Investigating individual growth rates in wild bottlenose dolphins using remote laser photogrammetry

Barbara Cheney, Randall S. Wells, Paul M Thompson

Research output: Contribution to conferencePoster

Abstract

Morphometric data are key to understanding many aspects of population and behavioural ecology, but are difficult to collect for wild cetaceans. We developed a laser photogrammetry system to remotely measure blowhole-dorsal fin lengths during bottlenose dolphin photo-identification surveys in NE Scotland. Total lengths were then estimated from relationships derived from measurements of stranded individuals. To determine the field method’s accuracy, we remotely measured 13 known length bottlenose dolphins in Sarasota Bay, Florida. The difference between the length measured during health assessments and our remotely measured length was small (median = 1.5cm). We then aimed to estimate age-specific lengths and individual growth rates in bottlenose dolphins from Scottish waters using field measurements of 90 known-age individuals. These animals ranged from new-born to 26 years old, with an average of 3 and maximum of 8 years of data for each individual. Estimated total lengths ranged from 128 cm for <2 week old calf to 352 cm for a 19 year old male, with considerable variation in size-at-age. Growth rates estimated using generalised logistic growth curves, showed variability between individuals, but were highest during the first year of life. Calves that died over their first winter were significantly shorter than calves that survived. Growth rates in males and females were similar until approximately 7 years old when male growth rates exceeded females. This method can be used to assign approximate age classes to individuals of unknown age to investigate demography. By incorporating these methods into long-term studies, repeat measurements of known individuals also provide new opportunities to investigate potential drivers of variation in growth rates (e.g., different habitat use, changes in food availability, disturbance) and the longer term consequences (e.g., survival, fecundity) of variation in early growth.
Original languageEnglish
Number of pages1
Publication statusPublished - Dec 2015
Event21st Biennial Society for Marine Mammalogy Conference -
Duration: 14 Dec 201518 Dec 2015

Conference

Conference21st Biennial Society for Marine Mammalogy Conference
Period14/12/1518/12/15

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photogrammetry
Tursiops truncatus
lasers
calves
demography
Scotland
food availability
fins
age structure
fecundity
methodology
ecology
winter
habitats

Cite this

Cheney, B., Wells, R. S., & Thompson, P. M. (2015). Investigating individual growth rates in wild bottlenose dolphins using remote laser photogrammetry. Poster session presented at 21st Biennial Society for Marine Mammalogy Conference , .

Investigating individual growth rates in wild bottlenose dolphins using remote laser photogrammetry. / Cheney, Barbara ; Wells, Randall S.; Thompson, Paul M.

2015. Poster session presented at 21st Biennial Society for Marine Mammalogy Conference , .

Research output: Contribution to conferencePoster

Cheney, B, Wells, RS & Thompson, PM 2015, 'Investigating individual growth rates in wild bottlenose dolphins using remote laser photogrammetry' 21st Biennial Society for Marine Mammalogy Conference , 14/12/15 - 18/12/15, .
Cheney B, Wells RS, Thompson PM. Investigating individual growth rates in wild bottlenose dolphins using remote laser photogrammetry. 2015. Poster session presented at 21st Biennial Society for Marine Mammalogy Conference , .
Cheney, Barbara ; Wells, Randall S. ; Thompson, Paul M. / Investigating individual growth rates in wild bottlenose dolphins using remote laser photogrammetry. Poster session presented at 21st Biennial Society for Marine Mammalogy Conference , .1 p.
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AB - Morphometric data are key to understanding many aspects of population and behavioural ecology, but are difficult to collect for wild cetaceans. We developed a laser photogrammetry system to remotely measure blowhole-dorsal fin lengths during bottlenose dolphin photo-identification surveys in NE Scotland. Total lengths were then estimated from relationships derived from measurements of stranded individuals. To determine the field method’s accuracy, we remotely measured 13 known length bottlenose dolphins in Sarasota Bay, Florida. The difference between the length measured during health assessments and our remotely measured length was small (median = 1.5cm). We then aimed to estimate age-specific lengths and individual growth rates in bottlenose dolphins from Scottish waters using field measurements of 90 known-age individuals. These animals ranged from new-born to 26 years old, with an average of 3 and maximum of 8 years of data for each individual. Estimated total lengths ranged from 128 cm for <2 week old calf to 352 cm for a 19 year old male, with considerable variation in size-at-age. Growth rates estimated using generalised logistic growth curves, showed variability between individuals, but were highest during the first year of life. Calves that died over their first winter were significantly shorter than calves that survived. Growth rates in males and females were similar until approximately 7 years old when male growth rates exceeded females. This method can be used to assign approximate age classes to individuals of unknown age to investigate demography. By incorporating these methods into long-term studies, repeat measurements of known individuals also provide new opportunities to investigate potential drivers of variation in growth rates (e.g., different habitat use, changes in food availability, disturbance) and the longer term consequences (e.g., survival, fecundity) of variation in early growth.

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