碩士 / 國立臺灣大學 / 海洋研究所 / 101 / Laticauda (Reptilia, Eplapidae) is a group of sea kraits that has to lay eggs, molt or digest food on the land. This research focuses on the feeding activities and diet compositions of L. laticaudata and L. colubrina in Kudakajima(with only L. laticaudata exist) and Ishgakijima(with both L. laticaudata and L. colubrina sympatry), Okinawa, Japan. The aim was to investigate possible diversifications of daily and seasonal activity patterns as well as diet compositions of sympatric populations comparing with those of allopatric populations. This study was conducted in Spring, Summer and Autumn in 2012, and the survey time in each season was about 23 days. In each survey, the occurrences of sea kraits at each site was recorded for 6 to 8 hours and lasted for 4 or 5 days. Sea kraits were caught to study their stomach contents.
Seasonal activity pattern of L. colubrina peaked in spring and declined in summer and autumn, but for L. laticaudata, two populations show difference in seasonal activity patterns. Population of L. laticaudata in Kudakajima started to appear in spring, remained active in summer and peaked in autumn. While in Ishigakijima, L. laticaudata was rarely found in spring but peaked in summer and declined in autumn. This shorter activity season in Ishigakijima population may be due to the separation of habitat uses related to sympatric competition. Furthermore, daily activities of L. colubrina peaked around 19:00~20:00 in 3 seasons, while in L. laticaudata daily activities differed among seasons but there was no difference between populations. In spring, L. laticaudata at both sites had their activities peaked around 19:00~20:00. In summer, the peak of activities occurred at 22:00. In autumn, they were active throughout the night after 19:00. The fixed daily activity patterns may be due to physiology constraint to avoid overheat or water loss. Most of the stomach contents from L. colubrina were Gymnothorax with a small portion of Conger. In L. laticaudata, more than half of the stomach contents of L. laticaudata in both populations were Gymnothorax. But the population in Kudakajima ingested other fishes such as Plotosus lineatus and fish eggs, while the populations in Ishigakijima ingested Ophichthidae. The relative head width showed the possibility of diet divergence. Head width of Ishigakijima population was smaller than that of Kudakajima population, this may enable them to consume smaller food items such as Ophichthidae.
| Identifer | oai:union.ndltd.org:TW/101NTU05279003 |
| Date | January 2013 |
| Creators | Shuo-Wen Chang, 張碩文 |
| Contributors | Cheng-Feng Dai, 戴昌鳳 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 55 |
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