[MARMAM] New article:High calf mortality in bottlenose dolphins in the Bay of Islands, New Zealand–a local unit in decline
Gabriela de Tezanos Pinto
gdet002 at aucklanduni.ac.nz
Thu Nov 6 01:11:04 PST 2014
On behalf or all the co-authors, we are pleased to announce the publication
of the following paper:
High calf mortality in bottlenose dolphins in the Bay of Islands, New
Zealand–a local unit in decline. DOI: 10.1111/mms.12174.
Please download the article from the following link:
Or by emailing me at: g.tezanospinto at massey.ac.nz
Gabriela Tezanos-Pinto (PhD)
Coastal-Marine Research Group, INMS
Massey University, New Zealand
Bottlenose dolphins (*Tursiops truncatus*) in the Bay of Islands, New
Zealand, have been studied for almost two decades. Since 2003, fewer than
150 dolphins visited the bay during each season and the local unit has
declined 7.5% annually from 1997 to 2006. The causes of decline are unclear
but probably include mortality and emigration. Here, we used a long-term
database to estimate reproductive parameters of female bottlenose dolphins
including recruitment rates. A total of 704 surveys were conducted in which
5,577 sightings of 408 individually identified dolphins were collected; of
these 53 individuals were identified as reproductive females. The calving
rate increased between periods (1997–1999 = 0.13, CL = 0.07–0.21; 2003–2005
= 0.25, CL = 0.16–0.35 calves/reproductive female/year). A 0.25 calving
rate suggests that on average, a female gives birth only once every four
years, which is consistent with the estimated calving interval (4.3 yr, SD
= 1.45) but still is lower than values reported for other populations.
Conversely, apparent mortality rates to age 1+ (range: 0.34–0.52) and 2+
(range: 0.15–0.59) were higher than values reported elsewhere. The high
apparent calf mortality in conjunction with a decline in local abundance,
highlight the vulnerability of bottlenose dolphins in the Bay of Islands.
Long-term studies are required to understand the causes of high calf
mortality and the decline in local abundance. Meanwhile, management should
focus on minimizing sources of anthropogenic disturbance and enforcing
compliance with current legislation.
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