Changes in habitat use patterns by bottlenose dolphins over a 10‐year period render static management boundaries ineffective

Hartel, Elizabeth F.; Constantine, Rochelle; Torres, Leigh G.

doi:10.1002/aqc.2465

Cited by 42 publications

(35 citation statements)

References 54 publications

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“…Dolphins in the Bay of Islands have changed their patterns of residency and habitat use over time, with an apparent shift in home range (Tezanos‐Pinto , Hartel et al . ). In a stable population that had not undergone a shift in home range, it would be expected that all calves would have equal survival probabilities.…”

Section: Methodsmentioning

confidence: 97%

High calf mortality in bottlenose dolphins in the Bay of Islands, New Zealand–a local unit in decline

Tezanos‐Pinto

Constantine

Mourão

et al. 2014

Marine Mammal Science

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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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Section: Methodsmentioning

confidence: 97%

High calf mortality in bottlenose dolphins in the Bay of Islands, New Zealand–a local unit in decline

Tezanos‐Pinto

Constantine

Mourão

et al. 2014

Marine Mammal Science

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“…Mann et al (2000) found bottlenose dolphin group sizes were largest for groups with calves up to 3 mo old, which may also in part explain the formation of large groups at GBI given the high frequency of neonates and calves recorded. Based on the variable patterns of site fidelity and habitat use observed in BOI (Constantine 2002, Tezanos-Pinto 2009, Hartel et al 2014, Tezanos-Pinto et al 2013, we anticipated new individuals would continue to be photo-identified for the duration of the study. The discovery curve reached a plateau after 17 mo of field effort, although a further 8 new individuals were added to the catalogue in the final summer season.…”

Section: Discussionmentioning

confidence: 99%

“…Research on the species in this region has primarily been driven by funding generated from dolphin tourism levies through the Department of Conservation (DOC), the government agency responsible for managing New Zealand's marine mammal species (e.g. Constantine & Baker 1997, Constantine et al 2003, Hartel et al 2014). As such, research on this population has not only been heavily focused on tourism effects (e.g.…”

Section: Introductionmentioning

confidence: 99%

Overlooking a potential hotspot at Great Barrier Island for the nationally endangered bottlenose dolphin of New Zealand

Dwyer¹,

Tezanos‐Pinto²,

Visser³

et al. 2014

Endang. Species. Res.

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Conservation initiatives are typically constrained by economic circumstances, a factor certainly true for marine mammal conservation in New Zealand. Most research in this field has been conducted following concerns over anthropogenic impacts on populations and has therefore been funded and/or driven by stakeholder interest. Bottlenose dolphins Tursiops truncatus are classified as 'Nationally Endangered' in New Zealand waters. Here, we present the first study on occurrence, site fidelity and abundance of this species off Great Barrier Island (GBI), a previously overlooked region within the home range of the North Island population. Dedicated boat-based photo-identification surveys were conducted monthly from 2011−2013, resulting in 1412 sighting records of 154 individuals. Dolphins were recorded during all months of the year, with a higher probability of encounter in deeper waters during summer and shallower waters during winter and spring. Group sizes (median = 35, mean = 36) were higher than previously reported for this population in other regions. Individual re-sighting patterns were variable; however, overall site fidelity was high (mean monthly sighting rate = 0.33). A Robust Design approach resulted in seasonal fluctuations in abundance and temporary emigration. Based on a super-population estimate, 171 dolphins (CI = 162−180) visited the area during 2011−2013. Our data suggest that GBI is a potential hotspot for bottlenose dolphins of the North Island population rather than a corridor to reach other destinations. We highlight the need for researchers, managers and funding agencies to consider the entire range of a population when conducting or funding research.

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“…Such long-term stability in habitat use is important when considering spatially explicit conservation measures, such as marine protected areas (Hartel, Constantine, & Torres, 2015;Wilson, Reid, Grellier, Thompson, & Hammond, 2004). The observed species-environment relationships and resulting habitat use patterns for both species remained stable over a decade.…”

Section: Conservation Implicationsmentioning

confidence: 97%

Fine‐scale habitat partitioning of Chilean and Peale's dolphins and their overlap with aquaculture

Heinrich

Genov

Riquelme

et al. 2019

Aquatic Conservation

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1. Predictive species distribution models (SDMs) have become powerful tools to determine habitat use patterns of mobile marine predators and their spatial overlap with potentially impacting anthropogenic activities.2. This study used SDMs to investigate fine-scale habitat use patterns of two poorly known and broadly sympatric coastal delphinids, Chilean dolphins (Cephalorhynchus eutropia) and Peale's dolphins (Lagenorhynchus australis), and their spatial interactions with intense aquaculture farming activities in the Chiloé archipelago, southern Chile. A long-term dataset (2002-2012) of boat-based dolphin sightings and concur-rently in situ collected environmental and anthropogenic variables was analysed using binomial Generalized Additive Models to investigate ecological drivers of each species' fine-scale distribution and to predict dolphin occurrence spatially.4. Chilean dolphins preferred shallow (<30 m deep), turbid waters, close to shore (<500 m) and river mouths which often placed them in sheltered bays and channels used intensively by shellfish farms. Peale's dolphins were also found in shallow waters but occurred over a wider range of conditions along more open or exposed coastlines. Both species had to navigate extensive salmon and shellfish farming sites to transit between areas of important habitat.5. Sightings and predicted occurrence maps showed a clear pattern of spatial habitat partitioning between species, which remained stable across the 11 year study period. The identification of important habitat for Chilean dolphins warrants the consideration of spatially explicit conservation measures to limit the potential effects of overlapping salmon and shellfish farming.6. The observed differences in ecological plasticity of the two sympatric species should be considered when evaluating and mitigating the effects of environmental change and ongoing anthropogenic pressures on their nearshore habitat. The estimated species-environment relationships could also be used to predict where dolphin habitat and anthropogenic activities are most likely to overlap in other parts of the species' ranges.

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Changes in habitat use patterns by bottlenose dolphins over a 10‐year period render static management boundaries ineffective

Cited by 42 publications

References 54 publications

High calf mortality in bottlenose dolphins in the Bay of Islands, New Zealand–a local unit in decline

High calf mortality in bottlenose dolphins in the Bay of Islands, New Zealand–a local unit in decline

Overlooking a potential hotspot at Great Barrier Island for the nationally endangered bottlenose dolphin of New Zealand

Fine‐scale habitat partitioning of Chilean and Peale's dolphins and their overlap with aquaculture

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