guysion phd proposal 2011-5-19
TRANSCRIPT
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Guy Sion PhD proposal 18 May 2011
The effects of body state on decision making in the gecko
Ptyodactylus guttatus
Proposal outline
1. Introduction
1.1. Background
1.1.1 Morphological characters
1.1.2. Energy reserves and decision making
1.1.3. Behavior
1.2. The goal
1.3. Hypotheses & ensuing predictions
2. Methods
2.1. Study organism
2.1.2. Study Area
2.1.3 Abiotic parameters
2.1.4. Sede Boqer study site
2.2. Marking
2.3. Body Measurements
2.4. Behavioral parameters
2.5. Body state
2.6. The experimental design
2.7. Predictions in tables
3. Timetable
4. Discussion
References
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1. Introduction:
Behavioral ecology studies the ecological and evolutionary basis for animal behavior.
The role of behavior is in enabling an animal to adapt to its environment. To achieve this goal to adapt,
the individual may use behavioral functions, such as reptiles basking or hiding under a rock to regulate
temperature behaviorally instead of physiologically (Huey et al., 1977). However, behavior may
change the course of evolution of an animal. A change in the environment may induce a response in the
behavior, that may in turn, impose a genetic change over time due to a new selective pressure. (Avital
and Jablonka, 2000). The behavior of an animal is a very important component in the understanding of
the evolutionary and ecological context. However, studying animal behavior takes time and allegedly
cannot be recorded from dead animals e.g. in museum collections. I claim I can learn on population
behavior from carcasses, by morphometric characters e.g. directional asymmetry (DA) can inform me
on the general risk taking and social status, of the population, and so is tail injury for social status. I
suggest the museum as an important resource to learn on the behavior of past and present populations.
In this study, I wish to predict an animal behavior, using the morphological component among the
factors that may affect the decision making of foraging strategy and social hierarchy. The behavior I
want to study is decision making and social status. The decision I will study is foraging strategy: how
far from cover will the lizard ambush for prey. The social status will be studied by proximity to a
covered perch, night lamps. I am interested especially in the effects of body state in terms of fat store
and body asymmetry on the decision making. Therefore, lizards that can shed their tail are ideal subject
for such experiments. The tail contains valuable fat deposition. Losing a tail is losing a fat storage. The
lizard I chose is Ptyodactylus guttatus, which was studied for DA (Werner et al., 1991). I suspect that
DA interact with body state, in that DA may reflect developmental instability and thus, affect behavior
to adapt to its environment; alternatively, that the DA may reflect an evolutionarily functional
importance or new adapted function. Thus, left biased DA individuals may adopt different foraging
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strategy from right biased DA individuals in order to adapt to the environment. The effect may be on
the decision or on the procedure of reaching it, or both. The parameters of body state I will study, relate
to fat store such as tail base width, and DA and its possible link to body fat percentage. Although these
connections are not known, one may argue it implies from the connection between DA and stress
(Kark, 2001) Thus, these morphometric characters may affect the individual decision making and risk
management.
1.1.1. Morphological characters:
1. Sex: The sex has a tremendous effect, on the use of energy and fat store. Energy loss of fat stored in
the tail has a different effect on females and males. Females reduce their clutch, while only males'
speed is reduced e.g. in Eulamprus tympanum a skink (Doughty and Shine, 1998). Females regenerate
their tails significantly faster than males (e.g., in Skink, Chapple and Swain, 2002). Females and males
may also differ in prey preferences (Castilla et al., 2008). Therefore, I expect possible different
behavior interests in the sexes, such as different prey fat content that yield a different fat percentage
level and different risk taking strategy. Thus, I treat the sexes separately to be compared in the end.
Doing that, in terms of morphology traits is not a precedent (Ligon, 1968; Perry, 1996; Lachman et al.,
2006; Werner et al., 2006).
2. Asymmetry:
A study on three species of Ptyodactylus geckos showed significant minor directional
asymmetry (DA). The study raises the question of the possible evolutionary role of minor DA and
suggests it as a potential base for evolutionarily functional DA. Moreover, DA side-dominance may
differ between related taxa and possibly between sexes (Werner et al., 1991).
Directional asymmetry, defined as a greater development of a character on one side of the plane
or planes of symmetry than on the other. The ecological meaning of minor directional asymmetry is an
open question. Unlike fluctuating asymmetry (FA), that results from the inability of organisms to
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develop in precisely determined paths, thus, indicates developmental instability (Van Valen, 1962), DA
is considered by some as a potentially functional basis for evolutionary processes. Recent studies link
DA with fitness with two different approaches: One approach is to see DA as another phenotypic
manifestation of developmental instability (Kark, 2001; Velickovic and Jakovsev-Todorovic, 2006).
Another approach is to search for functional importance of DA in the frame of evolution (Seligmann,
1998). Here I test possible relationships between DA and behavior, such as dominance and risk-taking
foraging strategy, using the gecko’s eye-size asymmetry as indicator of its social status and/or decision
making. The basis for using the animal eye size, derived from the brain-eye link, as optic nerve number
two, is actually an extension of the brain. Thus, possible link between risk taking and eye size could be
point to the brain directional asymmetry as it is explained in human morphometry difference of digit 2
and 4 from directional asymmetry of right and left hemisphere that induce aggression hormones and
causing digit DA (Coyne et al., 2007). Previous morphometric studies (Werner et al., 1991; Seligmann,
1998; Seligmann, 2003; Almog et al., 2005; Lachman et al., 2006) have used museum specimens, to
link assorted characters and taxa of Lepidosauria to tail injury. One important result was the useful use
of "Seligmann effect" to differentiate different populations to different species or sub-species by
excluding tail-injured individuals (Seligmann, 1998; Almog et al., 2005; Lachman et al., 2006).
This study observed live individuals in their natural habitat, to test the hypothesis that DA
correlates with risk-taking behavior. This connection of morphometric measurements of live
individuals with the behavioral field observations can give the lab measurements of dead animals, new
context and may demonstrate that museum specimens can inform about behavior. The prediction is
based on Seligmann (1998) finding that left-biased individuals have more tail injuries. A possible
explanation I raise is that left-biased individuals will tend toward riskier foraging strategies. According
to Seligmann (1998), minor directional asymmetry may occur, if there is small systematic difference,
tendency toward right or left, such as in the "Seligmann effect", with a possible evolutionary functional
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role. The "Seligmann effect", is an inherent different meristic biometry (inborn) difference between
those with tails and those with damaged tails. The effect predicts better statistical distinction for
taxonomic comparison of close taxa, (only the full-tail specimens are used, despite the smaller sample),
this due to the smaller variation, when you 'clean' the statistical noise of the tail injured individuals.
Obviously the morphologically extreme, deviating, specimens are expected to be accident prone.
(Seligmann, 1998; Almog, et al., 2005; Lachman et al., 2006). Hence, if one compares behavior of tail
retaining and tail losing of lizards, possibly some behavior difference is inborn, not due to the tail.
However, this next step of observing lizards in the wild and compare the behavior and risk-taking
strategy of left and right biased DA individuals, was never done before. Moreover, it also may function
as an external honest signal that may be disclosed to potential females or rival males and predators.
Studies on the effects of asymmetry on mate preferences shows preferences toward Symmetry
over FA (Fluctuating Asymmetry) in lizards (Lopez et al., 2002), and other taxa such as birds (Møller,
1992) or humans (Møller et al., 1995; Simmons et al., 2004). Studies on the effects of stress on
asymmetry (Leamy et al., 1999), shows that stress or exposure to toxic substances can cause FA and
DA.
Although DA was not considered as reliable indicator of developmental instability like the FA,
increasing evidence suggests that DA in addition to FA, may often reflect developmental instability of
bilateral traits, expressing stress (Graham et al., 1993; 1998; Kark et al., 2001).
3. Tail condition:
Since a substantial amount of fat is stored in the tail, it is an important energy storage organ in some
species of lizards (Bustard, 1967; Daniels, 1984). Thus, the state of the tail: Amputated tail, tailless or a
full intact tail may affect and disclose the body state of the individual, as the tailless individuals may
reduce energy stores and delay the animal’s next reproductive episode or reduce size and number of
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young (Smyth, 1974; Dial and Fitzpatrick, 1981; Wilson and Booth, 1998); Possibly, that a regenerated
tail may signal a lipid loss, regardless of the true lipid content. The information on tail condition is
disclosed by coloration: Intact tail has dark rings along the tail and a black tip. Regenerated tail is
unicolor.
4. Tail Base Width (TBW), may be used as an indicator of fat store and hence of body condition
(Bauwens, 1985; Donoghue, 1998; Doughty and Shine, 2003; Vervuast et al., 2008). Moreover, using
the tail-base width as the independent variable in a linear regression model may yield an accurate
prediction of tail fat content mass (g). This has newly been demonstrated by Doughty and Shine, (2003)
in lizards lacking abdominal fat bodies, possessing caudal fat only (Doughty and Shine, 2003). If tail
fat is proportional to body fat, thus, body fat may be as well be predicted by TBW, possibly in lizards
with abdominal fat as well. Predicting total body fat percentage may be obtained by the use of TBW
only, or with other morphometric characters such as mass and RA. A statistical model may be
constructed, to predict body fat percentage, by comparing results of body fat percentage, with
morphometric characters that may indicate fat percentage such as tail base width.
1.1.2. Energy reserves and decision making:
Energy requirement has great effect on risk taking. In dire straight even safety gets lower value.
Thus, decision-making procedure supposed to be effected by energy requirement in the form of body
state (Clark, 1994; Kotler et al., 2004; Simmonds et al., 2010). I predict that status and risk interact and
maybe rely on the body state. Body Index is an index for body state. Dual energy X-ray absorptiometry
(DEXA) enables to measure directly the body state, by measuring the body fat percentage. Instead of
evaluate it indirectly by a body index. Another advantage is in multiple measurements in-situ, during
the life time of the animal (Secor and Nagy, 2003). The PIXImus is such a machine that uses DEXA to
measure bone densitometry and body composition giving values for fat mass (g) lean mass (g) and fat
percentage. The process requires careful sedation of the animal. I will use Isufluran for the sedation.
The sedation might endanger the animal, and it is possible that some individuals will not survive the
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sedation. The use of Isofluran diminishes these dangers. It is relatively expensive, but safer to use. In
comparison to ether e.g., that may cause pulmonary edema. An example to a body condition index is
the tail base width (TBW). It may serve as a predictor of fat store in the tail. In combine with other
morphometric characters, such as mass/rastrum-anus (RA) (Werenr, 1971) with compare to DEXA
measurement results for body fat, a statistical model may be constructed for predicting body fat
percentage.
1.1.2.1. DEXA storage: The piximus store the DEXA data in the computer and allows
manipulating the scanned areas, so it is possible to compare the fat content of a specific zone
such as the tail, even if we scanned the whole animal. This way allows comparing the fat
content stored in a renewed tail and an intact tail.
1.1.3. Behavior:
Measurable expressions of risk, asset protection and energy reserves:
Social status by proximity to night lamps: The night lamps are preferable locations, occupied by
territorial males and their females who are in better body condition relative to non-territorial males
(Werner, 1972; Johnston and Bouskila, 2007).
Risk by foraging distance away from cover: Perch closer to the ground, riskier but more rewarding.
Perch on the high third of wall length will be considered as a high perch, as oppose to low perch or
ground perch
1.2. The goal:
To study what affects behavior such as decision making in general, and risk management in
particular, the possible interact with social status and to study possible relation of these behavior
with each other and possible relation of behavior to morphological traits. For that I use body state
and morphological components, as suspects that may affect decisions. A preferable result could lead
to recovering behavioral information from morphometric data from carcasses in museum
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collections.
To reach this goal, I intend to test the hypothesis that DA correlates with risk-taking behavior, as
predicted by Seligmann (1998). DA may function as an honest signal that may be perceived by females
(potential mates) or rival males and predators. Thus, this research should also explore the evolutionary
role of minor directional asymmetry, and mechanism that explain the relationships between DA, tail
injury, social hierarchy status and foraging strategy. To test the hypothesis that fat deposit in the tail is
proportional to whole body fat, experiments will use X-Ray to measure fat content, so body fat could
be predicted easily from morphometric data such as the tail base width, if hypothesis will be supported.
1.3. Hypotheses & ensuing predictions:
Predictions and experimental design:
1.3.1. Predictions based on the hypothesis that:
Morphometric characters (DA, Sex, tail condition, and fat%) affect decision making and risk
management:
(1). Behavior will be affected by DA. Left-biased individuals will tend toward riskier foraging
strategies.
(2). DA will be correlated with tail injury (Seligmann, 1998).
(3). Individuals with a deficit in their energy balance will be out active both in day and night to
obtain needed resources.
1.3.2. Predictions based on the hypothesis that:
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Directional asymmetry (DA) is correlated with dominance:
Individuals with a right biased DA will:
1. Be in better body condition (Higher body fat percentage).
2. Perch higher.
3. Tend to win over left biased individuals at male-male conflicts on territory.
4. Tend to win in competition for females.
5. Left biased individuals are preferred by predators, when given a choice.
6. Tend to be territorial, in proximity to night lamps.
1.3.3. Predictions based on the hypothesis that:
Tail injury (regenerated or amputated) bears a vulnerability honest signal:
Males with a regenerated tail will:
1. Tend to win at conflicts in captivity if tail is colored with rings to mimic intact tail. If tail is not
colored, tend to lose.
2. Males with regenerated tail will be preferred by females if tail is colored with rings to mimic
intact tail, against individuals whose intact tail is colored to mimic a regenerated tail. If tail is not
colored, they will tend to lose.
3. Preferred by predators, when given a choice.
4. Tend not to be present at lighted ambush spots, (under lamp).
5. If active at moonlight night, will not be exposed to moonlight, only shaded ambush spots.
Daylight activity predicted to be mostly of tailless individuals.
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1.3.4. Predictions based on the hypothesis that:
Fat deposited in the base of the tail is proportional to the total body fat content
Predictions:
1. Tail base width may serve as predictor of body fat percentage.
2. Constructing a statistical model for predicting body fat percentage, based on DEXA results and
morphometric parameters such as tail base width is possible.
1.3.5. The new model of predicting body fat percentage will be applied for geckos, and compared
against orthodox body condition indices (e.g. Mass/RA). The best method to explain the relation
between body index and risk taking: proximity to night lamp, longer activity, forage far from cover,
will be use.
Predictions:
1. Body fat percentage (as measured by DEXA) and predicting the body fat percentage, are
more reliable methods with a better (positive) correlation to risk-taking decision and risk
management, than the orthodox methods for body condition (e.g. Mass/RA). (Low body
index=Riskier foraging).
2. Individuals with low fat% (predicted or measured) will choose a high risk strategy:
1.3.5.1. Forage far from cover, closer to the ground.
1.3.5.2. Active in moon light nights.
1.3.5.3. Time out of cover will be longer.
1.3.5.4. Shorter inactivity period during winter
1.3.6. Predictions based on the hypothesis that:
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Sub-adults present foraging strategy that considers possible future competition on social status.
Sub-adults will:
1. Tend to condition the decision, whether to go out foraging, on the body state, status and
activity of other sub-adults, and not only on their own body condition.
2. Sub-adults winter inactivity period is predicted to be shorter than their physiological
ability that can allow them to stay under cover much longer, during winter. So in captivity the
sub-adults demonstrate endurance to famine, which is much longer than the winter inactivity
observed in the field.
1.3.7. Predictions based on both hypotheses that:
a. Dominancy is correlated with directional asymmetry (DA).
b. Sub-adults present foraging strategy that considers possible future competition on social status.
Sub-adults will:
1. Not tend to condition the decision, whether to forage, on the body state, status and
activity of other sub-adults, if they are left biased (DA).
2. Demonstrate shorter winter inactivity, if they are left biased (DA) compared with right
biased individuals (DA).
1.3.8. Predictions based on the hypothesis that:
Directional asymmetry of eye diameter is derived from directional asymmetry of the brain (right
hemisphere vs. left):
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1. Detour responses will be correlated with DA in that detour around a barrier will be to the left for
left biased geckos; and to the right, for right biased geckos.
(Modified from Vallortigara, Regolin, and Pagni, 1999; and Vallortigara, 2000).
2. Approaching food will be correlated with DA (opposite to left and right-biased). So one eye
detects food better and the other eye detects predator better- will be correlated with DA bias
(Modified from Rogers and Anson, 1979).
3. Brain morphology will differ according to DA of eye diameter; in that left biased geckos will
have a larger right brain hemisphere and right biased individuals will have a larger left brain.
4. Brain morphology will differ according to DA of eye diameter, in that left biased geckos will
have a higher neuron density in right brain and right biased individuals will have a higher
neuron density in left brain.
{ How on earth will you do all this, including the ontogenetic change? Maybe
you should sell it to Anat Barnea and she should seek a grant for your post-
doc. }
1.3.9. Predictions based on the hypothesis that:
Directional asymmetry of eye diameter is derived from directional asymmetry of the brain (right
hemisphere vs. left) and mediated by hormones:
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1. Stress hormones will differ with DA of eye diameter, in that left biased gecko will have a higher
stress hormone level and right biased individuals will have a lower stress hormone level.
2. Aggression hormones will differ with DA of eye diameter, in that left biased geckos will have a
higher hormone level and right biased individuals will have a lower hormone level, as seen in
human digits DA (Coyne et al., 2007).
1.3.9.1. Predictions based on the hypothesis that:
By controlling the environmental stress, population composition of DA is controlled:
1. Geckos that will be raised under constant conditions of temperature, excess food and low
exposure to predators, will have a higher rate of right biased DA individual than a group of
geckos that will be held under higher density, lower food regime and under stress induced by
exposure to predators.
2. Methods
2.1. Study organism
I chose the Israeli Fan-toed gecko lizard ( Ptyodactylus guttatus), as a study organism model,
since it is not endangered, a common lizard that show DA (Werner et al., 1991). Moreover, it
demonstrates behaviors related to social dominance. Some behavior such as status may be predicted
successfully by a morphological sign of tail loss (Sion, 2006) and observe behaviorally by the height of
the perch, as these rupicolous geckos are magnificent scansorial. The gecko P. guttatus uses caudal
autotomy to escape predators, followed by tail regeneration. Body size (adults are 60-90 mm) in this
species has a substantial effect on the social status of individuals (Frankenberg, 1978; D. Werner, 1972;
Werner, 1965, 1986, 1991; Johnston and Bouskila, 2007). Competitive exclusion based on body size
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was demonstrated in captivity (D. Werner, 1972), and is expected in the wild.
The dominant males are territorial; occupy the best perches for foraging (Werner, 1972;
Frankenberg, 1978), such as under night lamps. The females of a dominant male lay their eggs at the
same site (Frankenberg, 1978; Werner, 1965, 1986, 1991). The dominant males mate and prevent other
males to mate on their territory, threaten other males and thus affect their behavior (Johnston and
Bouskila, 2007). They are more active and aggressive and perch higher (Werner, 1972; Frankenberg,
1978);mostly in best body condition (Frankenberg, 1978; Johnston and Bouskila, 2007).
2.1.2. Study Area: Jerusalem (Hebrew University) for captivity behavior experiments. The
Shomron region, and Sede Boqer (Midrasha) in the Negev region, for collecting geckos, and
most outdoor observations in Sede Boqer.
2.1.3. Abiotic parameters: The parameters recorded will be: date, hour, and distance from cover,
wall temperature (º C), moon condition, and proximity to night lamp.
2.1.4. Sede Boqer study site:
The outdoor behavioral study was conducted at Midreshet Ben-Gurion in the northern
Negev desert. The study site was a complex of guest rooms surrounded by a two-meter high
wall, 13x150 meters. P. guttatus inhabited densely the southern part of the premises, and
geckos utilized many of the lamps erected on some of the buildings and on the southern
wall.
2.2. Marking: The study will take place both in the lab and in the field. Geckos will be collected and
marked under permits from the Nature Reserves Authority, Israel.
Short term mark will be made by non-poisonous (child-safe) felt tip pen, long term mark by Destron
and Trovan microchips (Pit Tags). The microchips will be injected subcutaneously with a needle
through a cut made by scalpel, closed by super glue. The incision is made alongside the abdomen, in
between the hind and fore leg. The cut is made closer to the hind leg. The chip is inserted gently by
hand toward the fore leg through the cut, while the chip advances subcutaneously toward the fore leg.
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When the chip does not touch the cut, the cut in the skin is closed with superglue. So it is between skin
and muscle.
2.3. Body Measurements: Sex, tail type and scars, weight by scale, while Rastrum-Anus (RA),
width of tail base and tail length, by caliper. Directional asymmetry will be studied and determined,
using comparison of left and right factors of body measurements: eye size and head size (by
caliper) while DA as shown in Van Valen (1962). If not caught, data will be collected such as, tail
condition and estimated body size.
2.4. Behavioral parameters: Foraging proximity to night lamps, foraging distance from cover, inactivity
period during winter (as the minimum number of consecutive days with no individuals of each group;
e.g. DA male adults), and determination of sex for possible sexual effect on behavior.
2.5. Body state: Body Index: an index for body state; an attempt to predict body fat percentage. Tail
base width and Mass/RA, Mass/RA ², Mass/RA ³, and residuals of body mass vs. RA (in linear
regression) will be compared, using DEXA measurement for body fat mass.
2.6. The Experimental design:
Calculating directional asymmetry: using comparison of left and right eye diameter. To neutralize
allometric effects of different body sizes, the subtraction of right eye diameter minus left eye
diameter will be divided by the mean value of eye diameter (Van Valen, 1962), and by percentage
of (RA) body size. This is called PERCRA, as suggested by Hoofien as an international word
(Werner, 1971). The data will be tested for possible links to behavior, such as social status, risk-
taking, and morphometric, such as sex, tail condition and body size and state.
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2.7. Predictions based on the hypothesis that:
Morphometric characters (DA, Sex, tail condition, and body index) affect decision making by
risk management:
Predictions:
1. Left biased DA will not forage in proximity to night lamps.
2. Left biased DA will have more tail injuries.
3. Left biased DA will forage far from cover.
4. Left biased DA will have lower fat percentage.
5. Right biased DA will forage in proximity to night lamps.
6. Right biased DA will have less tail injuries.
7. Right biased DA will forage closer to cover.
8. Right biased DA will have higher fat percentage.
9. Males will have more tail injuries than females.
Predictions/O
bservations
Proximity
to night
lamps
More tail
injuries
Forage far
from cover
Fat%
Left biased
DA- + + -
Right biased
DA+ - - +
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Males - +
2.9.1. Museum collection: The prediction that DA has a correlation with tail injury will be tested
by examining preserved specimens from the collection and live individuals from the field. A
secondary outcome is tackling the argument that a morphometric measurement, from
preserved cadavers, is problematic due to possible deformations during preservation:
Predictions:
1. Live geckos, left biased DA will have more tail injuries.
2. Preserved geckos, left biased DA will have more tail injuries.
Predictions More tail injuries
Left biased DA (Live geckos)
+
Left biased DA (Preserved geckos)
+
Thus a similar result with live and preserved specimens disproves preservation effects.
2.9.2. Lab behavioral manipulation:
The prediction that left biased DA is correlated with low status will be tested in the lab (in
addition to the field) by lamp proximity. In a small arena two males of the same size group could
compete for food, territory (night lamp) and on access to females. Left biased individuals will be
confronted with right biased individuals of the same body size, and individuals with no significant
asymmetry, with the same feeding regime.
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The prediction that, directional asymmetry individuals are preferred by predators when given a choice,
will be tested in the lab. Three different taxa representative: 1) snake 2) bird 3) cat; will be used as
predators, with two individuals in each trial. One with a DA of eye size (left or right) and the other
without DA of eye size, each encounter will be recorded to examine the preference if any, of the
predator (the geckos will not actually be eaten):
Predictions/T
reatments
Left
biased
DA
Right
biased
DA
No DA
Night lamp
- + +male-male
arena- +
+
Diurno-
nocturnal
foraging
- + +
Predators
preference+ - -
Females
preference- + +
2.9.4. Male-male Lab manipulation: In the same arena, the tendency to win at conflicts with a fake
tail will be tested. First the regenerated tail is colored with rings to mimic intact tail. Another
manipulation would be to mimic a regenerated tail, by coloring an intact original tail with a uniform
color to hide the dark rings.
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{First you will have to investigate how minor size and fat differences , and maybe last ,meal,
affect the outcome of contests between “equal” geckos. To be really exact and dependable, you
should first test the individual optimum temperature, to avoid a situation where one contestant
enjoys his optimum but the other not. Meaning, to apply the principle of correct comparative
physiology, to intra-specific work, especially where there is a reason to suspect that it matters
(Arad’s bimodal result)}.
The prediction that, individuals with tail injury (regenerated or not) are preferred by predators,
when given a choice, will be tested in the lab. Three different taxa representative: 1) snake 2) bird 3)
cat; will be used as predators, with two individuals at each trial. One with a tail injury and the other
with no tail injury (intact tail) encounter will be recorded to examine the preference if any, of the
predator.
The tail manipulation: In the same conditions a fake tail will be tested for predators' preference of
tail condition. First the tail is colored with rings to mimic intact tail. Another manipulation would be to
mimic a regenerated tail, by coloring an intact original tail with a uniform color to hide the dark rings.
2.9.3. Predictions based on the hypothesis that:
Tail injury (regenerated or not) bears a vulnerability honest signaling:
Origina
l tail
Tail injury
regenerated
or not
Fake
Reg.
tail
Fake
Orig.
tail
Night lamp + - + -
male-male
arena+ - - +
Diurno-
nocturnal
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foraging - + - +
Predators
preference- + + -
Females
preference + - - +
Moonlight
activity+ - + -
The male-male interaction experiments set will test those predictions; while behavior will be recorded
in the lab in a small arena where two adult males could compete on food, access to females and on
warm source as a night lamp.
2.9.5. Predictions based on the hypothesis that:
Fat deposited in the base of the tail is proportional to the total body fat content
Is the
column
Proportional
to the row?
Tail base
fat
content
Total body
fat content
Tail
fat%
Body
fat%
Tail base
width
+ + + +
Predicted tail
fat%
+ + + +
Predicted
body fat%
+ + + +
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2.9.6. Predicting fat percentage and risk managment:
Predictions based on the hypothesis that:
A reliable body index is strongly related to decision making and risk management.
Predicted
activity
Low fat% Low fat%
(Predicted)
Body condition
indices
(e.g. mass/RA)
Forage far
from cover + + -
Moon nights
activity+ + -
Time out of
cover + + -
Short winter
inactivity+ + -
Diurno-
nocturnal
activity
+ + -
2.97. Predictions based on the hypothesis that:
Regenerated tail has a different ability of fat deposition, thus a different risk predation strategy
is imposed.
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Proportional
Regenerated
tail
Original
tail
High fat% + -
moon light - +
Time out of
cover
- +
Forage far
from cover
- +
• Comparison between tails of the same tail length and body size.
Experimental design:
The piximus store the DEXA data in the computer and allows manipulating the scanned areas,
so it is possible to compare the fat content of a specific zone such as the tail, even if we scanned the
whole animal. This way allows comparing the fat content stored in a renewed tail and an intact tail.
The results of comparing the fat content stored in the two tail type will be tested for possible correlation
with behavioral parameters: Active in moon light nights, time out of cover, foraging distance of cover,
proximity to night lamp.
2.9.8. Predictions based on the hypothesis that:
Sub-adults presents foraging strategy, considers possible future competition on social status.
Condition
foraging activity
on:
Sub-adults
Right DA
Sub-adults
Left
DA
Adults Juveniles
Self fat% + + + +
Others fat% + - - -
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Forage far from
cover - + - +
physiological
ability to prolong
winter inactivity + + + -
Long winter
inactivity - + + -
Experimental design: The experiment will test the hypothesis that sub-adults present a foraging
strategy that reflects future competition on social status. Based on that hypothesis, I assume a certain
mechanism, that sub-adults winter inactivity period is shorter than their physiological ability that can
allow them to stay inactive much longer.
To test this prediction, I will combine field and lab observations and manipulations. The
winter inactivity length will be recorded in the field, and compare with the max. number of days
that sub adults can endure with no food or water. The prediction is, that the ability of the adults to
do so is much longer than the inactivity length, they demonstrate in the field. While the juveniles'
ability in the lab to survive long starvation will be close to that they demonstrate in the field. The
starvation will be monitored, and with the first sign of distress or apathy the individual will be fed,
or force fed if necessary.
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2.9.9. Predictions based on the hypothesis that:
Directional asymmetry of eye diameter is derived from directional asymmetry of the brain (right
hemisphere vs. left):
Eye diameter DA Right
DA
Left
DA
Detour response (R) + -
Detour response (L) - +
Larger right brain - +
Larger left brain + -Higher neural
density in right brain - +
Lower neural density
in right brain + -
Approaching threat,
predator (or model)
on right side (R eye) + -
Approaching food
on right side (R eye) + -
Stress hormone level - +
Aggression hormone
level + -
Stressful
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environment - +
3. Timetable:
Complete chapter on tail base as non-invasive body index, by September, 2010.
Done, awaits small calibration experiments for tail fat content- Will be done by May.
Complete chapter on asymmetry by December, 2010. Done, awaits the small experiment mention
above.
Complete fieldwork by June, 2011.
Complete lab experiments by September, 2011.
Complete the chapter on endocrinology, by September, 2011.
Complete museum measures by November, 2011.
Complete analysis by February, 2012.
Complete final report by June, 2012.
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