rake mark coverage than adult females and calves. These patterns suggest dolphins in colder, fresher waters may face elevated disease risk, while adult males may be particularly vulnerable to behavioral stress and related health consequences. Our findings are consistent with prior studies, lending validity to our machine learning models, while also revealing novel patterns of calf and male vulnerability in this threatened population. More broadly, our approach demonstrates the potential of automated image analysis to enable timely, non-invasive health assessments across cetacean populations in an era of rapid global change.

https://doi.org/10.1007/s13280-024-02017-4

Because climate change and the biodiversity crisis are driven by human actions, determining psychological mechanisms underpinning support for environmental action is an urgent priority. Here, we experimentally tested for mechanisms promoting conservation-related motivation and behavior toward a flagship species, wild Tamanend's bottlenose dolphins. Following evidence that empathy increases prosocial motivations and behavior, and that the ability to identify individual humans promotes empathy, we tested whether this relationship applied to the ability to identify individual dolphins. Participants identified dolphins from their dorsal fins at above chance levels, and better individuation correlated with higher empathy for dolphins and higher willingness to pledge environmental behaviors. Pairing a narrative with an image of an injured dolphin leads to higher donations relative to a narrative alone. Our novel finding that the ability to individually identify dolphins relates to empathy and conservation-related behavior suggests pathways for strengthening environmental attitudes and behavior.

Declining populations and extinctions of wildlife due to infectious disease have detrimental ecosystem effects, making infectious disease research an important topic amongst ecologists. Additionally, most emerging infectious diseases in humans are zoonotic, or of wildlife origins, making wildlife disease transmission also of interest to epidemiologists. To implement strategies to reduce disease transmission in wildlife and humans, both ecologists and epidemiologists must understand the behavioral mechanisms that contribute the evolution and transmission of pathogens among hosts. This dissertation examines how behavioral data can be used to inform data-driven contact network models which allow us to hypothesize as to pathogen ecology in a variety of host systems. In Chapter 1, I consider the type of behavior used to inform contact network models across wildlife taxa and find that unique structures exist among behavioral type which may drive the evolution of pathogen traits according to transmission strategy.

Next, in Chapter 2, I consider how behavior might change under disturbances and how this influences the transmission of pathogens. I increase the specificity of my host study system to focus on marine mammals, given the lack of both behavioral data and disease modeling work in these systems, despite their importance to overall ecosystem health. I find that anthropogenic disturbances can alter marine mammal behavior in a way that perturbs their network structures and makes epidemics worse and more likely to occur. vi

Finally, in Chapters 3 and 4, I consider the impact of host ecology on contact networks, and its subsequent influence on pathogen spread using a specific host system: the northwestern Atlantic bottlenose dolphins. In Chapter 3, I demonstrate that unique social behavior can drive epidemics in this system, and result in heterogenous infection risks across age and sex classes. In Chapter 4, I demonstrate that migratory behavior can explain the transmission of deadly disease across the entire US Atlantic Coast in this system. Taken together, this dissertation emphasizes the value of collecting behavioral data on wildlife populations and the usefulness of using a data driven approach to mathematically model disease consequences at multiple levels of host system specificity.

https://doi.org/10.1111/mms.13022

Barnacles can reveal much about the physiology, health, and spatial ecology of their cetacean hosts. Here, we examine how temperature and hydrodynamic factors impact presence of Xenobalanus globicipitis, a pseudo-stalked barnacle that attaches exclusively to cetaceans. We hypothesized that temperature is a key environmental factor (i.e., water temperature) and physiological factor, in that X. globicipitis prefers the warmest skin temperature for attachment, possibly as a mechanism for survival in colder waters. First, we demonstrate a global relationship between spatial ecology of host species and presence of X. globicipitis. Notably, X. globicipitis is absent in the four species occupying waters with the lowest sea surface temperature (SST) year-round, but present in migratory species that likely acquire the barnacle in waters with higher SST. Second, barnacle attachment location on common bottlenose dolphin (Tursiops truncatus) dorsal fins corresponds with fin temperature and hydrodynamics. Although body temperature may influence attachment location on the body of the animal, hydrodynamic forces, as previously proposed, determine how well barnacles can remain attached during the adult stage. X. globicipitis prevalence likely provides important bioindicator, ecological, and physiological information about its host. As parasitic infestation has some cost, these results have implications for cetacean health in warming seas.

https://doi.org/10.1007/978-3-031-35651-3_10

Infanticide by adult males is a striking example of sexual conflict; males can increase their reproductive success by killing an unrelated infant and accelerating the mother’s return to breeding condition. Reports of infanticide in cetaceans have quadrupled in the past decade, and infanticide has now been documented in six species of toothed whale, including multiple populations of common bottlenose dolphins (Tursiops truncatus). Evidence of infanticide in these species is consistent with the sexual selection hypothesis; perpetrators are predominantly adult males and targets are neonates. Toothed whales have long lactation periods that suppress estrus, making infanticide potentially adaptive for adult males. However, it remains unclear if infanticidal males are likely to sire the mother’s subsequent offspring. Here, we provide an overview of infanticide in cetaceans, evaluate the evidence for the sexual selection hypothesis, and propose a framework to predict infanticide risk in this clade. Toothed whales do not typically have dominance hierarchies, stable social groups, or monopolizable mating opportunities, all hallmarks of infanticide risk in terrestrial species. Instead, we hypothesize that infanticide risk in toothed whales is modulated by encounter rates with unfamiliar males.

• Long, K., Conkin, V., Jacoby, A-M., Krzyszczyk, E., Mann J. 2025. Calf-directed aggression at twobottlenose dolphin research sites: Implications for infanticide. SEAMAMMS, Jacksonville, Florida, April.

• van Biesen, M., Conkin, V., Jacoby, A-M., Patterson, E., Wallen, M., Mann, J., 2025. Assessing human-related injuries in a seasonal population of Tamanend’s bottlenose dolphins (Tursiops erebennus) in the Chesapeake Bay and lower Potomac River. SEAMAMMS, Jacksonville, Florida, April. Won best undergraduate speed talk.

• Collier, M., Urian, K., Jacoby, A., Mann, J., Bansal, S. 2024. Social behavior and seasonal movement structures mass epidemics in bottlenose dolphins (Tursiops spp.). 25th Biennial Conference on the Biology of Marine Mammals, Perth, Australia, November.

• Collier, M., Urian, K., Jacoby, A-M., Mann, J., Bansal, S. 2024. Social behavior and seasonal movement structures mass epidemics in bottlenose dolphins (Tursiops spp.). 25th Biennial Conference on the Biology of Marine Mammals, Perth, Australia. Nov

• Conkin, V., Collier, M., Jacoby, A-M., Mann, J. 2024. Behavioral Development and Maternal Care in Tamanend’s Bottlenose Dolphins (Tursiops erebennus) and Indo-Pacific Bottlenose Dolphins (Tursiops aduncus) Newborns. 25th Biennial Conference on the Biology of Marine Mammals, Perth, Australia. Nov

• Conkin, V., Collier, M. Jacoby, A.. Mann, J. 2024. Behavioral development and maternal care in Tamanend’s Bottlenose Dolphin (Tursiops erebennus) newborns. SEAMAMMS, Duke University, Beaufort, NC, April.

• Collier, M.,  Jacoby, A., Foroughirad, V., Mann, J., Bansal, S. 2023 Characterizing infectious disease risk in a sentinel marine mammal with social behavior data. Animal Behavior Society, Portland, OR, July 11-15.

• Jacoby, A.-M., & Murray, G. (2023, October 4-6). Historical reconstruction of common bottlenose dolphins in the Potomac River, USA [Oral presentation]. Student Conference on Conservation Science-New York. Online. 

• Jacoby, A.-M., & Murray, G. (2023, July 23-27). Reconstructing the historic occurrence of common bottlenose dolphins (Tursiops truncatus) in the Potomac River, USA to inform management [Oral presentation]. International Congress on Conservation Biology 2023, Kigali, Rwanda.

• Jacoby, A.-M., & Murray, G. (2023, March 17-19). Reconstructing the historic presence of bottlenose dolphins (Tursiops truncatus) in the Potomac River through local ecological knowledge [Oral presentation]. Southeast and Mid-Atlantic Marine Mammal Symposium, Mobile, AL, United States. 

• Smith, P., Mann, J., Marsh, A. 2023. Wildlife empathy: the importance of the individual. American Psychological Association, Washington, DC.

• Collier, M., Mann, J., Ali, S. Bansal, S. 2022. Modeling the impacts of human disturbance in cetaceans and pinnipeds: Do behavioral changes translate to disease consequences? 24th Biennial Conference on the Biology of Marine Mammals, Palm Beach, FL, August.

• Collier, M., Mann, J., Ali, S. Bansal, S. 2022. Modeling the impacts of human disturbance in
  cetaceans and pinnipeds: Do behavioral changes translate to disease consequences? SEAMAMMS, Miami, Florida May 2022.

• Dolezal, M., Foroughirad, V., Jacoby, A., Collier, M., Murphy, C., Fish, F., Mann, J.  2022. Some like it hot: Physiological and ecological factors in Xenobalanus globicipitis attachment to cetaceans. 24th Biennial Conference on the Biology of Marine Mammals, Palm Beach, FL, August.

• Jacoby, A., Collier, M., Wallen, M., Patterson, E.M., Mann, J. 2019. Bottlenose Dolphins (Tursiops truncatus) in the Potomac River and Chesapeake Bay, USA, World Marine Mammal Conference, Barcelona, Spain, December.

• Jacoby, A., Collier, M., Wallen, M., Patterson, E.M., Mann, J. 2019. Updated findings on bottlenose dolphins (Tursiops truncatus) in the Potomac River and Chesapeake Bay area. Southeast and Mid-Atlantic Marine Mammal Symposium (SEAMAMMS), Washington, DC, March 29-31.

• Mann, J., Jacoby, A.M., Wallen, M. M. and Patterson, E.M. 2017. The Potomac-Chesapeake Dolphin Project: preliminary findings and future directions. Southeast and Mid-Atlantic Marine Mammal Symposium (SEAMAMMS), Beaufort, NC, April 7-9.

• Urian, K., Fauquier, D. Barco, A. S., Clark, K., Doshkov, P., Engelhaupt, A., Gorgone, A., Mann, J., McFee, W., McLellan, W. A., Pabst, A., Read, A., Rittmaster, K., Sayigh, L., Silva, D., Speakman, T., Taylor, J., Thayer, V. Toth, J. and Young, R. 2017. Determining the stock identity of stranded bottlenose dolphins (Tursiops truncatus) from the unusual mortality event using the mid-Atlantic bottlenose dolphin catalog (MABDC). SEAMAMMS, Beaufort, NC, April 7-9.

• Urian, K., Horstman, S., Fauquier, D.,  Northeast and Southeast Atlantic Marine Mammal Stranding Network, Barco, S., Clark, K., Doshkov, P., Engelhaupt, A., Gorgone, A., Mann, J., McFee, W., McLellan, W., Pabst, A., Read, A., Rittmaster, K., Rowles, T., Sayigh, L., Silva, D., Speakman, T., Sullivan, J., Taylor, J., Thayer, V., Toth, J., Young, R. 2017. Images of the dead: photo-identification of stranded bottlenose dolphins yields critical information on life history, fishery interactions and unusual mortality events. 22nd Biennial Conference on the Biology of Marine Mammals, Halifax, Nova Scotia, October 22-27.