Sharing refuges on arid islands: ecological and social influence on aggregation behaviour of wall geckos

Abstract

BackgroundThe extent of social behaviour among reptiles is underappreciated. Two types of aggregations are recognized in lizards: ecological and social, i.e., related to the attraction to a site or to animals of the same species, respectively. As most lizards are territorial, aggregations increase the probability of aggressive interactions among individuals, a density-dependent behaviour.MethodsAfter some spurious observations of aggregation behaviour in the endemic Cabo Verde nocturnal gecko Tarentola substituta, we conducted a field-based study in order to thoroughly characterize it. We sampled 48 transects and 40 10 × 10 m quadrats on São Vicente Island to describe the incidence, size and composition of aggregations and to study the effect of gecko and refuge density, plus refuge quality, on refuge sharing. We hypothesize that when density of animals and scarcity of high-quality refuges is higher, lizards have increased probability of aggregating. We also predict a consistent pattern of size and composition of groups (male–female pairs, only one adult male per group) throughout the year if there is a selected behaviour to avoid agonistic interactions, and low thermal advantage to aggregating individuals.ResultsWe present one of the first evidences of aggregation for Phyllodactylidae geckos. We found that T. substituta forms aggregations around 30–40% of the time, and that refuges are almost always shared by a female-male pair, sometimes with a juvenile, probably a mechanism to avoid aggressive interactions. We also observed that refuge sharing is dependent on refuge quality, as medium–large (thermally more stable and positively selected) rocks are shared much more frequently than small ones, but independent of adult sizes. Refuge sharing is also directly related to the density of geckos and inversely related to the density of high-quality refuges. We found no relation between body temperatures of geckos and refuge sharing when controlling the effect of rock/air temperature, suggesting that huddling does not improve thermoregulation.DiscussionOur results suggest that in this harsh environment (rocks reach 46 °C) aggregation incidence is mainly driven by an ecological factor (scarcity of high-quality refuges) and its intersexual composition by social factors (avoidance of agonistic interactions by males, and possible increased reproductive success of the pair). This study sheds some light on the little explored gecko aggregation behaviour and other studies should follow.

The ecology of sleep in non‐avian reptiles

“…Conversely, aggregations could increase parasite load (but see Wikelski, 1999; Leu, Kappeler & Bull, 2010; Sih et al ., 2018). Little is known about the composition of such sleep aggregations, although the presence of male–female pairs or single adult males in a group of females appears common (Downes & Shine, 1998 a ; Kearney et al ., 2001; Leu, Kappeler & Bull, 2011; Barry, Shanas & Brunton, 2014; Vasconcelos, Rocha & Santos, 2017). In some species, (e.g.…”

Retreat Sites Shared by Two Liolaemus Lizard Species: Exploring the Potential Role of Scents

“…This is remarkable, because L. coeruleus lacks precloacal glands (Cei and Ortiz-Zapata, 1983), and it has been proposed that the lack of pheromonal glands would be associated with a low ability to use scents (e.g., Phrynosomatidae Fitzinger, 1843, Hews andBenard, 2001;Lacertidae Gray, 1825, Baeckens et al, 2015. Although precloacal glands produce chemical secretions (Valdecantos et al, 2014) with pheromonal properties (Labra et al, 2005;Valdecantos and Labra, 2017), there are other sources of scents in Liolaemus species, including feces (Labra et al, 2002), skin derivates (Labra, 2008a) and, presumably, substances produced by proctodeal glands in males (Valdecantos et al, 2015) and urodeal glands in females (Sánchez-Martinez et al, 2007).…”

“…Most animal species need to use retreat sites to protect themselves and/or their offspring (Mateo and Cuadrado, 2012) against different factors such as predation (Downes and Shine, 1998) or environmental conditions, such as extreme temperatures (Aguilar and Cruz, 2010;van den Berg et al, 2015). Evidence indicates that retreat sites are not chosen randomly, as they need to fulfill some basic requirements (e.g., Croak et al, 2008;van den Berg et al, 2015) such as an adequate size (Kroon et al, 2000;Caruso, 2016) or a proper three-dimensional structure (Croak et al, 2008). Besides these basic constraints, retreat site selection can also be modulated by intrinsic characteristics of the individuals, such as age, sex, or/and reproductive condition (Rutherford and Gregory, 2003;Vasconcelos et al, 2017).…”

“…Evidence indicates that retreat sites are not chosen randomly, as they need to fulfill some basic requirements (e.g., Croak et al, 2008;van den Berg et al, 2015) such as an adequate size (Kroon et al, 2000;Caruso, 2016) or a proper three-dimensional structure (Croak et al, 2008). Besides these basic constraints, retreat site selection can also be modulated by intrinsic characteristics of the individuals, such as age, sex, or/and reproductive condition (Rutherford and Gregory, 2003;Vasconcelos et al, 2017). All these requirements determine that retreat sites can be a scarce resource for which animals need to compete (Marvin, 1998;Penado et al, 2015).…”

Microhabitat sharing for basking between squamate species in Poland

“…These records are most often transient aggregations limited to certain life cycle phases, environmental changes and even high prey densities (Mouton 2011;Edgehouse et al 2014;Gardner et al 2015). In squamates, two types of aggregations are recognised: ecological (when individuals are attracted because of limited habitat availability due to external factors or too concentrated availability of resources, for example, food, shelter, basking sites) (Vasconcelos et al 2017) and social (when individuals are attracted to conspecifics to avoid predators by group defence, increased thermoregulation (including European lizards) or mating behaviour (Graves and Duvall 1995;Kearney et al 2001;Chapple 2003;Gardner et al 2015;Meek and Luiselli 2022b;Turner 2022). Noteworthy and rare are observations of intra-or interspecific interactions outside the specific context that requires aggregating behaviour, often correlated with resource use, for example, heat source, mating partner, hibernacula, shelter or biotic or abiotic structures for predation avoidance (Graves and Duvall 1995;Kearney et al 2001;Ajtić et al 2013;Turner 2022).…”