Abstract.--Cetacean occurrence, distribution and behavior were
investigated in Santa Monica Bay and nearby areas, California
(1997-2007). A total of 425 boat-based surveys documented three species
inhabiting the study area year-round--the common bottlenose dolphin,
Tursiops truncatus, the long-beaked common dolphin, Delphinus capensis,
and the short-beaked common dolphin, D. delphis, and ten species
occurring occasionally. Coastal bottlenose dolphins were mostly found
traveling, diving and feeding in waters within 0.5km of shore in 81.4%
of the sightings (n = 221), but were also observed occasionally in
offshore waters. All other species were seen > 0.5 km of shore, often
feeding near escarpments and submarine canyons. Endangered species, such
as blue whales (Balaenoptera musculus) and humpback whales (Megaptera
novaeangliae), were also recorded in the study area. This paper provides
new information as well as an update on data of the composition for the
local cetacean community, and offers information that should be
considered in the decision-making process associated with the newly
established MPAs, and their use. The presence of a diverse cetacean
fauna moving in and out the boundaries of these MPAs, also suggests the
need for long-term and regular cetacean monitoring in the area.
The waters of the Southern California Bight (SCB) support one of
the largest and most diverse cetofauna in the world, including 30
cetacean species (Bonnell and Dailey, 1993; Forney et al., 1995; Forney
et al., 1999; Schmitt and Bonnell, 2003; Carretta et al., 2006;
Soldevilla et al., 2006). Long-term and detailed ecological studies for
the SCB have been concentrated mostly on coastal common bottlenose
dolphin (hereafter bottlenose dolphin), Tursiops truncatus (Defran and
Weller, 1999; Defran et al., 1999; Lang, 2002; Bearzi, 2005a,b), whereas
only general information is available for other offshore species (Forney
et al., 1999; Appler et al., 2004; Barlow and Forney, 2007; Bearzi et
Within the SCB, Santa Monica Bay and its nearby areas (Fig. 1a)
represent a region with unique topographic and oceanographic features
(Bonnell and Dailey, 1993), likely to affect the species inhabiting it.
A better understanding of the ecology of the local cetacean community is
essential to protect these animals, the species they feed upon, and the
entire habitats in which they live (Yen et al., 2004; Fury and Harrison,
2008), as well as for making sound conservation and management decisions
for Marine Protected Areas (MPAs; Hastie et al., 2003; Wilson et al.,
This study, conducted between 1997-2007 (except for 2003-2004),
aims to provide data on occurrence, frequency, distribution and behavior
of cetacean species for Santa Monica Bay and adjacent areas. Further,
considering that: a) several MPAs have recently been approved by the
California Fish and Game Commission in the study area (http://www.
dfg.ca.gov/mlpa/southcoast.asp), and b) the Monitoring Enterprise is now
developing a South Coast MPA Monitoring Plan and it's leading
toward the implementation of the South Coast MPA Baseline Program
(http://monitoringenterprise.org/where/southcoast. php), the goal of
this paper is also to offer information helping to ensure that cetaceans
will be properly represented in any decision-making process regarding
MPAs. Cetaceans are umbrella species (Mann et al., 2000; Prideaux, 2005)
because conservation actions intended at mitigating threats to them can
result in protection for entire communities of organisms, as well as the
ecosystem itself. Since many cetaceans are now considered key species in
conservation planning worldwide, as widely discussed at the last
International Committee on Marine Mammal Protected Areas
(http://icmmpa.org/), this work hopes to emphasize to need to include
these animals for conservation strategies toward the local MPAs.
[FIGURE 1a OMITTED]
[FIGURE 1b OMITTED]
The Santa Monica Bay study area (approximately 460 [km.sup.2]) is a
shallow shelf, bounded by the Palos Verdes Peninsula to the south
(33[degrees]45'N 118[degrees]24'W), Point Dume to the north
(33[degrees]59'N 118[degrees]48'W) and the edge of the
continental shelf to the west. The bay contains two shallow water
submarine canyons (Dume and Redondo) and one deeper canyon, the Santa
Monica Canyon. This begins at a depth of about 100 m, at the edge of the
escarpment. The bay has a mean depth of about 55m and a maximum depth
450 m. A shallow shelf between the Santa Monica and Redondo Canyons
extends as a plateau from the 50m contour. The study area also extended
outside Santa Monica Bay, both along the coast (<500m from shore) to
the south (33[degrees]43'N 118[degrees]15'W), and to the north
(34[degrees]5'N 119[degrees]6'W), and in offshore waters
around Catalina (33[degrees]23'N 118[degrees]41'W) and Santa
Barbara Islands (33[degrees]27'N 119[degrees]3'W). The study
area is shown in Figure 1a and a map of the recently established Marine
Protected Areas is available at http://www.dfg.ca.
gov/mlpa/pdfs/scmpasl21510.pdf. The following protected locations are
included in the study area: Point Dume State Marine Reserve, Point Dume
State Marine Conservation Area, Point Vicente Stare Marine Conservation
Area No-Take, Abalone Cove Stare Marine Conservation Area, Cat Harbor
State Marine Conservation Area, Santa Barbara Island State Marine
Reserve, Bird Rock State Marine Conservation Area, Blue Cavern State
Marine Conservation Area No-Take, Long Point State Marine Reserve, Arrow
Point to Lion Head Point State Marine Conservation Area.
Mild temperatures, short rainy winters and long, dry summers
characterized the study area. Normal water surface temperatures range
from 11 to 22[degrees]C. During the 1997-98 EL Nino three peaks of sea
surface temperature (SST) anomalies were evident: May June 1997,
September--October 1997 and August 1998, with an increase in temperature
of + 2[degrees]C above the norm (Nezlin et al., 2003).
Data Collection and Analyses
Surveys were conducted from February 1997 to June 2002, and from
June 2005 to July 2007 with an average of 5.2 days on the water per
month (n = 425, Table 1). We followed routes, planned for even coverage
of the entire bay throughout the study period (Fig. 1B). Inshore
(distance from shore up to 1km) and offshore (distance from shore >
1km) routes were usually carried out with Beaufort scale 2 or less, sea
state 0 and visibility >300m. Surveys were conducted from 7 m
(1997-2000) and 10 m powerboats (2001-2002, 2006-2007), and a 17 m
sailboat (2005-2006), at an average speed of 18 km [h.sup.-1]. The
dolphins' positions and speeds ([+ or -] 30 m from the boat) were
approximated to the boat's position using a GPS.
When cetaceans were spotted, data on the number of animals, size
classes and behavior (for definitions see Bearzi, 2005a) and aggregation
with other species were recorded on laptop computers at five-minute
intervals and throughout the sighting. Boat speed was reduced in the
presence of dolphins and sudden speed or directional changes were
avoided. Behavioral data collected ad libitum from July to December 1996
(58 hours of field observations) provided a framework of information to
design the behavioral sampling procedures systematically adopted from
January 1997 (Bearzi, 2003).
Definitions of aggregation, close aggregation, mixed group, dolphin
school, focal group, behavioral state and mating follow Bearzi (2005a);
other cetacean groups spotted at distance and not belonging to the
observed focal group were recorded, but excluded from group size
During the sightings, color photographs were taken with 35mm Canon
EOS1N and A2 cameras equipped with 75-300mm lenses, and digital Canon 5D
equipped with 400mm lens to photo-identify bottlenose dolphins. During
the sighting, researchers also videotaped the animals' behavior
with Canon Hi8mm or Canon GL1 Digital Video Camcorders. Videos and
photos were reviewed in laboratory to validate field observations.
Data analyses were performed using Statview 5.01, Statistica 6.0
and Excel 2008; data on species distribution were plotted with Arcview
GIS 9.2. For sighting frequency analysis, different sightings of the
same individuals observed during the same day were considered only once.
Fieldwork was carried out under the current laws of California and
the General Authorization for Scientific Research issued by the National
Oceanic and Atmospheric Administration (files #856-1366 and #8561835).
Field Effort The majority of observations (94.1%, n = 425) were
conducted in good conditions (Beaufort scale [less than or equal to] 2,
sea state 0 and visibility > 300m) during 204 inshore and 221
offshore surveys. A total of 823 h were spent searching for cetaceans in
good weather conditions; 400h were spent observing 509 cetacean groups
encountered during sightings lasting on average 50 min (range 1-263
minutes; Table 1).
Occurrence, Frequency and Distribution
Percentage of sightings for all cetacean species and for the four
most frequently observed species in the study area are presented in
Figures 2a,b. Bottlenose dolphin was the species most frequently sighted
(43.4%, n schools = 221), followed by short-beaked common dolphin
(Delphinus delphis; 16.5%, n=84), and long-beaked common dolphin
(Delphinus capensis; 12.4%, n=63; Table 2). Risso's dolphin
(Grampus griseus), Dall's porpoise (Phocoenoides dalli), Pacific
white-sided dolphin (Lagenorhynchus obliquidens), gray whales
(Eschrichtius robustus), blue whales (Balaenoptera musculus), minke
(Balaenoptera acutorostrata), humpback (Megaptera novaeangliae) whales,
fin whales (Balaenoptera physalus), northern right whale dolphins
(Lissodelphis borealis) and killer whales (Orcinus orca) were sighted
occasionally or during their migrations.
Although cetaceans were observed during the entire study period, a
significant difference among the nine years of study was observed in the
overall sighting numbers t = 6.20, df = 8, P < 0.001; Fig. 3).
Mixed groups were occasionally recorded in the bay (5.3% of total
cetacean sightings, n = 27). The cetaceans found more often in
inter-specific groups were offshore bottlenose dolphins associated with
short-beaked and long-beaked common dolphins (44.4% of total mixed
sightings, n = 12), followed by mixed groups of bottlenose dolphins and
Risso's dolphins (29.6% of total mixed sightings, n = 8) and
bottlenose dolphins and gray whales (7.4% of total mixed sightings, n =
[FIGURE 2 OMITTED]
[FIGURE 3 OMITTED]
Bottlenose dolphins were observed mostly in inshore waters (81.4%,
n = 180), but offshore schools were also recorded (18.6%, n = 41)
outside the bay and out to Santa Barbara Island. Short-beaked and
long-beaked common dolphins were observed mostly in offshore waters
(98.3%), usually above escarpments and submarine canyons (62.7%, n =
111). Bottlenose dolphins and the two common dolphin species were often
recorded within and outside the boundaries of the four coastal designed
MPAs (Point Dume SMR and SMCA, Point Vicente SMCA, and Abalone Cove
SMCA); bottlenose dolphins were also found within Bird Rock and Blue
Cavern SMCAs near Catalina Island (Fig. 1a).
Gray whales were often recorded in inshore waters (31.4% of gray
whale sightings, n = 11), but also near Santa Monica Canyon (12.1%, n =
33) and the escarpment near Point Vicente (30.3%, n = 33). Gray whales
were observed within the boundaries of three designed MPAs: Point Dume
SMR, Point Vicente and Abalone Cove SMCAs (n = 5).
All other cetaceans were seen exclusively in offshore waters (Fig.
la). Risso's dolphin sightings occurred either in the bay, near the
escarpment or the Santa Monica Canyon (47.4%, n = 19), or at more than
15km from shore. Risso's dolphins were also recorded within the
Point Vicente SMCA (n = 1). Dall's porpoises also occurred mostly
in the bay (93.7%, n = 16) and, with the exclusion of one sighting,
always near Santa Monica and Redondo canyons or along the escarpment.
They were found inside the Point Dume SMR once. Of a total of nine
sightings, Pacific white-sided dolphins were observed exclusively inside
the bay with no distinctive preference for any bathymetric feature; they
were recorded twice within the Point Vicente and Abalone Cove SMCAs.
Northern right whale dolphins and killer whales were both recorded near
Dume Canyon and within the boundaries of the Point Dume SMR/SMCA. Minke
whales and humpback whales where both recorded in the bay (minke whale:
80.0%, n = 15; humpback whale: 75.0%, n = 4), with a preference for
slopes and escarpments. Humpbacks were found in vicinity of the Point
Vicente SMCA. Both of the fin whale sightings were seen in offshore
waters outside the bay. Of the seven sightings of blue whales, all of
them occurred inside the boundaries of the established MPAs and along
escarpments near Dume Canyon (n = 3), oft Point Vicente (n = 1), north
of Point Dume (n = 2), and within the Bird Rock SMCA near Catalina
Island (n = 1).
The behavioral budget recorded for bottlenose dolphins showed a
predominance of travel (42.2%; n 5-min samples = 2,381) and travel-dive
(24.5%) activities. Feeding at surface was observed in 4.0% of the
sightings, also in association with other activities such as travel
(travel-feeding: 5.9%), dive (dive-feeding: 1.3%), and socialize
(feeding-socialize: 0.9%; Table 3).
The budget for both common dolphin species, which are sympatric in
the bay (Bearzi, 2005b), showed a large number of activities also
characterized by travel (56.5%; n 5-min sample = 1,891). Travel-dive was
recorded only during 4.4% of the sightings. Feeding was observed in 9.1%
of the sightings, also in association with other activities such as
travel (travel-feeding: 12.3%), and dive (dive-feeding: 0.8%; Table 3).
Both species of common dolphins were regularly observed separating into
smaller groups of about 25-30 individuals to feed near the surface on
large schooling fish (M. Bearzi, pers. obs.).
Pacific white-sided dolphins and Risso's dolphins spent most
of the time traveling in the study area (respectively: 46.3%; n 5-min
sample = 108; 62.5%, n = 112), but other behavioral states were also
observed. Dall's porpoises were mostly dive-traveling (36.5%, n =
74). Gray whales were regularly observed traveling (75.8%; n = 128) from
Point Dume to Point Vicente and vice versa during their winter
migration, but some individuals were also seen in the inshore waters
(< 0.5 km) of the bay. Minke whales were mostly sighted during
dive-travel activities (48.0%, n = 50; Table 3).
Group sizes for the most observed species are illustrated in Table
4. The mean group sizes of coastal and offshore bottlenose dolphin
schools varied considerably (mean difference = 7.71, df = 40, t = 3.86,
P < 0.001), with the largest groups observed offshore. Both species
of common dolphins were usually observed in large schools (mean =
108.84, SD = 122.66, SE = 9.52, range = 1-600, n = 166), and the largest
group sizes were in offshore waters (mean = 115.98, SD = 123.83, SE =
9.95, range = 1-600, n = 155). Inshore common dolphins were mostly
observed alone in aggregation with bottlenose dolphins. Minke whales and
gray whales were usually observed alone or in pairs.
Occurrence and Distribution
Of the cetaceans inhabiting the study area, bottlenose dolphins
were the most often observed, followed by long-beaked and short-beaked
common dolphins, as previously recorded for the Southern California
Bight (Bonnell and Dailey, 1993; Forney and Barlow, 1998; Carretta et
al., 2006). Other cetaceans were occasional or rare inhabitants of the
bay and their occurrence reflects, in general and at smaller scale, the
occurrence of these species reported by other authors for the SCB
(Bonnell and Dailey, 1993; Barlow et al., 1998; Schmitt and Bonnell,
2003; Appler et al., 2004; Carretta et al., 2006; Soldevilla et al.,
Coastal bottlenose dolphins were regularly observed close to shore,
in agreement with data off the San Diego coastline (Defran and Weller,
1999; Defran et al., 1999; Dudzik et al., 2005; Lang, 2002). Sightings
of offshore bottlenose dolphin schools were recorded both along the
canyons and out to Santa Barbara and Catalina islands. The presence of
offshore bottlenose dolphins near these islands is in accordance with
other authors (see Bonnell and Dailey, 1993).
The general occurrence of short-beaked and long-beaked common
dolphins in offshore waters was consistent with Forney and Barlow (1998)
for the California coast. In the bay, short beaked and long-beaked
common dolphins showed a preference for submarine canyons, especially
Santa Monica and Redondo canyons, in accordance with previous data
collected in the area (Bearzi, 2005b). Dolphins are likely to aggregate
in these areas of upwelling (Hickey, 1992, 1993), taking advantage of
these nutrient-rich feeding grounds. Anchovies (Engraulis mordax),
common preys of short-beaked common dolphins in the Bight (Evans, 1975),
are known to be abundant around upwelling areas of submarine canyons and
escarpments (Mais, 1974; Hui, 1979).
Prey abundance near these bathymetric features may also explain the
presence of other cetacean species in the same areas. Competition for
resources along canyons was probably avoided by: 1) different species of
cetaceans feeding on different prey (Bearzi, 2005b), 2) the presence of
species at different seasons at these locations, and, most likely, 3)
productive feeding grounds rich enough in prey to support the feeding
requirements of various species.
The most observed cetacean species occurred throughout the entire
study period, including the strong 1997-98 El Nino (and following La
Nina). The overall presence of cetaceans in the bay during El Nino years
may have been related to prey abundance of some fish species, including
Pacific sardine (Sardinops sagax), white seabass (Atractoscion nobilis)
and splitnose rockfish (Sebastes diploproa), during this time of warmer
water temperature (California Department of Fish and Game, 2000).
Bottlenose and common dolphins are also known to be opportunistic
feeders that change their diet based on availability and abundance
(Heyning and Perrin, 1994; Bearzi et al., 1999).
The only exception to this trend was the Risso's dolphin that
disappeared from the bay at the beginning of the 1997-98 El Nino and
began to reappear in the area after the year 2000. This species was
rarely observed before the 1982-83 El Nino event in southern California
waters, but seemed to have increased above the continental shelf around
Catalina Island after this event (Shane, 1995; S. Shane, pers. comm.).
The disappearance of this species from the bay prior to and after the
1997-98 El Nino event may have been related to offshore movements of
California market squid, Loligo opalescens, one of their common prey
(Zeidberg et al., 2006).
In conclusion, the unique physical oceanography of the study area
have shaped a suitable habitat for several species of prey and,
consequently, for cetaceans. Santa Monica Bay could also act as an
"oasis" during years of poor productivity, as has been
documented for Monterey Bay during the 1997-1998 El Ninno (Benson et
Further studies on the relationships between oceanographic
conditions, prey availability and the distribution and abundance of
cetacean populations at different scales are needed to improve the
understanding of the ecology of the local cetacean community.
Behavioral Patterns of the Most Observed Species
Behavioral data collected for bottlenose dolphins were comparable
to those reported for the San Diego area (Hanson and Defran, 1993).
Coastal bottlenose dolphins spent most of the time traveling (this
study: 68.8% travel plus dive-travel; San Diego: 63.0% travel plus
dive-travel), and feeding was observed 19.0% of the time along the San
Diego coastline and 13.2% in the study area.
Data on behavioral patterns of free-ranging common dolphins
(Delphinus spp.) are scarce worldwide (Neumann, 2001b). Data for
short-beaked common dolphins in the study area were consistent with
observations for the same species in the north-western Bay of Plenty, in
New Zealand, where dolphins were seen mostly traveling (55.0% Neumann,
2001b; 57.0% this study). In Santa Monica Bay, both species of common
dolphins spent more time traveling, foraging and feeding at surface than
bottlenose dolphins (Table 3). The large amount of time spent traveling
by both species of common dolphins was probably related to the
distribution and availability of prey in the pelagic environment of the
bay that required movements between different foraging grounds (Bearzi,
Group Sizes of the Most Observed Species
Mean group sizes for the most common cetaceans observed in Santa
Monica Bay and adjacent areas were comparable to group sizes reported by
other authors for the SCB (Table 4). Coastal bottlenose dolphin groups
observed in the bay ranged from 1 to 35 individuals and were typically
composed of 2-15 individuals. Offshore bottlenose dolphin groups ranged
from 1 to 57 individuals and were typically composed of 10-20
individuals. The results of this study are similar to Hansen (1990) and
Scott and Chivers (1990). This species showed an increased group size
from inshore to offshore waters, in agreement with Defran and Weller
(1999), likely as a response to the patchily distributed food resources
of the pelagic
environment (Wells et al., 1980; Dailey et al., 1993).
Offshore bottlenose dolphins were also found in aggregations with
other cetaceans (Bearzi, 2005a), possibly facilitating schooling
behavior of prey and capture of food by these predators (Magurran, 1990;
Simila and Ugarte, 1993; Norris and Johnson, 1994).
Both species of common dolphins were regularly observed in large
schools, and orten recorded in rank formation during food search,
spreading out over a mile (M. Bearzi, pers. obs.). When a high
concentration of prey was found, dolphins separated into smaller groups
of 25-30 individuals, and exploited the resources present in different
feeding grounds. The presence of these subgroups is in agreement with
Evans (1994), suggesting a basic social unit for common dolphins of
about 30 individuals.
Cetacean Community and the Newly Established MPAs
Recently, many investigations on dolphins and whales (e.g., Gregr
and Trites, 2001; Harwood, 200l; Fury and Harrison, 2008) have helped to
identify key areas for cetaceans and, in some cases, have contributed to
the establishment or expansion of marine protected areas (Dawson and
Slooten, 1993; Hooker et al., 1999; Hoyt, 2005). Vice versa, some MPAs
have helped to protect cetaceans and their habitats, as well as the
species they feed upon (Hoyt, 2005).
Based on this study: 1) the presence of a rich and diverse cetacean
fauna in the study area, that includes several threatened and endangered
species, 2) the year-round and regular occurrence of three dolphin
species, including the bottlenose dolphins frequenting coastal waters,
3) the use of this areas as foraging grounds by several cetaceans
species, are all clear indications of the importance of these habitats
for the local cetacean community.
Several of the MPAs located in the study area represent foraging
hotspots and/or essential corridors for year-round species like
bottlenose dolphins, short-beaked and long-beaked common dolphins (this
study, Bearzi, 2005a,b; Bearzi, et al., 2009a), as well as habitats in
which endangered cetaceans like blue whales are found (this study).
Protecting these critical habitats for cetaceans as well as the species
they depend upon is the first step toward good management of MPAs (Hoyt,
Coastal bottlenose dolphins inhabiting the impacted waters oft Los
Angeles (Schiff, 2000) year-round and using the area as foraging ground
(this study; Bearzi, et al., 2009a), are top predators susceptible to
indirect threats like marine debris, chemical and acoustic pollution
(Simmonds and Hutchinson, 1996; Nowacek et al. 2007, Weilgart 2007,
Stavros et al. 2008). Anthropogenic effects on these animals are usually
difficult to assess, but dolphins bioaccumulate toxins and suffer
immunological and reproductive disorders as a consequence (Simmonds and
Hutchinson, 1996; Bossart 2007; Blasius and Goodmanlowe, 2008). Over 80%
of bottlenose dolphins in the study area were found carrying skin
diseases and body malformations (Bearzi et al., 2009). These diseases
are usually correlated to poor quality of water and presence of
contaminants (Bossart, 2007). Bottlenose dolphins are now used worldwide
as key indicators of the status and health of coastal habitats because
they represent important marine ecosystem sentinels (Wells et al.,
2004). Long-term population monitoring data on these dolphins area
powerful tool for tracking the progression of poorly understood diseases
that may be relevant both to dolphin and human health.
In general, cetaceans are often viewed as flagship species (Mann et
al., 2000; Prideaux, 2005). In the study area, and the established MPAs
within, there is a substantial overlap in distribution between cetaceans
and other apex and non-apex species (e.g. seabirds, fish, zooplankton;
Bearzi, 2005). The overlap usually coincides with upwelling and
nutrient-rich feeding areas. Conservation measures aimed at mitigating
threats to cetaceans are expected to result in protection for other
organisms as well.
Continuous monitoring is essential to identify not only the areas
used preferentially by cetaceans within and outside the boundaries of
the MPAs, but also the subset of critical habitats they use for
different behavior, and the type of behaviors in which they are most
vulnerable to human activities. Monitoring distribution, occurrence and
behavior of these key species, as well as their threats, is essential in
any decision-making process involving MPAs, as has also been suggested
at the last International Committee on Marine Mammal Protected Areas
In conclusion, this paper provides new ecological baseline data on
dolphins and whales, and offers preliminary information for better
establishing goals for use of the newly established MPAs (e.g., control
of human activities such as fishing, whale watching). The implication
for MPA design and implementation in the study area is that a more
flexible definition of MPAs for these cetaceans is needed. It also
stresses the strong need of regular and long-term monitoring of
cetaceans within and outside the boundaries of the MPAs. This will help
to keep the definition of MPAs more adaptable, thereby facilitating the
changes necessary to protect cetaceans, as well other species present in
The field research for the years 1997-2005 was funded by the
Coastal Environmental Quality Initiative Fellowship and Ocean
Conservation Society; field research for 2006-2007 and the entire data
analyses were funded by the Santa Monica Bay Restoration Commission.
This study would not have been possible without the help of the many Los
Angeles Dolphin Project assistants and volunteers. Special thanks also
go out to Maptech, Logger, and ESRI.
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Maddalena Bearzi (1) * and Charles A. Saylan (2)
(1,2) Ocean Conservation Society, P.O. Box 12860, Marina del Rey,
CA 90295, USA
* Corresponding author: M. Bearzi, P.O. Box 12860, Marina del Rey,
90295, CA, USA, ph. 310.8225205, fax 310.8225729, email@example.com
Table 1. Number of surveys and summary of research effort in
Santa Monica Bay for the years 1997 2007. No surveys were
conducted on December 1999, October 2000, July 2001, September
2001, July 2005, December 2005, May 2006, and February-April
1997 1998 1999 2000 2001
Inshore surveys 16 55 39 33 27
Offshore surveys 34 41 32 31 26
Total number of surveys 50 96 71 64 53
Hours spent in the field 144 224 178 149 137
Hours spent searching for cetac. 110 136 130 105 82
Hours spent with cetaceans 34 88 48 44 55
N of 5-min behavioral samples 295 1,065 698 525 675
2002 2005 2006 2007 Total
Inshore surveys 9 3 14 8 204
Offshore surveys 12 7 28 10 221
Total number of surveys 21 10 42 18 425
Hours spent in the field 73 68 194 56 1,223
Hours spent searching for cetac. 44 48 134 34 823
Hours spent with cetaceans 29 20 60 22 400
N of 5-min behavioral samples 396 265 638 234 4,791
* Inshore and offshore surveys conducted during the same day were
considered as two separate surveys.
Table 2. Sighting frequencies (sightings/hour) of the three most
observed cetacean species in the bay.
1997 1998 1999 2000
Number of sightings 19 61 33 24
Sighting frequency (sights/hour) 0.13 0.27 0.19 0.16
Delphinus delphis *
Number of sightings 6 7 6 6
Sighting frequency (sights/hour) 0.04 0.03 0.03 0.04
Delphinus capensis *
Number of sightings 2 12 10 9
Sighting frequency (sights/hour) 0.01 0.05 0.06 0.06
2001 2002 2005
Number of sightings 20 7 10
Sighting frequency (sights/hour) 0.14 0.10 0.15
Delphinus delphis *
Number of sightings 15 9 8
Sighting frequency (sights/hour) 0.01 0.12 0.12
Delphinus capensis *
Number of sightings 4 4 3
Sighting frequency (sights/hour) 0.03 0.05 0.04
2006 2007 Total
Number of sightings 29 18 221
Sighting frequency (sights/hour) 0.15 0.32 0.18
Delphinus delphis *
Number of sightings 19 8 84
Sighting frequency (sights/hour) 0.10 0.14 0.07
Delphinus capensis *
Number of sightings 16 3 63
Sighting frequency (sights/hour) 0.08 0.05 0.05
* This calculation does not include Delphinus spp. not recognized
at the species level.
Table 3. Overall behavioral state budget recorded for the most
observed species. Behavioral state data at less than 0.5% level
were not included in the table. A hyphen between two behavioral
states refers to activities performed simultaneously by different
focal group individuals during 5-min sample (e.g., Dive Travel).
of observed Tot
Species Behavioral states N 5-min states samples
Samples (approx. %)
Bottlenose Travel 1,004 42.17 2,381
dolphin Travel-Dive (a) 583 24.49
Travel-Socialize 199 8.36
Travel-Feeding 140 5.88
Feeding 96 4.03
Dive 44 1.85
Travel-Dive- 38 1.60
Socialize 37 1.55
Dive-Feeding 32 1.34
Travel-Milling 23 0.97
Travel-Dive- 23 0.97
Feeding-Socialize 21 0.88
Travel-Dive- 17 0.71
Dive-Socialize 17 0.71
Travel-Dive- 15 0.63
Travel-Socialize- 14 0.59
Dive-Socialize- 7 0.29
Milling 4 0.17
Dive-Milling 3 0.13
Travel-Dive- 3 0.13
Travel-Dive-Play- 2 0.08
Socialize-Milling 2 0.08
Travel-Feeding- 2 0.08
Dive-Feeding- 2 0.08
Travel-Dive-Feeding 2 0.08
Travel-Dive-Feeding 2 0.08
Dive-Feeding- 1 0.04
Feeding-Socialize- 1 0.04
Dive-Feeding- 1 0.04
Travel-Feeding- 1 0.04
Common Travel 1,069 56.53 1,891
dolphin (1) Travel-Feeding 232 12.27
Feeding 173 9.15
Travel-Socialize 135 7.14
Travel-Dive 84 4.44
Travel-Dive-Socialize 36 1.90
Dive 27 1.43
Travel-Feeding-Sociali 21 1.11
Travel-Dive-Feeding 20 1.06
Dive-Feeding 5 0.79
Socialize 8 0.42
Travel-Dive-Feeding-So 8 0.42
Travel-Socialize-Milli 5 0.26
Travel-Milling 3 0.16
Travel-Dive-Milling 2 0.11
Travel-Dive-Milling-Fe 2 0.11
Milling 1 0.05
Species Behavioral states
Travel-Milling-Feeding l 0.05
Travel-Dive-Milling-So 1 0.05
Risso's Travel 70 62.50 112
dolphin Travel-Feeding 9 8.04
Travel-Dive 8 7.14
Travel-Socialize 6 5.36
Feeding 3 2.68
Dive-Feeding 2 1.79
Travel-Dive-Feeding 2 1.79
Milling 2 1.79
Dive-Milling- 1 0.89
Travel-Milling 1 0.89
Dall's Travel-Dive 27 36.49 74
porpoise Dive 21 28.38
Dive-Feeding 15 20.27
Travel 10 13.51
Travel-Milling 1 1.35
Pacific Travel 50 46.30 108
white-sided Travel-Socialize 20 18.52
dolphin Feeding 8 7.41
Travel-Feeding 7 6.48
Travel-Dive 4 3.70
Feeding-Socialize 4 3.70
Dive-Milling 4 0.70
Dive 3 2.78
Milling 3 2.78
Travel-Play 3 2.78
Travel-Dive-Play 1 0.93
Travel-Dive-Feeding 1 0.93
Travel-Dive- 1 0.93
Gray whale Travel 97 75.78 128
Travel-Dive 27 21.09
Dive 3 2.34
Feeding 1 0.78
Minke whale Travel-Dive 24 48.00 50
Travel 12 24.00
Feeding 8 16.00
Dive 6 12.00
(1) this data includes both species of short-beaked and
long-beaked common dolphins.
(a) simultaneous behavior occurring during 5-min sample.
(b) the behavioral state play was only used in data collected
Table 4. Group sizes for the nine most observed species and mean group
sizes reported by other authors.
Mean SD SE Count Min Max
Bottlenose dolphin 9.94 7.59 0.53 203 1 57
Inshore 8.30 5.01 0.39 162 1 35
Offshore 16.41 11.66 1.82 41 1 57
Common dolphin 108.84 122.66 9.52 166 1 600
Inshore 8.27 13.61 4.10 11 1 40
Offshore 115.98 123.83 9.95 155 1 600
Pacific white-sided d 17.27 10.40 3.13 11 5 45
Dall's porpoise 6.67 4.56 1.32 12 2 15
Risso's dolphin 9.67 7.35 1.90 15 3 29
Gray whale 1.70 0.70 0.15 23 1 3
Minke whale 1.33 0.50 0.17 9 1 2
Bottlenose dolphins 19.8 Defran and Weller (1999), San
Diego, inshore dolphins
18 Hansen (1990), Southern
California, offshore dolphins
15.7 Lang (2002), San Diego, inshore
12.7 Lang (2002), Santa Barbara,
10 Scott and Chivers (1990), Eastern
tropical Pacific Ocean,
9.1 Dudzik et al. (2005), San Diego,
Common dolphin 67.1 Shane 1994, Catalina Island,
98 Au and Perryman 1985, Eastern
77.6 Smith et al. 1986, California
5.4-661 Barlow 1995, California waters
Pacific 10.3 Shane 1994, Catalina Island,
11.5-75.4.1 Barlow 1995, California waters
Dall's porpoise 4.7 Shane 1994, Catalina Island,
4.5 Smith et al. 1986, California
3.3 Barlow 1995, California waters
Risso's dolphin 13.1 Shane 1994, Catalina Island,
8.3-25 Barlow 1995, California waters
Gray whale 2.1 Reilly et al. 1983, California
3-5.3 Forney et al. 1995, California
Minke whale 1.1 Barlow 1995, California waters
1.0 Forney et al. 1995, California
1.8 Shane 1994, Catalina Island,
(1) group sizes for D. delphis and D. capensis are cumulated for
comparison with other authors.