|LADP researcher photographing bottlenose dolphins
Behavior and association patterns are observed and comprehensive data recorded into a database that includes – among other information – oceanographic conditions, satellite data, bioacoustic information and digital video providing us with a wide array of information that we may draw upon to enhance our understanding of these complex animals.
For specific information about our methodology, see the OCS peer-reviewed publications on bottlenose dolphins.
Bottlenose dolphins are regular visitors of California waters and are considered in many locations worldwide to be indicators and sentinels of the status and health of coastal habitats. Systematic monitoring of these free-ranging animals can provide key data for understanding their habitat use as well as tracking the progression of poorly known diseases and emerging and re-emerging pathogens that may impact both dolphin and human health.
Understanding the ecology and dynamics of these coastal and offshore dolphins in California waters – as well as their site fidelity and spatial overlap – is useful not only for decisions affecting new Marine Protected Areas established in California, but these findings also have implications for future genetic and population studies leading to protection of these species.
SKIN DISEASES AND PHYSICAL DEFORMITIES IN
Our past studies show that bottlenose dolphins in Santa Monica Bay suffer skin lesions and physical deformities. Ours was the first investigation of this kind on the West Coast of United States! The presence of these diseases is related to environmental factors like sea temperature and salinity, but also to man-made pollutants in our waters. This concerns us because it has potential implications for human health. Our current research aims to continue monitoring of these animals both along the coast and in offshore waters to shed light on the occurrence and frequency of these diseases, and compare data with other studies in California and other areas worldwide.
SUPPORT L.A. DOLPHIN PROJECT'S CONTINUED RESEARCH
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|Bottlenose dolphins with skin diseases found off Los Angeles|
From 1997 to 2007, the OCS research team found a variety of dermal lesions and physical deformities on free-ranging bottlenose dolphins in the Southern California Bight, which raised concerns about the health status of this species and potential negative effects on the entire coastal and offshore populations. As explained in one of our scientific papers, over 80% of bottlenose dolphins found in our study area were discovered carrying skin diseases and/or body malformations (see publications).
Investigations of skin lesions and physical deformities in wild bottlenose dolphins are generally scarce and localized and the majority of investigations have been focused on dead or captive animals. The cause of these lesions is still unknown, but an increasing number of studies on wild bottlenose dolphins suggest that lesions and deformities are anthropogenically induced.
Data are collected with laptop computers. When dolphins are spotted, data on the number of animals, behavior, and aggregations with other species are recorded at 5-minute intervals throughout the sighting.
For each sighting of dolphin schools, an attempt is made to photograph all individuals present in the group. Images of dolphin dorsal fins and bodies taken during photo-identification studies offer an excellent tool to assess the presence and prevalence of epidermal diseases because of their visibility. For all distinct individual that have been photo-identified, the best digital images are analyzed for prevalence and extent of skin lesions and the presence of physical deformities using the software ACDSee Pro (each image is enlarged to observe dermal lesions in detail).
|OCS research assistant Amber collects data at sea|
The current research provides a further step toward assessing the presence and frequency of skin diseases and physical deformities on both already identified animals and new animals present in the area. Further, it offers data for comparison with other study areas in which these types of lesions have been investigated and new ground for discussion on the health of these animals and the impact of anthropogenic activities.
Bottlenose dolphins are apex predators and vulnerable to indirect threats, such as chemical pollution, acoustic pollution and marine debris. Direct anthropogenic effects on these marine mammals are difficult to assess, but dolphins bioaccumulate toxins and may suffer immunological and reproductive disorders as a consequence. Coastal dolphins are particularly susceptible to harmful threats, as they inhabit regions where pollution is usually abundant. Coastal animals in the Eastern North Pacific are known to have the highest levels of DDT concentration of all marine mammals, which seriously affects reproductive rate.
The presence of skin diseases in bottlenose dolphins is related to environmental factors, but also to man-made pollutants in our waters.
This study aims to provide key data to better understand the extent of this problem and the potential implications for human health.
CALIFORNIA DOLPHIN ONLINE CATALOG
Over three decades of research have been conducted on coastal bottlenose dolphins (Tursiops truncatus) along the California and Baja California coasts. During this time period, photo-identification images, including related sighting metadata, were collected by several scientists in different locations, including: San Quintin and Ensenada, Baja California, Mexico; San Diego, Orange County, Santa Monica Bay, Santa Barbara, Monterey Bay and San Francisco, in California, USA. Some of these data sets – including our large OCS dataset for the entire Santa Monica Bay and adjacent waters – are now available for online comparisons and analyses.
In the last years, OCS has spearheaded a statewide effort – conducted in collaboration with other organizations and universities – for the development of a centralized, shared, digital repository for historical and future data that can be openly accessed by researchers around the world. This photo-catalog and online database was named the "California Dolphin Online Catalog" (or CDOC) and was launched online in January 2012.
The CDOC is now hosted by the Duke University OBIS- SEAMAP program and is open access. OBIS-SEAMAP (Ocean Biogeographic Information System Spatial Ecological Analysis of Megavertebrate Populations), is a spatially referenced online database, aggregating marine mammal, seabird and sea turtle observation data from across the globe.
You can now view the OBIS-SEAMAP, browse through species and databases – including our OCS database (login required) – and download data.
|The California Dolphin Online Catalog in OBIS-SEAMAP|
To date, principal investigators have contributed data identifying 697 individual dolphins collected in areas extending from Ensenada, Baja California, Mexico to Monterey Bay, California, USA during 1981-2001.
|Comparison of best photo-ID individuals of bottlenose dolphins|
Further development will be focused on adding more recently collected data from all the areas ranging from Ensenada, Baja California, Mexico to San Francisco, California, USA, refining the online application, and seeking collaboration and input from other interested data holders.
If you are working with coastal bottlenose dolphins along the West Coast of North America – either as a researcher or a citizen scientist – and are interested in collaborating in this effort, please contact OCS Research Director Dr. Maddalena Bearzi.
MOVEMENT PATTERNS OF COASTAL BOTTLENOSE DOLPHINS
Past collaborative studies on coastal bottlenose dolphins (Tursiops truncatus) found along the California coastline - including research conducted by OCS researchers – show that these animals display extensive travel and high mobility along the entire California coast and Northern Baja California, Mexico. We'd now like to know more about these movement patterns...
In the last few years, the OCS research team – in collaboration with other scientists along the California and Mexico coasts – investigated the occurrence and movement data of coastal bottlenose dolphins from boat-based photo-identification surveys over a 20-year period (from 1981 to 2001). The study was carried out in six study areas ranging from Ensenada, Baja California in the south to Monterey Bay, California in the north.
Our primary objective was to determine movements between study areas, movement reversals, travel speed and travel distances. The results of this collaborative effort were recently published in a peer-review scientific paper (Hwang, A., et al. 2013. Range characteristics and movement patterns of common bottlenose dolphins (Tursiops truncatus) off California and Northern Baja California, Mexico).
This paper confirmed that this population of coastal bottlenose dolphins travels regularly and extensively between near shore locations from Ensenada to Monterey Bay. These coastal movements are likely due to the interplay between environmental variables, prey preferences, distributional characteristics, and the behavioral repertoires and distinctive foraging strategies of these animals.
|Bottlenose dolphin leaping in California|
This long-term study on the occurrence and movement of coastal bottlenose dolphins from boat-based photo-identification surveys offers a great foundation for current and future collaborative research among scientists on the West Coast of United States.
For instance, OCS scientists recently worked together with researchers in San Francisco to exchange images and analyze range movement expansion of bottlenose dolphins along the Northern California and Oregon coasts. In addition to the northward range extension, scientists in San Francisco Bay observed bottlenose dolphin predation on Chinook salmon, previously unreported as prey for these coastal dolphins.
OCS will continue to collect and share data with other researchers to better understand range characteristics, foraging hotspots and movement patterns for these animals.
An issue of concern for our OCS research team, as well as other scientists along the West Coast of United States, is that the wide range movements of bottlenose dolphins may contribute to their feeding success, but they also expose this coastal population to an array of epidemiologic risks (see OCS Project on Skin Diseases and Physical Deformities on Bottlenose Dolphins).
The coastal corridors have many natural and anthropogenic environmental threats and bottlenose dolphins can be at risk by being exposed to localized toxins, toxins that they might otherwise avoid if they were a less mobile species.
For instance, OCS discovered that our study area of Santa Monica Bay is a foraging hotspot for coastal bottlenose dolphins. These animals spend a considerable amount of time along these shores searching for food and feeding
EFFECTS OF OCEAN RECREATIONAL USERS ON COASTAL
Coastal bottlenose dolphins have been observed near swimmers, kayakers, stand-up paddle boarders and surfers along near shore corridors in the Santa Monica Bay, California. We are currently conducting coastal boat-based focal follows of dolphin schools to determine the occurrence and type of encounters between ocean recreational users and coastal dolphins, as well as the effects of these activities on these animals' behavior.
|Bottlenose dolphins socializing near shore|
Coastal surveys (distance from shore <1 km) are conducted from powerboats and sailboats, generally in the morning and early afternoon, in good weather conditions. Behavioral data are collected with laptop computers. Number of animals, size classes, behavior, and aggregation/association with other marine mammal species are recorded at 5-min intervals throughout all sightings. When coastal bottlenose dolphins are observed in proximity of ocean recreational users (ORUs), data on these animals are recorded to determine changes in school size, behavioral state, group formation, and surfacing mode, before, during, and after their encounters with ORUs.
|OCS researchers use a dinghy to follow dolphins near shore|
Coastal boat-based focal follows of dolphin schools are conducted, among other things, to determine:
This study represents the first attempt to describe and quantify potential effects of surfers, kayakers, stand-up paddle boarders, and swimmers on coastal bottlenose dolphins in the Santa Monica Bay, California. Results from this study might help to better understand the impact of recreational activities on these animals and reinforce the use of a precautionary approach.