-2-
ABSTRACT
Prey selection and foraging patterns are two very im¬
portant behaviors for Leptasterias hexactis. In order to try
to understand these behaviors more fully studies would have to
be done in the lab where Leptasterias could be closely mon¬
itored and their environment manipulated. This should be done
in the most natural circumstances and with the least amount
of disturbance to the asteroids to preserve their usual patterns,
Clay plates with different prey items to select from and
different distributions of prey were suspended in a 80 1 tank.
The plates were large enough, it was hoped, to represent an
area of rock that would normally be occupied by the Leptasterias.
The starfish were never handled but could be observed while
foraging and selecting prey. A flat sea table was also used
and again the animals were observed but not disturbed.
Data obtained from these and smaller finger bowl exper¬
iments has revealed something about the frequency of eating,
movement associated with the density of food in the environ¬
ment, and that Leptasterias might possibly recognize different
prey densities and choose prey accordingly. It is strongly
suspected that prey selection has a component of learning
involved in the behavior. The Leptasterias also seem to op¬
timize food choices. Comparisons of calories per individual
prey per hour to consume show that the prey with the highest
caloric yield are chosen. This is dependant however on
the environment, what prey are present and the relative sizes
and densities of the prey.
7. Rad
INTRODUCTION
There are two ways a starfish could feed in its en¬
vironment. It could just feed randomly on the prey it happens
to be near, or it could select prey according to certain cri¬
teria. Prey preferences have been documented for many starfish
(Menge, 1972a; Feder, 1959). But obviously more than prefer¬
ence must be involved in the selection of a meal. The
densities of different preferred prey, the spaceing of the
preferred animals and times between contacts with the prey
might all affect what is eventually chosen as the final prey,
And looking at these parameters in detail might enlighten the
question of how the animal selects its food.
The more intriguing question, however, is can the Lep¬
tasterias learn to assimilate the data about densities, prey
items and contact time in order to make decissions in each
different environment about what will be the best prey to
select for consumption? The behavior of selecting food is
very complex and might have a component of learning about
the terrain rather than just an instinctive or biochemical
basis.
These questions could be studied quite readily in
Leptasterias. Leptasterias are small six armed starfish found
readily in the lower intertidal zone around Monterey Bay.
Because of their small size, they were the best choice for in
lab experiments. They could be put into a controlled habitat
that approximated in size their own natural habitat.
Leptasterias are also food generalists and are found in
many habitats with their diet varying according to surroundings.
This was also an attribute needed for the experiments since an
attempt to determine what prey would be chosen in different
habitats was a key component of the preject.
Finally, Leptasterias have no distant chemoreception
(Menge, 1972) so their knowledge of their surroundings must
come from contact. This makes it easier to determine what
prey is actually recognized since contact is necessary, rather
than trying to decide if the starfish sensed something.
T Prag
-4-
Menge (1972, 1974) studying Leptasterias in the Puget
Sound region has found that they eat most in late summer and
least in the winter. This might be due to winter storms as
well as immobilization of the females due to brooding. Lep
tasterias also respond to light, feeding more at night.
He has also analysed their diets, including prey eaten
and calories of prey consumed. He states that prey is
chosen selectively and varies with their habitat. The food
eaten by Leptasterias around the Monterey Bay area was not studied,
so their regular diet was not necessarily used for the following
experiments. In fact the prey items were rather randomly
chosen for their abundance and ease of attainment. Since the
object of the experiments was only to try to find the criteria
for different foods being selected any combination of foods that
would be eaten was fine, as long as there were sessile and mo¬
bile foods and there was a definite preference for certain foods.
The lack of knowledge of their regular prey proved no problem
The question that originally sparked enthusiasm for a
detailed look at foraging patterns and prey selection in
Leptasterias was that of why a starfish, an animal with
limited perceptual abilities, would often pass over numerous
prey items while foraging when it seemingly had no assurance
that
it would find something better with further wandering. Is it
possible that starfish are able to optimize prey selection?
Does their behavior suggest that they can recognize different
environments and prey densities and forage accordingly? If
they can forage in a selective and optimal manner, what are
the components of this behavior - learning, instinct or a
combination of factors?
7 Peock
2.
3.
METHODS
The determination of what Leptasterias chooses to eat,
when to eat and where to eat required a number of different
experiments. Five different experimental procedures are
described below. They were used to answer specific questions
as well as yielding data that was eventually combined to show
differences in patterns due to different environments.
1. Six small finger bowls, each 10 cm in diameter, were
filled with between 15 and 25 potential prey items and one
Leptasterias. The prey items included L. planaxis, C.
digitalis, C. scabra, T. funebralis and M. californianus.
The bowls were kept in running sea water and checked once
a day. Any empty shell was noted for that day and re¬
moved. This set up was used to test food preferences.
As the animals slowly ate their favorite foods, they were
left with less and less desirable prey to chose from.
The order, in which they ate the foods, should serve as
an indicator of the preference for that food. Since all
food was in such a small space, it was assumed to be
equally detectable and thus food choices were by preference
rather than chance.
One small bowl, with four Leptasterias in it, was filled
only with M. californianus. The question addressed by this
experiment was to see if providing Leptasterias with only
one food source for a certain period would make them
ingestively conditioned to the M. californianus and come
to prefer it over other food. After conditioning the
animals for 19 days, they were transfered to four seperate
bowis each containing M. californianus, L. planaxis and
C. digitalis. All bowls had running sea water and were
checked daily.
Three Leptasterias were released into a 801 tank (1m X 2.2m
X .4m). Water was constantly running except at a low tide
once a day from approximately 8 AM to noon. The lighting
was constant and the temperature, taken at intervals over
two weeks, was constant at 15'C f .25°. These Leptasterias
served as a set of "hungry" starfish and were used as
1 feal
5.
-6
controls for eating experiments as well as subjects for
chemosensitivity experiments. By "hungry" I mean that no
food was in the tank and the starfish received food only
when presented with it. This was control of when and how
much they ate could be maintained.
Six Leptasterias and five Pisaster were established in a
sea table (10 cm deep, .75m X .6m). Rocks with prey items
were placed in the sea table. The prey was very abundant.
One set of experiments was run using B. glandula as the
most abundant food item. Rocks covered with B. glandula
covered approximately 75% of the bottom of the sea table.
Another experiment was run with C. digitalis and C. scabre
approximately 70 limpets were placed on six flat rocks in
the sea table. There were no changes in the tide. The
animals had a natural light/dark cycle, although direct
sunlight was kept off them by a shade. The positions and
feeding of these starfish were checked periodically.
Nine Leptasterias and two Pisaster ochraceus were placed
on a series of clay plates that were suspended by string
vertically in a 801 tank. The tiles were originally 900cm
but were epoxied together to form plates that varied in
size from 30 X 60 cm to 30 X 180cm. A variety of limpets,
T. funebralis, L. planaxis, B. glandula and M. californianus
were introduced onto the plates. Different concentrations
of different species were used on the plates, some sparsely
populated and others abundantly. The plates were under
constant lighting and running sea water (temp - 15°C +.25).
The animals received a low tide from approximately 8 AM
to noon each day of the experiment. These animals were
closely monitored from three to ten hours a day. Obser¬
vations, on a map of the plates, were made as to what
potential prey was touched, at what time and at what place
on the plate. Feeding choices were observed and handling
of prey noted. The shells from the finished food items
would fall to the bottom of the tank under the plate and
could later be secured to confirm species and make measure¬
ments.
The plates and the number of each prey item on them are
7 Ral
-7
presented in figure 3. Below is a description of the distri¬
bution of the prey, pertinent facts about the size of the prey
and the size of the plates with the number of star'on each.
Plate 1- Abundant B. glandula and large M. californianus.
This food is easy to capture but takes a long time for
handling and eating. In fact the M. californianus proved
to be too large (over 3cm) for the Leptasterias to
handle efficiently. Two Leptasterias were on the plate
which measured 30cm X 90cm. This plate was meant to
represent an abundance of sessile organisms in patches.
2- Again abundant B. glandula and large M. californianus.
Plate
Only one Leptasterias was on this plate which measured
30cm X 60cm. This plate was meant to represent an abun¬
dance of sessile organisms well dispersed.
3- One small patch of B. glandula and small M. califor
Plate
nianus. This plate was meant to be sparsely populated.
Two Leptasterias were on this 30cm X 90cm plate.
4- One small patch of B. glandula and small M. cal¬
Plate
ifornianus. Two Leptasterias were on this 30cm X 90cm
plate also. This plate was suppose to be abundant rela¬
tive to plate 3.
Plate 5- Small to medium M. californianus (small less than 1 cm,
medium 1 to 2cm)oon this plate. It measured 30cm X 180cm
and contained two Leptasterias and two Pisaster. The
plate was meant to represent very abundant conditions.
The Leptasterias used were collected from two places,
Yankee point and Pescadero point. The sizes ranged from three
centimeters to seven centimeters with the average at 4.8 centi¬
meters. The Pisasters used came from many different areas
around Hopkins Marine Station. They ranged in size from four
to seven centimeters with an average of 5.3 centimeters.
T. Peccl
RESULTS AND DISCUSSION
Food Preference
Leptasterias has a food preference hierarchy that is
shown in figure 1 and 2. The most obvious evidence for this
scheme comes from the isolated Leptasterias in small bowls and
their different prey choices. Two different bowl experiments
were run. In these experiments, Leptasterias had available, in
a small area, 15 to 25 individuals of 4 species of prey in one
experiment and 7 individuals of 5 species in another. It is
assumed that all prey were encountered and the small size of
the container would limit the effectiveness of any escape
responses. The most frequently taken species were the limpets
and L. planaxis. Rarely were the M. californianus of T. fune¬
bralis taken and never before the more preferred species were
gone.
B. glandula was not included in the food bowls, but can be
placed into this preference hierarchy by observations made on
the clay plates and in the sea table. Here B. glandula was
the fourth choice after the limpets, L. planaxis and M. califor¬
nianus. One can see this by looking at figure 3 for plates 3,
4 and 5. The preference for B. glandula however is variable.
The choice of M. californianus over B. glandula is dependent
on the size of the Mytilus and the density of B. glandula.
Large M. californianus and plentiful B. glandula will lead to
more meals on B. glandula. This is seen again in figure 3 for
plates 1 and 2. B. glandula were abundant on the first two
plates and M. californianus were to large to handle efficiently,
so more B. glandula were eaten. Plates 3 and 4 had only one
small patch of B. glandula and smaller M. californianus, so
M. californianus were seen to be more preferred. Of course
these choices always follow the more preferred limpets and
L. planaxis.
Even though L. planaxis is known to be preferred from
bowl experiments, figure 3 shows that is was not often taken
outside of the finger bowls. This is because the animal often
crawls out of the searching range of the Leptasterias. In the
T teo
-9-
sea table it would crawl up the sides above the water line.
On the plates it would crawl out of the water and up the
strings that suspended the plate.
Also note that T. funebralis was never taken. This is
because this potential prey species has an effective escape
response and can avoid Leptasterias. They seem to be able to
crawl away faster, or if they feel really pursued, will let go
of the plate and fall to the bottom of the tank. C. pelta and
limatula also have effective escape responses and were never
caught on the plates. C. digitalis, C. paradigitalis and C.
scabra are what is meant by all use of the term "limpets"
since these are the species easily caught by the starfish.
It is possible that the above mentioned prey species,
with escape responses, are caught in the wild, where they might
possibly be trapped in a crevice or cornered. (Menge, 1972a).
But on the clay plates their behavior was effective in preventing
capture.
Ingestive Conditioning
To see if these Leptasterias could be ingestively con¬
ditioned four were placed in a bowl with M. californianus.
After 19 days and observations of 22 feedings on Mytilus,
they were transferred to individual bowls with a variety of foods.
The next day they were observed eating either limpets or
L. planaxis. It does not appear that after 19 days of exposure
to only M. californianus that they learned to prefer it. This
does not mean that they could not be injestively conditioned.
They might have a stronger conditioning to the other more pre¬
ferred foods. Or there might be a longer time period needed to
condition them. Also they might have to be conditioned to food
during a certain time in their life cycle.
Ingestive conditioning experiments done on Pisaster ochraceus
by Landenberger (1968) showed that it took three months of
constant feeding to get the starfish to show a preference of
T. funebralis. And this quickly degenerated within a week
when presented with a choice of Mytilus or T. funebralis.
Later, it will be shown that limpets are not only the
prefered choice but also provide the most calories per unit time
1fec
-10-
for the animal. It would be adaptive then that the Leptasterias
not lose the preference for the more desired prey after only a
short exposure to another prey.
Sensing of Food
Menge (1972a) tested the long range chemosensitivity of
Leptasterias with a Y maze and obtained negative results.
Experiments for ranges of less than a centimeter had not been
done however. The "hungry" Leptasterias in the 801 tank were
model subjects for chemosensitivity tests since they hadn't
eaten for frome2 to 11 days.
When individuals were actively searching for food, a
potential prey item would be placed on the side of the tank
just out of reach of the podia on the tips of their arms.
This could be above, below or behind. Often the starfish would
pass within millimeters of the prey items and never change
course. However, if the potential prey was placed in front of
or where one of the arms of the Leptasterias would touch it, the
response was always positive and on each occasion the prey was
consumed after the first touch.
Table 1 shows the number of times that food was closely
missed and also shows the positive result when food was encount¬
ered. It is assumed that if the starfish had known food was
near, through chemosensory means, it would have moved towards
the food, since feeding after contact occurred in 100% of the
cases. Contact chemoreception and tactile sensitivity seem to
be the only methods that Leptasterias has to detect potential
prey items. Both would limit the perceptual field of the
Leptasterias to its diameter.
It has been stated that in the well mixed intertidal
zone, chemosensitivity might be of dubious value since the
direction signals could be mixed up (Menge 1972a). However,
an ability to sense something close would not have been dis¬
advantageous. Also since asteroids seem to have only tactile or
contact shemosensory means to explore their environment, no
vision or distant chemosensitivity, a question arises as to
why they pass over potential prey items when they have no
assurance that they will encounter more desirable ones?
7 Petel
-11-
Feeding Patterns
Frequency of Eating
Landenberger (1968) reported that Pisaster ochraceus are
insatiable feeders. Data from experiments on the clay plates
and from the feeding bowls shows that Leptasterias and small
Pisaster ochraceus tend to have eating bouts followed by spaces
that range from two to four or more days. Figures 4 and 5 show
these results. Feder (1970) also noted "periods when individual
sea stars do not feed."
The animals will often eat more than one item a day, in
fact it may eat two or three in quick succession. Dropping
the shell of one prey item and quickly securing another has
been observed. The animals often move while eating and could
be scanning the area for the next meal or possibly making a
determination of prey density which might influence consumption.
Animals that are presented with an abundance of food in
a small area, like the bowl experiments, did seem to eat a
somewhat larger amount than those on the plates. So the
frequency of contact and abundance of food might have a posi¬
tive effect on eating response.
Movement Related to Searching and Eating
Starfish are capable of moving quite rapidly on occasion.
The "hungry" starfish in the 80 1 tank were in general active
and have been measured moving at over 30cm per minute. On the
other hand, when prey is abundant, in the area that the starfish
occupies, it will usually remain in one spot and eat an area
bare of easily caught prey before moving on, if not disturbed.
The sea table experiment provided evidence that Leptasterias
and Pisaster, in an area with abundant prey, will tend to stay
in that area. Figure 6 shows this. Most of these asteroids
spent near or over 50% of the days they were monitored in one
place eating the available food.
One experiment was run with B. glandula as the predominant
food and another experiment with limpets as the most abundant.
Either food seemed to be attractive enough, when in such large
amounts, to hold the animals in one spot. Observations were
made of two Pisasters remaining on a rock with 16 limpets and
T fer
-12-
eating every one of them before they left the rock.
The starfish also seem to return to the same rocks where
they once found food. But whether this is due to a retention
of a geographical location linked with food or just chance
wanderings was not determined. It was noted though that the
starfish in the sea table knew to stay near the bottom and on
the rocks to find their food, while the starfish, on the clay
plates, seemed to know that most of their food items migrate
to the tops of the plates so that is where they spend most
of their search time. Landenberger (1966) was able to train
Pisaster ochraceus to move to the bottom of the tank, where
food was placed, on signal. He also observed Pisaster re¬
maining near pillars from which most of the Mytilus, that made
up their food supply, dropped.
Although the plates were arranged to have varying amounts
of food in an attempt to see different searching patterns,
this was not totally successful. Plates 1 and 2, which had
an extreme abundance of sessile prey led to a reduction in
foraging and a choice of mainly B. glandula for food. This was
expected from the sea table experiments. Plates 3, 4 and 5,
which were similar except that 4 and 5 had many more limpets,
L. planaxis, and T. funebralis yielded similar foraging acti¬
vities when compared (see Table 2). Either the difference in
number of prey between the plates was not significant to yield
a large difference in foraging activity or just the act of
chosing moving prey requires that the Leptasterias move a certain
amount. The Leptasterias on plates 4 and 5 had the oppor¬
tunity to reject more prey items before the final choice.
Whereas the Leptasterias on plate 3 didn't have the same op¬
portunity. Also the food on plates 4 and 5 was often bunched
so that the starfish on these plates encountered food as fre¬
quently as those on plate 3 though the density encountered was
higher.
Although movement of the starfish on the clay plates was
closely monitored, no clear search patterns were discernable.
The starfish seemed to wander along almost randomly as noted
by Feder (1970), although they do stay closer to the top where
most of the food is. Also, they often pass over many prey items
/ Peat
-13
before selecting one. The criteria for the final choice also
could not be discerned.
Selection of Prey Items
Each potential prey item that is passed near and touched
is usually felt out by the arm that touches it. Occasionally
the starfish will move over to the prey item as though to eat
but then pass it over. As stated before, the actual criteria
for selection is not certain but it seems clear that the time
between the last meal, the kind of prey item that is contacted
as well as how often prey is contacted are important.
Figure 7 shows that "hungry" starfish will rarely pass
over the first meal they touch, while it is quite common for
the well fed starfish on the plates to walk over five to ten
highly preferred prey items (including species they will eventu¬
ally choose) before eating. Perhaps because of past experiences
plate asteroids assume they will find more prey because food is
abundant, whereas the "hungry" starfish in the 80 1 tank only
encounter food when it is presented to them so might take the
first available since it is all they are likely to find from
their knowledge of prey density in their environment.
A couple of the "hungry" starfish were fed within periods
that the starfish on the plates would normally eat. So as
far as consumption of food, they should not have been any
hungrier than those on the plates. But they still took the
first item given, whereas those on the plates, even after not
eating for a few days, would still pass potential prey over.
Caloric Basis of Prey Selection
Observed prey preferences may stem from a biochemical basis
that makes it more advantages that the starfish select a certain
prey over another. Figure 8 shows that the calories per food
item per hour that it takes to eat the prey item compare favorably
to the preference list. C. digitalis, C. paradigitalis, C.
scabra and L. planaxis were seen to be prefared. Of these, the
limpets yield the most calories per unit time.
Another consideration, besides just the time specific
yield of calories for a prey item, is how easy it is to catch.
This is also shown on figure 8. If a food is high in calories
7 Pea
7. Reck
-14-
but takes a long time to catch or eat the calories per hour to
consume the prey may make it not worth catching. C. pelta is very
high on the scale caloricly but it has an effective escape
response from starfish that makes it hard to catch if not
trapped, which is virtually impossible on the flat vertical clay
plates used in the experiment. So C. pelta were never seen eaten.
L. planaxis although not as high in calories as limpets are
easy to catch if they are in the search range of the asteroid
and not too hard to consume so they seem to be preferred after
the more catchable limpets.
Many starfish will subsist on B. glandula as a food source
if it is abundant and there is a lack of more preferred prey that
is easy to catch. The B. glandula won't escape and the starfish
can stay and eat its fill.
T. funebralis not only has a low caloric value but also
has an effective escape response. They were never seen eaten
in the sea table or on the plates by Leptasterias. The Pisaster
did eat T, funebralis in the sea table when B. glandula was
predominant, but the Pisasters move faster than Leptasterias
and also can handle larger prey items, making T. funebralis
a more caloricly feasible food.
-15
GENERAL DISCUSSION
From the experiments just cited, a few generalizations
can be made about some aspects of the feeding behavior of
Leptasterias. Although the experiments were performed with an
arbitrary set of prey items this would not necessarily be
different from a starfish moving into a new environment. The
presentation of different prey is still valid and the even¬
tual choices still have signigicance when looked at as a model
of feeding strategy.
The abundance of the prey items affects gross average
movement of the feeding asteroids. It would be expected though
that starfish in havitats of abundant food would have less
reason to move in search of food or to continue to explore the
environment and this is what was observed. Both starfish in
the sea table and those on the plates 1 and 2 which were abun¬
dant with sessile organisms are evidence of this.
The frequency of eating proved surprising. Landenberger
(1968) expressed the opinion that cold blooded animals ex¬
perience neither hunger nor satiation as understood by humans.
So why don't the starfish feed at a more constant rate? One
thought is that they use the time between meals to explore
their habitat. Another is that they consume food at a rapid
rate for a few days and then must give their bodies time to
digest and distribute the stomachs contents.
The fact that starfish are generally more selective when
there is an abundance of food and less selective when food is
scarce has been observed (Menge, 1972; Sioan, 1980). This
investigation indicates they will take a prey item on the first
contact when prey densities are low but will pass over prey
when densities are high. Both of these would suggest some sort
of ability to remember and recall facts as to the content and
density of prey in the environment while foraging.
It was seen that the starfish in the food bowls had
definite prey preferences and these choices remained fairly
constant in the experiments with simulated environments.
Leptasterias lacks vision and long range chemoreception so
unless they have some means of remembering what they have
7 ferd
-16-
previously encountered, while exploring their environment, it
would be hard to understand how they could take a chance in
passing up one potential prey item in the expectation of finding
another.
The fact that 19 days of exposure to another known food
item doesn't change the selection of more preferred items, when
seen again in small but recognizable amounts, shows that pre¬
ferences are based on more than just short term prior exposure
and abundance. Also since preferred items are usually nutri¬
tionally superior to other items of prey, having a preference
does serve a purpose and this preference should be exploited
as much as possible.
To optimize caloric intake per unit of feeding time,
including exploration, capture and ingestion, it would not
be in the best interest of the starfish to just consume the
most plentiful prey or even whatever prey it comes across, but
to know what is available in its environment and how it fits
into the preference scheme.
Actual selection probably depends on the prey species
(related to prey preference, ease of capture and nutritional
value), the number of contacts with this species in the en¬
vironment and the time between encounters. Depending on the
environment a less prefered species might be eaten because
the chances of finding the other more preferred is not high.
Diets are seen to vary with locality (Mauzey et al.,
1968; Menge, 1972a; Menge and Menge, 1974) and since starfish
often wander into areas of idfferent prey densities, some
component of learning might be associated with feeding behavior
in each new situation. Despite their limited means of perception,
through searching behavior and tactile assessment of the en¬
vironment, the starfish might learn enough about the surround¬
ings to apply this knowledge to a set of internal criteria to
select the best prey item.
Of course much more work needs to be done on this problem
of selective feeding. Putting more Leptasterias in different
environments and increasing the monitoring of contacts with
prey and time between meals will be necessary. It seems fairly
obvious however that feeding in starfish is not random or chance
but is a complex behavior with many components, some environ¬
mental and some intrinsic to the animal.
7 Peat
ACKNOWLEDGEMENTS
I would like to thank my advisor, Chuck Baxter, for
his constant assistance, without which I would have been
stumped many times. And also for his enlightening bits of
information that often opened up new doors in how to approach
and understand a problem or result. Those I have worked near,
exchanged ideas with and received help from in the lab also
have my warmest thanks.
7. Fead
7 Pecck
-18
Feder, H. M. 1959. The food of the starfish, Pisaster ochraceus,
along the California coast. Ecol. 40: 721-724.
Feder, H. M. 1970. Growth and predation by the Ochre seastar,
Pisaster ochraceus, in Monterey Bay, California. Ophelia
8: 161-185.
Harrold, C. 1981. Feeding ecology of the asteroid Pisaster
giganteus in a kelp forest system. Ph. D. thesis. Ucsc.
Landenberger, D. E. 1966. Learning in the Pacific starfish
Pisaster giganteus. Anim. Behav. 14: 414-418.
Landenberger, D. E. 1968. Studies on selective feeding in
the Pacific starfish Pisaster in Southern California.
Ecol. 49: 1062-1075.
Mauzey, K.P. 1966. Feeding behavior and reproductive cycles
in Pisaster ochraceus. Biol. Bull. 131: 127-144.
Mauzey, K. P.; C. Birkeland; P. K. Dayton. 1968. Feeding
behavior of asteroids and escape responses of their prey
in the Puget Sound region. Ecol. 49: 603-619,
Menge, B. A.
1972a. Foraging strategy of a starfish in
relation to actual prey availability and environmental
predictability. Ecol. Monogr. 42: 25-50.
Menge, J. L. and B. A. Menge. 1974. Role of resource
allocation, aggression and spatial heterogeneity in
coexistence of two competing intertidal starfish. Ecol.
Monogr. 44: 189-209.
Pyke, G. H.; H. R. Pullian; E. L. Charnov. 1974. Optimal
foraging: a selective review of theory and tests. O.
Rev. Biol. 52: 137-154.
Schoener, T. W. 1971. Theory of feeding strategies. A.
Rev. Ecol. & Syst. 2: 369-404.
Sloan, N. A. 1980. Aspects of the feeding biology of asteroids.
Oceanogr. Mar. Bid. Ann. Rev. 18: 57-124.
-19-
FIGURE LEGENDS
Fig. 1 & 2) Number of prey remaining in food bowls over a
12 day period. The foods preferred will be consumed the
fastest. So order of preference is limpets, L. planaxis,
T. funebralis and M. californianus. Two seperate experiments
were run.
Fig. 3) The first block shows the number of each prey item
that was maintained on the plates. The second block shows
the number eaten out of all the prey items that were ever on
the plate. The replaced prey as well as the original are
included.
L - limpets (C. digitalis, C. scabra, C. paradigitalis)
PL - Littorina planaxis
B - Balanus glandula
M - Mytilus californianus
T - Tegula funebralis
Fig. 4) Shows what food is eaten and how often by the
starfish on the plates. Number of meals, total calories for
all meals and calories per day are shown for each starfish.
B - Balanus glandula
D - C. digitalis
PD - C. paradigitalis
S - C. scabra
M - Mytilus californianus
PL - L. planaxis
Fig. 5) See fig. 4 for key. Shows what food was eaten and
how often by the starfish in the feeding bowls. Number of
meals, total calories for all meals and calories per day are
shown for each starfish.
Fig. 6) Bars represent the largest percentage of time, out
of the complete time the experiment was run, that the starfish
remained in one area. Data was from the sea table experiments,
one with abundant limpets and the other with B. glandula.
P - Pisaster ochraceus
L - Leptasterias hexactis
F Peal
0
-20-
Fig, 7) Comparison, of the percent of meals taken on the
first touch, between hungry starfish which usually have no
food, and starfish on clay plates which do have access to food.
Fig. 8) Caloric content of individual prey per time to consume
as well as ease of capture on the plates.
D - C. digitalis
PD - C. paradigitalis
S - C. scabra
P - C. pelta
PL - L. planaxis
T - T. funebralis
B - B. glandula
M - M. californianus
TABLE LEGENDS
Table 1) Chemosensitivity tests. When the starfish does
not contact the prey item it seems to not realize it is
present. On contact the starfish will take the food.
Starfish used were the hungry starfish.
Table 2) Average daily movements for individual starfish and
description of the different plate environments they occupy.
C
7. Peccl
-21-
-0

0

-
—
S

ONINIVWHA XAAd 4O AHAWON

0
—
—
-

—

oa-
ONINIVWAA XAAd HO AHAMON
7. Pead
+



36
L
O
oc

OS


OS
oe
N
OS

O PIO
—
ope
—
Po
OS
e
0

oc
0
8
-22-
1 Peag
Kep
soo
soo
o
su o
oun


la


-23
1Pecte
O
9
5
0
-




OT-
Kep
s
sreou o
seo o
steoy
JO 'ON
—
-24
1see


a
2


O-
-25
Sa




8



a
a





taatatakakatakavoa-
VHAV ANO NI LNHAS AWIL 40 ADVLNADAAd LSADAVI
rea
-26
1 Petet
2
-

20

: 0 —
Z0



2
0
PREY
T. funebralis
B. glandula
L. planaxis
californianus
C. digitalis
paradigitalis
C. scabra
C. pelta
H
KCAL,
(dry
4.50
3.34
4.90
4.78
4.96
4.99
4.95
5.08
60
54
48
42
30
24
SIZE
EATEN
.5-1
.5-.8
.5-1
1-1.5
7-1.5
7-1.5
7-1.5
7-1.5
SIZE
FOR
WT
.6
.8
1.4
1.5
1.4
1.3
1.5
D PD
-27
WET
WT. (Q
.020
.001
.046
.054
.14
.14
.12
.15
CAL.7
TIME
CALC.
TO EAT
%H,0
INDV.
MPrTa
hrsl
5-7
0054
24.30
73.2
8-10
0003
1.002
73.6
5-7
0173
84.77
62.3
83.0
43.97
12-15
0092
3-5
77.1
0321
159.22
.0349
174.15
3-5
75.1
142.56
3-5
76.0
0288
3-5
179.83
76.4
.0354
Easy to cap¬
ture and handle.
Easy to capture,
harder to handle.
Very hard to

capture on plates.
1
E
S PPLTBM
tpeate
0



—1
-28
7 Pecle
—
25

—



.



—





OE



2


58.

a




9.



5

95

2.

tecd