1) The 3-spined stickleback fish is favored for studies of animal behavior because it displays great morphological variation, lives in both saltwater and freshwater, and exhibits elaborate breeding behaviors like nest-building and parental care. 2) Males build nests out of plant materials and defend territories during breeding season, courting females and caring for eggs until they hatch about a week later. 3) Some evidence shows cooperative behavior between sticklebacks, such as cooperative predator inspection following a tit-for-tat strategy, and partner-dependence where fish consider their partner's size when inspecting predators.

1. ASSIGNMENT TITLE
3-spined stickleback fish
Subject Ethology
Submitted by Aftab Badshah
Roll no 11
Bs Zoology Sem 5TH
Submitted to Mam Brekhna
Deptt: Zoology UCSS
Dated Friday, 24 Oct 2014
3 - S P I N E D S T I C K L E B A C K F I S H

2. O V E R V I E W
Scientific Classification
Kingdom Animalia
Phylum Chordata
Class Actinopterygii
Order Gasterosteiformes
Family Gasterosteidae
Genus Gasterosteus
Species G.aculeatus
Why called as 3-spined stickleback
it bears10-14 dorsal fins in front of which are the three spines that give the fish its name
Why favored for studies of animal behavior????????
 It showsgreatmorphological variationthroughoutitsrange,idealforquestionsabout
evolution andpopulationgenetics
 Most populationsliveinseawaterbutbreedinfreshorbrackishwater and verytolerantof
changesinsalinity,asubjectof interesttophysiologists.
 It displayselaboratebreedingbehaviorlike defendingaterritory,buildinganest, takingcare
of the eggsand fryetc and itcan be social livinginshoalsoutsidethe breedingseason
makingita popularsubjectof enquiryinfish ethology andbehavioral ecology.
 Its antipredatoradaptations,host-parasite interactions,sensoryphysiology,reproductive
physiology,and endocrinology have alsobeenmuchstudied
Characteristics
 Size usually 5 cm (2 in) long (but may reach,exceptionally, twice that length)
 Body laterally compressed and scales are absent
 Tail The base of the tail is slender
 Fins
o The caudal fin has 12 rays
o The dorsal fin has 10-14 rays;
o The anal fin has eight to 11 rays and is preceded by a short spine
o The pelvic fins consist of just a spine and one ray
o The pectoral fins are large, with 10 rays
 Coloration
o drab olive or silvery green dorsal side
o In males during the breeding season, the eyes become blue and the lower head, throat,
and anterior belly turn bright red
o The throat and belly of breeding females can turn slightly pink

3. Habitat
 Found only in the Northern Hemisphere,
 usually inhabits coastal waters or freshwater bodies
 can live in either fresh, brackish, or salt water
 prefers slow-flowing water with areas of emerging vegetation.
 It can be found in ditches, ponds, lakes, backwaters,quiet rivers, sheltered bays, marshes,and
harbours.
Diet
a bottom-feeder, basically on benthic prey, normally the chironomid larvae being the most abundant
prey; however, this fish species can also consume terrestrial prey on the surface.[8]
It can cannibalize
eggs and fry.[9]
Life history
 Many populations take two years to mature ,others 3 years,but some in extreme latitudes take
even 1 year
 Mostly experience only one breeding season before dying
Reproduction
 Breeding season
o From late April until July, males and females move from deeper waters to shallow areas.
 Building ofnests
o Each male defends a territory where he builds a nest on the bottom.
o Starts by digging a small pit.Then fills it with plant material (often filamentous algae),
sand, and various debris which he glues together with spiggin, a proteinaceous substance
secreted from the
o He then creates a tunnel through the more or less spherical nest by swimming vigorously
through it.
o Nest building typically takes 5–6 hours. though it may also be spread out over several
days.
 Territorial Courtship
o After nest building , the male courts gravid females that pass by with a zigzag dance.
o approaches a female by swimming very short distances left and right, and then swims
back to the nest in the same way.
o If the female follows, the male often pokes his head inside the nest, and may swim
through the tunnel.
o The female then swims through the tunnel as well, where she deposits 40−300 eggs.
 Mating behavior
o The male follows to fertilize the eggs. The female is then chased away by the male.

4. o For the duration of the eggs' development, the male will chase away other males and non-
gravid females.
o He may, however, court other gravid females (more than one batch of eggs can be
deposited in the same nest).
 Parental behavior
o The male takes care of the developing eggs by fanning them.
o He lines himself up with the entrance of the nest tunnel and swims on the spot.
o The movement of his pectoral fins creates a current of water through the nest, bringing
fresh (well-oxygenated) water to the eggs progressively during day and night
o Fanning levels tend to increase until the eggs are about to hatch, which takes 7–8 days at
18−20 °C.
o Fanning levels also increase when the water is poorly oxygenated
o Towards the end of the egg development phase, the male often makes holes in the roof
and near the rim of the nest, presumably to improve ventilation of the nest during fanning
at a time when the eggs are more metabolically active.
 Hatching ofyoungs
o Once the young hatch, the male attempts to keep them together for a few days, sucking up
any wanderers into his mouth and spitting them back into the nest.
o Afterwards,the young disperse and the nest is either abandoned by the male, or repaired
in preparation for another breeding cycle.
An exceptional case ofparental behavior in sticklebacks
In Nova Scotia, a form of three-spined stickleback departs from the usual pattern of parental care.
Unlike other sticklebacks that nest on the substrate,Nova Scotian male sticklebacks build nests in
mats of filamentous algae. Surprisingly, almost immediately after fertilization, the males disperse the
eggs from the nest and resume soliciting females for eggs. Hence,there appears to have been a loss of
parental care in this population. Because these males have reduced dorsal pigmentation, resulting a
pearlescent white appearance,they have been dubbed "white sticklebacks". It is currently unknown
whether they are a distinct species, or simply a morph of the common Atlantic stickleback.[20][21]
Cooperative Behavior
Some evidence indicates the existence of cooperative behavior among three-spined sticklebacks,
mainly cooperative predator inspection. Predator inspection appears to allow acquisition of
information about the risk a potential predator presents, and may deter attack, with the cost being an
increased chance of being attacked if the predator proves to be hungry.
Tit-For-Tat Strategy
 Sticklebacks are known to cooperate in a tit-for-tat (TFT) strategy when doing predator
inspection. The idea behind TFT is that an individual cooperates on the first move and then
does whatever its opponent does on the previous move. This allows for a combination of
collaborative (it starts by cooperating), retaliatory (punishes defection), and forgiving
(respond to cooperation of others, even if they had defected previously) behavioral responses.
When three-spined sticklebacks approaching a live predator were provided with either a

5. stimulated cooperating companion or a stimulated defecting one, the fish behaved according
to tit-for-tat strategy,supporting the hypothesis that cooperation can evolve among egoists.
 Typically, sticklebacks operate in pairs. Individuals have partners with which they repeatedly
perform pairwise predator inspection visits. Two reciprocal pairs per trial occur significantly
more often than what was expected due to chance. These results provide further evidence for
a tit-for-tat cooperation strategy in sticklebacks.

Stickleback behavior is often cited as an archetypal example of cooperative behavior during
predator inspection. Fish from three sites differing in predation risk inspected a model
predator in pairs and reciprocated both cooperative moves and defections by the partner, but
not on every opportunity.
 Sticklebacks that originated in the two sites containing piscivorous fish were more likely to
reciprocate following a cooperative move than following a defection. Individuals from
higher-risk sites were generally more cooperative. Individuals accompanied by a model
companion show reciprocal moves of cooperation and defection in response to the model's
movements about a third of the time. Both examples of stickleback behavior demonstrate the
elements of a strategy of cooperation that may resemble tit-for-tat.
Partner-Dependence
 The tit-for-tat cooperation strategy has been shown to be evident in sticklebacks. In addition,
the size of a stickleback's partner fish may also be a factor in determining what a stickleback
will do when both fish are faced with a predator. Two sticklebacks simultaneously presented
to a rainbow trout, a predator much larger in size, will have differing risks of being attacked.
Usually, the larger of the two sticklebacks has a higher risk of being attacked.
 Individual sticklebacks are more likely to move closer to a trout (or some other predator)
when a larger potential partner moves close to the trout than when a smaller partner
approaches the trout. Although both large and small partners behave similarly, a small
partner's behavior affects the strategy of the test fish more than that of the large partner.
 Regardless of whether it is alone or with a partner that cooperates,a larger fish will approach
a predator more closely than does a smaller fish. If a partner defects,then a stickleback's
condition-factor (i.e. its ability to flee) determines how closely it approaches the predator
rather than the stickleback's size. [26]
Both the strategy and reaction to different-sized partners
seem to be dependent on whether the partner cooperates or defects.