Contextualized Display Behavior during Natural Interactions by Common Side-Blotched Lizards (Uta stansburiana, Squamata, Phrynosomatidae)
Many previous studies on competition focused on outcomes of competition and less on behavioral changes during or immediately following intra- or interspecific interactions. I performed 300 h of observation of three lizard species (Side-blotched Lizards, Uta stansburiana; Sagebrush Lizards, Sceloporus graciosus; Western Fence Lizards, Sceloporus occidentalis) and recorded 1,045 natural encounters, 403 of which were unconfounded by presence of another individual lizard. Despite potential competition amongst these species, I found little evidence that Uta modify perch characteristics or engage in aggressive interactions toward either of the heterospecific lizards. However, Uta do alter interspecific display behavior depending on whether interactions are intrasexual or intersexual. Moreover, Uta move shorter distances following interactions with S. graciosus but greater distances after interactions with S. occidentalis. Uta appear to reserve aggressive or more-intense interactions for intersexual intraspecific encounters, most of which are initiated by males. Together these findings suggest that these three lizard species are not broadly engaged in competitive interactions and that habitat characteristics or microhabitat preferences enable co-occurrence.ABSTRACT
Photos showing (A) study site with light-colored pumice forming dunes at base of rimrock and eroding boulder field in juniper woodland, (B) in-contact basking between Sceloporus graciosus (S.g.) and Uta stansburiana (U.s.), (C) in-contact basking between Sceloporus occidentalis (S.o.) and Uta stansburiana, and (D) all three species foraging under same brush.
Hourly rate of intraspecific (Uta–Uta) interactions (filled squares) and interspecific interactions between Uta and Sceloporus graciosus (shaded diamonds) or S. occidentalis (open diamonds) over time for two study years.
Average (±SE) change in (A) sum of head bobs or (B) movement distance by lizards in the 5 min before relative to the 5 min after the start of interactions, split by focal-animal (Uta) sex and either the sex (squares) or species (diamonds) of the interaction partner.
Proportion of interactions between Uta and (A) S. graciosus or (B) S. occidentalis (split by interactor sex) showing male- or female-initiated events as positive or negative scores, respectively. Closed symbols = Uta interactions with heterospecific males; open = Uta with heterospecific females; squares = Uta males as focal animal; circles = Uta females. Interaction intensity scores are: 0 = no reaction; ±1 = unidirectional displays; ±2 = reciprocal displays; ±3 = perch displacement; ±4 = unidirectional chasing; 5 = reciprocal chasing or attempted biting (fighting). Dashed line shows neutral event initiation between species with the shaded area between ±5% showing where events are approximately neutral.
