1. 2/5/2011
Site fidelity among Grey Whales (Eschrichtius robustus) as determined by
photographic identification in Bahía Magdalena, Baja California Sur, Mexico
Margaret V. du Bray, Eduardo Najera-Hillman
Whitman College, Walla Walla, WA USA
School for Field Studies: Center for Coastal Studies, Puerto San Carlos, BCS,
Mexico
ABSTRACT: Eschrichtius robustus (grey whales) within Bahía Magdalena, Baja
California Sur, Mexico, are an economically and culturally important species. A
migratory species, they travel from their feeding grounds in Arctic waters to
winter and calve in Mexico. Bahía Magdalena is one of the notable areas where
grey whales are found during the winter. As has been done elsewhere,
photographic identification was performed by the School for Field Studies in
order to assess site fidelity and short-term movements of grey whales within the
bay. It was expected that whales would exhibit high site fidelity. Whales were
observed and photographed from pangas in the bay. The photographs were
organized into a photographic catalog. The catalog from the year 2011 was
compared to catalogs from the years 1998-1999, 2003, 2004, 2005, 2007, and
2009-2010. Whales were visually identified using markings including barnacles,
scars, and injuries. Two whales were resighted. One was initially sighted in 2003
and the other was initially sighted in 2004. No whales were resighted on different
days within 2011. The results of this study indicate that there is low site fidelity

2. among grey whales in Bahía Magdalena. More data is required to continue to
study this phenomenon. The study does demonstrate that photographic
identification studies should focus on the Santo Domingo Estuary, where whales
are more likely to surface. This allows for more comprehensive photographs.
Additionally, whales with distinct marks should be focused upon for photographs.
Finally, more research is necessary to examine short-term movement patterns
within the bay.
LITERATURE REVIEW
Sources which discussed the ecology and habitats of grey whales
(Eschrichtius robustus) were analyzed to understand patterns of populations in
Bahía Magdalena, Mexico. Other sources, which focused on photographic
identification, were examined in order to understand the context of prior research
relating to cetaceans. These sources were also helpful in developing a
methodology. Prior research was categorized four ways: ecology of grey whales,
techniques for photographic identification, social organization as determined by
photographic identification, and the use of photographic identification to
determine anthropogenic causes of scarring.
Ecology and Population Dynamics of Grey Whales within Bahía
Magdalena. Grey whales are a migratory species. They travel 20,000 km from
their feeding grounds in Alaska to the calving grounds in the Pacific waters near
Mexico. Bahía Magdalena, Baja California Sur, Mexico, is one area where grey
whales calve and mate from December to March. The bay is utilized differently

3. by different groups of whales; mothers with calves are more likely to be found in
protected areas, like the estuaries in the Santo Domingo channel. Single males
and females, both mature and immature, are more likely to be found in areas
within Magdalena and Almejas Bays. The three areas within the bay are
considered separate locations with different utilities (Perez-Cortez et al. 2004).
Photographic Identification: Techniques. Marine mammals have been
documented and identified using photographic identification since the mid-1970s.
Traditionally, cameras with a single-lens reflex and either black and white or color
film were used (Shane 1990). More recently, digital photography has replaced
traditional film photography (Meyer 2006). Most photographers involved in
photographic identification of marine mammals have used digital single-lens
reflex cameras with zoom lenses (Wursig and Jefferson 1990).
Identification strategies have included technological programs and visual
matches. Technological programs have become popular for image matching and
identification in marine species. The FinBase system is a notable example of
these programs. This program has matched images of individuals by matching
distinctive marks on fins (Adams 2006). Other researchers have used algorithms
and affine invariant grids and curves in order to match the markings and shape of
fins and flukes (Ranguelova et al. 2004, Gope 2005). Data has also been
generated by examining light and dark patches on flukes and fins. The data
generated by these methods has been entered into databases and was available
for comparison at later dates. Other research has been conducted without the
use of computer-based programs. In this case, photographs were sorted before

4. one clear picture of each individual was chosen for closer analysis. All
distinguishing marks of an individual were noted. The tables generated by this
initial cataloguing were then available to document resightings (Karczmarski
1998).
Social Organization and Population Dynamics as Determined by
Photographic Identification. The social organization of two populations of pilot
whales was studied through the use of photographic identification. Pilot whales
were identified through key features including fins and saddle patterns. Once the
photographs were catalogued, researchers examined them for site fidelity and
pod dynamics. The photographs suggested that pilot whales return to specific
locations seasonally, as many were seen in the same location year to year.
Photographs have indicated that pilot whales are likely to remain with their pod.
Furthermore, pilot whales were found in pods composed primarily of females and
sub-adult males (Shane 1990).
The western grey whale population has also been studied in order to
understand social organization and population composition. Because this
population is critically endangered, researchers have attempted to categorize the
numbers and the status of the population. A catalog of distinct features was
created based on photographs taken during monitoring sessions. The
photographs were then used to determine resightings and create a database in
which researchers could examine population dynamics in the future.
Researchers have suggested the need for continued research in order to monitor
the population dynamics (Yakovlev and Tyurneva 2003).

5. The Use of Photographic Identification to Determine Causes of
Anthropogenic Scarring. The western grey whale population is threatened by
whaling. Researchers speculate that the population is also threatened by its
interactions with vessels and entanglements in fishing gear. The body of the grey
whale was partitioned into twenty-one sections, and evidence of scars was
examined within each section. Scars were categorized as no scar, entanglement,
vessel collision, unknown scar, partially visible, or not visible scars. Among
western grey whales, the right side was more likely to show scarring than the left.
18.7% of grey whales were scarred due to fishing entanglements and 2.0% were
scarred due to vessel collisions. The researchers have suggested that continued
research is required due to inadequate information about the population.
Furthermore, they have suggested that more research must be carried out in
order to estimate the fatalities resulting from entanglements and collisions with
vessels; current data only demonstrates the number of whales that survive these
encounters (Bradford et al. 2009).
INTRODUCTION
Grey whales (Eschrichtius robustus) are a culturally and economically
significant species within Bahía Magdalena, Baja California Sur, Mexico (Dedina
2000). Grey whales are a migratory species; from Alaska, they travel 20,000 km
to Baja California Sur to mate and calve. Pregnant females often calve in Bahía
Magdalena and raise their calves in the sheltered waters. Previously an
endangered species, grey whales are now considered to be threatened; their
population numbers appear to be increasing (Perez-Cortez et al. 2004).

6. Grey whales are an economically viable species; where they were
previously hunted, now they provide income for locals involved in the tourism
industry. The increase in tourism within the Bay potentially threatens the grey
whales. Bahía Magdalena is also polluted by the effluent from the local sardine
cannery. These two issues are among the greatest immediate impacts affecting
the grey whale calving grounds in Bahía Magdalena (Dedina 2000).
Photographic identification is a widely used technique for understanding
population dynamics among other species. Research has examined group
relations and site fidelity among pilot whales (Shane 1990). Photographic
identification has also been used to assess anthropogenic impacts. Researchers
have also used photographic identification among the western grey whale
population in order to generate a database. This will allow future researchers to
monitor the size and status of the critically endangered population in Japan and
Russia (Yakovlev and Tyurneva 2003). Researchers have analyzed
anthropogenic effects on grey whales among the same population. Photographic
databases have allowed researchers to compare scars from fishing
entanglements and vessel collisions, and thereby estimate the numbers of
whales impacted by these interactions. It also estimated the extent to which this
is an ongoing problem (Bradford et al. 2009).
Photographic identification has been used in the Western grey whale
population to examine site fidelity. This study demonstrated that the grey whales
had high site fidelity, particularly related to their feeding ground (Weller et al.
1999, as cited in Swartz et al. 2006).

7. Within Bahía Magdalena, photographic identification has been used since
the 1960s. The research has yielded a significant photographic database that
allows researchers to recognize the whales sighted in the bay (Swartz, S. L. et al.
2006). Because the migration patterns of grey whales are so well-known, they
are a particularly viable species to study with photographic identification.
Observing grey whales in breeding areas is particularly useful due to the high
numbers of whales that visit calving grounds annually. Dorsal regions were
focused on due to their distinctive marks. Breeding patterns were examined in
several studies as a result of photographic identification (Jones 1990, Urban et
al. 2003).
Prior research has examined the phenology of whales in the bay, as well
as movements within the bay. This research also examined the areas (Boca,
Estuary, etc) in which specific populations might be found, and reproductive rates
(Urban et al. 2003). Studies focused in tandem on genetic distinctions within the
eastern grey whale population and the photographic identification that allowed
examination of interyear site fidelity. The study demonstrated that grey whales in
Bahía Magdalena had low interyear site fidelity, and that they were sighted
across differing spans of time. This research documents the difficulty of
identifying whales throughout their life, as they are born with very few marks and
add them as they age (Alter et al. 2009).
Photographic identification has evolved in the past decade. Whereas film
cameras (black and white and color) were used to document populations, digital
photography has become more prevalent (Shane 1990, Meyer 2006). Using

8. digital single-lens reflex cameras and zoom lenses, photographers have been
able to document populations of cetaceans (Wursig and Jefferson 1990).
Different methods of analyzing the photographs have also been used; affine
invariant curves have been used to analyze tails and fins; other computer
programs have been used to match cetaceans within an already-generated
database (Ranguelova et al. 2004, Gope 2005, Adams 2006). Still other
researchers continue to visually match photographs (Karczmarski 1998).
The staff and students at the School for Field Studies’ Center for Coastal
Studies in Bahía Magdalena began documenting grey whale sightings using
photography in 1998. Photographs were taken in 1998, 1999, 2003, 2004, 2005,
2007, 2009, 2010, and 2011. The database generated by this documentation has
been used for several research projects in the past decade. Very little research
has examined the site fidelity among grey whales. While previous research has
demonstrated that different areas of the Bay are used by specific groups of
whales, no one has yet demonstrated that certain whales return each year to the
same areas of the bay.
This research used the existing photographic identification catalog
generated by past students and professors. This was combined with data
collected in the year 2011 to examine whether there is site fidelity among this
population of grey whales. Photographs from 2011 were categorized by location
within Bahía Magdalena in order to study short-term movement patterns. I
hypothesize that grey whales will show site fidelity within Bahía Magdalena. Due
to the challenges of photographing grey whales, it is unlikely that the

9. photographic catalog will demonstrate consistent, year-to-year site fidelity among
grey whales. If grey whales are matched across the database, this will be noted
as site fidelity. Additionally, I hypothesize that solitary whales will move between
the Boca and the main portion of the bay; mothers and calves will stay primarily
in the Estuary.
METHODS AND MATERIALS
Location and Temporality Grey whales were monitored and
photographed approximately once a week from the beginning of February until
the end of March annually. Monitoring was only carried out in favorable weather
conditions (Beaufort < 2). Whales were monitored by students and faculty from 8-
9m fiberglass pangas with 115 hp motors in several regions of Bahía Magdalena.
Bahía Magdalena is approximately 31 km long and 22 km wide. It is connected to
the Pacific Ocean by a 6 km mouth. Monitored areas included the Santo
Domingo Channel estuary, the main part of the bay, and the mouth of the bay.
The area was limited to regions between the coordinates 24°20’N-25°20’N and
111°30’W-112°10’W.

10. Figure 1. Map showing the range of grey whales and the study site located
within their winter breeding and calving grounds
Study Site
Winter Breeding Grounds

11. Figure 2. Map showing the specific locations within Bahía Magdalena where
whales were monitored
Field Work Pangas slowly approached whales after a sighting. Fast
speeds were prevented to avoid disrupting the behavior of the whales. Surface
water temperature and depth were taken. A GPS waypoint position and longitude
and latitude were noted. The behavior and the number of individuals sighted
were also recorded. Photographs were taken using several cameras. These
cameras usually had a variable focal length which allowed whales to be
photographed at a distance and up-close. The dorsal region was a point of focus
due to notable characteristics in that region of the body. Behavioral pictures were
also taken, which showed other regions of the body. Multiple pictures of each

12. whale were taken and those with the best angle and clarity were entered into the
photographic database.
Data Analysis Photographs from the database were visually compared.
Two pictures were compared at a time. Markings including scars and injuries
were used as criteria for identifying individuals. Particular attention was paid to
markings along the back and knuckles of the whales, as these were most
commonly photographed. Images showing individuals with the same markings
were documented as a resighting of an individual. An individual was resighted
only if it was seen on a different day than that on which it was originally sighted.
The years of the sightings were recorded in a database. If an individual was not
previously in the database, it was considered a new sighting and was given a
number corresponding to the initial month, year, and date of the sighting.
Resightings of whales were noted in a database. The database was used
to examine the number of individuals which had been resighted, and at what
times. If whales were matched across years in the photographic catalog, it was
considered a resighting. The years in which the whale was not sighted were
considered to be years in which the whale might have been present, but was not
photographed or sighted.
RESULTS
The photographs from all whale-watching days in 2011 were sorted and
organized into a photographic catalog.
The total number of whales sighted and photographed in 2011 was 81.
Whales were not sighted or photographed more than once in 2011. Two mothers

13. with calves were sighted and photographed showing similar markings (Figures 3
and 4).
473 whales were sighted and photographed from 1998 to 2011, excepting
the years 2000, 2001, 2002, and 2006, when no photographs were taken or were
lost (Table 1). Out of a total of 473 whales photographed and catalogued from
1998 to 2011, only two were resighted (Table 3). Variance was measured to
understand the difference in the number of whale sightings and photographs
annually. Variance here demonstrates the numerical difference of whales
photographed year to year. There was a strong variance in the number of whales
sighted and photographed year to year (variance = 1908.8).
Previous data calculated the number of whales sighted per year. This was
compared with the number of whales per year as calculated in 2011 (Table 2).
The body region which was used for photographic identification was
recorded by year. Until 2005, the right side was exclusively photographed. In
2009 and 2010, more flukes were recorded than in previous years. In 2011, right
and left sides were photographed (Table 5).
The number of photographs taken this year was compared with the
number of photographs used from each site. The Boca de Bahía Magdalena had
the highest number of used photographs. The Estuary had the second most used
photos (Table 4).

14. Figure 3. Mother and calf showing similar white markings
Figure 4. Mother and calf showing similar white markings
Table 1. The number of whales sighted as demonstrated by the photographic
catalog
Database
by Year
1998-
1999
2003 2004 2005 2007
2009-
2010
2011
# Whales
sighted
53 160 56 46 42 32 81
Table 2. Previous data showing the number of whales identified, including
resightings
Year
Days of
Effort
Useful
Photos
Individuals
Re-
sightings
1998 1 4 1 -
1999 7 60 54 2
2004 12 78 64 -
2005 8 102 48 21
2007 6 108 70 -
2009 4 17 14 1
2010 4 32 25 -
2011 17 110 81 -

15. Table 3. The number of whales resighted, including the dates initially sighted and
resighted, and the photos used to identify them
SFS ID #
Photo #
initial
sighting
SFS ID #
resighting
Photo #
Resighting
Date
Initially
Sighted
Date
Resighted
SFS270 l103a3b
IMG 2537,
IMG 2538,
IMG 2539,
IMG 2541,
white spot
calf, white
spot cow
and calf,
white spot
cow right
side
February-
03
February-
11
SFS093
l304a8,
l304a19b
SFS233 IMG 0349
February-
04
February-
11
Table 4. The number of photos taken per three sites, the number used, and the
percentages
Location
Number
of Photos
Taken
Number
of Photos
Used
Ratio
Estuary 429 80 0.18
Main Bay 255 27 0.1
Boca 9 3 0.33
Table 5. Showing which body region, by year, was used for identification
Body
Region
# Whales
98-99
# Whales
2003
# Whales
2004
# Whales
2005
# Whales
2007
# Whales
2009-
2010
# Whales
2011
Right
Back
53 158 57 43 34 7 45
Left Back 0 2 0 5 8 12 36
Fluke 0 0 0 0 0 13 0

16. DISCUSSION
Conclusions from Hypotheses The hypothesis that whales would show
site fidelity in Bahía Magdalena was partially supported. The results indicate that
very few whales return to Bahía Magdalena across the years. Furthermore, the
whale resightings occurred across a large time span (6-7 years). It was expected
that whales would be resighted within a short time span. That they were not
further indicates low site fidelity. Prior research found that interyear site fidelity
existed among grey whales, but that the proportion of those resighted was very
low and was found across a long time span (Alter et al. 2009).
Because whales were only sighted and photographed once over the
season (they were not resighted on different days within 2011), short-term
movement patterns cannot be determined. Future research should continue to
examine whether whales are returning annually to Bahía Magdalena, and focus
on their movement patterns within Bahía Magdalena.
Data Analysis The high variance in the number of whales seen year to
year indicates the strong differences in the number of whales seen between
years. Some years have as few as 32 whales, while others had as many as 160.
The difference in numbers makes it difficult to compare the whales. If even
numbers of whales were photographed across the years, it would suggest that
there was a greater potential for the same whales to return to Bahía Magdalena.
Because the data fluctuates so greatly, however, it is difficult to say that the
same whales return.

17. Previous data collected and analyzed by past student Laura Conner was
compared to data that was analyzed in 2011. There were discrepancies between
the number of whales that were counted by Conner and by the current
researchers. This can be accounted for because several whales within previous
databases were found to be labeled as different whales. These whales, however,
were identified as being the same. Additionally, because the photographs were
organized into a catalog prior to 2011, there may have been some organizational
mistakes. These two situations account for the variance in the number of
individuals identified in older databases between previous research and current
research.
The percentage of used pictures by location initially indicates that future
researchers should focus their attention on the Boca de Bahía Magdalena.
However, the percentage is drawn from a very small sample. Only nine pictures
were taken within the Boca, out of which, three were used. Future researchers
should focus their attentions on the Estuary. The greatest number of pictures was
taken there (429). Because whales are closely grouped in the Estuary, there is
the greatest likelihood that multiple regions of the body can be photographed.
Additionally, prior research has indicated that mothers with calves breathe much
more often than single adult whales. As a result, it is likely that mothers and
calves spend more time on the surface (Rodriguez de la Gala-Hernandez et al.
2008). This allows them to be photographed more frequently and amplifies the
importance of continuing to study the Estuary. This area is likely to provide
researchers with comprehensive photographs for identification.

18. Prior research has largely focused on female grey whales within Bahía
Magdalena. Due to their proximity to calves, they are inherently able to be
identified as female (Jones 1990). Females are also focused upon in order to
understand changes in breeding cycles and the impact on the population size
(Swartz et al. 2006, Jones 1990). This practice should be continued due to the
relative ease with which females and calves can be photographed.
The Estuary is also the most useful place to take pictures because, in the
other two regions of the bay, the whales are more likely to fluke. Whales in their
wintering grounds are less likely to fluke than they are when they migrate. As a
result, fluke photographs do not allow a large number of comparisons (Jones
1990). Additionally, fluke photographs may make it more difficult to examine the
short-term movement patterns of the whales. If a whale fluke is photographically
captured in one region of the bay, but the body is captured in another, no visual
match can be made. The 2009-2010 photographs included a number of fluke
pictures. While more fluke pictures might allow photographic identification, the
current data, which focused more on the back and knuckles, does not allow that.
Some research indicates that flukes are generally not helpful for identification
(Jones 1990). As a result, the main part of the bay and the Boca, where whales
were most likely to fluke, should be not be the focus for photographic
identification purposes.
In 2011, researchers begin traveling to the estuary, which allowed them to
intensely focus on photographing the sides of whales. Future research should
continue to focus on photographing both sides of the whale, so that

19. comprehensive photographic identification can be carried out. While past years
have primarily focused on the right side of whales, capturing the left side as well
as the right will lead to a more holistic understanding of which whales return, and
how their markings are changing. Prior research has demonstrated that
photographing the whales from multiple angles is more comprehensive. It allows
researchers to better visualize marking patterns, and as a result, makes re-
identification simpler. Additionally, this practice prevents counting one individual
as two (Jones1990).
The number of whales photographed in past years must be viewed with
some skepticism. Due to the poor photographic quality, particularly in the year
2003, it is very difficult to match whales across the year. While ten whales had
markings distinctive enough to be matched across the year, the majority of the
photographs were too poor to match, and as a result, the number of whales from
2003 is likely an overestimation.
Research Concerns and Recommendations There are several reasons
that might undermine the quality of the conclusions of this research. Visual
identification is challenging when different types of technology are used. The
earliest photographs were taken with film cameras and were scanned into the
photographic catalog. Photographic quality was lost during scanning, which
makes it challenging to compare whales from earlier years.
Photographs were also taken from multiple directions and angles. It is
conceivable that photographs were taken of the same whale, but either from
different sides or different angles. Without photographs of both sides of the

20. whale’s body, it is difficult to match the two sides of the whale. As a result, some
photographs may be of the same whale, but are not counted as a resighting
because the photographs were of different sides and were unable to be matched.
A better method of counting and photographing whales might reduce the
variability in the number of pictures taken, and would allow photography of all
sides of the whales. If one panga in the group was dedicated to recording the
number of whales and the position, and another boat photographed, it would
allow the photographer to get multiple angles of the same whale while others
recorded.
Cameras with built in GPS would also aid in this process. By looking at
specific GPS coordinates, the location of the whale could easily be recorded, but
could also distinguish one whale from another. This would reduce the number of
pictures that had to be visually matched along with the possibility for mistakes.
Additionally, when whales lack distinct marks, such as injuries, scars,
large white patches, or large groups of barnacles, it is difficult to make a
comparison. Many whales are covered in grey dapples. Without extremely high
resolution and matching software, these marks do not provide enough data to
make a positive identification.
When paired with visual identification, matching software, such as a
variation on that which is used for dolphin databases, would provide the most
conclusive data regarding the site fidelity of grey whales in Bahía Magdalena
(Adams 2006). The matching software would be more effective than the human
eye at detecting patterns in markings (particularly for those whales without

21. distinct marks). Innovative software has begun to examine whether the knuckles
of whales are an identifying feature. Some software matches have been made
using the area under the knuckles as a feature (Nutch 2006). If implemented with
grey whales in Bahía Magdalena, this might further the identification process.
While software has not yet been implemented in this way, it is conceivable
that, with the correct algorithm, aging software could be used for grey whales.
Because their markings change as they get older, it is difficult to look at a picture
of a young whale and extrapolate what it would look like as a mature adult. If
aging software were properly manipulated, it might create an estimation of what
the adult whale would look like.

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