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Surfacing characteristics and diving behaviour of blue whales in Sri Lankan waters
Abstract
Surfacing behaviour and dive characteristics were quantified from focal follows of individual blue whales between January–March 2012 and 2013. During this period individual whales were followed from small boats to observe their surfacing patterns and breathing behaviour. Data on time at first surface, length of surface interval, number of blows, final dive time and whether or not the whale ‘fluked up’ before a deep dive were recorded. A step-wise modelling approach was used to estimate a number of surfacing characteristics: mean Inter-Breath Interval (IBI), bout duration and the number of surfacings in a bout. First, dives were classified as either surface dives or deep dives based on the occurrence of arching or fluking behaviour at the surface prior to a deep dive. The mean IBI of surface dives was 17.6 s (SD = 26.14) and for deep dives, 640.3 s (SD = 214.38). To account for temporal dependence between dive types, a first-order Markov chain was used to estimate the transition probability between dive types. Time series of dive types were then simulated, using Monte Carlo methods, while accounting for heterogeneity in IBI of the different dive types. The mean IBI of blue whales in Sri Lanka, obtained from the Monte Carlo methods, was 84.7 s (SD = 11.17). The mean bout duration was 145 s (SD = 28.31), with the mean number of breaths per surface bout being 9.3 (SD = 1.43). Whales also lifted their tail flukes out of the water on 55% of terminal dives, which is considerably more frequent than elsewhere in the world. These results significantly advance our understanding of blue whales in Sri Lankan waters. More specifically, this information is essential for the calculation of precise abundance estimates as it informs the detection probability parameters for line transect surveys. In this way it will help formulate better management decisions related to the conservation of this population.
... Mean dive time was 11.1mins, and modal time was 10-12mins. These dive times are similar to the mean deep dive time of 10.7mins recorded by de Vos et al. (2013b) in the same area, and may be indicative of foraging depth (cf Doniol-Valcroze et al., 2011). In contrast, among a (smaller) sample of dive times recorded from blue whales (presumed to be on passage) in the Maldives, dives of 10-11mins were particularly uncommon (Anderson, 2005). ...
... And while de Vos et al. (2014 did find an interannual shift in blue whale distribution offshore, that was related to interannual differences in oceanographic conditions. Furthermore, de Vos et al. (2013b) found no change in the frequency of fluking up before deep dives in the presence or absence of whale-watching vessels. Nevertheless, the data presented here do suggest that blue whales were more latitudinally dispersed during 2010-13 than in 2007-2009; one possible explanation could be disturbance by whale-watching vessels. ...
... Wijeyeratne, 2008) whale watching activities have expanded rapidly (Fig. 7), as too has boat-based cetacean research (e.g. Ilangakoon, 2012a;2012b;de Vos et al., 2013a;2013b;2014b;Randage et al., 2014;Priyadarshana et al., 2016). reported is probably the great increase in the number of observers, following the expansion of whale watching. ...
Cetaceans were observed off the South coast of Sri Lanka in the month of April, every year over a seven-year period, 2007–13. During 48 days atsea a total of 290 cetacean sightings were recorded. Blue whales were abundant, accounting for 61% (n = 177) of all sightings. This concentrationof blue whales was predicted and discovered based on a migration hypothesis and there was evidence of the expected net westward movement inApril. Nevertheless, most blue whales seen were not obviously on passage and many appeared to be feeding. Mothers with calves and likelyreproductive behaviour (breaching and rushing) were also observed. There were five sightings of Bryde’s-type whales (B. brydei/edeni); four wereidentified as B. brydei, one was identified as B. edeni. Sperm whales were sighted 16 times within a narrow band centred just outside the 1,000misobath. Modal group size was 10–12; based on size most individuals appeared to be mature females or immatures. Spinner dolphin (n = 35 sightings)was the most abundant species, accounting for 67% of all cetaceans seen by number of individuals. They were frequently associated with tuna andseabirds. Risso’s dolphin was only seen once, despite being reported as common around Sri Lanka in the early 1980s. They were taken in largenumbers by local fisheries, which may have reduced local abundance. Other species recorded were: dwarf sperm whale (n = 3 sightings); shortfinnedpilot whale (n = 3); common bottlenose dolphin (n = 9); Indo-Pacific bottlenose dolphin (n = 3); pantropical spotted dolphin (n = 4); andstriped dolphin (n = 4). Since the discovery of blue whales off southern Sri Lanka, commercial whale watching centred on the fishing port of Mirissahas developed rapidly, bringing new revenue to the region but also the potential for disturbance to the whales.
... Protozoan parasites have been detected in both North Atlantic right whales (Eubalaena glacialis) and bowhead whale feces (Balaena mysticetus) (Hughes-Hanks et al., 2005). Therefore the main purpose of this work was to ascertain if the Northern Indian Ocean blue whale also preferentially preyed on euphausiids, as visual observations of diving behavior suggest they may be targeting deeper water species around Sri Lanka (de Vos et al., 2013). Secondarily, these samples were used to identify other species such as parasites that exist within the gut flora of the blue whales within the Northern Indian Ocean. ...
... Feeding on these epibenthic animals necessitates deeper foraging dives. Within the NIO, blue whales have been frequently documented "fluking up, " or lifting their tail flukes before a deep dive (de Vos et al., 2013). These whales have been observed accelerating in to the terminal surfacing as they present the high arch and then the fluke (de Vos et al., 2013), enabling them to flip vertically and sink to depth likely because the high descent angles enable faster acceleration when the body is vertically oriented, due to lowered pressure drag as the projected area is significantly decreased compared to when the body is broadside to vertically acting buoyant forces (Goldbogen et al., 2006). ...
... Within the NIO, blue whales have been frequently documented "fluking up, " or lifting their tail flukes before a deep dive (de Vos et al., 2013). These whales have been observed accelerating in to the terminal surfacing as they present the high arch and then the fluke (de Vos et al., 2013), enabling them to flip vertically and sink to depth likely because the high descent angles enable faster acceleration when the body is vertically oriented, due to lowered pressure drag as the projected area is significantly decreased compared to when the body is broadside to vertically acting buoyant forces (Goldbogen et al., 2006). ...
Blue whales are little studied, face significant anthropogenic threats and within the Northern Indian Ocean, have a restricted range, making them an archetype for conservation needs of megafauna around the world. We studied feeding behavior of blue whales using dietary DNA metabarcoding of fecal samples. While globally blue whale populations feed predominantly on Euphausiidae, 87% of prey DNA amplicons extracted from fecal samples from this population were sergestid shrimp, demonstrating that blue whales can locate and feed on dense swarms of other types of prey when they occur. Within the Indian Ocean sergestids are present within the top 300 m, which correlates with the deep scattering layer observed by hydroacoustics. Studies suggest that this requirement to dive deeper in search of prey likely explains the prevalence of fluke up diving within this population of blue whales relative to other parts of the globe. Furthermore, this study revealed the presence of acanthocephalan endoparasites within the stomach and intestines of the Northern Indian Ocean blue whales. This represents the first record of Acanthocephala in blue whales in the Northern Indian Ocean and highlights the need for further studies on both the ecto- and endoparasitic flora and monitoring of health of these cetaceans for their management and conservation.
... The blue whale is classified as endangered with an estimated 5000 to 10,000 blue whales remaining worldwide. Unlike blue whale populations in other parts of the world, those in the Northern Indian Ocean do not appear to migrate beyond this single ocean basin (Anver, 2012;de Vos, Christiansen, Harcourt, & Pattiaratchi, 2013). Sperm whales are currently listed as a vulnerable species and are protected by a whaling moratorium (Fig. 1). ...
... The possible movement of whales is especially important in Mirissa since "one of the most heavily trafficked shipping routes in the world is 15 miles off the southern coast of Sri Lanka. This is the major channel for ships headed to the Indian Ocean" (Dixon, 2012; see also Anver, 2012;de Vos et al., 2013). Whales in this channel are at risk of being killed by collisions with large container vessels that use the shipping lanes. ...
... It is difficult to establish how the inappropriate behaviour of tour boats fully impacts on the whale population. The relatively recent 'discovery' of whales off the Mirissa coast has meant there is comparatively little data available on the ecology of blue whales at this site (de Vos et al., 2013). Whale watching can have a wide variety of short-term effects on whales (Parsons, 2012;Higham et al., 2009) and this appears to be occurring at this site. ...
Whale watching creates an economic value for whales beyond consumption and therefore assists in the conservation of the species. However sustainable management is needed to avoid deleterious impacts on the whales and the industry. This paper uses a range of qualitative methods to examine the characteristics, management and perceived sustainability of the relatively newly established whale watching industry in Sri Lanka. It is clear that the laissez faire development of the industry has resulted in some poor conservation outcomes for the whales as well as variable tourist experiences. The Sri Lankan government has introduced legislated regulations aimed at managing the industry however it must ensure adequate human and financial resources are provided to ensure the effective implementation of the regulations and therefore the sustainability of the industry.
... The blue whale is classified as endangered with an estimated 5000 to 10,000 blue whales remaining worldwide. Unlike blue whale populations in other parts of the world, those in the Northern Indian Ocean do not appear to migrate beyond this single ocean basin (Anver, 2012;de Vos, Christiansen, Harcourt, & Pattiaratchi, 2013). Sperm whales are currently listed as a vulnerable species and are protected by a whaling moratorium (Fig. 1). ...
... The possible movement of whales is especially important in Mirissa since "one of the most heavily trafficked shipping routes in the world is 15 miles off the southern coast of Sri Lanka. This is the major channel for ships headed to the Indian Ocean" (Dixon, 2012; see also Anver, 2012;de Vos et al., 2013). Whales in this channel are at risk of being killed by collisions with large container vessels that use the shipping lanes. ...
... It is difficult to establish how the inappropriate behaviour of tour boats fully impacts on the whale population. The relatively recent 'discovery' of whales off the Mirissa coast has meant there is comparatively little data available on the ecology of blue whales at this site (de Vos et al., 2013). Whale watching can have a wide variety of short-term effects on whales (Parsons, 2012;Higham et al., 2009) and this appears to be occurring at this site. ...
Whale watching creates an economic value for whales beyond consumption and therefore assists in the conservation
of the species. However sustainable management is needed to avoid deleterious impacts on the whales
and the industry. This paper uses a range of qualitative methods to examine the characteristics, management
and perceived sustainability of the relatively newly established whale watching industry in Sri Lanka. It is clear
that the laissez faire development of the industry has resulted in some poor conservation outcomes for the
whales as well as variable tourist experiences. The Sri Lankan government has introduced legislated regulations
aimed at managing the industry however itmust ensure adequate human and financial resources are provided to
ensure the effective implementation of the regulations and therefore the sustainability of the industry.
... Approximate observation effort (in time) spent within the shipping lanes was less than 2% of the total time spent searching but 10% of sightings were within the shipping lanes and 32% within 5km. This, in combination with several reports of blue whale fatalities in recent years (de Vos et al., 2013;Priyadarshana et al., 2016) renders it important to understand the abundance of the NIO population and its distribution in order to estimate the relative risk of vessel collisions and their impact on the population. ...
... During encounters, blue whales typically surfaced five to 10 times before diving for approximately 10mins. This corresponds to findings by de Vos et al. (2013) who collected data off the southern coast of Sri Lanka. Their records show that the typical blue whale surfacing pattern consisted of three to 20 (average 11) breathing bouts followed by a dive averaging 640s (10.7mins). ...
This study fills a knowledge gap on the presence and movement of blue whales in the NIO, highlighting the importance of data that can be obtained from platforms of opportunity. Blue whales were recorded off the southern coast of Sri Lanka during the southwest monsoon season. Whilst blue whales are regularly recorded on the continental slope of southern Sri Lanka during the northeast monsoon season (NEM) (December–March) and during the two inter-monsoonal periods (March–April and September–October), limited data are available for the SWM (May–September) mostly due to unfavourable weather conditions and a lack of survey effort. It has been suggested that a population of blue whales in the northern Indian Ocean (NIO) remains in lower latitudes year-round, taking advantage of the rich upwelling areas off Somalia, southwest Arabia and western Sri Lanka. Data from this study support a hypothesis that a certain number of individuals remain off the southern coast of Sri Lanka during the SWM, suggesting that the productivity in this region is sufficient to support their year-round presence.
... The dives of marine mammals (the time elapsed between two consecutive breaths) can generally be divided into relatively longer dives, during which the animal engage in some activity (e.g. foraging or traveling), and relatively shorter dives, when the animal replenishes its oxygen stores by taking a series of deep breaths in relatively rapid succession [21][22][23]. In this paper we will refer to these two dive types as long dives and short dives, respectively. ...
... The surfacing breathing patterns (hereafter referred to as surfacing patterns) of minke whales were investigated by first investigating the temporal dependence between dive types (the behavioral process) [39], by estimating the transition probability between dive types [22,23,40]. We ran separate analyses for each activity state, to test if minke whales structure their surfacing pattern differently depending on their activity. ...
Animal behavioral patterns can help us understand physiological and ecological constraints on animals and its influence on fitness. The surfacing patterns of aquatic air-breathing mammals constitute a behavioral pattern that has evolved as a trade-off between the need to replenish oxygen stores at the surface and the need to conduct other activities underwater. This study aims to better understand the surfacing pattern of a marine top predator, the minke whale (Balaenoptera acutorostrata), by investigating how their dive duration and surfacing pattern changes across their activity range. Activities were classified into resting, traveling, surface feeding and foraging at depth. For each activity, we classified dives into short and long dives and then estimated the temporal dependence between dive types. We found that minke whales modified their surfacing pattern in an activity-specific manner, both by changing the expression of their dives (i.e. density distribution) and the temporal dependence (transition probability) between dive types. As the depth of the prey layer increased between activities, the surfacing pattern of foraging whales became increasingly structured, going from a pattern dominated by long dives, when feeding at the surface, to a pattern where isolated long dives were followed by an increasing number of breaths (i.e. short dives), when the whale was foraging at depth. A similar shift in surfacing pattern occurred when prey handling time (inferred from surface corralling maneuvers) increased for surface feeding whales. The surfacing pattern also differed between feeding and non-feeding whales. Resting whales did not structure their surfacing pattern, while traveling whales did, possibly as a way to minimize cost of transport. Our results also suggest that minke whales might balance their oxygen level over multiple, rather than single, dive cycles.
... A second researcher recorded i) distances from the vessel to the whale(s) using a laser range finder (Bushnell 10 × 42), ii) bearings to the whale(s) from the vessel using a digital compass (Celestron TrekGuide) and iii) swim heading of the whale(s) relative to the research vessel. This information was collected at 1 minute intervals if whales were surfacing frequently, otherwise during each surfacing bout (time period between the first surfacing and the last surfacing before a long dive, de Vos et al., 2013). A third researcher drove the vessel and assisted in keeping track of individual whales with the aid of photo-identification (Canon 50D, 400 mm lens). ...
Swim-with-whale tourism is a lucrative and rapidly growing industry worldwide. Whale-watching can cause negative effects on the behaviour of targeted animals. Although this is believed to be particularly true for close-up interactions, such as swim-with operations, few empirical studies have investigated this. In 2016, the Western Australian State Government commenced a swim-with humpback whale (Megaptera novaeangliae) trial in the Ningaloo Marine Park, where 11 commercial licences were granted. The swim-with trial was conducted during both the northern and southern whale migration (August to November), during which we assessed potential short-term behavioural effects on humpback whales to swim-with activities. From both an independent research vessel (n = 300 h) and on-board commercial swim-with vessels (n = 357 h), we collected group-follow data (n = 224) on whale behaviour before, during and after swim-with activities. Behavioural effects on whales were investigated, including movement patterns (deviation and directness index, heading, swim speed), surfacing patterns (dive duration and respiration rate) and occurrence of agonistic behaviours. Results showed that the most common type of vessel approach to place swimmers in the water was in the path of whales (89.8% of interactions). During in-path approaches, vessels travelled significantly faster (P = .002) compared to when approaching from the side (side/line abreast approaches). When vessels approached in the whales' path, whales exhibited horizontal and vertical avoidance strategies by adopting a less predictable path (deviating from 32° to 46°), increasing turning angles away from the vessel (heading from 73° to > 90°), increasing swim speeds (from 1.68 to 1.89 ms −1), and decreasing the duration of their dives (from 224 to 194 s). Whales displayed a higher frequency of agonistic behaviours when a swim-with vessel was < 100 m distance from them compared to > 100 m away (P = .011). Young-of-year calves were present during 19.6% (18 of 92) of group-follows that included swim attempts. To reduce potential impacts on whales and increase swimmer safety, we recommend to avoid in-path vessel approaches, not place swimmers in the water with groups of whales that perform agonistic behaviours, and avoid swimming with young-of-year calves.
... The second researcher recorded the i) distance from the research vessel to the whale(s) using a laser range finder (Bushnell 10 x 42 Fusion 1 mile laser), ii) bearing of the whale(s) from the research vessel using a digital compass (Celestron TrekGuide) (Gordon, 2001) and iii) heading of the whale(s). This information was collected every minute if the whale was surfacing frequently, otherwise it was collected once during a surfacing bout (time period between the first surfacing and the last surfacing before a long dive, de Vos et al., 2013). The third researcher drove the vessel and would assist in keeping track of individual whales with the aid of photo-identification. Humpback whales can be identified from from the shape of their dorsal fin (Katona and Whitehead 1981) and/or distinctive marks, colouring and scars, which were photographed using a Canon 50D camera with a 400 mm lens. ...
During the 2016 swim-with humpback whale trial in Ningaloo Marine Park, Western Australia, we assessed potential impacts on whales, risks to the safety of swimmers, and the efficacy of the Department of Parks and Wildlife trial swim-with-whale protocols. From an independent research vessel and on-board whale-watch vessels, trained observers collected group-follow data on whale behaviour in the absence ('control') and presence ('impact') of whale-watch vessels, and 'after' swim-with interactions.
... In terms of dives, two forms can be distinguished: short dives that serve replenishing oxygen and long dives that consist of physiological activities such as hunting or traveling (Christiansen et al. 2011, De Vos et al. 2013. A dive is the time between two consecutive breaths (Christiansen et al. 2011), data on sequences of breaths vary. ...
Knowledge of the distribution of cetacean species in an ecosystem is essential for species conservation efforts. As highly productive estuarine system, the St. Lawrence Estuary in Eastern Canada is a crucial summer feeding ground for large whales. To gain insight into potential ecological preferences of whales within this area and their foraging strategies, it is important to study their distribution and habitat use. Aim of this master thesis was to determine the spatial
distribution of cetaceans in the study area with respect to preferred depth zones. Habitat selection of six whale species (Mysticetes and Odontocetes) was investigated according to the occurrence of whales in maximum depth classes. For spatial analysis, GPS positions were analyzed via geographic information system software. The main focus of the study was on the highly abundant minke whale, with the aim to scientifically approach a conjecture made in earlier observations, according to which they characteristically occur close to shore. Therefor concrete habitat use was considered on an individual basis to examine variability in exploitation of the
environment. Individual GPS tracks were recorded and sightings were matched to a catalogue of previously identified individuals. In an attempt to preserve this species, minke whales were investigated according to absence or presence of behavioral reactions towards
attempted and successful biopsies. General results suggest a strong preference of five out of six whale species towards certain depth classes. Minke whales seem to show three categories of GPS tracks
- feeding, foraging and traveling – that are distinct to each other by several features. Large-scale site fidelity is demonstrated by the minke whale, which reoccurred to the same feeding ground. Four out of five minke whales responded towards biopsies, indicating moderate
reactions with some variation on an individual basis.
All in all, this thesis provides a broad overview on the distribution of cetaceans in the St. Lawrence Estuary and gives insight to the implied complex foraging- and migrating structures of the minke whale. It further points to potential sensitivity of individual minke whales towards changes in the environment, e.g. in the form of behavioral disturbance. It has been shown that techniques to study cetaceans on a basis of minimal impact can be profitable to both researcher and research object.
... This may be due to the relative abundance of this species in the sea lanes just off Sri Lanka. Moreover, blue whales in Sri Lanka typically make short, shallow dives [11,12] and spend a relatively high proportion of their time feeding, socializing, and resting at the surface making them relatively more vulnerable to blunt trauma impacts. ...
The greatest threat to cetaceans in Sri Lankan waters was considered to be the direct take of small- and medium-sized cetaceans using harpoons and/or as bycatch until recently. However, ship strikes have probably been occurring for years but have not been recognized for what they were. For the current study, only animals with visible and prominent injuries related to collisions were evaluated. Data gathered between 2010 and 2014 included the species, morphometry, location, and date; tissue samples were collected for genetic analysis. When possible, a complete necropsy was conducted; otherwise, partial necropsies were conducted. The study confirmed 14 reports of ship strikes between whales and vessels out of all the strandings reported from 2010 to 2014. Most strikes ( n=09 , 64%) involved blue whales (Balaenoptera musculus), although three other species were also documented, one Cuvier’s beaked whale, two great sperm whales, and one Bryde’s whale, as well as one unidentified baleen whale. Collision hotspots such as the southern waters of Sri Lanka are areas that warrant special attention in the form of vessel routing measures or speed limits, research on cetacean ecology, distribution, daily and seasonal movements, public service announcements, increased law enforcement presence, and other measures.
... Senigaglia et al. [107] found no changes in the travelling speed or respiration rate of humpback whales (Megaptera novaeangliae) in relation to whale-watching activity off New Caledonia and Australia. Similarly, blue whales in Sri Lankan waters did not display behavioral changes in the presence of whale-watch boats [108]. Nevertheless there is public concern that persistent close approaches by tour boats may have a negative impact by disrupting the normal behavior patterns of whales [109]. ...
... Senigaglia et al. [107] found no changes in the travelling speed or respiration rate of humpback whales (Megaptera novaeangliae) in relation to whale-watching activity off New Caledonia and Australia. Similarly, blue whales in Sri Lankan waters did not display behavioral changes in the presence of whale-watch boats [108]. Nevertheless there is public concern that persistent close approaches by tour boats may have a negative impact by disrupting the normal behavior patterns of whales [109]. ...
Blue whales in the Northern Indian Ocean are a morphologically and acoustically distinct population restricted to these waters. Off Sri Lanka a portion of the population concentrates near shore where they are exposed to a range of anthropogenic threats. We review available data to determine anthropogenic threats/stressors faced by this population and assign subjective rankings for the population-level severity of each threat/stressor based on severity, scope, and immediacy. With the cessation of direct illegal catches on this population in the late 1960s, we ranked ship strike as the most important population-level threat. Incidental catch, which includes entanglement and bycatch, is also important as it can result in death. Other less important stressors that may negatively impact this population include threats resulting from oil and gas development and pollution. However, some stressors can have a long-term cumulative impact that is difficult to assess. The most important research needed for the conservation of these whales is to obtain an estimate of the size of the population using photo-identification methods.
... Recent meta-analyses by Senigaglia et al. [33] did not show any changes in respiration rate in the presence of whale-watch boats. Similarly, blue whales in Sri Lankan waters did not display changes in fluking behaviour in the presence of whale-watch boats [34]. Secondly, in 2012 there was an increase in the number of whale-watching boats on the water compared to 2011 [35]. ...
Blue whale (Balaenoptera musculus) movements are often driven by the availability of their prey in space and time. While globally blue whale populations undertake long-range migrations between feeding and breeding grounds, those in the northern Indian Ocean remain in low latitude waters throughout the year with the implication that the productivity of these waters is sufficient to support their energy needs. A part of this population remains around Sri Lanka where they are usually recorded close to the southern coast during the Northeast Monsoon. To investigate inter-annual variability in sighting locations, we conducted systematic Conductivity-Temperature-Depth (CTD) and visual surveys between January–March 2011 and January–March 2012. In 2011, there was a notable decrease in inshore sightings compared to 2009 and 2012 (p < 0.001). CTD data revealed that in 2011 there was increased freshwater in the upper water column accompanied by deeper upwelling than in 2012. We hypothesise that anomalous rainfall, OPEN ACCESS J. Mar. Sci. Eng. 2014, 2 535 along with higher turbidity resulting from river discharge, affected the productivity of the inshore waters and caused a shift in blue whale prey and, consequently, the distribution of the whales themselves. An understanding of how predators and their prey respond to environmental variability is important for predicting how these species will respond to long-term changes. This is especially important given the rapid temperature increases predicted for the semi-enclosed northern Indian Ocean.
The Indian Ocean Sanctuary was established in 1979 in an effort to allow exploited stocks of whales to recover from Passed away in the 2004 Indian Ocean tsunami during fieldwork in Thailand. to establish comprehensive management and conservation measures for species within these waters. The current study took place in the offshore waters of Sri Lanka in early 2003. During three research cruises conducted between 29 March and 17 June 2003 the R/V Odyssey covered a total track line of 4,480km around the island resulting in 52 confirmed group sightings of 11 species from three cetacean families. As the tracklines were designed to locate sperm whales (Physeter macrocephalus) for tissue sampling, they accounted for the greatest number of sightings. Only two species of balaenopterids, the blue whale (Balaenoptera musculus) and the Bryde's whale (Balaenoptera edeni), were recorded with the blue whale being the most frequently sighted species. Spinner dolphins (Stenella longirostris) were the most dominant species in terms of numbers. Some small odonotocetes such as the common bottlenose dolphin (Tursiops iruncatus), striped dolphin (Stenella coeruleoalba) and Fraser's dolphin (Lagenodelphls hosei) were observed in mixed-species groups, while one group of melon-headed whales (Peponocephala electro) was seen associating with a group of sperm whales. Risso's dolphins (Grampus griseus) were frequently sighted throughout the research cruise, with one unusual record of a large mating group. Many sightings were made in the vicinity of the numerous submarine canyons around Sri Lanka's coastline highlighting their potential role in enhancing productivity in the offshore waters. It is concluded that Sri Lankan offshore waters hold a rich, but little surveyed cetacean fauna that warrants further studies and implementation of conservation measures to protect these populations.
A visual aerial line transect survey for common minke whales (Balaenoptera acutorostrata) was conducted off West Greenland in August and September 2007. A total of 8,670km of survey effort covered 11 strata in sea states <5 with a total stratum area of 213,807km2. The 27 sightings of common minke whales were all within a strip width of 300m and the average time from first detection to when the sighting passed abeam was 1.7 sec. Due to the uniform and narrow distribution of the detections, strip census methods were used to analyse the survey. Two methods were deployed to correct the strip census estimates for whales missed by the observers and whales that were submerged during the passage of the plane. Method 1 included all detections of common minke whales (n = 27) and correction for an instantaneous availability that included submergence of whales. Using data from sea states <3 (n = 22) the 'at surface' abundance of common minke whales was 1,866 (CV = 0.30) whales. A correction for whales missed by the observers with a simple mark-recapture estimator resulted in a corrected abundance of 1,904 (CV = 0.30) whales. Adjusting for the availability bias resulted in a fully corrected estimate of 16,609 (95% CI7,172-38,461) common minke whales. Method 2 used only detections of common minke whales that were observed to break the surface (n = 19). Applying this method to effort data at sea state <3 (n = 14) resulted in an 'at surface'abundance of 1,174 (CV = 0.39) whales. A correction for whales missed by the observers increased the abundance to 1,198 (0.39) whales. Adjusting for the availability bias resulted in a fully corrected estimate of 22,952 (95% CI 7,815-67,403) common minke whales.
Records of large whale strandings in Sri Lanka since 1889 are scattered throughout the
available literature but have never been subject to any analyses. Stranding records of the
Cetacean families Balaenopteridae and Physeteridae, occurring between 1889 and 2004
are compiled here into a single comprehensive list and examined in terms of species
composition, area of coastline from where strandings have been recorded and month.
Records are compiled through a literature survey of published historical data and
supplemented with recent unpublished data collected by the author. According to the
present data six species of large whales including , Balaenoptera musculus, Balaenoptera
physalus, Balaenoptera acutorostrata, Balaenoptera edeni, Megaptera novaeangliae of
the family Balaenopteridae and Physeter macrocephalus of the family Physeteridae have
stranded along Sri Lanka's coastline. Strandings have occurred all round the island with the
majority being on the west coast. Overall, the largest number of stranding events has
occurred in the months of August and November but there are species-wise differences in
the stranding data.
The largest southern hemisphere humpback whale Megaptera novaeangliae stock
(E1) uses the east coast of Australia as a migratory corridor to travel between their high-latitude
feeding grounds in the Southern Ocean and low-latitude breeding grounds in northeast Queensland
and the south-west Pacific Ocean. The population is recovering at close to the maximum rate
of growth (rm), and the increasing abundance of whales passing within sight of land has facilitated
the development of a growing land- and vessel-based whale watching industry. We observed the
behaviour of 156 individual pods of humpback whales passing Sydney, New South Wales, during
their 2006 and 2007 northern migration and monitored vessel−whale interactions with respect to
the Australian National Guidelines for Whale and Dolphin Watching 2005. We applied generalised
linear mixed models with random effects to compute the odds of changing to the current
behaviour state. We found that in the presence of vessels, whales were more likely to remain on
the surface breathing or to cease surface breathing and switch to generally short, shallow diving
than was the case when no vessels were present. Northerly migrating whales off Sydney were
more likely to remain on the surface breathing in the presence of vessels, rather than taking some
form of vertical avoidance (deep, long dives) as reported elsewhere. Given the high rate of population
increase of stock E1 and the low level of behavioural changes seen, it appears that for this
population at least, adult humpback whales migrating to their breeding grounds are relatively
robust to disturbance by whale watching.
Activity budgets can provide a direct link to an animal’s bioenergetic budget and is thus a valuable unit of measure when assessing humaninduced nonlethal effects on wildlife conservation status. However, activity budget inference can be challenging for species that are difficult to observe and require multiple observational variables. Here, we assessed whether whalewatching boat interactions could affect the activity budgets of minke whales (Balaenoptera acutorostrata). We used a stepwise modeling approach to quantitatively record, identify, and assign activity states to continuous behavioral time series data, to estimate activity budgets. First, we used multiple behavioral variables, recorded from continuous visual observations of individual animals, to quantitatively identify and define behavioral types. Activity states were then assigned to each sampling unit, using a combination of hidden and observed states. Three activity states were identified: nonfeeding, foraging, and surface feeding (SF). From the resulting time series of activity states, transition probability matrices were estimated using first-order Markov chains. We then simulated time series of activity states, using Monte Carlo methods based on the transition probability matrices, to obtain activity budgets, accounting for heterogeneity in state duration. Whalewatching interactions reduced the time whales spend foraging and SF, potentially resulting in an overall decrease in energy intake of 42%. This modeling approach thus provides a means to link short-term behavioral changes resulting from human disturbance to potential long-term bioenergetic consequences in animals. It also provides an analytical framework applicable to other species when direct observations of activity states are not possible.
Sri Lanka is a developing island nation in the northern Indian Ocean. Travellers and historians have documented whales in the waters around the island as far back as the 14 th century but the first scientific records of live cetaceans from vessel-based research observations were documented only in the early 1980s. Sri Lanka's waters have high cetacean species richness with 27 species recorded to date and year-round abundance. Small cetaceans are however increasingly threatened due to the developing fisheries industry, with bycatch being a major cause for concern. Other identified threats include increasing shipping traffic and unregulated marine tourism. Cetaceans are protected by national legislation but implementation of the relevant laws and conservation measures is hampered by resource constraints. The prevailing gaps in knowledge are also due to a lack of resources to carry out dedicated long-term research on cetaceans in a developing country with more immediate human development priorities. Therefore strengthened law enforcement and finding adequate resources for sustained systematic research that can inform management decisions are priorities in Sri Lanka.
A visual aerial line transect survey for common minke whales (Balaenoptera acutorostrata) was conducted off West Greenland in August-September 2007. A total of 8670 km of survey effort covered 14 strata in sea states
The short-term effects of tourist boats on the behaviour of Indo-Pacific bottlenose dolphins Tursiops aduncus were investigated off the south coast of Zanzibar, Tanzania, by comparing dolphin group behaviour in the presence (impact) and absence (control) of tourist boats. Groupfollows were conducted from a carefully maneuvered (non-invasive) independent research vessel and behavioural data on group activity were collected using scan sampling methods. By using a timediscrete Markov chain model, the transition probabilities of passing/changing from one behavioural state to another were calculated and compared between impact and control situations. The data were further used to construct behavioural budgets. In the presence of tourist boats, dolphins were less likely to stay in a resting or socialising activity but were more likely to start travelling or foraging, as inferred from the Markov chain model. The behavioral budgets showed that foraging, resting and socialising all decreased as an effect of tourist boat presence, while travelling increased. The behavioural responses are likely to have energetic implications, mainly by increasing physical demands. Further, the results demonstrate that the current level of tourism intensity off the south coast of Zanzibar affects the dolphins' cumulative behavioural budget. Regulations on dolphin tourism are therefore urgently needed to minimise potential long-term negative effects on the dolphins.
Surfacing, respiration, and dive characteristics are described for presumably undisturbed bowhead whales in the Beaufort Sea during August and early September 1980–1982. The interval between respirations (blow interval) was relatively constant during different activities such as skim feeding at the surface, social interactions, and feeding in the water column. Durations of adjacent surfacings and dives were positively correlated, and number of blows per surfacing was correlated with duration of surfacing. Mean blow interval, number of blows per surfacing, duration of surfacing, and duration of dive were all greater in 1982 than in the previous 2 years, presumably because of increased feeding in the water column in 1982. Blow rates were lower in 1982 than in 1980–1981, possibly due to less socializing in 1982. There was a tendency for increased dive durations in deeper water, but the data were not consistent on this point. In general, calves exhibited short dives and surfacings, especially while nursing. Nursing mothers were inactive and had lower blow rates than other adults.
In 1984 and 1985, during surveys designed primarily to census dugongs, six species of sea turtles were counted
from the air at an overall sampling intensity of 9% over a total area of 31 288 km2 within the northern sections
of the Great Barrier Reef Marine Park. The sea turtles were not identified to species. We attempted to correct
sightings for perception bias (the proportion of animals visible in the transect which are missed by observers),
and to standardise for availability bias (the.proportion of animals that are invisible due to water turbidity)
with survey-specific correction factors. The resultant minimum population estimate in November 1985 was
(mean ± s.e.) 32 187 ± 2532 sea turtles at an overall density of 1.03 ± 0.08 km-2, a precision of 8%. We
consider this to be a gross underestimate of numbers present. Significant differences between population and
density estimates obtained from repeat surveys of the same areas were accounted for by differences in
Beaufort sea state and cloud cover. The analysis of covariance data suggested that we had not been successful
in standardising all biases. Turtles were widely distributed throughout the Great Barrier Reef lagoon from
inshore seagrass beds to mid- and outer-shelf reefs. Highest densities were observed on inshore seagrass beds
and on mid-shelf reefs, particularly between Murdoch Island and Cape Melville, and in Princess Charlotte
Bay. Maps of density and distribution are given. We discuss the value and limitations of this survey regime for
censusing sea turtles.
Narwhals (Monodon monoceros L.) occur in the Atlantic sector of the Arctic where for centuries they have been subject to subsistence hunting by Inuit in Greenland and Canada. Scientific advice on the sustainable levels of removals from narwhal populations provides the basis for quotas implemented in both Greenland and Canada. The scientific advice relies heavily on extensive aerial surveys that are the only feasible way to acquire data on narwhal densities and abundance throughout their range. In some areas lack of information on abundance, in combination with high exploitation levels, has caused conservation concerns leading to restrictions on the international trade in narwhal tusks. Narwhals also are regarded as highly sensitive to habitat disturbance caused by global warming. This study analyzed data from aerial sighting surveys covering four major narwhal hunting grounds in Greenland. The surveys were conducted as double observer experiments with 2 independent observation platforms, 1 at the front and 1 at the rear of the survey plane. The sighting data were analyzed using mark-recapture distance sampling techniques that allow for correction for whales that were missed by the observers. The surveys also were corrected for animals that were submerged during the passage of the survey plane, using diving and submergence data from satellite-linked time-depth recorders deployed on 2 free-ranging narwhals. The abundance of narwhals on the wintering ground in West Greenland in 2006 was 7,819 (95% confidence interval [CI]: 4,358–14,029). The abundances of narwhals in Inglefield Bredning and Melville Bay, northwest Greenland in 2007 were 8,368 (95% CI: 5,209–13,442) and 6,024 (95% CI: 1,403–25,860), respectively. The abundance of narwhals in East Greenland in 2008 was 6,444 (95% CI: 2,505–16,575). These surveys provide the first estimates of narwhal abundance from important hunting areas in East and West Greenland and provide larger and more complete estimates from previously surveyed hunting grounds in Inglefield Bredning. The estimates can be used for setting catch limits for the narwhal harvest in West and East Greenland and as a baseline for examining the effects of climate change on narwhal abundance.
Aerial line transect surveys of the density of humpback whales (Megaptera novaeangliae) conducted off West Greenland eight times between 1984 and 2007 were used to estimate the rate of increase on the summer feeding ground. Only surveys in 1993,2005 and 2007 had enough sightings to construct independent density estimates, whereas the surveys in 1984-85 and 1987-89 had to be merged and treated as two surveys. The annual rate of increase was 9.4% yr1 (SE = 0.01) between 1984 and 2007. This rate of increase is higher than the increase estimated at the breeding grounds in the West Indies, but is of the same magnitude as the observed rate of increase at other feeding grounds in the North Atlantic. A matrix model based on observed life history parameters revealed that the theoretical growth rate of a humpback whale population ranged between 1 and 11%. This confirms that the observed growth in West Greenland is within the plausible values. The survey in 2007 was used to make a fully corrected abundance estimate including corrections for whales that were submerged during the passage of the survey plane. The line transect estimate for 2007 was 1,020 (CV = 0.35). When the estimate was corrected for perception bias with mark-recapture distance sampling (MRDS) methods, the abundance increased to 1,505 (0.49). A correction for availability bias was developed based on time-depth-recorder information on the time spent at the surface (0-4m). However, used directly this correction leads to a positively-biased abundance estimate and instead a correction was developed for the non-instantaneous visual sighting process in an aircraft. The resulting estimate for 2007 was 3,272 (CV = 0.50) for the MRDS analysis. An alternative strip census estimate deploying a strip width of 300m resulted in 995 (0.33) whales. Correction for perception bias resulted in 991 (0.35) whales and corrected for the same availability bias as for the MRDS method resulted in a fully corrected estimate of 2,154 (0.36) humpback whales in West Greenland in 2007.
Observations of feeding and ventilatory behavior of individual fin whales (Balaenoptera physalus)were made from various vessels during the months of May–September, 1981–1987, in the waters off eastern Long Island, N.Y., U.S.A. Intervals between blows were measured and recorded to the nearest second. Information about behavior was recorded, as were location, depth, and surface temperature at sounding dives. Animals observed feeding at the surface were noted as such, ail others were considered non-surface-feeding animals. Data were compiled by individual, month, year, and analyzed for mean interblow interval during surface activity bouts; mean dive duration; and overall mean blow interval.Overall mean blow intervals (±SE) of 47.89 ± 0.81 set for surface-feeding (n= 10,411), and 57.92 ±0.97 sec for non-surface-feeding animals (n= 11,024), differed significantly (Mann-Whitney U, P < 0.001). Interblow intervals for surface activity bouts (±SE) of 12.29 ± 0.05 set for surface-feeding (n= 7,894), and 13.58 ± 0.06 set, for non-surface-feeding animals (n = 8,187), also differed significantly (Mann-Whitney U, P < 0.001), as did mean dive duration (159.53 ± 2.16 sec, n= 2,517, for surface-feeding animals; 185.86 ± 2.53 set, n= 2,837, for non-surface-feeding animals). Yearly comparisons of blow intervals between surface-feeding and non-surface-feeding animals during surface activity bouts yielded significant differences for each year except 1981, while comparisons of dive durations yielded significant differences for all years except 1981, 1982, and 1985.
1. Blue whale locations in the Southern Hemisphere and northern Indian Ocean were obtained from catches (303 239), sightings (4383 records of ≥ 8058 whales), strandings (103), Discovery marks (2191) and recoveries (95), and acoustic recordings. 2. Sighting surveys included 7 480 450 km of effort plus 14 676 days with unmeasured effort. Groups usually consisted of solitary whales (65.2%) or pairs (24.6%); larger feeding aggregations of unassociated individuals were only rarely observed. Sighting rates (groups per 1000 km from many platform types) varied by four orders of magnitude and were lowest in the waters of Brazil, South Africa, the eastern tropical Pacific, Antarctica and South Georgia; higher in the Subantarctic and Peru; and highest around Indonesia, Sri Lanka, Chile, southern Australia and south of Madagascar. 3. Blue whales avoid the oligotrophic central gyres of the Indian, Pacific and Atlantic Oceans, but are more common where phytoplankton densities are high, and where there are dynamic oceanographic processes like upwelling and frontal meandering. 4. Compared with historical catches, the Antarctic (‘true’) subspecies is exceedingly rare and usually concentrated closer to the summer pack ice. In summer they are found throughout the Antarctic; in winter they migrate to southern Africa (although recent sightings there are rare) and to other northerly locations (based on acoustics), although some overwinter in the Antarctic. 5. Pygmy blue whales are found around the Indian Ocean and from southern Australia to New Zealand. At least four groupings are evident: northern Indian Ocean, from Madagascar to the Subantarctic, Indonesia to western and southern Australia, and from New Zealand northwards to the equator. Sighting rates are typically much higher than for Antarctic blue whales.
Nature-based tourism activities have been developing over the last decade, but it is still difficult to manage these activities sustainably. This sector is increasingly focusing on whales and dolphins in coastal communities, but the exact effects of these tourism activities are unclear. Markov chain modeling may help researchers assess the effects of tourism activities on the behavioral budget of small cetaceans. Matrix models have been used widely in population ecology to provide successful management guidelines. From June 2000 to August 2001, I collected information on the behavioral state of bottlenose dolphin (Tursiops spp.) schools from a population residing in Doubtful Sound, Fiordland, New Zealand. In addition, I recorded the occurrence of boat and dolphin interactions. I then calculated the transition probabilities of passing from one behavior to another by using a first-order, time-discrete Markov chain model. Behavioral transitions during which a boat-dolphin interaction occurred were compiled in an "impact" chain. All other transitions were tallied in a control chain. I then quantified the effect of boat-dolphin interactions during behavioral transitions by comparing the behavioral transition probabilities of both chains. Socializing and resting behaviors were disrupted by interactions with boats to a level that raises concern. Both the duration of bouts and the total amount of time spent in both these behavioral states were substantially decreased. Dolphins were significantly more likely to be travelling after an interaction with a boat. However, the overall behavioral budget of the population was not significantly affected. Therefore, the bottlenose dolphin population seems to be able to sustain the present level of boat interactions because of its low intensity. More effort is needed to develop prognosis analyses in order to understand how the effect of boat interactions on dolphins changes with variations in intensity.
Relatively little is known about the distribution of cetaceans in Indian seas due to lack of systematic surveys. For collecting data on species distribution, 35 opportunistic surveys were conducted onboard FORV Sagar Sampada between October 2003 and February 2007 in the Indian EEZ and contiguous seas. In 5,254 hours of sighting effort, a total of 473 cetacean records were made with 5,865 individuals. The occurrence of 10 species from three cetacean families was confirmed. The Indo-Pacific bottlenose dolphin was the most frequently sighted species, whereas the spinner dolphin was dominant in terms of abundance. Long-beaked common dolphins, Indo-Pacific hump-backed dolphin and sperm whales were also recorded at frequent intervals. Cetaceans were found to have a wide geographical distribution in the Indian EEZ and contiguous seas. High abundance and species richness were recorded in the Southeastern Arabian Sea and southern Sri Lankan waters. From the information collected during the present study, the platform of opportunity has proved to be a useful means for cetacean survey.
Lunge feeding by rorqual whales (Balaenopteridae) is associated with a high energetic cost that decreases diving capacity, thereby limiting access to dense prey patches at depth. Despite this cost, rorquals exhibit high rates of lipid deposition and extremely large maximum body size. To address this paradox, we integrated kinematic data from digital tags with unsteady hydrodynamic models to estimate the energy budget for lunges and foraging dives of blue whales (Balaenoptera musculus), the largest rorqual and living mammal. Our analysis suggests that, despite the large amount of mechanical work required to lunge feed, a large amount of prey and, therefore, energy is obtained during engulfment. Furthermore, we suggest that foraging efficiency for blue whales is significantly higher than for other marine mammals by nearly an order of magnitude, but only if lunges target extremely high densities of krill. The high predicted efficiency is attributed to the enhanced engulfment capacity, rapid filter rate and low mass-specific metabolic rate associated with large body size in blue whales. These results highlight the importance of high prey density, regardless of prey patch depth, for efficient bulk filter feeding in baleen whales and may explain some diel changes in foraging behavior in rorqual whales.
Transportation networks play a crucial role in human mobility, the exchange of goods and the spread of invasive species. With 90 per cent of world trade carried by sea, the global network of merchant ships provides one of the most important modes of transportation. Here, we use information about the itineraries of 16 363 cargo ships during the year 2007 to construct a network of links between ports. We show that the network has several features that set it apart from other transportation networks. In particular, most ships can be classified into three categories: bulk dry carriers, container ships and oil tankers. These three categories do not only differ in the ships' physical characteristics, but also in their mobility patterns and networks. Container ships follow regularly repeating paths whereas bulk dry carriers and oil tankers move less predictably between ports. The network of all ship movements possesses a heavy-tailed distribution for the connectivity of ports and for the loads transported on the links with systematic differences between ship types. The data analysed in this paper improve current assumptions based on gravity models of ship movements, an important step towards understanding patterns of global trade and bioinvasion.
Mean surfacing rate was 38.6 ±9.47 surfacings per hour (range 26-60), with no significant differences in surfacing rates among individuals. The general surfacing pattern consisted of about four surfacings, interspersed by short-duration dives of 37.8 ±31.98 seconds. After the fourth surfacing, there was a longer duration dive of 4.43 ±2.37 minutes. -from Author
We develop methodology for correcting for visibility bias by calculating and applying survey-specific correction factors in strip transect aerial surveys of aquatic fauna and incorporating their associated errors into the population estimate. The technique is applicable at all densities of the target species. Perception bias (the proportion of groups of the target species that are visible in the transect yet missed by observers) is corrected for using a modified Petersen estimate calculated for each of 2 teams of 2 observers with 1 team on either side of the aircraft. Within a team, each observer reports their uncolluded observations into a separate track of a 2-track tape recorder, so that after the survey, each group can be characterized as being seen by only 1 (specified) or both members of the team. A correction factor is also suggested to standardize for the proportion of animals that are unavailable to observers because of water turbidity.
We received data from eight bowhead whales (Balaena mysticetus) equipped with satellite-monitored radio tags for 3-33 days. Of 42 306 dives made by the eight whales during 1695 h, 9573 were sounding dives (> 1 min duration). The mean duration of sounding dives for individuals varied from 6.9 to 14.1 min (mean = 10.4 +/- 2.4 min, n = 8). Five whales made dives greater than or equal to 61 min; the longest dives for the other three lasted 56, 45, and 32 min. Five tags measured maximum depths of 29 499 dives during 1220 h and time at depth during 1228 h. All five whales dived > 100 m; the deepest dive was 352 m. Whales spent most of their time at depths less than or equal to 16 m, but three whales spent most of their time at depths > 48 m during some sampling periods. Mean surfacing rates ranged from 18.2 to 47.0/h (mean = 26.2 +/- 9.0/h, n = 8). Tags were exposed to air for 4.0-7.3% of the time (mean = 5.5 +/- 0.95%, n = 8), and whales were potentially visible from aircraft for 8.5-16.4% of the time (mean = 11.1 +/- 2.4%, n = 8). Three whales made longer sounding dives and had lower surfacing rates when in greater than or equal to 90% ice cover. No consistent diel patterns were found.
Describes a series of survey techniques, commenting on effective search range, strip and line transects, methods based on measurement of observer behaviour, methods based on survey of cues, shipboard acoustic survey, land-based visual survey, and land-based acoustic survey; discusses data collection and data analysis; outlines how to model perpendicular distance data from line transects; comments on the effects of whale movement; reviews survey design; and reports on cue counting and estimation of surfacing rate. -P.J.Jarvis
Behaviour of bowhead whales summering in the Canadian Beaufort Sea in 1980–1984 was observed from an aeroplane circling at altitudes high enough to avoid disturbance (≥ 457 m). Factors that might affect surfacing and respiration behaviour were assessed with univariate and multivariate analyses. Calves (age < 1 year) were not considered. The interval between successive blows in a surfacing was more stable over time and over different activities than were the other variables but was significantly longer in surface-feeding whales. Surface feeders also made longer surfacings. The number of blows per surfacing and duration of surfacing were highly correlated, and both variables were more consistently correlated with the duration of the previous dive than with the duration of the subsequent dive. There were considerable interyear variations in respiration and surfacing characteristics that could not be attributed to any measured factor. Effects of water depth on number of blows per surfacing could not be separated from interyear effects, but duration of surfacing appeared to be greater in deeper water. Whales in groups had longer blow intervals, as did mothers with calves and socializing whales. Underwater blows were associated with socializing, at least at times, but their function is uncertain. The results have implications with regard to bowhead energetics, sightability during aerial surveys, and interpretation of behaviour in the presence of human disturbance.
We received data from eight bowhead whales (Balaena mysticetus) equipped with satellite-monitored radio tags for 3-33 days. Of 42 306 dives made by the eight whales during 1695 h, 9573 were sounding dives (>1 min duration). The mean duration of sounding dives for individuals varied from 6.9 to 14.1 min (mean = 10.4 ± 2.4 min, n = 8). Five whales made dives 61 min; the longest dives for the other three lasted 56, 45, and 32 min. Five tags measured maximum depths of 29 499 dives during 1220 h and time at depth during 1228 h. All five whales dived >100 m; the deepest dive was 352 m. Whales spent most of their time at depths 16 m, but three whales spent most of their time at depths >48 m during some sampling periods. Mean surfacing rates ranged from 18.2 to 47.0/h (mean = 26.2 ± 9.0/h, n = 8). Tags were exposed to air for 4.0-7.3% of the time (mean = 5.5 ± 0.95%, n = 8), and whales were potentially visible from aircraft for 8.5-16.4% of the time (mean = 11.1 ± 2.4%, n = 8). Three whales made longer sounding dives and had lower surfacing rates when in 90% ice cover. No consistent diel patterns were found.
Seven major types of sampling for observational studies of social behavior have been found in the literature. These methods differ considerably in their suitability for providing unbiased data of various kinds. Below is a summary of the major recommended uses of each technique: In this paper, I have tried to point out the major strengths and weaknesses of each sampling method. Some methods are intrinsically biased with respect to many variables, others to fewer. In choosing a sampling method the main question is whether the procedure results in a biased sample of the variables under study. A method can produce a biased sample directly, as a result of intrinsic bias with respect to a study variable, or secondarily due to some degree of dependence (correlation) between the study variable and a directly-biased variable. In order to choose a sampling technique, the observer needs to consider carefully the characteristics of behavior and social interactions that are relevant to the study population and the research questions at hand. In most studies one will not have adequate empirical knowledge of the dependencies between relevant variables. Under the circumstances, the observer should avoid intrinsic biases to whatever extent possible, in particular those that direcly affect the variables under study. Finally, it will often be possible to use more than one sampling method in a study. Such samples can be taken successively or, under favorable conditions, even concurrently. For example, we have found it possible to take Instantaneous Samples of the identities and distances of nearest neighbors of a focal individual at five or ten minute intervals during Focal-Animal (behavior) Samples on that individual. Often during Focal-Animal Sampling one can also record All Occurrences of Some Behaviors, for the whole social group, for categories of conspicuous behavior, such as predation, intergroup contact, drinking, and so on. The extent to which concurrent multiple sampling is feasible will depend very much on the behavior categories and rate of occurrence, the observational conditions, etc. Where feasible, such multiple sampling can greatly aid in the efficient use of research time.
1. During aerial or boat-based surveys for large-bodied diving taxa (e.g. marine mammals and marine turtles), a proportion of animals present will be missed because they are submerged and out of view, leading to ‘availability bias’ in abundance indices. Information on dive–surfacing patterns can improve corrections for availability bias. However, as dive data are typically limited, availability correction factors are often based on poorly resolved dive and surface times, and diving heterogeneity is not considered.
Aerial surveys have been used to estimate population abundance of both terrestrial and marine species; in the marine environment this has largely been used for air-breathing species that spend time regularly at the surface. Whale sharks spend a large proportion of their time close to the surface and so are amenable to aerial survey techniques. This study presents the results of six years of synoptic aerial belt-surveys done nearly daily during the peak whale shark season around the island of Mahe, Seychelles. A total of 580 survey flights were flown providing 699.7 hours of survey record. A seasonal peak of shark sightings per hour was recorded in September or October in most years with the maximum on a single survey of 28.4 h -1 in October 2006. The aerial survey data were used to generate an estimate of relative population abundance indicating that highest mean annual relative population estimate was also in 2006, with an estimate of 38, while the lowest mean estimate was 11 in 2004. These estimates were then compared to weekly capture-mark-recapture estimates of abundance based on unique individual identification data. The results indicate that the use of aerial survey data alone may give an acceptable indication of instantaneous relative population abundance but further refinement is necessary to estimate absolute regional abundance.
Dive habits of four Northeast Pacific blue whales (Balaenoptera musculus) were studied using satellite-monitored radio tags. Tags summarized dive-duration data into eight 3-h periods daily. One tag additionally summarized dive depth and time-at-depth information for these same periods. Tracking periods ranged from 0.6 to 12.7 d and provided data for 17 three-hour summary periods, representing 2,007 dives (788 of which provided depth information). Total number of dives during a 3-h summary period ranged from 83 to 128. Seventy-two percent of dives were ≤ 1 min long. All whales spent >94% of their time submerged. Average duration of true dives (dives >1 min) ranged from 4.2 to 7.2 min. Seventy-five percent of depth-monitored dives were to ≤16 m, accounting for 78% of that animal's time. Average depth of dives to >16 m was 105 ± 13 m.
Summary 1. Megaplanktivores such as filter-feeding sharks and baleen whales are at the apex of a short food chain (phytoplankton-zooplankton-vertebrate) and are sensitive indicators of sea-surface plankton availability. Even though they spend the majority of their time below the surface it is still not known how most of these species utilize vertical habitat and adapt to short-term changes in food availability. 2. A key factor likely to control vertical habitat selection by planktivorous sharks is the diel vertical migration (DVM) of zooplankton; however, no study has determined whether specific ocean-habitat type influences their behavioural strategy. Based on the first high-resolution dive data collected for a plankton-feeding fish species we show that DVM patterns of the basking shark Cetorhinus maximus reflect habitat type and zooplankton behaviour. 3. In deep, well-stratified waters sharks exhibited normal DVM (dusk ascent-dawn descent) by tracking migrating sound-scattering layers characterized by Calanus and euphausiids. Sharks occupying shallow, inner-shelf areas near thermal fronts conducted reverse DVM (dusk descent-dawn ascent) possibly due to zooplankton predator-prey interactions that resulted in reverse DVM of Calanus . 4. These opposite DVM patterns resulted in the probability of daytime-surface sighting differing between these habitats by as much as two orders of magnitude. Ship-borne sur- veys undertaken at the same time as trackings reflected these behavioural differences. 5. The tendency of basking sharks to feed or rest for long periods at the surface has made them vulnerable to harpoon fisheries. Ship-borne and aerial surveys also use surface occurrence to assess distribution and abundance for conservation purposes. Our study indicates that without bias reduction for habitat-specific DVM patterns, current surveys could under- or overestimate shark abundance by at least 10-fold.
Definitive studies on the response of marine mammals to anthropogenic sound are hampered by the short surface time and deep-diving lifestyle of many species. A novel archival tag, called the DTAG, has been developed to monitor the behavior of marine mammals, and their response to sound, continuously throughout the dive cycle. The tag contains a large array of solid-state memory and records continuously from a built-in hydrophone and suite of sensors. The sensors sample the orientation of the animal in three dimensions with sufficient speed and resolution to capture individual fluke strokes. Audio and sensor recording is synchronous so the relative timing of sounds and motion can be determined precisely. The DTAG has been attached to more than 30 northern right whales (Eubalaena glacialis) and 20 sperm whales (Physeter macrocephalus) with recording duration of up to 12 h per deployment. Several deployments have included sound playbacks to the tagged whale and a transient response to at least one playback is evident in the tag data.
Whaling in the Arabian Sea by the whaling fleets Slava and Sovetskaya Ukraina Center for Russian Environmental Policy Marine Mammal Council
- Y A Mikhalev
Mikhalev, Y.A., 2000. Whaling in the Arabian Sea by the whaling fleets Slava and Sovetskaya Ukraina. In: Yablokov, A.V., Zemsky, V.A. (Eds.), Soviet Whaling Data (1949–1979). Center for Russian Environmental Policy Marine Mammal Council, Moscow, pp. 141–181.
Submergence Times and Abundance Estimation of Blue Whales off Sri Lanka Sightings and acoustic detections of cetaceans in the offshore waters of Sri Lanka
- A De Vos
- F Christiansen
- R G Harcourt
- C B A Pattiaratchi
- R Clark
- C Johnson
- G Johnson
- I Kerr
- R Payne
- P T Madsen
de Vos, A., Christiansen, F., Harcourt, R.G., Pattiaratchi, C.B., 2011. Submergence Times and Abundance Estimation of Blue Whales off Sri Lanka. Report of the IWC conservation committee SC/63/WW7. de Vos, A., Clark, R., Johnson, C., Johnson, G., Kerr, I., Payne, R., Madsen, P.T., 2012. Sightings and acoustic detections of cetaceans in the offshore waters of Sri Lanka: March–June 2003. J. Cetacean Res. Manage. 12 (2), 185–193.
Hawaiian Islands Humpback Whale National Marine Sanctuary
- R W Baird
- A D Ligon
- S K Hooker
- H I Kihei
- T A Branch
- K M Stafford
- D M Palacios
- C Allison
- J L Bannister
- C L K Burton
- E Cabrera
- C A Carlson
- B G Vernazzani
- P C Gill
- R Hucke-Gaete
- K C S Jenner
- M N M Jenner
- K Matsuoka
- Y A Mikhalev
- T Miyashita
- M G Morrice
- S Nishiwaki
- V J Sturrock
- D Tormosov
- R C Anderson
- A N Baker
- P B Best
- P Borsa
- R L Brownell
- S Childerhouse
- K P Findlay
- T Gerrodette
- A D Ilangakoon
- M Joergensen
- B Kahn
- D K Ljungblad
- B Maughan
- R D Mccauley
- S Mckay
- T F Norris
- O Whale
- S Rankin
- F Samaran
- D Thiele
- K Van Waerebeek
- R M Warneke
Baird, R.W., Ligon, A.D., Hooker, S.K., 2000. Sub-surface and Night-time Behaviour
of Humpback Whales Off Maui, Hawaii: A Preliminary Report. Hawaiian Islands
Humpback Whale National Marine Sanctuary, Kihei, HI.
Branch, T.A., Stafford, K.M., Palacios, D.M., Allison, C., Bannister, J.L., Burton, C.L.K., Cabrera,
E., Carlson, C.A., Vernazzani, B.G., Gill, P.C., Hucke-Gaete, R., Jenner, K.C.S., Jenner,
M.N.M., Matsuoka, K., Mikhalev, Y.A., Miyashita, T., Morrice, M.G., Nishiwaki, S.,
Sturrock, V.J., Tormosov, D., Anderson, R.C., Baker, A.N., Best, P.B., Borsa, P., Brownell,
R.L., Childerhouse, S., Findlay, K.P., Gerrodette, T., Ilangakoon, A.D., Joergensen, M.,
Kahn, B., Ljungblad, D.K., Maughan, B., McCauley, R.D., Mckay, S., Norris, T.F., Whale,
O., Rankin, S., Samaran, F., Thiele, D., Van Waerebeek, K., Warneke, R.M., Dolphin
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blue whales Balaenoptera musculus in the Southern Hemisphere and northern Indian
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