Social boldness in male green anole lizards correlates with baseline vasopressin activity

Across species, individuals within a population differ in their level of boldness in social encounters with conspecifics. This boldness phenotype is often stable across both time and social context (e.g., reproductive versus agonistic encounters). Various neural and hormonal mechanisms have been suggested as underlying these stable phenotypic differences, which are often also described as syndromes, personalities, and coping styles. Most studies examining the neuroendocrine mechanisms associated with behavioral boldness examine subjects after they have engaged in a social interaction, whereas baseline neural activity that may predispose behavioral variation is understudied. The present study tests the hypotheses that physical characteristics, steroid hormone levels, and baseline variation in Ile3-vasopressin (VP, a.k.a., Arg8-vasotocin) signaling predispose social boldness. Behavioral boldness in agonistic and reproductive contexts was extensively quantified in male green anole lizards (Anolis carolinensis), an established research organism for social behavior research that provides a crucial comparison group to investigations of birds and mammals. We found high stability of boldness across time, and between agonistic and reproductive contexts. Next, immunofluorescence was used to colocalize VP neurons with phosphorylated ribosomal protein S6 (pS6), a proxy marker of neural activity. VP-pS6 colocalization within the paraventricular and supraoptic nuclei of the hypothalamus was inversely correlated with aggression boldness, but not reproductive behavior boldness. Our findings suggest that baseline vasopressin release, rather than solely context-dependent release, plays a role in predisposing individuals toward stable levels of aggressive boldness toward conspecifics by inhibiting behavioral output in these contexts.

Green Anole lizards (Anolis carolinensis) deposit eggs in nests of the Trap Jaw Ant, Odontomachus brunneus

Squamates eggs are rarely found in ant nests, and are largely restricted to the nests of neotropical fungus gardening in the tribe Attini. Ponerine ant nests have not previously been reported as nesting cavities for squamates, including the Green Anole (Anolis carolinensis). The current study reports the association of Green Anole eggs and hatchlings with the subterranean nest chambers of the trap jaw ant, Odontomachus brunneus. Hatching rates suggest that O. brunneus nests may be used communally by multiple females, which partition spatial resources with other recently introduced Anolis species in their native range. This new nesting strategy is placed in the context of know associations between frogs, snakes, legless worm lizards and ants.

Routine handling does not lead to chronic stress in captive green anole (Anolis carolinensis)

Routine handling has been shown to affect stress levels in a variety of animal species. This could result in a general decrease in welfare and may confound the results of scientific experiments or observations on captive study animals. In reptiles, there seems to be variation in the effects of handling on stress levels. Furthermore, most studies on reptiles only look at the effect of handling in the short term. In this study we quantified the physiological and behavioural impact of being held, twice daily, for 1 min at a time over a three-week period on the green anole (Anolis carolinensis). Measurements were collected at the end of the three-week repeated handling period. Our results showed no effect of repeated handling on body mass, tail-base width, heterophil to lymphocyte ratios (H/L ratios), behaviour and faecal corticosterone metabolite (FCM) levels for both males and females in the experimental treatments ('handled', 'unhandled'). Our study animals did score very highly for several stress-indicating variables in the three weeks preceding the experiments — suggesting that they had experienced considerable stress during capture, transport and temporary housing in the pet store.