Age determination and age related factors in the teeth of Western North Atlantic bottlenosed dolphins

• Main Author: Aleta A. Hohn
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 1980
• Subjects: North Atlantic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.519.9712; http://swfsc.noaa.gov/publications/CR/1980/8026.PDF

Teeth were taken from 120 bottlenose dolphins, Tursiops truncatus, which had stranded on the midAtlantic coast of the United States. The number of annual growth layer groups (GLGs) for each animal was used to construct a growth curve. The growth rate of coastal North Atlantic Ocean TuurSiOps is similar to other cetaceans in having a high initial rate of growth, with no dif-ferences in growth between females and males. In females, the first dentinal GLG is thickest and is followed by GLGs which become progressively nar-rower. In males, the second GLG is thicker than the first; GLGs beyond number two become progressively smaller but at a slower rate than in fe-males. In males and females, the translucent layer makes up proportionally larger parts of the GLG as the animal ages, but in males the percent trans-.lucent layer remains constant at about 50 % while in females it continues to increase up to about 70 % of the GLG. These two factors, GLGs width and translucent layer width, indicate that the sex and age of the animal influence the deposition of GLGs. Incremental layers are also present, averaging 12 per GLG, and seem similar to incremental layers described in other marine mammals. A plot of the relationship of percent growth of the last GLG to time of death suggests that the deposition of GLGs is relatively constant, at least during the first half of the year, and that North Atlantic Ocean Tzirsiops give birth in the fall as well as in the spring.