Population size, social structure and residence pattern of Irrawaddy dolphins (Orcaella brevirostris) in Cowie Bay, Sabah, Malaysia
Irrawaddy dolphins (Orcaella brevirostris) in Cowie Bay, southeast of Sabah were first recorded in 1999. This study was aimed at collecting baseline data on the population size, social structure and residence pattern of the Irrawaddy dolphins in the bay. Boat surveys were conducted monthly during ne...
Saved in:
| Main Author: | |
|---|---|
| Format: | Thesis |
| Language: | English English |
| Published: |
2013
|
| Subjects: | |
| Online Access: | https://eprints.ums.edu.my/id/eprint/42652/1/24%20PAGES.pdf https://eprints.ums.edu.my/id/eprint/42652/2/FULLTEXT.pdf https://eprints.ums.edu.my/id/eprint/42652/ |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Summary: | Irrawaddy dolphins (Orcaella brevirostris) in Cowie Bay, southeast of Sabah were first recorded in 1999. This study was aimed at collecting baseline data on the population size, social structure and residence pattern of the Irrawaddy dolphins in the bay. Boat surveys were conducted monthly during neap tide, from October 2009 until September 2010. Data for population size were collected using line transect distance sampling and photo-identification mark-recapture methods and were analysed using DISTANCE 6.0 and MARK 6.1 programs. Data for social structure and residence pattern were collected using photo-identification as well; and were analysed using SOCPROG 2.4 program. Twenty-seven individuals had permanent marks that enabled them to be identified. The population size estimated via DISTANCE 6.0 was negatively biased due to the low number of detections (N=5, 95%CI=2 – 12; CV=0.46). CAPTURE within program MARK 6.1 estimated the population size to be very small (N=31, 95%CI=28 – 34; CV=0.06). Associations between individual dolphins were non-random, preferred companionships and long-term companionships were present among the individuals. Standard deviation of the observed half weight index was significantly larger than standard deviation of the random half weight index (p=0.0009054). The social structure was driven by stable associations over time, and it was a closed population. More than half (n=15) of the identified individuals were commonly seen (7 months or more) throughout the sampling period in the study area. Results indicate that the Cowie Bay population of Irrawaddy dolphins is small, and are resident. |
|---|