Scat on the doorstep: Refuge choice in a group‐living lizard is influenced by the presence of scat piles

Abstract

Group living often requires strong levels of communication between individuals. This communication is usually studied in the context of visual or auditory communication. However, chemical communication is the most widely used form of communication. We examined the role of chemical communication in mediating social decisions in a group-living lizard, Egernia stokesii. Specifically, we examined the extent to which scat-piling, a behaviour by which individuals deposit scat in a communal area, affected the refuge choice of individual E. stokesii. To achieve this, we examined individual refuge choice in response to scat piles or single scats and against two types of scat stimuli, one being their own scat and the other being scat belonging to an unrelated and unfamiliar conspecific. We show that lizards behave differently when presented with a scat pile compared with a single scat, and whether the scat stimulus was their own or sourced from an unfamiliar conspecific. When scats were in piles, individuals spent more time inspecting, more time in, and more often chose the treatment refuge as their final refuge choice, at a trial's end, when the treatment was their own scat compared with when the treatment was the refuge with the unfamiliar scat. In contrast, for individual scat treatments, individuals spent more time inspecting and more often ended up in the treatment refuge with an unfamiliar scat compared with when the treatment was their own scat. These results suggest that individuals are responding to information contained within multiple components of the scatsboth their volume and their source. These results have implications for understanding how social aggregations are maintained within squamates, where sociality has evolved independently from other vertebrate lineages.

Scat piling and strong frugivory of the Balearic lizard, Podarcis lilfordi (Günther, 1874)

“…Attracted conspecifics could detect shrubs with ripe fruits that are close by with a greater probability. This attraction, thanks to inadvertent chemical signals, would lead to a positive feedback loop: lizards exploit plants with ripening fruits for several days or weeks while using rocky crevices in the area immediately adjacent to the scat pile as safe refuges [ 46 ]. By doing so they continuously accumulate faeces and increase the attractiveness of the place for new lizards.…”

Investment in chemical signalling glands facilitates the evolution of sociality in lizards

“…In other words, species that lack glands are not necessarily constrained by their ability to obtain chemical information [78]. For example, some lizard species 'scat pile', where they essentially have a latrine near their refuges and these act as information centres [79,80]. The family-living Egernia 'group' clade [81], for instance, lack epidermal glands, but tongue-flick assays indicate that they are able to recognize kin solely based on the scent (often of scats) alone [79, [82][83][84][85][86].…”

Nomenclature of supra-generic units within the Family Scincidae (Squamata)

“…The Egerniini of Welch (1982), and the earlier Egernina of De Vis (1888), which need to be treated as independent due to the different stems employed in the formation of the names, apply to a much more geographically restricted (Australia, the Solomon Islands, New Guinea and the Maluku Archipelago of Indonesia) and less species-rich (62 species in 8 genera) lineage for which there have been many fewer uses of the terms Egerniini/Egerninae/Egernidae (although again the informal name Egernia group of Greer (1979) has a much greater usage). While I have been able to identify 40 uses of these names (with or without the double -i) since Welch (1982) created Egerniini (Egerniidae: Hedges & Conn 2012;Pyron et al 2013;Zug 2013;Hedges 2014;Sy 2015;Bahmani et al 2016Bahmani et al , 2018Feizi et al 2016;Paluh & Bauer 2017;Čerňaňský et al 2020;Čerňaňský & Syromyatnikova 2021;Egerniinae: Hitchmough et al 2016;Bull et al 2017;Halliwell et al 2017a-c;Atkins et al 2018Atkins et al , 2020Foster et al 2018;Norval et al 2018Norval et al , 2021Bower et al 2019;Chapple et al 2019Chapple et al , 2021Ortiz et al 2019;Thorn et al 2019Thorn et al , 2021Treilibs et al 2019;While et al 2019;Norval & Gardner 2020;Pearson et al 2020;Ridley et al 2020;Stampe et al 2020;Thompson et al 2020;Watson et al 2020…”