How do lizards determine dominance? Applying ranking algorithms to animal social behaviour

Abstract

Dominance relationships are a defining feature of the social organization of many animal species. Populations structured by absolute dominance usually maintain a generally linear hierarchy, while relative dominance occurs, for example, within territorial populations where an animal is likely to be dominant within its territory. Because relative dominance is dependent on social context, the traits associated with it are often unclear. Green anole lizards, Anolis carolinensis, are an ideal system in which to determine dominance-related traits, as anoles use territorial defence in most natural environments, but establish a dominance hierarchy at high densities such as those that occur in captivity. We hypothesized that anoles use similar morphological and behavioural traits to determine social status under both forms of social organization. To test this, we studied a natural population of anoles to determine the traits most predictive of male territory size and quality (as measured by the number of females overlapping a male's territory). While these measures of territory may be related, they measure different components of territorial success. We then used mathematical ranking algorithms to quantify dominance in a tournament of paired arena trials, and identified traits associated with rank. Our results showed that lizards with wider heads had higher social rank, while those with longer heads were more successful at territorial defence. We also found that, independently of morphology, lizards who behaved more aggressively ranked higher in dominance trials, although behaviour did not predict measures of territory. Together, our results indicate that different traits may determine absolute and relative dominance in the green anole.

Do differences in bite force and head morphology between a native and an introduced species of anole influence the outcome of species interactions?

“…Finally, greater absolute bite force goes hand in hand with a larger body and head size (Herrel et al, 2001a;Lailvaux et al, 2004;Husak et al, 2006;Henningsen & Irschick, 2012;Bush et al, 2016) and this study confirmed the strong positive correlation between size and absolute bite force. While species differences in head and body size seem to suffice to explain differences in absolute bite force between species for females, relative to their size, A. cristatellus males bite harder than A. oculatus males.…”

“…Downes & Bauwens, 2002;Herrel et al, 2004b; see Discussion), although not all tests have supported this hypothesis (Langkilde & Shine, 2007;Edwards & Lailvaux, 2013). Finally, previous studies have suggested that greater bite forces are associated with a larger head and greater body size (Herrel et al, 2001b;Lailvaux et al, 2004;Husak et al, 2006;Henningsen & Irschick, 2012;Bush et al, 2016), and head morphology may be directly impacted by exploitative competition for food (Adams & Rohlf, 2000;Grant & Grant, 2014) and interference competition through agonistic encounters (Adams, 2004).…”

The dominance, prestige, and leadership account of social power motives

“…through superior physical strength). As such, fairly stable dominance rankings based on the number of victories/defeats in dyadic contests can be observed in simple animals such as crayfish (Fero & Moore, 2008), lizards (Bush, Quinn, Balreira, & Johnson, 2016), or birds (Valderrábano-Ibarra, Brumon, & Drummond, 2007). Moreover, they can often be observed in more human-like species such as monkeys (e.g.…”

Aggression and dominance: an interdisciplinary overview

“…In most gregarious birds and mammals, the ontogeny of dominance relationships generally conforms to one of two major patterns. In the most common case, dominance is determined by intrinsic factors such as body size, fighting ability, personality traits, or other attributes that directly affect the ability to win fights [31,32]. In these cases, dominance status fluctuates over time and in association with changing competitive ability and health.…”