The Evolution of Sociality and the Polyvagal Theory

The polyvagal theory (PT), offered by Porges (2021), proposes that the autonomic nervous system (ANS) was repurposed in mammals, via a second vagal nerve, to suppress defensive strategies and support the expression of sociality. Three critical assumptions of this theory are that (1) the transition of the ANS was associated with the evolution of social mammals from asocial reptiles; (2) the transition enabled mammals, unlike their reptilian ancestors, to derive a biological benefit from social interactions; and (3) the transition forces a less parsimonious explanation (convergence) for the evolution of social behavior in birds and mammals, since birds evolved from a reptilian lineage. Two recently published reviews, however, provided compelling evidence that the social asocial dichotomy is overly simplistic, neglects the diversity of vertebrate social systems, impedes our understanding of the evolution of social behavior, and perpetuates the erroneous belief that one group, non-avian reptiles, is incapable of complex social behavior. In the worst case, if PT depends upon a transition from asocial reptiles to social mammals, then the ability of PT to explain the evolution of the mammalian ANS is highly questionable. A great number of social behaviors occur in both reptiles and mammals. In the best case, PT has misused the terms social and asocial. Even here, however, the theory would still need to identify a particular suite of behaviors found in mammals and not reptiles that could be associated with, or explain, the transition of the ANS, and then replace the asocial and social labels with more specific descriptors.Comment: 15 pages, 1 figur

DISTRIBUTION AND STATUS OF THE SUWANNEE COOTER, PSEUDEMYS CONCINNA SUWANNIENSIS, IN THE ALAFIA RIVER (HILLSBOROUGH COUNTY, FLORIDA, USA)

The Suwannee Cooter, Pseudemys concinna suwanniensis, is a geographically limited turtle of conservation concern that inhabits Florida rivers draining into the northeastern Gulf of Mexico. Threats impacting its conservation status include take for human consumption, predation of turtles and nests, loss or degradation of nesting and basking habitat, water quality degradation, and boat strikes. Our surveys revealed that the Alafia River, which drains into Hillsborough Bay (northeastern Tampa Bay), is likely the stronghold of the southern distribution of P. c. suwanniensis. Multiple survey methods during 2015-2020 revealed that a substantial population of Suwannee Cooters inhabits much of this blackwater river system, including the main channel and at least one of its two primary tributaries. GIS analysis showed that more than half of the shoreline within the occupied extent is currently protected by conservation lands, although additional protection of private lands and improved habitat management protocols are needed to assure the population’s conservation

Plasticity in nest site choice behavior in response to hydric conditions in a reptile

Natural selection is expected to select for and maintain maternal behaviors associated with choosing a nest site that promotes successful hatching of offspring, especially in animals that do not exhibit parental care such as reptiles. In contrast to temperature effects, we know little about how soil moisture contributes to successful hatching and particularly how it shapes nest site choice behavior in nature. The recent revelation of exceptionally deep nesting in lizards under extreme dry conditions underscored the potential for the hydric environment in shaping the evolution of nest site choice. But if deep nesting is an adaptation to dry conditions, is there a plastic component such that mothers would excavate deeper nests in drier years? We tested this hypothesis by excavating communal warrens of a large, deep-nesting monitor lizard (Varanus panoptes), taking advantage of four wet seasons with contrasting rainfall amounts. We found 75 nests during two excavations, including 45 nests after a 4-year period with larger wet season rainfall and 30 nests after a 4-year period with smaller wet season rainfall. Mothers nested significantly deeper in years associated with drier nesting seasons, a finding best explained as a plastic response to soil moisture, because differences in both the mean and variance in soil temperatures between 1 and 4 m deep are negligible. Our data are novel for reptiles in demonstrating plasticity in maternal behavior in response to hydric conditions during the time of nesting. The absence of evidence for other ground-nesting reptile mothers adjusting nest depth in response to a hydric-depth gradient is likely due to the tradeoff between moisture and temperature with changing depth; most ground-nesting reptile eggs are deposited at depths of ~ 2–25 cm—nesting deeper within or outside of that range of depths to achieve higher soil moisture would also generally create cooler conditions for embryos that need adequate heat for successful development. In contrast, extreme deep nesting in V. panoptes allowed us to disentangle temperature and moisture. Broadly, our data suggest that ground-nesting reptiles can assess soil moisture and respond by adjusting the depth of the nest, but may not, due to the cooling effect of nesting deeper. Our results, within the context of previous work, provide a more complete picture of how mothers can promote hatching success through adjustments in nest site choice behavior

Varanus Panoptes (Yellow-Spotted Monitor) Toxic Prey Avoidance

Although large predatory animals are capable of capturing and consuming large prey, most regularly consume smaller prey (e.g., Hart and Hamrin 1990. In Hughes [ed.], Behavioural Mechanisms of Food Selection, pp. 235–253. Springer-Verlag, Berlin). Large monitor lizards are no exception. For example, Varanus bengalensis reaches 1.75 m in total length but 75% of its diet consists of small invertebrates (Auffenberg 1994. The Bengal Monitor. The University Press of Florida, Gainesville. 560 pp.). Generalist predators such as large monitor lizards use different foraging strategies to obtain different prey, a pattern well documented for V. bengalensis (Auffenberg 1994, op. cit.). One foraging behaviour noted was regular searches for dung beetles (Scarabaeidae) in the dung pats of (mainly) large mammals. Herein we document similar foraging behaviour in the Yellow-spotted Monitor, Varanus panoptes, in northern Australi