Ross P.S.,Canadian Department of Fisheries and Oceans |
Dungan S.Z.,Trent University |
Hung S.K.,Hong Kong Cetacean Research Project |
Jefferson T.A.,Cetos Research Organization |
And 11 more authors.
Aquatic Conservation: Marine and Freshwater Ecosystems | Year: 2010
1.Numbering no more than 100 individuals and facing many threats, the geographically isolated Eastern Taiwan Strait population of Indo-Pacific humpback dolphins (Sousa chinensis) is in peril. The estuarine and coastal waters of central-western Taiwan have historically provided prime habitat for these dolphins, but environmental conditions today bear little resemblance to what they were in the past.2.The humpback dolphins must share their habitat with thousands of fishing vessels and numerous factories built upon thousands of hectares of reclaimed land.3.They are exposed to chemicals and sewage released from adjacent terrestrial activities. Noise and disturbance associated with construction, vessel traffic and military activities are features of everyday life for these animals.4.Measures to slow the pace of habitat deterioration and reduce the many risks to the dolphins are urgently needed. As one practical step in this direction, this paper describes the habitat needs of these small cetaceans so that decision makers will be better equipped to define 'priority habitat' and implement much needed protection measures under the terms of local legislation.5.The preferred habitat of these dolphins in Taiwan consists of shallow (<30 m), near-shore marine waters with regular freshwater inputs.6.For such a small, isolated and threatened population, 'priority habitat' should not be limited to areas of particularly intensive dolphin use or high dolphin density, but rather it should encompass the entire area where the animals have been observed (their current 'habitat'), as well as additional coastal areas with similar bio-physical features ('suitable habitat'). Such a precautionary approach is warranted because the loss of only a few individuals could have serious population-level consequences.7.While conventional socio-economic analysis might suggest that implementing protection measures over an area stretching ~350 km north-south along Taiwan's west coast and ~3 km out to sea would be too 'costly', the loss of this charismatic species from Taiwan's waters would send a troubling message regarding our collective ability to reconcile human activities with environmental sustainability. © 2010 John Wiley & Sons, Ltd.
Handel S.,University of Tennessee at Knoxville |
Todd S.K.,College of the Atlantic |
Zoidis A.M.,College of the Atlantic |
Zoidis A.M.,Cetos Research Organization
Bioacoustics | Year: 2012
Since the groundbreaking work of Payne and McVay (1971), humpback songs have been conceptualized in terms of the upward hierarchical organization of sound units within phrases, and phrases within themes. Songs change within each season and all whales in a geographical region detect and sing the reshaped song. Here we propose two properties that act to make relearning the evolving song possible. First, each level of the hierarchical structure constrains the others. We estimated the degree of constraint using information theory and found that the theme, phrase, and prior sound unit reduced the source entropy of the current sound unit equally. Different sound units are found in each theme and phrase; each theme and phrase 'uses up' some of the sound units. Second, the rhythm of the sound units acts to simplify the phrase structure. The timing between sound units often separates adjacent phrases by longer silent durations, and in spite of huge differences in the number of sound units within phrases, the overall duration of the phrases often are equal, allowing the whale to anticipate phrase repetitions. Humpback and human songs share the same hierarchical structure, but there are striking differences in the sound unit sequence. © 2012 Taylor & Francis.
Zoidis A.M.,Cetos Research Organization |
Lomac-MacNair K.S.,Cetos Research Organization |
Chomos-Betz A.E.,Cetos Research Organization |
Day A.J.,Cetos Research Organization |
McFarland A.S.,Cetos Research Organization
Aquatic Mammals | Year: 2014
Ontogeny of behavior in young humpback whale (Megaptera novaeangliae) calves likely reflects preparation for adulthood, including courtship and reproductive activities, predator avoidance, and prey capture. Reproductive strategies differ for males and females, with males competing aggressively for females, while females focus their energy on raising calves; thus, certain behaviors may develop differently in each sex. In addition to these forces driving behavioral development, ambient conditions, such as Beaufort sea state, may also impact behaviors by requiring adaptations to different environments, some of which are louder or more energetic. Herein, we examine the roles of sex, seasonal period, and sea state on Hawaiian humpback whale calf behavioral development. We used underwater video recordings to document when calves were (1) at the surface without their mothers, (2) in physical contact with or in close proximity to (within 5 m) of their mothers, (3) playing, (4) milling, (5) interacting with divers, or (6) vocalizing (social sounds). We analyzed footage of 199 groups (1,485.5 min) in which a calf was present using linear mixed effects models. Sex of the calf was determined in 107 groups (64 females, 43 males). Results indicate that males played or were surface active significantly more often than females, and that calves were at the surface without their mothers significantly more often during January and February than March, and significantly more during the end of January than the beginning of February, indicating that spatial proximity to the mother varies. There were no significant findings characterized by sea state though trends were evident. Behavioral differences by calf sex may be attributable to differences by sex in adult social roles-that is, males may need a higher level of fitness and ability to compete for access to females. Greater mother/calf separation midseason may drive development of motor skills, independence, and fitness in preparation for migration.