Factors influencing the distribution pattern of different ages of hauled out harbor
seals were studied for a 5-week period in Spring 1991. Particular emphasis was
placed on the impact of substrate characteristics on the observed age distribution.
The seals in this area utilize irregularly-shaped offshore rocks for haul out.
Aggressive behavior was almost completely absent in this area and seals were
never observed battling over haul out space. Substrate features which were
examined included: distance to an escape channel; % total and individual algal
cover; size of hauling ground; and degree of incline to reach the hauling ground.
These features at least partly resulted in the observed segregation of ages as adults
were limited by the size of the hauling ground, while subadults and juveniles
were limited by the % algal cover and degree of incline. Social organization may
be an additional influence on the age-structured distributions, but the short term
of this study prevented any extensive investigation into the social structure of this
population.
INTRODUCTION:
The distribution of the harbor seal, Phoca vitulina, in the eastem Pacific
extends from Baja Califomnia, Mexico to the northern coast of Alaska (Knudtson
1977). Throughout its range, the harbor seal hauls out on a variety of substrates
which include: cobblestone and sandy beaches, sloping rock outcroppings and
rock platforms, emergent offshore tidal rocks, rocky shorelines with large
boulders and rubble, sandbars, mudflats, sheltered crevices or sea caves, and
tidepools (Riedman 1990). In addition to hauling out in order to give birth and
nurse its young, it has been postulated that hauling out is an important aspect of
maintaining the harbor seal's daily energy budget as it spends 44-50% of its time
hauled out (Riedman 1990, Sullivan 1982, Newby 1973). Several abiotic factors
have been recorded as influencing haul out behavior of harbor seals, such as: tidal
height (Scheffer and Slipp 1944, Venables and Venables 1955, Bishop 1968.
Loughlin 1974, Schneider and Payne 1983, Osbomn 1985); wave intensity
(Venables and Venables 1955, Bishop 1968, Schneider and Payne 1983, Slater
and Markowitz 1983); disturbance (Scheffer and Slipp 1944, Venables and
Venables 1955, Stewart 1984, Osbom 1985); and time of day (Stewart 1984.
Osborn 1985, Calambokidis et al 1987). In terms of biotic factors influencing
haul out, Bishop (1968) noted that the presence of other hauled out seals is an
important stimulus to general haul out. Furthermore, Sullivan (1982) and
Osborn (1985) reported that harbor seals have a greater tendency to haul out in
areas where other seals are resting than areas which contain no resting seals even
though the uninhabited areas are physically suited for haul out.
Many past researchers of harbor seal behavior have addressed the issue of
social organization among hauled out seals (Scheffer and Slipp 1944, Bishop
1968, Loughlin 1974, Knudtson 1977, Wilson 1978). These researchers either
supported or rejected the presence of social organization based on whether
individuals formed groups within the hauling ground area. More recently,
Sullivan (1982) and Osbom (1985) have commented on social organization by
noting that harbor seals of Humboldt Bay, California and Elkhom Slough,
California respectively form groups based on age and sex. Sullivan studied the
interactive and dominance behavior of the seals and provided a detailed analysis
on the effectiveness of various behaviors in obtaining and retaining haul out
space. Sullivan and Osborn both concluded that the observed age and sex
groupings were the result of a complex hierarchy system headed by adult males.
This paper addresses the age distribution of harbor seals hauling out on
irregularly shaped offshore rocks and presents data on substrate characteristics
which influence the age distribution of seals within the hauling grounds.
MATERIALS AND METHODS:
This study was conducted at Hopkins Marine Station (HMS), which is
located in the city of Pacific Grove at the souther tip of Monterey Bay,
California (see Map 1). This study was conducted from 4-22-91 to 5-27-91 for a
total of 127 hours of observation. The dimensions of the entire study area are
approximately 57 x 29 meters (see Map 2). Due to the close proximity of the
study area to shore, observations were made with the naked eye and with the aid
of binoculars. By using the natural boundaries formed by the irregular
configuration of the rocks, the study area was divided into 21 distinct hauling
grounds (see Maps 2-5). Only 2 of these hauling grounds are accessible at high
tide, and thus observations were conducted for the full duration of the daytime
ebbing tidal cycle.
For each seal that hauled out, its age class, sex, time of haul out, interaction
with other seals, and duration of haul out were recorded. Furthermore, its initial
location and movements were recorded on the appropriate map. Four age classes
were noted: adult (4+ years), subadult (2-4 years), juvenile (1-2 years), and pup
(El year). Age class was primarily based on size using age-size data compiled by
Fisher (1952) and Bishop (1968) (see Fig. 1), although pelt characteristics were
used to distinguish some pups and juveniles. Seals were measured by comparing
them to known-length areas on the rocks. Sex was indicated by the presence or
absence of a penile opening and penile line, or the presence of teats visible on
lactating females. However, most hauled out seals were not sexed because they
did not position themselves on the rocks with their ventral side towards shore and
sex-determination was almost impossible once the pelt dried.
Tidal height, wave intensity, and disturbance were recorded each day
Tidal height was measured in feet and was given by the tide schedule for
Monterey Bay. The maximum and minimum tidal heights during which
observations were made were +4.1 feet and +0.2 feet. Seals were not present in
the study area at a tidal height less than -O.5 feet because the channels within the
study area were too shallow for the seals to swim in them. Wave intensity was
measured daily at each of the 21 hauling grounds. Multiple recordings were
made throughout the observation period at one hour intervals. It was noted that
wave impact remained constant throughout the study period until the tide level
dropped below +2 feet. Once the tide height dropped below +2 feet, the wave
intensity factor would decrease by one category. Wave intensity never changed
by more than one category during any obervation period. There were five levels
of wave intensity based on the percent of the hauling ground covered by wave
splash: (1) hauling ground unaffected by wave splash; (2) 0-25% covered; (3) 25-
50% covered; (4) 50-75% covered; and (5) 75-100% covered. Because the entire
hauling ground was not exposed at higher tide heights, these percentages were
based on the area of the hauling ground exposed between wave sets. Only the
available haul out area was considered, meaning that the portion of the hauling
grounds which was underwater due to the tide was ignored. A "disturbance" was
said to have occurred if any seal returned to the water via quick ungulations of its
body which have been described by Sullivan (1982) as escape behavior. Time
and type of disturbance were recorded as well as the seals' subsequent reaction to
the disturbance.
Physical characteristics of the rocks which were measured included 1)
distance to escape channel; 2) % total algal cover; 3) % algal cover by
Mastocarpus papillatus (narrow blade version), Mastocarpus papillatus (broad
blade version), Endocladia muricata, and Iridaea flaccida; 4) size of hauling
ground; and 5) degree of incline to reach hauling ground. Distance to an escape
channel was measured in meters and given by the mean observed distance
between a seal and the water's edge. Total and individual algal cover was
assessed by using a 50-cm square grid subdivided into 5-cm squares. Relative
percentages were recorded for each 50-cm square section within a hauling
ground and the mean taken for the overall percent-cover. Due to the irregular
shape of most hauling grounds, the size of the hauling ground was based on the
number of large adult males which could be accommodated within the area. This
number is not the maximum number of adult seals ever observed in the area. It
is important to note that this value does not indicate the total number of
individuals able to haul out in a given area because the area occupied by one large
adult equals that of two subadults or three juveniles based on area comparisons in
hauling grounds where all age classes hauled out together. Site 14 was the
reference area used for these area calculations because the number of adult males
within the site and the amount of space they occupied could be measured and then
applied to other hauling grounds. Some of the smaller areas (i.e. sites 3, 6, 7, 13,
17, and 19) consisted of small, single rocks, and in these cases the central width
and length were measured in meters and the mean taken if there was more than
one rock. Although adults were observed hauling out in these areas on a few
occasions, the same unit of measure was not used because: 1) adults very rarely
hauled out in these areas and 2) the entire body of the adult did not fit on the rock
- both its head and tail hung over the edges. Degree of inclination was measured
using a protractor with an attached plumb. The angle of the side of the rock used
for hauling out was measured and the mean taken if there were multiple haul out
routes to the hauling ground.
RESULTS:
Factors influencing overall haul out: Because only 9.5% (2 of 21) of the
hauling grounds were available at high tide, an inverse relationship was observed
between tide height and total number of seals hauled out. Wave action had a
varying effect on haul out in terms of the numbers of seals hauled out and their
distribution. Waves always approached the study area from the northwest. Due
to the position of the hauling sites, sites 1-13 and 19-21 always experienced wave
actions of the same intensity factor. Sites 1-13 and 19-21 received direct wave
action from the incoming ocean swells, yet these sites provided protection for
sites 14-18. A positive relationship was observed between the wave intensity
factor for sites 1-13 and 19-21 and the number of seals hauled out in the more
protected sites 14-18. A factor of 5 produced an overall average increase of
104% in haul out at sites 14-18; a 4 produced an overall average increase of 64%;
a 3 produced an average increase 36%; and factor of 2 had no significant effect
on haul out in sites 14-18. These percent-increases are based on the average
maximum number of seals hauled out on calm days when the entire study area
experienced a wave intensity factor of 1. The maximum number of seals hauled
out in sites 14-18 on days of heaviest wave action was still less than the maximum
total number of seals that hauled out when all hauling grounds were accessible.
Disturbances were recorded on 7 days. Disturbances were the result of kayaks on
3 days, a helicopter 1 day, and human presence on the shore and in the intertidal
zone the remaining 3 days. After fleeing the hauling ground, some seals
eventually rehauled in the same area while others relocated to a new hauling
ground. On six occasions, seals within a hauling ground fled as a group but no
apparent cause for flight was observed. However, on each of these occasions, the
tide height was less than +1 feet. No rehaul was observed on any of these
occasions. A disturbance often affected those hauling grounds nearest the
disturbance and on 3 occasions, the disturbance did not result in site-abandonment
by all seals. The seals which remained were always adult males and they were
always the highest up within the hauling ground.
Age-structured distribution: The seals in the study area did exhibit an age
structured distribution in some areas, yet a mixing of age classes was the norm
Figures 2-5 illustrate for each hauling ground the percent days that each age class
was observed hauled out with respect to the total number of days any haul out
occurred within the particular site. Upon inspection of these graphs, it is
apparent that not all age classes were observed at each hauling ground, nor were
they observed hauled out with the same frequency. Table 2 provides a summary
of this data. Adults were never observed in sites 7, 17, and 19; subadults never in
sites 12 and 14; juveniles never in sites 9, 12, 14, and 16; and mother/pup pairs
never in sites 3, 7, 13, 14, 16, and 17. It is important to note that mothers were
not counted as adults because it was the pup's ability to remain hauled out which
determined where the mother hauled out. Especially in early May, it was not
uncommon for a mother and pup to unsuccessfully haul out in several areas
before finding a rock that the pup could climb up and not be washed off by a
wave.
Although most hauling grounds were used by more than one age class, this
does not imply that different age classes always hauled out together in these areas.
This was significant for sites 3, 7, 9, 15, 16, and 17 where only once did more
than one age class use the hauling ground at the same time. All other hauling
grounds, except for site 14, were occupied by 2 or more age classes concurrently.
When the age classes mixed on the hauling ground, juveniles and subadults were
at times observed occupying areas higher up on the rocks than adults. The
distribution of the age classes was not constant throughout the daily haul out
period, nor was it consistent from day to day. On 10 occasions a juvenile was
observed hauling out later than an adult, yet the juvenile hauled out to a higher
position on the rocks.
Interactions among seals: Interaction among these seals was very limited.
Most seals seen eliciting social behavior on the rocks were mother/pup pairs.
Intra-pair behavior consisted of naso-naso contact, nursing, and scratching. Most
agonistic behavior seen was performed by mother seals protecting their pups
from other curious seals. These behaviors included growling and head thrusts
with and without biting. The only social interaction observed which did not
involve a mother/pup pair was a large adult which pushed a subadult off a rock so
that it could haul out onto the rock. There was no fighting among these two seals
the bigger one simply pushed the smaller one off into the water. Cuts and blood
were often seen on these seals, but these marks were not the result of a aggressive
battle on the hauling grounds. Rather, either the seals had the cuts at the time of
haul out, indicating they were the result of an in-water confrontation, or the
marks were made by the sharp barnacles on the rocks when the seal moved
around.
Substrate physical features and age class haul out: Adults were able to
haul out at almost all hauling grounds unless the rocks were too small to
accommodate their larger size. When a juvenile was observed at a higher
position in the hauling ground than an adult, the juvenile was always resting on a
rock too small for an adult. Adults were seen hauled out twice at sites 2 and 3,
once at sites 13 and 21, and never at sites 7, 17, and 19. Table 2 indicates that,
except for site 2, the space available at these sites ranged from
0.375 m2 to 1.8 m2. Although site 2 had large enough rocks, it was only exposed
at a tidal height of +1.8 feet and less. Juveniles and subadults often arrived at this
site before any adults, but on the two occasions that adults were observed at site 2
they were the first to arrive. No relation was observed between degree of
incline, percent algal cover, or distance to escape channel and an adult's
ability/preference to haul out at a particular site.
Degree of incline and the percent algal cover did limit subadult and
juvenile haul out. If the total algal cover was greater than 50%, then either 1) the
incline had to be less than 20' or 2) % Mastocarpus (narrow blade) cover was less
that 20% or 3) % Iridaea cover was less than 10% (see Table 3). Iridaea and
Mastocarpus (narrow blade) were the most slippery of the four types of algae
surveyed with Iridaea being the most slippery of all. On several days, both
subadults and juveniles were seen attempting to haul out on rocks which had an
algal cover of 80% or greater and an incline of 50' or greater. However, each of
these attempts was unsuccessful because the seals were slipping down on the algae
faster than they could climb up it. Although sites 3, 7, and 17 met the above
conditions for haul out, subadults were only observed at these sites twice, once,
and once respectively. Most often, juveniles arrived at these areas first and
occupied all the available hauling area. Subadults were observed gliding by these
sites, looking at the seals (juveniles) on the rocks, and proceeding to a different
site to haul out. Site 1 did not meet the above conditions for haul out, vet both
subadults and juveniles were seen at this hauling ground on four occasions. On
each of these days, the seals did not haul out until the area had been exposed to
the sun and wind for a minimum of three hours which made the algae less
slippery. No relation was apparent between area of hauling ground or distance to
escape channel and ability/preference of subadults and juveniles to haul out.
Pup haul out was also influenced by degree of incline and percent algal
cover. However, even more influential was the presence of other seals. An
inverse relation was observed between the presence of juveniles, subadults, or
male adults and the likelihood that a mother/pup pair would haul out at the same
site as these other individuals. But, if the other seals were another mother/pup
pair, haul out was quite likely. Once again, no relation was observed between
distance to escape channel and mother/pup preference to haul out.
DISCUSSION:
Tide height, wave action and disturbance can be said to be the classic
factors which have been studied in relation to overall haul out numbers. As with
other studies, this study showed an inverse relationship between tide height, wave
action, and disturbance with number of seals hauled out. However, with
reference to disturbances, seals were observed leaving a hauling ground in mass
although no apparent disturbance had occurred to produce such a reaction.
Because the tide height was always less than +1 foot when this occurred and these
seals always rehauled in a new area which had easy access to deep water, it is
possible that the escape channel at the original site had reached a critical
minimum depth and this forced the seals to leave. These were the only instances
that distance to an escape route appeared to influence haul out, but the impact was
on general haul out, not age-specific haul out.
Sullivan's work with harbor seals in Humboldt Bay also involved a
substrate of irregularly shaped offshore rocks. His project was centered around
explaining why there existed a predictable spatial patter of the various age
classes within the hauling grounds. The age-structured distribution that he
repeatedly observed was a vertical stratification of age classes in which adult
males occupied the highest, most protected sites while younger seals were forced
to haul out at progressively less favorable areas which were more susceptible to
wave splash. The result was a pyramid shaped distribution with adult males at the
top. Sullivan's group of seals were very social as they aggressively competed for
haul out space on the rocks. Sullivan recorded the frequency and success rate of
eight different aggressive behaviors for each age class. In the end, he concluded
that the age-structured distributions were the result of different success rates of
aggressive behavior for each age class. In other words, the adult males were at
the top of the pyramid because they were the most successful in battles for space
Likewise, the younger animals which occupied less favorable areas were less and
less successful.
In this study, vertical stratification topped by adult males was observed in
two manners, between sites and within sites. An example of "between-site'
vertical stratification is that site 14 (adults only) and site 17 (primarily subadults
and juveniles) are in the same proximity with site 14 being higher than 17.
Within-site" stratification means that when all age classes were present at one
hauling ground, at times adults were the highest and juveniles and pups were the
lowest. However, within-site vertical stratification was not stable and changed
from day to day as subadults and juveniles were also observed as being the
highest age class. Therefore, the spatial age patterns which Sullivan observed
were present in the study area but they did not occur with the same predictable
regularity.
The complex social interactions that Sullivan had observed and concluded
were the cause of the age-structured distribution were not seen in this study. One
possible explanation for this lack of aggressive behavior is that space is not a
limited resource in this area. This is likely since even on the day with the largest
total count, there was still space left for haul out but no seals tried to obtain this
space. Furthermore, there were several occasions where a seal approached a
hauling ground which was occupied by a smaller age class and after surveying
this hauling ground, the bigger seal proceeded to haul out at a different location
rather than forcing the smaller seal off the rock. Perhaps this was because space
was not limited and it was more costly to engage in conflict than to simply find
another area to haul out. Another possible reason for limited aggressive
behavior involves the social organization of the population. Perhaps the
population Sullivan observed had a very high turnover rate and thus the social
hierarchy had to be reestablished daily. The seals of this study may have been
part of a more stable population where the social organization is more or less
permanently established. An observation which gives some weight to this
argument is that at site 14 where only large adult males were seen hauled out, not
once did another age class even attempt haul out at this site even though the
physical features were such that younger age classes should be able to haul out
there. Site 14 was the most protected site and there was always space available
for more seals to haul out. But, this area may be known within the population as
being only for adult males and no other seals want to challenge that fact.
Although this study did not attempt to define the social structure of the
population, this does not mean that some form of social organization fails to exist,
nor does it imply that social organization did not in some way influence the
observed age-structured haul out.
Since the same age distributions were observed in this study as Sullivan's
study, even in the absence of aggressive behavior, this suggests that there is a
factor other than aggression which influences the age-structured patterns.
Sullivan did not investigate other possibilities for the patterns he observed. This
study explored the possibility that the physical features of the hauling grounds
influenced the age distribution. Size of hauling ground, degree of incline, and
percent algal cover were observed to have different relations with the haul out
success of different age classes. Degree incline and percent algal cover had no
significant effect on adult haul out. Two possible explanations for this are that 1)
adult bodies are long enough to span over the slippery sections of algae, and/or 2
adults possess better coordinated haul out manuevers such that a steep incline does
not pose a problem. However, smaller age classes do not possess these assets and
thus are hindered by a steep incline and high percentage of algal cover.
There is no reason to assume that the physical features examined in this
study are the only features which may influence haul out behavior. Those
features chosen for any study will be highly dependent on the type of substrate
being used for haul out. For example, distance from an escape channel was not
shown to have an impact on haul out for any age class in this study. However,
other investigators which have studied seal haul out behavior on sandbars and
mudflats have repeatedly noted a preference by all age classes for area in close
proximity to an escape channel. Scheffer and Slipp (1944) studied seals on
mudflats in Washington State and observed that those seals which hauled out did
not allow themselves to be farther than 5 feet from the water's edge and would
abandon a site if the escape channel depth was below 1.5 feet. Davis and Renouf
(1987) studied seals on sandbars at Miquelon and also observed that the seals
would only haul out in close proximity to an escape channel. In fact, grouping
was thought to be the result of a limited number of sites with suitable escape
routes.
Opinions on the presence of age structure has also varied with the type of
substrate being used. Pitcher and McAllister (1981) and Pitcher and Calkins
(1983) studied seals on gravel beaches in the Gulf of Alaska. Neither study
observed age-structured grouping. Bishop (1968) studied harbor seal behavior
on sandy beaches in the Gulf of Alaska. He reported "strong gregariousness
among seals yet saw little social structure as the sexes and ages were often
intermixed. He did note that dominance was related to size and that there was
social pressure towards a spatially static group. On the other hand, Scheffer and
Slipp (1944), on mudflats, concluded that the seals were loosely gregarious.
Davis and Renouf (1987), observed a predictable age-structured arrangement on
sandbars, yet the seals failed to interact socially to a significant degree.
This study does not provide specific data on the relative influence of
substrate physical features and social organization on age-structured distributions.
Instead, it suggests that haul out behavior may first be guided by the physical
requirements of haul out. Then, working within these boundaries, the social
organization further dictates where each age class hauls out. This appears to be
especially true when the substrate being used for haul out is irregularly shaped
rocks, yet substrate physical features may not be as important a factor for other
substrates (i.e. beaches, sandbars, mudflats). This study does not discredit the
presence nor the importance of social structure within harbor seal populations.
Rather, it illustrates the need to consider the physical features of potential hauling
grounds before drawing conclusions on the significance of social organization
within a population.
i

e

52
5


.


-

2




— —
180 -
160
140 -
120
100 -
FIG 1: Standard length in relation to age based on a compilation
of data by Fisher (1952) and Bishop (1968).


k
—
Age (years)
FIG 2: Percent days that adults hauled out in each site as a
function of total number days (N) any haul out occurred in each site.
N=23 15 14 15 14 17
10 11 19 14 8
20 15 12 6
20 2
100.0% -
90.0% -
80.0%
70.0%
60.0%
50.0%
40.0%
30.0%
20.0% -
10.0%
0.0%
8 9 10 11 12
14 15 16 17 18 19 20 21
SITE NUMBER
FIG 3: Percent days that subadults hauled out in each site as a
function of total number days (N) any haul out occurred in each site.
N=23 15 14 15 14 17
10 11 19 14 8
20 21
20 20 15 12 6
100.0%
90.0%
80.0%
70.0%
60.0% -
50.0%
40.0%
30.0%
20.0%
10.0%
0.0%
8 9 10 11 12 13 14 15 16 17 18 19 20 21
SITE NUMBER
FIG 4: Percent days that juveniles hauled out in each site as a
function of total number days (N) any haul out occurred in each site.
N=23 15 14 15 14 17 10 11 19 14 8 2
7 20 21 21 20 20 15 12 6
100.0%
90.0% -
80.0%
70.0%
60.0%
50.0%
40.0%
30.0%
20.0%
10.0%
0.0%
8 9 10 11 12 13 14 15 16 17 18 19 20 21
SITE NUMBER
FIG 5: Percent days that mother/pup pairs hauled out in each site as a
function of total number days (N) any haul out occurred in each site.
N= 23 15 14 15 14 17 10 11 19 14 8
7 20 21 21 20 20 15 12 6
100.0%
90.0%
80.0%
70.0%
60.0%
50.0%
40.0%
30.0% -
20.0%
10.0%
0.0%
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
SITE NUMBER
TABLE 1: Mean maximum numbers of seals hauled out in sites 14-18 as a
function of the wave intensity factor of sites 1-13 and 19-21.
% comparisons were based on the total number of 25 seals
hauled out when a factor of 1 (no wave action) was present.
WAVE INTENSITY OF SITES 1-13, 19-21.
BASE
VALUE
14
14
11
17
8
8
15
2
3
2
E 16
2
3
3
1
2

4
17
2
17
23
15
18
12
12
11
27 34 41 51
25
TOTALS:
25
TABLE 2: Age classes observed within each hauling ground.
(+ present, - absent)
JUVENILE
MOTHER/PUP
ADULT SUBADULT
SITE
+
2
4
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
10
11
12
13
14
15
16
17
18
19
20
21
TABLE 3: Measurement of specified substrate characteristics for each
hauling ground.

88
85

SITE
35
93
30
50
5
15
4 Adults
32
2
15
85
25
65
2
8.
2 Adults
18.
09
12
10
5
85
0
10
O5x15
21
95
—30
10
60
0
1 Adults
0
5
23
55
60
20
—20
0
8 Adults
15
6
015
30
—10
65
2
LOX10
5
15
15
15
0
015
8
10
O5x25
45
1 Adults
30
95
45
10
0
80
45
35
50
0
5
3 Adults.
53
91
10
015
50
10
35
5
2 Adults
15
11
90
UM
05
UM
UM
4 Adults.
15
15
90
12
05
UIM
UM
17
UM
25
4 Adults
13
05.
90
45
40
15
8
0
O5x20
14
0
0
50
0
0
0
10
12 Adults
15
20
0.
0
0
0.
45
0
3 Adults
50
40
16
L0
10
0
1Adult
0
62
17
30
0
0
20
0.75
80
0
O5x015
18
20
85
20
60
—20
0
8 Adults.
35
99
19
10
10
80
0
10
9
12X 10
20
15
60
90
4 Adults
11
5
5
0
21
2.5
90
UM
UM
UM
25
L5x12
20
UM = Twas unable to measure the exact algal composition of these rocks because the
conditions were never such that it could be safely measured. % total algae and % Iridaea are
estimates based on photographs - both are very visible at a distance.
ACKNOWLEDGEMENTS:
1 would like to extend my deepest thanks and appreciation to our T. A.,
Terri Shaw. Her encouragement and willingness to discuss my project at
all stages was very beneficial and helped me to remain focused throughout
the quarter. I am also very thankful for Terri's frankness in pointing out
and discussing potential weakness, not only during the actual study but also
during the process of writing this paper. I would also like to thank my
fellow classmates Teri Nicholson and Kirsten Hackney for their help in
identifying individuals and discussing seal behavior at the neighboring Seal
Rock area. Finally, I would like to thank Alan Baldridge for always being
interested in my research and for sharing his insight and knowledge of the
harbor seals in this particular location.
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