Seeing signs of cetacean health: Visual health assessments

HuDoNet recently hosted global expert Dr Marie-Françoise Van Bressem for a webinar on visual health assessments to study the health and welfare of wild cetaceans.

A juvenile humpback dolphin with tattoo skin disease (B Atkins).

Marie is a veterinarian with a PhD in veterinary sciences and is Head of the Cetacean Conservation Medicine Group at the Peruvian Centre for Cetacean Research. Her research has focused on infectious diseases, skin disorders and injuries, skeletal pathologies and visual health assessments in cetaceans. The implications of disease and other health conditions for cetacean welfare and conservation are of primary interest, and her work has taken her across the Americas, Europe, Africa and the Middle East.

During the webinar, Marie explained how using high-resolution photography from boats, drones, and underwater sources allows researchers to non-invasively identify skin diseases, body deformities, and anthropogenic injuries like ship strikes or net entanglements. Scoring body condition can provide information about an animal’s nutritional status and, in some circumstances, its prospects for survival. We were introduced to specific viral and bacterial conditions such as tattoo skin disease and lobomycosis. Furthermore, the presence of external parasites and epibionts can be indicators of underlying illness or compromised immunity. 

Repeated observations of known individuals are particularly valuable, allowing researchers to follow changes in health over time. Ultimately, these assessments are vital tools for conservation management, allowing scientists to track wound healing and disease progression as well as to evaluate the impact of environmental threats on wild populations.

Repeated observations show  wound healing over time (Elwen and Leeney 2010).

Looking at Indian Ocean humpback dolphin health

Discussion turned to Marie’s previous work on Indian Ocean humpback dolphins, including examination of one particular skull collection. Many showed bone lesions associated with Crassicauda spp., a nematode that infests the cranial sinuses of several species of dolphins. Such infestations can cause substantial damage and may represent a considerable physical stressor for affected animals.

It may be possible to assess skull collections to provide valuable information on parasite loads and health. The lesions are relatively easy to recognise using published photographs as a guide, making it feasible for non-specialists to conduct initial assessments and seek expert confirmation where needed. For HuDoNet, this raises an intriguing possibility: historical collections distributed across the species’ range may contain biological information that has not yet been fully explored.

Evidence of a nematode infection in the skull of a dolphin (Van Bressem et al. 2020).

Advice for researchers getting started

Marie also offered practical advice for researchers interested in incorporating visual health assessments into their work. Her central message was to start simply, be descriptive and work collaboratively.

• Read the literature and study images first: Begin by reading relevant scientific papers to familiarise yourself with the visual presentations of diseases, injuries, and skin conditions.

• Keep classifications simple and descriptive*: Avoid creating too many overly detailed subcategories. Be descriptive and categorise findings into broad groups, such as:

  • Skin Lesions: Known conditions like tattoo skin disease or lobomycosis.

  • Injuries: Further categorised by origin, such as anthropogenic (ship strikes, entanglements) or predators.

  • Unknown Origin: A category to capture unidentifiable markings.

• Engage in open-minded discussions: The most crucial element when starting is to continuously exchange views. Discuss what you see with peers and supervisors, and then specialists. Getting a second opinion and having collaborative discussions are the best ways to train the eye and make accurate, collective decisions.

*Marie shared a sample excel sheet describing what she saw in 10 example photos of humpback dolphins. Please send us an email if you would like to see it: iohudonet@gmail.com

This humpback dolphin has lobomycosis-like disease, skin nodules, possible entanglement scars and an orange discolouration on the dorsal fin (B Atkins).

Visual health assessment therefore does not need to begin with a complicated diagnostic protocol. Clear descriptions, repeatable categories and a collaborative approach can provide valuable information  and, over time, build an increasingly informative picture of the health of individual animals and populations.