Age determination of common bottlenose dolphins (Tursiops truncatus) using dental radiography pulp:tooth area ratio measurements

• Published in: PloS one Vol. 15; no. 11; p. e0242273
• Main Authors: Herrman, Jean M, Morey, Jeanine S, Takeshita, Ryan, De Guise, Sylvain, Wells, Randall S, McFee, Wayne, Speakman, Todd, Townsend, Forrest, Smith, Cynthia R, Rowles, Teresa, Schwacke, Lori
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 20.11.2020; Public Library of Science (PLoS)
• Subjects: Age; Age determination; Age Determination by Teeth - methods; Age Determination by Teeth - veterinary; Aging (Biology); Animal behavior; Animals; Animals, Wild; Aquatic mammals; Assessments; Biology and Life Sciences; Birth; Bone density; Bottle-Nosed Dolphin; Carbon dating; Cetacea; Chronology; Common bottlenose dolphin; Data collection; Data interpretation; Dental caries; Dental pulp; Dental Pulp - diagnostic imaging; Dental Pulp - physiology; Dentin; DNA methylation; Dolphins; Dolphins & porpoises; Earth Sciences; Fecundity; Female; Life history; Male; Marine mammals; Medical examination; Medicine and Health Sciences; Physiological aspects; Populations; Radiography; Radiography, Dental; Ratios; Social Sciences; Teeth; Tooth - diagnostic imaging; Tooth - physiology; Tursiops truncatus; Wildlife; United States; Sarasota Florida; California; Florida; United States > US; Connecticut
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0242273

Age is an important parameter to better understand wildlife populations, and is especially relevant for interpreting data for fecundity, health, and survival assessments. Estimating ages for marine mammals presents a particular challenge due to the environment they inhabit: accessibility is limited and, when temporarily restrained for assessment, the window of opportunity for data collection is relatively short. For wild dolphins, researchers have described a variety of age-determination techniques, but the gold-standard relies upon photo-identification to establish individual observational life histories from birth. However, there are few populations with such long-term data sets, therefore alternative techniques for age estimation are required for individual animals without a known birth period. While there are a variety of methods to estimate ages, each involves some combination of drawbacks, including a lack of precision across all ages, weeks-to-months of analysis time, logistical concerns for field applications, and/or novel techniques still in early development and validation. Here, we describe a non-invasive field technique to determine the age of small cetaceans using periapical dental radiography and subsequent measurement of pulp:tooth area ratios. The technique has been successfully applied for bottlenose dolphins briefly restrained during capture-release heath assessments in various locations in the Gulf of Mexico. Based on our comparisons of dental radiography data to life history ages, the pulp:tooth area ratio method can reliably provide same-day estimates for ages of dolphins up to about 10 years old.