The (dis)advantages of dominance in a multiple male group of Anolis carolinensis lizards

Journal Pre-proof The (dis)advantages of dominance in a multiple male group of Anolis carolinensis lizards Glenn Borgmans, Steven Van De Panhuyzen, Raoul Van Damme

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S0944-2006(20)30006-4

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https://doi.org/10.1016/j.zool.2020.125747

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ZOOL 125747

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Zoology

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16 January 2020

Please cite this article as: Borgmans G, Van De Panhuyzen S, Van Damme R, The (dis)advantages of dominance in a multiple male group of Anolis carolinensis lizards, Zoology (2020), doi: https://doi.org/10.1016/j.zool.2020.125747

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The (dis)advantages of dominance in a multiple male group of Anolis carolinensis lizards Glenn Borgmans* Department of Biology, University of Antwerp, Universiteitsplein 1, 2610 Antwerp, Belgium Centre for Research and Conservation, Royal Zoological Society of Antwerp, Antwerp, Belgium Steven Van De Panhuyzen Department of Biology, University of Antwerp, Universiteitsplein 1, 2610 Antwerp, Belgium

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Raoul Van Damme Department of Biology, University of Antwerp, Universiteitsplein 1, 2610 Antwerp, Belgium * Corresponding author. E-mail: [email protected]

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The (dis)advantages of dominance in a male group of A. carolinensis lizards are investigated using behavioural experiments Dominant males in a group have priority access to prey and potential sexual partners but may run a higher risk of predation No evidence was found that dominant males have a higher risk of injuries or a higher energetic cost Our results show that dominant male A. carolinensis lizards in a group obtain clear benefits which outweigh the disadvantages

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Highlights:

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Abstract

Male Anolis carolinensis lizards will fight and form social dominance hierarchies when placed in

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habitats with limited resources. Dominance may procure benefits such as priority access to food, shelter or partners, but may also come with costs, such as a higher risk of injuries due to aggressive

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interaction, a higher risk of predation or a higher energetic cost, all of which may lead to an increase in stress While most research looks at dominance by using dyadic interactions, in our study we investigated the effect of dominance in a multiple male group of A. carolinensis lizards. Our results showed that dominant males in a multiple male group had priority access to prey and potential sexual partners but may run a higher risk of predation. We could not confirm that dominant males in a multiple male group had a higher risk of injuries from aggressive interactions or a higher energetic

cost by being dominant. Overall our results seem to indicate that dominant male A. carolinensis lizards in a multiple male group obtain clear benefits and that they outweigh the disadvantages.

Keywords: Anolis carolinensis; reptiles; dominance; multiple male group

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1. Introduction Many animal species show a disparity between defending territories during the breeding season and living together in groups at other times of the year. This group living comes with a cost in the form of increased competition for resources (Huntingford and Turner, 1987, Krebs

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and Davies, 1993). Such competition will often lead to the formation of dominant-subordinate

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social structures (Huntingford and Turner, 1987, Pusey and Packer, 1977). Research on social hierarchies in lizards has shown that the benefits of dominant social status

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include priority of access to food (Pfeffer, 1959), shelter (Carothers, 1981), potential mates (Carpenter, 1967, Ruby, 1981), and other resources such as high quality home ranges (Fox et

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al., 1981, Fox, 1983) or superior perch sites (Bels, 1984, Tokarz, 1985). However, beside these benefits, there can also be severe costs to attaining and maintaining high social status.

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Dominant individuals may run a higher risk of getting injured because they have to engage in aggressive interactions more often, especially when the hierarchy is being established (e.g.

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Vitt et al., 1974). Once the social order is formed, dominant males must continue signalling their competitive abilities to maintain their status, often through behavioural displays that are energetically costly, and may render them conspicuous to predators (Magnhagen, 1991, Alberts, 1994, Amsler, 2010, Catano et al., 2015). Dominance hierarchies also have an effect on subordinate individuals. Not only may low status force individuals into suboptimal areas and reduce mating opportunities, it may also interfere with basic physiological processes

(Brackin, 1978). Low ranking males might be inhibited from performing their full range of thermoregulatory behaviour (Regal, 1980), which could contribute to decreased resistance to disease (Bels, 1984). Despite sometimes detrimental effects, the behavioural and physiological correlates of low social status appear effective in preventing overt attack by dominants (Carothers, 1981, Tokarz, 1987). In general, advertisement of status probably benefits both dominant and subordinate lizards by precluding the need for repeated and potentially costly encounters to evaluate relative social position (Alberts, 1994).

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While previous research looking at dominance hierarchies in lizards has mostly focused on dyadic interactions, the effect of dominance in multiple male groups also deserves attention. It has been shown that aggressive interactions are more common at higher density (Brattstrom,

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1974, Dugan and Wiewandt, 1982) and that this produces severe physiological stress in

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subordinate individuals (Crews and Garrick, 1980). Even in the absence of overt physical attacks, the stress of continuous exposure to threat displays can reduce activity and feeding by

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subordinate lizards (Pawley, 1969, Tubbs, 1976, Castle, 1990). We investigated the costs and benefits of high social ranking using a multiple male group of

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Anolis carolinensis lizards. The Green anole has been the subject of research into animal aggression for many years. The endocrinological and neural correlates of aggression and

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social status are well-documented for this species as are many aspects of its behaviour (summary in Wilczynski et al., 2015). Furthermore it has been shown that while male A.

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carolinensis will strongly defend their home territories during the breeding season (Jenssen et al., 1995), they are more likely to live in small groups when not breeding (Jenssen et al., 1996). In captivity, adult males will also fight and form social dominance hierarchies when placed in habitats with limited resources (Evans, 1936, Greenberg and Crews, 1990).

To our knowledge no research has been carried out looking at the possible (dis)advantages of dominance in a multiple male A. carolinensis group. We expect dominant males to obtain priority access of resources (food items and potential mates), but have a higher risk of injuries, predation and a higher physiological cost of maintaining a dominant position than subordinate males.

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2. Material and methods 2.1 Animals and housing

The experiments reported in this study were performed between January 2016 and May 2016.

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All procedures were carried out with the approval of the University of Antwerp’s Ethical

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Committee for Animal Trials (Ethische Commissie Dierproeven, ECD, file nr. 2013-70). Forty male adult A. carolinensis lizards were obtained from a licensed commercial supplier in

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Belgium. In the laboratory, lizards were placed into individual glass terraria (30x40x70cm, width x length x height). Full spectrum halogen reflector light bulbs with a 30° light arc

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(40W), mounted in the roof of the cages, were switched on during daytime (6:00 h - 20:00 h), providing a shallow thermogradient (air temperatures between 20 and 30° C) within the cages.

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The maximum temperature of 30° C falls within the preferred body temperature range of A. carolinensis (Licht, 1968) and corresponds to the mean body temperature recorded in the field

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(Lailvaux and Irschick, 2007). At night, ambient temperature was never below 20° C. Relative humidity was monitored with a hygrometer (TH50 hygrometer, Hama) and kept constant at around 60% by misting the terraria when necessary. The walls of adjacent cages were lined with white paper to preclude visual contact between individual lizards. Each cage contained a diagonally-placed wooden perch with a diameter of 2 cm (which is the preferred perch diameter for A. carolinensis, Gilman and Irshick, 2013) and two banana leaves (± 20

cm x 10 cm) under which lizards could hide. Animals were provided with ad libitum water and were fed with common house crickets (Acheta domesticus) twice a week and with wax moth larvae (Galleria mellonella) once a week. Crickets were dusted with an ultrafine calcium carbonate supplement containing vitamin D3 (Repti Calcium, Zoo Med Europe). During the course of the experiments seven individuals died in four different cages. All deaths occurred after the period of dominance position assessment (see section 2.3) and thus did not have an effect on the establishment of dominance. Identities of deceased individuals are noted

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in Table 2. 2.2 Experimental design

The lizards remained under the conditions described above for seven weeks after their arrival

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in the laboratory to allow animals to recover from transport and their stay at the local supplier.

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After this period, baseline measurements were taken as described below (see section on physiological measurements). Subsequently, males were divided into groups of four based on

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their snout-vent length (SVL). This was done to ensure a minimal effect of body size on formation of dominance relations within a group as previous research has shown that body

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size plays an important role in establishing dominance in dyadic interactions in A carolinensis lizards (Jenssen et al., 2005, Losos, 2011). This size matching was necessary in the light of

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another study that looked at the effect of personality on dominance ranking. Individuals of the same group differed less than 1.44 mm in SVL. Body size ranges in mm of the ten

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experimental groups were the following: 56.9-58.4, 59.1-59.7, 59.9-60.8, 61.1-62, 62.1-62.2, 62.3-62.8, 62.9-63.1, 63.2-63.8, 64.1-64.8, 65.5-66.8. Groups were housed in larger cages (40x50x100 cm, width x length x height) containing four diagonal perches: two 50 cm, one 75 cm and one 100 cm long. These branches allowed individuals to bask without having to interact with other individuals. Group cages were maintained in the same light and temperature conditions as described above. Transport of individuals from their home cages to

the group cages was done by placing animals in separate plastic boxes with a perforated lid and placing them in a dark cardboard box during transport. Prior to putting individuals in the group cages they received colour markings (blue, purple, orange or white, individuals were assigned a specific colour at random) on their sides and back with a non-toxic water based paint marker to allow for individual recognition for the duration of the experiments. This is a well-known non-invasive method for marking individuals and has been used without problem in A. carolinensis and other lizard species (e.g. Henningsen and Irschick, 2012, Hollis et al.,

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2004, Lopez and Martin, 2001, Robson and Miles, 2000, Rodda et al., 1988). When individuals lost their colour markings (for example by moulting) they were caught and the markings were reapplied. Following transport, the plastic boxes were placed in the group

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cages and lids were simultaneously removed to ensure individuals had access to the group cage at the same time and no males had the advantage of earlier residence. The plastic boxes

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were removed the next day during feeding to minimize disturbance during the first hours of

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group formation. 2.3 Assessing dominance position

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Perch height has been shown a trustworthy proxy for dominance position in Anolis carolinensis (Greenberg and Crews, 1990). Dominant males are thought to monopolize high

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perch sites to increase the effectiveness of their advertisement displays and to facilitate surveillance (Andrews, 1971). We noted the position of each lizard and assigned it a rank

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between 1 and 4 (1= hiding, 2= sitting on the floor of the cage, 3= sitting on one of the perches, 4= highest location). This was repeated thrice a day (at 10:00, 13:00 and 16:00) for three weeks and the average of the scores was calculated to obtain the relative dominance position of each individual in the cage. 2.4 Experiments

The lizards’ behaviour was observed in the following contexts: aggressive interactions, access to food recourses, access to potential mates and predation using continuous focal animal sampling with observation software (JWatcher v1.0 , Blumstein et al., 2006). Observations were done live from a distance of three meters in a darkened secondary room to ensure minimal disturbance of the presence of an observer. All observations were carried out between 9:00 h and 17:00 h, when the lizards were fully active (pers. obs.). 2.4.1 Aggression during group establishment

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To test whether males that later on became the dominant individuals within a group performed a higher number of aggressive interactions towards other individuals during dominance formation, we observed each cage the first 30 minutes after group formation. The

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following behaviours were scored (Table 1): number of aggressive interactions, number of

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dewlap displays, number of push-ups. 2.4.2 Food experiment

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To test whether dominance grants priority access to food resources, a food experiment was carried out. This experiment was carried out 26 days after the group formation and was done

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twice for each group of individuals. Animals were only fed once during a week prior to the food experiments to ensure that animals were prone to react to food being presented. In these

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experiments four wax moth larvae (Galleria mellonella) were presented in a tray placed in the centre of the cage bottom. The number of wax moth larvae eaten by each individual was noted

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and for each individual lizard in the cage, we also noted the following behaviours (Table 1): number of aggressive interactions performed towards other individuals, number of dewlap displays, number of push-ups. Each experiment lasted 30 minutes. The experiment was repeated two days after the first experiment. 2.4.3 Mating experiment

To test whether dominance permits priority access to potential mating partners, a mating experiment was carried out. This experiment was carried out one week after the food experiment. A female A. carolinensis lizard was placed in a small transparent plastic container with a perforated lid and presented centrally in the cage. For each individual lizard in the cage, we noted the following behaviours (Table 1): number of times a male touched the plastic box containing the female, number of aggressive interactions performed towards other individuals, number of dewlap displays, number of push-ups. Each experiment lasted 30

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minutes. This experiment was repeated after two days with another female to avoid a possible effect of repeating the experiment with a familiar female. Males also did not have contact with the females prior to the experiments.

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2.4.4 Predation experiment

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To test whether dominance leads to a higher risk of predation, a predation experiment was carried out. The predation experiment was carried out one week after the mating experiment

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and was done twice for each group of individuals. A natural predator of A. carolinensis lizards (Curly-tailed lizard, Leiocephalus carinatus) was placed in a plastic container and presented

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centrally in the cages. For each individual lizard in the cage, we noted the number of times a lizard was hiding and the number of lateral head movements (as a proxy for alertness, Table

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1). Each experiment lasted 30 minutes. This experiment was repeated after two days.

2.5 Physiological measurements To examine the effect of dominance position on physiological condition, we performed measurements on each individual. Heterophil to lymphocyte ratios were measured at three different points in time: (1) just prior to forming the experimental quartets, (2) one week after putting the animals together (by then, a stable hierarchy is formed, Wingfield and Marler,

1988) and (3) at the end of the experiment, i.e. 7 weeks after group formation. Morphometrics were measured at points 1 and 3. 2.5.1 Morphometrics We measured snout-vent length (SVL) and tail width (at the base of the tail, which is considered to be an indicator of fat deposited and hence condition, Bauwens, 1985) using digital calipers (0.1 mm, Absolute, Digimatic) and body mass using an electronic balance (0.01 g, Scout pro, Ohaus). Tail width measurements were corrected for SVL by using the

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residuals from a linear regression of tail width against SVL (both variables log-10 tranformed).

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2.5.2 Heterophil to lymphocyte (H/L) ratio

Heterophils and lymphocytes are two types of white blood cells that play a role in the immune

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system of reptiles. Heterophils (neutrophils in mammals and amphibians) are part of the innate immune system, while lymphocytes are part of the acquired immune system. High

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ratios of heterophils to lymphocytes in blood samples are considered an indication of high glucocorticoid and stress values in all vertebrate taxa (review in Davis and Maerz, 2008),

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including reptiles (Saad and Elridi, 1988, Morici et al., 1997, Lance and Elsey, 1999, Case et al., 2005, Chen et al., 2007, Borgmans et al., 2018, 2019).

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Blood samples (max 60 µl) were obtained from the post-orbital sinus by inserting a capillary

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tube (75 mm, 60 µl) between the eye and the eyelid (MacLean et al., 1973). Animals were held in hand to immobilise them to facilitate drawing blood. The use of post-orbital sinus sampling can cause some acute stress but is unlikely to have any long term effects as Balcombe et al. (2004) have shown that the acute respons lasted for up to two hours maximum. Our lab has extensive experience using this technique and no animals suffered long term negative effects or died from this treatment. Blood smears were made following

Walberg (2001). Air-dried smears were fixed in 90% ethanol for fifteen minutes and stained with Hemacolor®, Merck Millipore. The numbers of heterophils and lymphocytes visible in ten fields (magnification: 40x10, field size: 0.2 x 0.2 mm, WILD Heerbrugg M20, Switzerland) were counted and used to calculate H/L ratios. 2.6 Statistical analyses All statistical analyses were carried out with SPSS (IBM SPSS statistics v.26). Cage number was put in all analyses as a random factor and individual was added as a fixed factor. All

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behavioural data was summed by a value of 0.5 and subsequently square root transformed to control for zero inflated data. Average values for all subordinate males together are presented in the figures.

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We used Kendall’s coefficient of concordance (W) to evaluate whether individuals within a

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cage consistently occupied similar vertical positions relative to one another (and, hence, whether we could safely identify dominant and subordinate lizards). Kendall’s coefficient of

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concordance showed us that hierarchies in all cages were significantly constant trough time

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(Table 2).

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The link between aggressiveness and gained dominance rank, and the effects of dominance rank on access to food and to potential partners and exposure to predators were tested using

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Generalized linear models (GzLM) with dominance status as a fixed factor. Data for the behaviours scored in the food, mating and predation experiments were summed per individual across both repetitions for each experiment. All behavioural data on aggressive interactions, dewlap displays and push ups was expressed as number of behaviours per hour to allow for comparison across experiments. This comparison was done using GzLMs with experiment, dominance status and their interaction as a factor.

One-way repeated measures ANOVAs were used to gauge the effect of dominance and time on body mass, tail widths, and H/L ratios of the lizards. Three points (first and last time point for body mass and tail width) in time were considered: before the formation of tetrads, one week after the formation, and after 7 weeks (at the end of the experiments). The assumption of normality was tested with a Shapiro-Wilk test. Mass was log10-transformed and H/L ratio was square root transformed to ensure normality. When Mauchly’s test of sphericity was violated, a Greenhouse-Geisser correction was applied to the corresponding degrees of

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freedom. Whenever a repeated measures ANOVA found a statistical difference, a post hoc analysis with Bonferroni adjustment was carried out to investigate pairwise differences between the three points in time measured.

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3. Results

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3.1 Dominance and aggressiveness

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We found no connection between the number of aggressive interactions in which males engaged during group formation and their subsequent dominance ranking. Males that interacted were not more likely to become dominant (Wald χ21 = 0.12, p = 0.73, fig 1A).

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However, once the hierarchy established, dominant males tended to behave more aggressively towards other males when presented with valuable resources. This was the case in the food

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experiments (Wald χ21 = 3.64, p = 0.056, fig 1A) and the mating experiments

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(Wald χ21 = 3.32, p = 0.07, fig 1A), although the difference just failed to meet the 0.05 significance level in both cases. The number of aggressive interactions was found to be significantly different across the experiments (Wald χ22 = 6.42, p < 0.05, fig 1A). The number of interactions rose considerably when food was presented compared to the 30 minutes after group formation (p < 0.05, fig 1A) but did not differ compared to the mating experiment (p = 0.38). No difference was found

between the 30 minutes after group formation and the mating trial (p = 0.96). The difference across experiments was similar for dominant and subordinate individuals (interaction effect experiment*dominance status, Wald χ22 = 1.03, p = 0.6). 3.2 Dominance and social displays Males that subsequently became the dominant individuals within a group did not perform more dewlap displays (Wald χ21 = 0.013, p = 0.91, fig 1B) or push ups (Wald χ21 = 0.004,

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p = 0.95, fig 1C) in the 30 minutes after group formation. However, when presented with prey in the food experiments, dominant males performed more dewlap displays (Wald χ21 = 4.56, p < 0.05, fig 1B) and push ups (Wald χ21 = 6.13, p < 0.05, fig 1C). A similar effect of dominance rank was seen when a female was introduced into the cage (dewlap displays: Wald

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χ21 = 4.24, p < 0.05, fig 1B, push-ups: Wald χ21 = 2.99, p = 0.08, fig 1C). The number of

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dewlap displays (Wald χ22 = 8.9, p < 0.05, fig 1B) and push ups (Wald χ22 = 7.98, p < 0.05, fig 1C) was found to be significantly different across experiments. Number of dewlap displays

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and push ups performed was higher in the 30 minutes after group formation compared to the food experiment (dewlap displays: p < 0.05, fig 1B, push-ups: p < 0.05, 1C) and tended to be

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higher compared to the mating experiment, but this was not reflected in the statistical results (dewlap displays: p = 0.06, fig 1B, push-ups: p = 0.21, 1C). No difference was found between

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the food and mating trial (dewlap displays: p = 1, push-ups: p = 0.98). The difference across experiments in number of dewlap displays (interaction effect experiment*dominance status,

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Wald χ22 = 1.35, p = 0.51) and push ups (interaction effect experiment*dominance status, Wald χ22 = 0.82, p = 0.66) performed was similar for both dominant and subordinate males.

3.3 Dominance and access to resources

Dominant males were able to eat more wax moth larvae than subordinate individuals in the food experiment (Wald χ21 = 36.9, p < 0.001, fig 2A). Dominant males did not approach the plastic box containing a potential mate more often than subordinate individuals in the mating experiment (Wald χ21 = 0.18, p = 0.68, fig 2B).

3.4 Dominance and predation

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Dominant males were found to perform a higher number of lateral head movements in the presence of a predator (Wald χ21 = 3.67, p = 0.05, fig 3A) and to hide less frequently

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(Wald χ21 = 7.24, p < 0.01, fig 3B) than subordinate individuals.

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3.5 Physiology

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3.5.1 Body mass

Both dominant and subordinate lizards exhibited a rise in body mass over time (F1,13 = 46.33,

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p < 0.001, fig 4A). The rise in body mass tended to be different between dominant and subordinate males (dominance*time effect: F1,13 = 4, p = 0.067), and dominant males had an

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overall higher body mass (F1,13 = 12.14, p < 0.01). When comparing (future) dominant and subdominant males at the start of the trial period, no significant difference in body mass was

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found (fig 4A, ANOVA, F1,13 = 1.69, p = 0.22). However, 8 weeks later, at the end of the trial period, dominant males outweighed subdominant individuals (fig 4A, ANOVA, F1,13 = 14.17, p < 0.01).

3.5.2 Tail width

Tail width did not change significantly over time (treatment effect: F1,13 = 4.52, p = 0.63, fig 4B). The change in tail width did not differ between dominant and subordinate individuals (dominance*time effect: F1,13 = 0.005, p = 0.95), but dominant males were found to have a significantly larger tail width (dominance effect: F1,13 = 6.45, p < 0.05). 3.5.3 H/L ratio Average H/L ratio changed significantly over time (treatment effect: F2, 26 = 8.4, p < 0.01, fig

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4C), and at a similar rate in dominant and subordinate individuals (interaction effect: F2, 26 = 0.86, p = 0.44), there was also no overall difference across time in H/L ratios between dominant and subordinate individuals (dominance effect: F1,13 = 0.5, p = 0.49). H/L ratios

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were lowest at one week after group formation compared to before (p < 0.05) and at the end (p < 0.05), but did not differ between the latter (p = 1). Although we found no overall

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difference across time, H/L ratio between dominant and subordinate individuals did seem to differ highly at the end of the trial period (fig 4C). An ANOVA was carried out looking at the

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difference for only this period. We found that H/L ratio for dominant individuals was

4. Discussion

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significantly higher than subordinates (dominance effect: F1,13 = 7.09, p < 0.05).

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4.1 Advantages of dominance

A possible advantage of dominance is that dominant males have priority access to food

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resources (Alberts, 1994). This has been shown in a number of review studies (Richards, 1974, Syme, 1974, Kaufmann, 1983), including a large body of work on primates (Harcourt, 1987). In contrast, fairly little research has been done on lizards and rare examples can be found in Pfeffer (1959) and Summers and Andrews (1996). Pfeffer (1959) showed that dominant males had priority in the feeding order at carcasses in Komodo monitors (Varanus komodoensis). Summers and Andrews (1996) investigated priority to food in female A.

carolinensis lizard and found no difference between dominant and subordinate females in number of prey items eaten. Our results showed that dominant males ate more wax moth larvae than subordinate males in our food experiment and thus further proves this hypothesis. We find further support in our physiological results which showed that body mass increased significantly over time and that dominant males had a higher body mass at the end of the trial period. Tail width was also found to be significantly bigger for dominant males. This shows that what is found for dominant males in the behavioural observations concerning priority to

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food items is reflected in their physiology. Furthermore, these results can serve as an indication that the priority over food resources of dominant individuals has an ecological relevance. The rise in body mass and tail width shows that dominant males not only

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compensate for the possible higher energetic cost connected to their dominance status, but also obtain an extra advantage in the form of an increased growth rate and a bigger body size

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which may ultimately lead to an increase in reproductive success.

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Another advantage that dominant males could have is priority over potential mates which could ultimately lead to a higher reproductive success. This association between dominance

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and reproductive success has been supported by meta-analysis reviews on, for example, birds (Fiske et al., 1998) and primates (Rodriguez-Llanes et al., 2009, Majolo et al., 2012) and has

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also found support in a number of studies on lizard species (Carpenter, 1967, Ruby et al., 1981). Our results showed that there were no differences in number of times individuals

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touched the box containing the female. We did find that dominant males performed more dewlap displays and push ups. So while our results do confirm that dominant males perform more social displays towards potential mates (Alberts, 1994), they did not show a concurrent rise in actual mating attempts. This could be explained partially by the fact that females were restrained and therefore could not perform their full array of natural behaviour that would occur during mating. Individuals were kept at temperatures and day-lengths that maintained

reproductive activity (Lovern et al., 2004), so this was unlikely to have had an effect on the mixed results of the mating experiment. Previous research has shown that the presence of females can serve as a priming stimulus, resulting in heavier testes and more advanced spermatogenic activity in groups of male anoles (Crews and Greenberg, 1981). This could possibly have had an effect on the results as males did not have contact with females prior to the mating experiment.

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4.2 Disadvantages of dominance One hypothesis on the disadvantages of dominance is that dominant individuals have a higher risk of injuries due to a higher number of aggressive interactions (Riechert, 1988, Arnott and

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Elwood, 2009, Holekamp and Strauss, 2016). This theory is relatively well documented in lizards. Examples include a higher incidence of blindness in one eye in Cuban rock iguanas

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(Cyclura nubile) as a consequence of facial biting during male combat (Alberts, 1994), a higher chance of tail loss in Sceloporus magister (Vitt et al., 1974) and a general lower

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survivorship in wild male spiny lizards (Sceloporus jarrovi, Marler and Moore, 1988, 1991). Two results lend support to the idea that dominance may come at the expense of higher injury

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risk: (1) dominant individuals had a higher number of aggressive interactions in the food experiment and (2) the number of aggressive interactions in the food experiment was

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significantly higher than at 30 min after group formation. However, the statistical significance of these results differs from its biological meaning. We saw that in all experiments average

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values including standard error never exceed a value of one aggressive interaction per hour. So even while dominant males almost had double the amount of aggressive interactions in the food experiment, in reality this difference is negligible and thus shows a very low occurrence of aggressive interactions. This low number of aggressive interactions is surprising as the groups of four individuals within all cages were size matched and although low aggression might be expected once dominance hierarchies are formed (Yang et al., 2001, Forster et al.,

2005, Korzan et al., 2007), a higher number of aggressive interactions might be expected during dominance formation. A possible explanation might be found in the fact that it has been shown that male A. carolinensis can recognize and avoid interactions with previous opponents (Forster et al., 2005) and thus in our experiments subordinate males could avoid aggressive interactions with winners of previous interactions. While we observed a relatively low amount of aggression across the experiments, we did see a high number of social displays. Our results showed that dominant males performed more

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social displays (both dewlap displays and push ups) in the food and mating experiments. The number of social displays differed among experiments and was found to be lower in the food experiment compared to the 30 minutes after group formation, but did not differ between the

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other experiments. We found no difference between dominant and subordinate males in

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number of socials displays performed in the 30 minutes after group formation. This result is not surprising as this is the period in which hierarchies are forming and it can be expected that

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all males perform social displays to a certain degree to determine dominance. This is supported by the fact that we found the highest number of both dewlap displays and push ups

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in this period. When we link these results to the number of aggressive interactions observed, we seem to find that even at a higher density, males will rely more on ritualized social

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displays instead of aggressive interactions to form dominance hierarchies. Furthermore, the fact that we find higher numbers of social displays for dominant males compared to

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subordinates in the experiments conducted after dominance hierarchies were formed, suggests that maintaining these hierarchies will be done mainly by using social display behaviour instead of aggressive interactions, confirming what was found in previous research (Alberts, 1994, Wilson, 2000). Another possible disadvantage of dominance is that it might be energetically costly to maintain a dominant position. Our social display results showed that dominant males did

perform more social displays in the food and mating experiments. Previous research has shown that social displays in lizards (Brandt, 2003, Lailvaux and Irschick, 2006a, Husak et al., 2006, Husak and Fox, 2006, Sullivan and Kwiatkowski, 2007) and more specifically in Anolis lizards (Bennet et al., 1981, Leal, 1999) are energetically costly and thus our results indicate that there might be a difference in energetic cost between dominant and subordinate males. The results we found in the predation experiment seem to point in the same direction as we found that dominant males had a higher number of lateral head movements (a proxy for

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alertness) in the presence of a predator. Both of these results could indicate a higher energetic cost for dominant males and thus that being dominant could be more stressful. However, we do not find clear support for this in our physiology results. Changes in both body mass and

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tail width (a proxy for body condition) throughout the trial period did not show a higher net energetic cost of dominance in dominant males. Only our H/L ratio results pointed towards a

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potential higher cost of dominance for dominant males compared to subordinate males as we

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found that dominant males had a significantly higher H/L ratio at the end of the trial period. H/L ratio has been shown to be positively correlated to levels of glucocorticoids (Borgmans et al., 2018, 2019, Davis et Maerz, 2008, Case et al., 2005, Chen et al., 2007, Lance and Elsey,

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1999, Morici et al., 1997, Saad and Elridi, 1988) and thus the higher H/L ratio for the dominant males could indicate a higher level of stress. We also found that the H/L ratios for

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both dominant and subordinate males were lowest at one week after group formation. As

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mentioned above previous research has found a strong link between circulation androgen levels and a supressed immune system and thus this decrease in H/L ratio’s in subordinates could partially be explained by the fact that it has been shown that subordinate A. carolinensis males have depressed circulating androgen levels at one week after a dominance interaction (Greenberg and Crews, 1990). While Greenberg and Crews (1990) found this depression only in subordinate individuals, our results showed a decrease for both dominant and subordinates.

Why the dominant individuals showed this same depression in H/L ratio we do not know. Perhaps there are some factors of being housed in a multiple male group compared to the usual dyadic interactions that play a role here, but this needs to be investigated further. So while dominant males in our study engaged more frequently in energetically expensive behavioural displays, they increased in weight faster and had better body conditions than subordinate males by the end of the trial. This suggests that the benefits associated with a high ranking position (increased food intake) outweighed any energetic costs. A possible

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explanation for this can be found in previous research looking at the link between dominance and performance. It has been found that how well an individual can engage in display and aggressive behaviour is dependent on its body condition (Huyghe et al., 2005, Poisbleau et al.,

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2006, Husak et al., 2007), as individuals in better physical condition can better sustain

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vigorous behaviour. Our body mass and especially the tail width results do seem to indicate that dominant animals had an overall better body condition than subordinates and that

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although the higher amount of display behaviour might have been energetically more costly, they were able to sustain it due to their better condition. This might also indicate that body

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condition could be an important determinant of dominance in multiple male groups, but as the main aim of this study was not to identify possible determinants, further research is needed to

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confirm this.

Another disadvantage of dominance is that dominant individuals may have a higher risk of

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predation by being more visible (Magnhagen, 1991, Alberts, 1994, Amsler, 2010, Catano et al., 2015). This theory is supported by previous research on Vervet monkeys (Chlorocebus pygerythrus, Teichroeb et al., 2015). In contrast, in birds it has been shown that subordinate individuals start foraging sooner after disturbance by a predator and thus have a higher risk of predation (Laet, 1985, Hegner, 1985, Hogstad, 1988). Other examples of research showing a higher risk of predation for subordinate individuals include white-faced capuchins (Cebus

capucinus, Hall, 1997) and male collared lizards (Crotaphytus collaris, Baird, 2018). Our results do seem to indicate that dominant males have a higher risk of predation as we found that dominant males hid less frequently than subordinate males. However, there are more factors besides hiding that play a role in the risk of predation. For example dominant males might compensate the higher risk of predation by being more vigilant (higher number of lateral head movements), having a better view of the surrounding (higher average horizontal position) or have a better body condition (higher body mass and tail width) which gives them

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a higher chance of escaping. Some evidence for all of these examples can be found in our results and so while the lower amount of hiding behaviour could indicate a higher risk of predation, more research is needed to look into this in more detail. An interesting future

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avenue could be to investigate the running speeds of dominant males as some research has shown a link between a larger body size and faster running speeds (Huey and Hertz, 1982,

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Husak, 2006)

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An important fact we would like to mention is that males are kept at local suppliers at much higher densities than used in our experiments, with as many as 100 individuals kept together

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(personal observations). These kind of situations are likely to have a huge impact on both dominant and subordinate individuals and deserves more attention from scientific research.

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Therefore, further research should be carried out looking at hierarchies at even higher population densities, as it has been shown that aggressive interactions are more common at

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higher density (Brattstrom, 1974, Dugan and Wiewandt, 1982) and that this produces severe physiological stress in subordinate individuals (Crews and Garrick, 1980). Other interesting options to continue this line of research could be for example: to look at how our findings can be extrapolated to situations in the field, to measure the actual risk of predation through survivor analyses and to measure the effects of dominance on actual reproductive success.

5. Conclusions Our results showed that dominant males in a multiple male group had priority access to food and displayed more towards potential mates, confirming previously formulated hypothesis on the advantages of dominance. Furthermore, we found that dominant males did not perform

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more aggressive interactions than subordinate males across different experiments and thus we could not confirm the hypothesis that dominant males have a higher risk of injuries and while we found higher amount of display behaviour for dominant individuals our physiological

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results did not provide us with clear results and we were not able to confirm the theory that being either dominant or subordinate in a multiple male group is stressful. Our predation

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experiment showed that dominant males hid less, providing some support for the hypothesis

Acknowledgements

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that dominance can lead to an increased risk of predation.

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The authors would like to thank J Scholliers and J Mertens for their assistance in the practical

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work.

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This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

References Alberts, A.C., 1994. Dominance hierarchies in male lizards: implications for zoo management programs. Zoo. Biol. 13: 479-490. Amsler, S.J., 2010. Energetic costs of territorial boundary patrols by wild chimpanzees. Am. J. Primatol. 72: 93-103. Andrews, R.M., 1971. Structural habitat and time budget of a tropical Anolis lizard. Ecol. 52: 262270.

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Arnott, G., Elwood, R.W., 2009. Assessment of fighting ability in animal contests. Anim. Beh. 77: 991-1004. Baird, T.A., 2018. Live fast and prosper: early territory defence is not costly in male collared lizards (Crotaphytus collaris). Biol. J. Lin. Soc. 123: 628-635.

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Balcombe, J.P., Barnard, N.D., Sandusky, C., 2004. Laboratory routines cause animal stress. J. Am. Assoc. Lab. Anim. Sci. 43: 42-51.

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Bauwens, D., 1985. Demografische kenmerken en aantalsdynamiek in een populatie van de levendbarende hagedis (Lacerta vivipara). Universitaire Instelling Antwerpen.

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Bels, V., 1984. Ethological problems of the anoline lizards in captivity. Acta. Zool. Pathol. Ant. 78: 85-100. Bennett, A.F., Gleeson, T.T., Gorman, G.C., 1981. Anaerobic metabolism in a lizard (Anolis bonairensis) under natural conditions. Physiol. Zool. 54: 237-241.

na

Blumstein, D., Evans, C., Daniel, J., 2006. JWatcher 1.0. See http://www. jwatcher.ucla.edu.

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Borgmans, G., Palme, R., Sannen, A., Vervaecke, H., Van Damme, R., 2018. The effect of environmental provisioning on stress levels in captive green anole (Anolis carolinensis). Anim. Welfare 27: 35-46. Borgmans, G., Palme, R., Sannen, A., Vervaecke, H., Van Damme, R. 2019. The effect of cage size on stress levels in captive green anole (Anolis carolinensis). Anim Welfare 28: 455-464.

Jo

Brackin, M.F., 1978. The relation of rank to physiological state in Cnemidophorus sexlineatus dominance hierarchies. Herpetologica 34: 185-191. Brandt, Y., 2003. Lizard threat display handicaps endurance. P. Roy. Soc. Lon. B. Bio. 270: 10611068. Brattstrom, B.H., 1974. The evolution of reptilian social behavior. Am. Zool. 14: 35-49. Carothers, J.H., 1981. Dominance and competition in an herbivorous lizard. Behav. Ecol. Sociobiol. 8: 261-266.

Carpenter, C.C., 1967. Aggression and social structure in iguanid lizards. In: Lizard Ecology: A symposium. pp 87-105, Columbia, Missouri, USA: University of Missouri Press. Case, B.C., Lewbart, G.A., Doerr, P.D., 2005. The physiological and behavioural impacts of and preference for an enriched environment in the eastern box turtle (Terrapene carolina carolina). Appl. Anim. Behav. Sci. 92: 353-365. Castle, E., 1990. Husbandry and breeding of chameleons Chamaeleo spp at Oklahoma City Zoo. International Zoo Yearbook 29: 74-84. Catano, L.B., Gunn, B.K., Kelley, M.C., Burkepile, D.E., 2015. Predation risk, resource quality, and reef structural complexity shape territoriality in a coral reef herbivore. PloS one 10: e0118764.

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Chen, X., Niu, C., Pu, L., 2007. Effects of stocking density on growth and non‐specific immune responses in juvenile soft‐shelled turtle, Pelodiscus sinensis. Aquac. Res. 38: 1380-1386. Crews, D., Garrick, L.D., 1980. Methods of inducing reproduction in captive reptiles. Reproductive biology and diseases of captive reptiles. pp 49-70. Crews, D., Greenberg, N., 1981. Function and causation of social signals in lizards. Am. Zool. 21: 273-294.

-p

Davis, A.K., Maerz, J.C., 2008. Sex-related differences in hematological stress indices of breeding paedomorphic mole salamanders. J. Herpetol. 42: 197-201.

re

Dugan, B., Wiewandt, T., 1982. Socio-ecological determinants of mating strategies in iguanine lizards. Iguanas Of The World: Their Behavior, Ecology And Conservation. William Andrew Publishing, New Jersey, USA: 303-319.

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Evans, L.T., 1936. A study of a social hierarchy in the lizard, Anolis carolinensis. Pedagog. Sem. J. Gen. 48: 88-111.

na

Forster, G.L., Watt, M.J., Korzan, W.J., Renner, K.J., Summers, C.H., 2005. Opponent recognition in male green anoles, Anolis carolinensis. Anim. Behav. 69: 733-740. Fox S., 1983. Home-range quality and aggression in Uta stansburiana. Lizard Ecology: Studies On A Model Organism. Chiron, New York: 97-107.

ur

Fox, S.F., Rose, E., Myers, R., 1981. Dominance and the acquisition of superior home ranges in the lizard Uta stansburiana. Ecology 62: 888-893.

Jo

Fiske, P., Rintamäki, P.T., Karvonen, E., 1998. Mating success in lekking males: a meta-analysis. Behav. Ecol. 9: 328-338. Gilman, C.A., Irschick, D.J., 2013. Foils of flexion: the effects of perch compliance on lizard locomotion and perch choice in the wild. Func. Ecol. 27: 374-381. Greenberg, N., Crews, D., 1990. Endocrine and behavioral responses to aggression and social dominance in the green anole lizard, Anolis carolinensis. Gen. Comp. Endocr. 77: 246-255. Greenberg, N., Scott, M., Crews, D., 1984. Role of the amygdala in the reproductive and aggressive behavior of the lizard, Anolis carolinensis. Physiol. Behav. 32: 147-151.

Hall, C.L., Fedigan, M., 1997. Spatial benefits afforded by high rank in white-faced capuchins. Anim. Behav. 53: 1069-1082. Harcourt, A.H., 1987. Dominance and fertility among female primates. J. Zool. 213: 471-487. Henningsen, J.P., Irschick, D.J., 2012. An experimental test of the effect of signal size and performance capacity on dominance in the green anole lizard. Func. Ecol. 26: 3-10. Hegner, R.E., 1985. Dominance and anti-predator behaviour in blue tits (Parus caeruleus). Anim. Behav. 33: 762-768. Hogstad, O., 1988. Social rank and antipredator behaviour of willow tits Parus montanus in winter flocks. Ibis 130: 45-56.

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Holekamp, K.E., Strauss, ED, 2016. Aggression and dominance: an interdisciplinary overview. Curr. Opin. Behav. Sci. 12: 44-51. Hollis, K.L., Blouin, L.A., Romano M.C., Langworthy-Lam K.S., Siegenthaler J., 2004. Maintaining a competitive edge: dominance hierarchies, food competition and strategies to secure food in green anoles (Anolis carolinensis) and firemouth cichlids (Thorichthys meeki). Int. J. Comp. Psychol. 17: 222-240.

-p

Huey, R.B., Hertz, P. E. 1982. Effects of body size and slope on sprint speed of a lizard (Stellio (Agama) stellio). Journal of Experimental Biology, 97(1): 401-409.

re

Huntingford, F.A., Turner, A. K. 1987. Animal Conflict. Chapman and Hall, London.

lP

Husak, J.F. 2006. Does speed help you survive? A test with collared lizards of different ages. Functional Ecology, 20(1): 174-179. Husak, J.F., Fox, S.F., 2006. Field use of maximal sprint speed by collared lizards (Crotaphytus collaris): compensation and sexual selection. Evolution 60: 1888-1895.

na

Husak, J.F., Fox, S.F., Lovern, M.B., Van Den Bussche, R.A., 2006. Faster lizards sire more offspring: sexual selection on whole-animal performance. Evolution 60: 2122-2130.

ur

Husak, J.F., Irschick, D.J., Meyers, J.J., Lailvaux, S.P., Moore, I.T., 2007. Hormones, sexual signals, and performance of green anole lizards (Anolis carolinensis). Horm. Behav. 52: 360-367.

Jo

Huyghe, K.B., Vanhooydonck, B., Scheers, H., Molina‐Borja, M., Van Damme, R., 2005. Morphology, performance and fighting capacity in male lizards, Gallotia galloti. Func. Ecol. 19: 800-807. Jenssen, T.A., Congdon, J.D., Fischer, R.U., Estes, R., Kling, D., Edmands, S., Berna, H., 1996. Behavioural, thermal, and metabolic characteristics of a wintering lizard (Anolis carolinensis) from South Carolina. Func. Ecol. : 201-209. Jenssen, T.A., Greenberg, N., Hovde, K.A., 1995. Behavioral profile of free-ranging male lizards, Anolis carolinensis, across breeding and post-breeding seasons. Herpetol. Monog. 10: 41-62. Jenssen, T.A., Decourcy, K.R., Congdon, J.D., 2005. Assessment in contests of male lizards (Anolis carolinensis): how should smaller males respond when size matters? Anim. Behav. 69: 13251336.

Kaufmann, J.K., 1983. On the definitions and functions of dominance and territoriality. Biol. Rev. 58: 1-20. Korzan, W.J., Höglund, E., Watt, M.J., Forster, G.L., Øverli, Ø., Lukkes, J.L., Summers, C.H., 2007. Memory of opponents is more potent than visual sign stimuli after social hierarchy has been established. Behav. Brain. Res. 183: 31-42. Krebs, J.R., Davies, N.B., 1993. An Introduction to Behavioural Ecology. Blackwell Science, Hoboken, NJ, USA. Laet, J.F., 1985. Dominance and anti‐predator behaviour of Great Tits Parus major: a field study. Ibis 127: 372-377.

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Lailvaux, S.P., Irschick, D.J., 2006. A functional perspective on sexual selection: insights and future prospects. Anim. Behav. 72: 263-273. Lailvaux, S., Irschick, D.J., 2007. Effects of temperature and sex on jump performance and biomechanics in the lizard Anolis carolinensis. Func. Ecol. 21: 534-543. Lance, V.A., Elsey, R.M., 1999. Plasma catecholamines and plasma corticosterone following restraint stress in juvenile alligators. J. Exp. Zoo. Part A 283: 559-565.

-p

Leal, M., 1999. Honest signalling during prey–predator interactions in the lizard Anolis cristatellus. Anim. Behav. 58: 521-526.

re

Licht, P., 1968. Response of the thermal preferendum and heat resistance to thermal acclimation under different photoperiods in the lizard Anolis carolinensis. Am. Midl. Nat. 79: 149-158.

lP

Lopez, P., Martin, J., 2001. Pheromonal recognition of females takes precedence over the chromatic cue in male Iberian wall lizards Podarcis hispanica. Ethol. 107: 901-912.

na

Losos, J.B., 2011. Lizards In An Evolutionary Tree: Ecology And Adaptive Radiation Of Anoles. Univ. of California Press. Lovern, M.B., Holmes, M.M., Wade, J., 2004. The green anole (Anolis carolinensis): a reptilian model for laboratory studies of reproductive morphology and behavior. Ilar J. 45: 54-64.

ur

MacLean, G.S., Lee, A.K., Wilson, K.J., 1973. A simple method of obtaining blood from lizards. Copeia 1973: 338-339.

Jo

Magnhagen, C., 1991. Predation risk as a cost of reproduction. Trends Ecol. Evol. 6: 183-186. Majolo, B., Lehmann, J., de Bortoli Vizioli, A., Schino, G., 2012. Fitness‐related benefits of dominance in primates. Am. J. Phys. Anthropol. 147: 652-660. Marler, C., Moore, M., 1988. Evolutionary costs of aggression revealed by testosterone manipulations in free-living male lizards. Behav. Ecol. Sociobiol. 23: 21-26. Marler, C.A., Moore, M.C., 1991. Supplementary feeding compensates for testosterone-induced costs of aggression in male mountain spiny lizards, Sceloporus jarrovi. Anim. Behav. 42: 209-219.

Morici, L.A., Elsey, R.M., Lance, V.A., 1997. Effects of long-term corticosterone implants on growth and immune function in juvenile alligators, Alligator mississippiensis. J. Exp. Zool. 279: 156162. Pusey, A.E., Packer, C. 1977. The ecology of relationships. In: Behavioral Ecology: An Evolutionary Approach (Krebs, J.R. & Davies, N.B., eds), 4th edn, pp. 254-283. Oxford: Blackwell Science. Pawley, R., 1969. Further notes on a captive colony of Marine iguanas Amblyrhynochos cristatus at Brookfield Zoo, Chicago. International Zoo Yearbook 9: 41-44. Pfeffer, P., 1959. Observations sur le Varan de komodo. Varanus komodoensis. Ouwens 1912.

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Poisbleau, M., Fritz, H., Valeix, M., Perroi, P., Dalloyau, S., Lambrechts, M.M., 2006. Social dominance correlates and family status in wintering dark-bellied brent geese, Branta bernicla bernicla. Anim. Behav. 71: 1351-1358. Regal, P.J., 1980. Temperature and light requirements of captive reptiles. Reproductive Biology and Diseases of Captive Reptiles, JB Murphy and JT Collins, eds. Society for the Study of Amphibians and Reptiles.79-91.

-p

Richards, S.M., 1974. The concept of dominance and methods of assessment. Anim. Behav. 22: 914930.

re

Riechert, S.E., 1988. The energetic costs of fighting. Am. Zool. 28: 877-884.

Robson, M., Miles D., 2000. Locomotor performance and dominance in male tree lizards, Urosaurus ornatus. Func. Ecol. 14: 338-344.

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Rodda, G.H., Bock, B.C., Burghardt, G.M., Rand, A.S., 1988. Techniques for identifying individual lizards at a distance reveal influences of handling. Copeia 1988: 905-913.

na

Rodriguez-Llanes, J.M., Verbeke, G., Finlayson, C., 2009. Reproductive benefits of high social status in male macaques (Macaca). Anim. Behav. 78: 643-649.

ur

Ruby, D.E., 1981. Phenotypic correlates of male reproductive success in the lizard, Sceloporus jarrovi. In: Alexander RD, Tinkle DW (eds) Natural Selection and Social Behavior. Chiron Press, New York, pp 97-107.

Jo

Saad, A.H., El Ridi, R., 1988. Endogenous corticosteroids mediate seasonal cyclic changes in immunity of lizards. Immunobiology 177: 390-403. Summers, C.H., Andrews, T.J., 1996. Aggression, and the acquisition and function of social dominance in female Anolis carolinensis. Behaviour 133(15-16): 1265-1279. Sullivan, B.K., Kwiatkowski, M.A., 2007. Courtship displays in anurans and lizards: theoretical and empirical contributions to our understanding of costs and selection on males due to female choice. Func. Ecol. 21: 666-675. Syme, G.J., 1974. Competitive orders as measures of social dominance. Anim. Behav. 22: 931-940.

Teichroeb, J.A., White, M.M.J., Chapman, C.A., 2015. Vervet (Chlorocebus pygerythrus) intragroup spatial positioning: dominants trade-off predation risk for increased food acquisition. Int. J. Primatol. 36: 154-176. Tokarz R.R., 1985. Body size as a factor determining dominance in staged agonistic encounters between male brown anoles (Anolis sagrei). Anim. Behav. 33: 746-753. Tokarz, R.R., 1987. Effects of corticosterone treatment on male aggressive behavior in a lizard (Anolis sagrei). Horm. Behav. 21: 358-370. Tubbs, A.A., Ferguson, G.W., 1976. Effects of artificial crowding on behavior, growth and survival of juvenile spiny lizards. Copeia 1976: 820-823.

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Vitt, L.J., Congdon, J.D., Hulse, A.C., Platz, J.E., 1974. Territorial aggressive encounters and tail breaks in the lizard Sceloporus magister. Copeia 1974: 990-993. Walberg, J., 2001. White blood cell counting techniques in birds. Sem. Avian Exotic Pet Med. 10, 7276.

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Wilczynski, W., Black, M.P., Salem, S.J., Ezeoke, C.B., 2015. Behavioural persistence during an agonistic encounter differentiates winners from losers in green anole lizards. Behaviour 152: 563-591. Wilson, E.O., 2000. Sociobiology. Harvard University Press. Cambridge, MA, USA.

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Wingfield, J. C., and P. Marler. 1988. Endocrine basis of communication: reproduction and aggression. Pages 1647-1677 in E. Knobil and J. D. Neill, eds. The physiology of reproduction. Raven, New York.

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Yang, E.J., Phelps, S.M., Crews, D., Wilczynski, W., 2001. The effects of social experience on aggressive behavior in the green anole lizard (Anolis carolinensis). Ethol. 107: 777-793.

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Figure 1. Number of aggressive interactions (A), number of dewlap displays (B) and number of push-ups (C) for Anolis carolinensis lizards during the 30 minutes after group formation (GF), the food experiment and the mating experiment. Behaviours are expressed as number of behaviours per hour to allow comparison across experiments. Shown are means and standard errors for dominant males (black bars) and subordinate males (grey bars).

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Figure 2. Number of larvae eaten (A) and number of box approaches (B) for Anolis carolinensis lizards during the food experiment. Shown are means and standard errors for dominant males (black bars) and subordinate males (grey bars).

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Figure 3. Number of head movements (A) and number of times hiding (B) for Anolis carolinensis lizards during the predation experiment. Shown are means and standard errors for dominant males (black bars) and subordinate males (grey bars).

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Figure 4. Body mass (A), tail base width (B) and H/L ratios (C) for Anolis carolinensis lizards before group formation, one week after group formation (only for H/L ratios) and at the end of the trial period. Shown are means and standard errors for dominant males (black bars) and subordinate males (grey bars).

Table 1. Ethogram of behavioural observations for male A. carolinensis lizards. Behaviour

Definition

Aggressive interactions Dewlap displays Push-up

Number of times individuals had an aggressive interaction with another individual Number of times individuals (partially) extend their dewlap (often combined with push-ups) Number of times individuals perform a push-up with (two or all) of their legs Number of times a specific individual touched the box containing the female in the mating experiment Number of times spent remaining stationary while (partially) remaining hidden from sight Number of times individuals move their head laterally from on stationary position to another

Box touches

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Hiding Head movement

able 2. Average vertical position values given per cage for individuals marked orange (O), purple (P), blue (B) and white (Wh), highlighted values represent dominant males within each cage, asterisks represent individuals that died.N represents sample size, W represents Kendall's coefficient of concordance which is chi² distributed, df represents degrees of freedom and P represent the P-values indicating whether W varies from 0 (totally random).

O

P

B

Wh

N

W

2

df

p

1

2.83*

2.45

1.44*

3.29

56

0.42

70.07

3

<0.001

2

3.63

2.61

1.97*

1.79*

56

0.46

77.84

3

<0.001

3

2.29

3.45

2.13

2.14

47

0.28

39.44

3

<0.001

4

2.34

3.39

1.99

2.28

47

0.26

36.68

3

<0.001

5

2.97

3.2

2.06

1.77

47

0.33

46.36

3

<0.001

6

2.27

2.21

2.69

2.83

47

0.02

0.071

3

0,019

7

3.71

1.99

1.64*

2.66*

47

0.57

80.41

3

<0.001

8

3.43

2.4

1.43*

2.74

47

0.46

64.57

3

<0.001

9

2.51

2.83

1.87

2.79

47

0.14

20.05

3

<0.001

10

2.13

2.04

3.96

1.97

3

<0.001

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Cage number

0.79

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47

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T

111.36